National Key R&D Program of China(2016YFD0600201) Program for Changjiang Scholars and Innovative Research Team of Ministry of Education of China(IRT_15R09)
Abstract Forests are large and persistent carbon (C) sink mainly through the C sequestration of tree growth, which can mitigate the rising rate of CO2 concentration in the atmosphere. According to C availability in trees, two mechanisms involved in controlling tree growth are attributed to limitations to C input and C utilities. Since many environmental factors influence the activities of C-source and C-sink of trees interdependently, it is difficult to quantify how the sensitivity of C-source or C-sink activity to environmental changes affects tree growth. Therefore, it is of significance to understand physiological mechanisms underlying potential limitations to tree growth in order to predict tree growth and forest C sink under global change scenarios. In this review, the debates on the C-source and C-sink limitations to tree growth were firstly introduced. Second, we discussed responses of tree growth to biotic and abiotic stresses, such as defoliation, drought and low temperature from the perspective of C-source/sink limitations. Finally, we proposed three priorities for future studies in this field: (1) to explore the regulating mechanisms on the allocation of non-structural carbohydrates (NSC) in trees, and to determine what conditions and what extent trees actively allocate the photosynthates to NSC storage at the expense of growth; (2) to strengthen studies on the tree C-sink, and determine the photosynthates allocated to all components of tree C-sink, especially the missing C-sinks such as the activities of roots and related microorganisms; and (3) to implement studies on interactions among C metabolism, mineral nutrition and hydraulics physiology, and fully understand the C-water-nutrient coupling and its effects on tree growth. Keywords：carbon sink;carbon source;non-structural carbohydrates;stress;tree growth
Fig. 1A conceptual framework of the mechanisms of carbon source-sink limitations to tree growth. From a-b-c pathway, carbon assimilation is reduced by biotic and abiotic stresses (such as defoliation, drought and low temperature), hence tree growth is limited by available carbon (i.e. carbon source limitation). From d-e-c pathway, the storage of non-structural carbohydrates (NSC) is an active process, which decreases available carbon for tree growth (carbon source limitation). From f-h-i pathway, tree growth is constrained by biotic and abiotic stresses directly, leading to NSC accumulation and thus limitation to photosynthesis (i.e. carbon sink limitation). Solid lines represent direct effects, and dotted lines represent feedbacks. + and - represent positive and negative effects, respectively.
AinsworthEA, RogersA ( 2007). The response of photosynthesis and stomatal conductance to rising [CO2]: Mechanisms and environmental interactions Plant, Cell & Environment, 30, 258-270. DOI:10.1111/j.1365-3040.2007.01641.xURLPMID:17263773 [本文引用: 1] This review summarizes current understanding of the mechanisms that underlie the response of photosynthesis and stomatal conductance to elevated carbon dioxide concentration ([CO2]), and examines how downstream processes and environmental constraints modulate these two fundamental responses. The results from free-air CO2 enrichment (FACE) experiments were summarized via meta-analysis to quantify the mean responses of stomatal and photosynthetic parameters to elevated [CO2]. Elevation of [CO2] in FACE experiments reduced stomatal conductance by 22%, yet, this reduction was not associated with a similar change in stomatal density. Elevated [CO2] stimulated light-saturated photosynthesis (Asat) in C3 plants grown in FACE by an average of 31%. However, the magnitude of the increase in Asat varied with functional group and environment. Functional groups with ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco)-limited photosynthesis at elevated [CO2] had greater potential for increases in Asat than those where photosynthesis became ribulose-1,5-bisphosphate (RubP)-limited at elevated [CO2]. Both nitrogen supply and sink capacity modulated the response of photosynthesis to elevated [CO2] through their impact on the acclimation of carboxylation capacity. Increased understanding of the molecular and biochemical mechanisms by which plants respond to elevated [CO2], and the feedback of environmental factors upon them, will improve our ability to predict ecosystem responses to rising [CO2] and increase our potential to adapt crops and managed ecosystems to future atmospheric [CO2].
Alvarez-UriaP, K?rnerC ( 2007). Low temperature limits of root growth in deciduous and evergreen temperate tree species Functional Ecology, 21, 211-218. DOI:10.1111/fec.2007.21.issue-2URL [本文引用: 2]
BaderMKF, LeuzingerS, KeelSG, SiegwolfRTW, HagedornF, SchleppiP, K?rnerC ( 2013). Central European hardwood trees in a high-CO2 future: Synthesis of an 8-year forest canopy CO2 enrichment project Journal of Ecology, 101, 1509-1519. DOI:10.1111/1365-2745.12149URL [本文引用: 1] Rapidly increasing atmospheric CO2 is not only changing the climate system but may also affect the biosphere directly through stimulation of plant growth and ecosystem carbon and nutrient cycling. Although forest ecosystems play a critical role in the global carbon cycle, experimental information on forest responses to rising CO2 is scarce, due to the sheer size of trees. Here, we present a synthesis of the only study world-wide where a diverse set of mature broadleaved trees growing in a natural forest has been exposed to future atmospheric CO2 levels (c. 550ppm) by free-air CO2 enrichment (FACE). We show that litter production, leaf traits and radial growth across the studied hardwood species remained unaffected by elevated CO2 over 8years. CO2 enrichment reduced tree water consumption resulting in detectable soil moisture savings. Soil air CO2 and dissolved inorganic carbon both increased suggesting enhanced below-ground activity. Carbon release to the rhizosphere and/or higher soil moisture primed nitrification and nitrate leaching under elevated CO2; however, the export of dissolved organic carbon remained unaltered. Synthesis. Our findings provide no evidence for carbon-limitation in five central European hardwood trees at current ambient CO2 concentrations. The results of this long-term study challenge the idea of a universal CO2 fertilization effect on forests, as commonly assumed in climate–carbon cycle models.
BaderMKF, SiegwolfR, K?rnerC ( 2010). Sustained enhancement of photosynthesis in mature deciduous forest trees after 8 years of free air CO2 enrichment Planta, 232, 1115-1125. DOI:10.1007/s00425-010-1240-8URLPMID:20700744 [本文引用: 1] Carbon uptake by forests constitutes half of the planet's terrestrial net primary production; therefore, photosynthetic responses of trees to rising atmospheric CO(2) are critical to understanding the future global carbon cycle. At the Swiss Canopy Crane, we investigated gas exchange characteristics and leaf traits in five deciduous tree species during their eighth growing season under free air carbon dioxide enrichment in a 35-m tall, ca. 100-year-old mixed forest. Net photosynthesis of upper-canopy foliage was 48% (July) and 42% (September) higher in CO(2)-enriched trees and showed no sign of down-regulation. Elevated CO(2) had no effect on carboxylation efficiency (V (cmax)) or maximal electron transport (J (max)) driving ribulose-1,5-bisphosphate (RuBP) regeneration. CO(2) enrichment improved nitrogen use efficiency, but did not affect leaf nitrogen (N) concentration, leaf thickness or specific leaf area except for one species. Non-structural carbohydrates accumulated more strongly in leaves grown under elevated CO(2) (largely driven by Quercus). Because leaf area index did not change, the CO(2)-driven stimulation of photosynthesis in these trees may persist in the upper canopy under future atmospheric CO(2) concentrations without reductions in photosynthetic capacity. However, given the lack of growth stimulation, the fate of the additionally assimilated carbon remains uncertain.
BarryKM, PinkardEA ( 2013). Growth and photosynthetic responses following defoliation and bud removal in eucalypts Forest Ecology and Management, 293, 9-16. DOI:10.1016/j.foreco.2012.12.012URL [本文引用: 1] CABALA, a productivity model for temperate plantation eucalypts, accounts for the impact of eucalypt defoliation on growth but does not yet account for differences in damage type. Consideration of both leaf and bud damage may result in a more realistic representation of growth outcomes for sites with different pest ecologies. We tested whether bud, as compared to leaf damage, elicited similar responses in two commercially important eucalypt species. Growth, biomass and physiological responses of young pot-grown plants to artificial removal of approximately 40% of leaf area (L treatment) or both leaves and buds (LB treatment) was assessed over a 4 month period of recovery. We identified that responses to defoliation were similar between the two species (Eucalyptus globulus and Eucalyptus nitens). Time series analysis highlighted that growth (height and stem diameter) was significantly reduced by defoliation during the study, which was more pronounced following LB treatment than L alone. At the end of the study, leaf area, stem height and diameter increment were not significantly affected by treatment, but total above-ground, stem biomass and foliar N were. This suggests that changes in patterns of biomass allocation occurred to maintain leaf area and capacity for light interception. Increased photosynthetic rate, which occurred for plants of both defoliation treatments but to a greater extent for the LB than L treatment, also contributed to recovery following defoliation. There was no evidence that photosynthetic rate increase was driven by changes in foliar nitrogen or chlorophyll, as there was not a statistically significant and strong relationship between the two factors. These results give us confidence that the process-based models used to predict the impacts of defoliation on productivity (1) can assume similar responses to defoliation for E. globulus and E. nitens and (2) should account for differences in physiological responses to foliage and bud damage. (C) 2013 Elsevier B.V.
BauerleWL, HinckleyTM, CermakJ, KuceraJ, BibleK ( 1999). The canopy water relations of old-growth Douglas-???r trees Trees, 13, 211-217. DOI:10.3897/CompCytogen.v13i3.35346URLPMID:31428293 [本文引用: 1] Chromosomes of four Miscanthus (Andersson, 1855) species including M. sinensis (Andersson, 1855), M. floridulus (Schumann & Lauterb, 1901), M. sacchariflorus (Hackel, 1882) and M. lutarioriparius (Chen & Renvoize, 2005) were analyzed using sequentially combined PI and DAPI (CPD) staining and fluorescence in situ hybridization (FISH) with 45S rDNA probe. To elucidate the phylogenetic relationship among the four Miscanthus species, the homology of repetitive sequences among the four species was analyzed by comparative genomic in situ hybridization (cGISH). Subsequently four Miscanthus species were clustered based on the internal transcribed spacer (ITS) of 45S rDNA. Molecular cytogenetic karyotypes of the four Miscanthus species were established for the first time using chromosome measurements, fluorochrome bands and 45S rDNA FISH signals, which will provide a cytogenetic tool for the identification of these four species. All the four have the karyotype formula of Miscanthus species, which is 2n = 2x = 38 = 34m(2SAT) + 4sm, and one pair of 45S rDNA sites. The latter were shown as strong red bands by CPD staining. A non-rDNA CPD band emerged in M. floridulus and some blue DAPI bands appeared in M. sinensis and M. floridulus. The hybridization signals of M. floridulus genomic DNA to the chromosomes of M. sinensis and M. lutarioriparius genomic DNA to the chromosomes of M. sacchariflorus were stronger and more evenly distributed than other combinations. Molecular phylogenetic trees showed that M. sinensis and M. floridulus were closest relatives, and M. sacchariflorus and M. lutarioriparius were also closely related. These findings were consistent with the phylogenetic relationships inferred from the cGISH patterns.
BeerC, ReichsteinM, TomelleriE, CiaisP, JungM, CarvalhaisN, RodenbeckC, ArainMA, BaldocchiD, BonanGB, BondeauA, CescattiA, LasslopG, LindrothA, LomasM, LuyssaertS, MargolisH, OlesonKW, RoupsardO, VeenendaalE, ViovyN, WilliamsC, WoodwardFI, PapaleD ( 2010). Terrestrial gross carbon dioxide uptake: Global distribution and covariation with climate Science, 329, 834-838. DOI:10.1126/science.1184984URLPMID:20603496 [本文引用: 1] Terrestrial gross primary production (GPP) is the largest global CO(2) flux driving several ecosystem functions. We provide an observation-based estimate of this flux at 123 +/- 8 petagrams of carbon per year (Pg C year(-1)) using eddy covariance flux data and various diagnostic models. Tropical forests and savannahs account for 60%. GPP over 40% of the vegetated land is associated with precipitation. State-of-the-art process-oriented biosphere models used for climate predictions exhibit a large between-model variation of GPP's latitudinal patterns and show higher spatial correlations between GPP and precipitation, suggesting the existence of missing processes or feedback mechanisms which attenuate the vegetation response to climate. Our estimates of spatially distributed GPP and its covariation with climate can help improve coupled climate-carbon cycle process models.
BerdanierAB, ClarkJS ( 2016). Multi-year drought-induced morbidity preceding tree death in Southeastern US forests Ecological Applications, 26, 17-23. DOI:10.1890/15-0274URLPMID:27039506 [本文引用: 1] Recent forest diebacks, combined with threats of future drought, focus attention on the extent to which tree death is caused by catastrophic events as opposed to chronic declines in health that accumulate over years. While recent attention has focused on large-scale diebacks, there is concern that increasing drought stress and chronic morbidity may have pervasive impacts on forest composition in many regions. Here we use long-term, whole-stand inventory data from southeastern U.S. forests to show that trees exposed to drought experience multiyear declines in growth prior to mortality. Following a severe, multiyear drought, 72% of trees that did not recover their pre-drought growth rates died within 10 yr. This pattern was mediated by local moisture availability. As an index of morbidity prior to death, we calculated the difference in cumulative growth after drought relative to surviving conspecifics. The strength of drought-induced morbidity varied among species and was correlated with drought tolerance. These findings support the ability of trees to avoid death during drought events but indicate shifts that could occur over decades. Tree mortality following drought is predictable in these ecosystems based on growth declines, highlighting an opportunity to address multiyear drought-induced morbidity in models, experiments, and management decisions.
BondBJ, CzarnomskiNM, CooperC, DayME, GreenwoodMS ( 2007). Developmental decline in height growth in Douglas-?r Tree Physiology, 27, 441-453. DOI:10.1093/treephys/27.3.441URLPMID:17241986 [本文引用: 2] The characteristic decline in height growth that occurs over a tree's lifespan is often called "age-related decline." But is the reduction in height growth in aging trees a function of age or of size? We grafted shoot tips across different ages and sizes of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees to determine whether the decline in height growth is mediated by tree size or by the age of the apical meristem. We also evaluated whether reduced carbon assimilation plays an important role in height growth decline. In one experiment we cut shoot tips from old-growth, young-mature and seedling trees and grafted them onto 2-year-old graft-compatible rootstock in a seed orchard in Lebanon, Oregon. In another experiment we performed reciprocal grafts between lateral branches of old-growth trees accessible from the canopy crane at Wind River, Washington and young-mature trees in a nearby plantation. We measured growth (diameter and elongation of the dominant new stem) and mortality annually for three years in the Seed Orchard experiment and for two years in the Reciprocal Graft experiment. In the Seed Orchard experiment we also measured photosynthetic capacity (determined from the response of net carbon assimilation to the intercellular CO(2) concentration of the leaf, or A/C(i) curves), leaf mass per area (LMA) and carbon isotope composition (delta(13)C) of cellulose in 1-year-old foliage. Grafting caused changes in both growth and physiology of the grafted stems. Within two years after grafting, growth and physiology of all combinations of scions and rootstock exhibited characteristics of the rootstock. In some cases, the change in growth was dramatic-cuttings from old-growth trees showed a 10-fold increase in stem elongation rate within 2 years of grafting onto seedling rootstock. Similarly, carbon isotope discrimination of new foliage on shoots from old-growth trees increased by nearly 3 per thousand and 2 per thousand after grafting onto young-mature and seedling rootstock, respectively, whereas discrimination decreased by a similar magnitude in scions from young-mature trees after grafting on old- growth trees. Furthermore, differences in carbon assimilation estimated from carbon isotope discrimination and A/C(i )relationships were small relative to growth differences. Our results confirm that size, not age, drives developmental changes in height growth in Douglas-fir. Reduced carbon assimilation does not play an important role in height growth decline.
BrédaN, HucR, GranierA, DreyerE ( 2006). Temperate forest trees and stands under severe drought: A review of ecophysiological responses, adaptation processes and long-?term consequences Annals of Forest Science, 63, 625-644. DOI:10.1051/forest:2006042URL [本文引用: 2]
BurnettAC, RogersA, ReesM, OsborneCP ( 2016). Carbon source-sink limitations differ between two species with contrasting growth strategies Plant, Cell & Environment, 39, 2460-2472. DOI:10.1111/pce.12801URLPMID:27422294 [本文引用: 1] Understanding how carbon source and sink strengths limit plant growth is a critical knowledge gap that hinders efforts to maximize crop yield. We investigated how differences in growth rate arise from source-sink limitations, using a model system comparing a fast-growing domesticated annual barley (Hordeum vulgare cv. NFC Tipple) with a slow-growing wild perennial relative (Hordeum bulbosum). Source strength was manipulated by growing plants at sub-ambient and elevated CO2 concentrations ([CO2 ]). Limitations on vegetative growth imposed by source and sink were diagnosed by measuring relative growth rate, developmental plasticity, photosynthesis and major carbon and nitrogen metabolite pools. Growth was sink limited in the annual but source limited in the perennial. RGR and carbon acquisition were higher in the annual, but photosynthesis responded weakly to elevated [CO2 ] indicating that source strength was near maximal at current [CO2 ]. In contrast, photosynthetic rate and sink development responded strongly to elevated [CO2 ] in the perennial, indicating significant source limitation. Sink limitation was avoided in the perennial by high sink plasticity: a marked increase in tillering and root:shoot ratio at elevated [CO2 ], and lower non-structural carbohydrate accumulation. Alleviating sink limitation during vegetative development could be important for maximizing growth of elite cereals under future elevated [CO2 ].
CavieresLA, RadaF, AzócarA, García-Nú?ezC, CabreraHM ( 2000). Gas exchange and low temperature resistance in two tropical high mountain tree species from the Venezuelan Andes Acta Oecologica, 21, 203-211. DOI:10.3109/02841868209134006URLPMID:6293262 [本文引用: 1] An intercomparison of therapy level exposure secondary standards from the Nordic countries was made at 60Co gamma radiation at the secondary standard dosimetry laboratory in Helsinki . One standard seemed to be in error by about one per cent and another was found to be unreliable. From the analysis it was concluded that inter-comparisons of secondary standards can be made with an overall uncertainty of about 0.2 per cent. This uncertainty is of the same size as the difference between primary standards, which may therefore play a role in the evaluation of differences between secondary exposure standards.
Chapin IIIFS, SchulzeE, MooneyHA ( 1990). The ecology and economics of storage in plants Annual Review of Ecology and Systematics, 21, 423-447. DOI:10.1146/annurev.es.21.110190.002231URL [本文引用: 1]
Chapin IIIFS, ZavaletaES, EvinerVT, NaylorRL, VitousekPM, ReynoldsHL, HooperDU, LavorelS, SalaOE, HobbieSE, MackMC, DíazS ( 2000). Consequences of changing biodiversity Nature, 405, 234-242. DOI:10.1038/35012241URLPMID:10821284 [本文引用: 1] Human alteration of the global environment has triggered the sixth major extinction event in the history of life and caused widespread changes in the global distribution of organisms. These changes in biodiversity alter ecosystem processes and change the resilience of ecosystems to environmental change. This has profound consequences for services that humans derive from ecosystems. The large ecological and societal consequences of changing biodiversity should be minimized to preserve options for future solutions to global environmental problems.
ChavesMM, FlexasJ, PinheiroC ( 2009). Photosynthesis under drought and salt stress: Regulation mechanisms from whole plant to cell Annals of Botany, 103, 551-560. DOI:10.1093/aob/mcn125URLPMID:18662937 [本文引用: 1] Plants are often subjected to periods of soil and atmospheric water deficits during their life cycle as well as, in many areas of the globe, to high soil salinity. Understanding how plants respond to drought, salt and co-occurring stresses can play a major role in stabilizing crop performance under drought and saline conditions and in the protection of natural vegetation. Photosynthesis, together with cell growth, is among the primary processes to be affected by water or salt stress.
CollettNG, NeumannFG ( 2002). Effects of simulated chronic defoliation in summer on growth and survival of blue gum (Eucalyptus globulus Labill.) within young plantations in northern Victoria. Australian Forestry, 65, 99-106. DOI:10.1080/00049158.2002.10674860URL [本文引用: 1]
DannouraM, EpronD, DesalmeD, MassonnetC, TsujiS, PlainC, PriaultP, GérantD ( 2019). The impact of prolonged drought on phloem anatomy and phloem transport in young beech trees Tree Physiology, 39, 201-210. DOI:10.1093/treephys/tpy070URLPMID:29931112 [本文引用: 2] Phloem failure has recently been recognized as one of the mechanisms causing tree mortality under drought, though direct evidence is still lacking. We combined 13C pulse-labelling of 8-year-old beech trees (Fagus sylvatica L.) growing outdoors in a nursery with an anatomical study of the phloem tissue in their stems to examine how drought alters carbon transport and phloem transport capacity. For the six trees under drought, predawn leaf water potential ranged from -0.7 to -2.4 MPa, compared with an average of -0.2 MPa in five control trees with no water stress. We also observed a longer residence time of excess 13C in the foliage and the phloem sap in trees under drought compared with controls. Compared with controls, excess 13C in trunk respiration peaked later in trees under moderate drought conditions and showed no decline even after 4 days under more severe drought conditions. We estimated higher phloem sap viscosity in trees under drought. We also observed much smaller sieve-tube radii in all drought-stressed trees, which led to lower sieve-tube conductivity and lower phloem conductance in the tree stem. We concluded that prolonged drought affected phloem transport capacity through a change in anatomy and that the slowdown of phloem transport under drought likely resulted from a reduced driving force due to lower hydrostatic pressure between the source and sink organs.
DawesMA, HagedornF, HandaIT, StreitK, EkbladA, RixenC, K?rnerC, H?ttenschwilerS ( 2013). An alpine treeline in a carbon dioxide-rich world: Synthesis of a nine-year free-air carbon dioxide enrichment study Oecologia, 171, 623-637. DOI:10.1007/s00442-012-2576-5URLPMID:23340765 [本文引用: 2] We evaluated the impacts of elevated CO2 in a treeline ecosystem in the Swiss Alps in a 9-year free-air CO2 enrichment (FACE) study. We present new data and synthesize plant and soil results from the entire experimental period. Light-saturated photosynthesis (A max) of ca. 35-year-old Larix decidua and Pinus uncinata was stimulated by elevated CO2 throughout the experiment. Slight down-regulation of photosynthesis in Pinus was consistent with starch accumulation in needle tissue. Above-ground growth responses differed between tree species, with a 33 % mean annual stimulation in Larix but no response in Pinus. Species-specific CO2 responses also occurred for abundant dwarf shrub species in the understorey, where Vaccinium myrtillus showed a sustained shoot growth enhancement (+11 %) that was not apparent for Vaccinium gaultherioides or Empetrum hermaphroditum. Below ground, CO2 enrichment did not stimulate fine root or mycorrhizal mycelium growth, but increased CO2 effluxes from the soil (+24 %) indicated that enhanced C assimilation was partially offset by greater respiratory losses. The dissolved organic C (DOC) concentration in soil solutions was consistently higher under elevated CO2 (+14 %), suggesting accelerated soil organic matter turnover. CO2 enrichment hardly affected the C-N balance in plants and soil, with unaltered soil total or mineral N concentrations and little impact on plant leaf N concentration or the stable N isotope ratio. Sustained differences in plant species growth responses suggest future shifts in species composition with atmospheric change. Consistently increased C fixation, soil respiration and DOC production over 9 years of CO2 enrichment provide clear evidence for accelerated C cycling with no apparent consequences on the N cycle in this treeline ecosystem.
DawesMA, H?ttenschwilerS, BebiP, HagedornF, HandaIT, K?rnerC, RixenC ( 2011). Species-specific tree growth responses to 9 years of CO2 enrichment at the alpine treeline Journal of Ecology, 99, 383-394. DOI:10.1111/j.1365-2745.2010.01764.xURL [本文引用: 3] 1. Using experimental atmospheric CO2 enrichment, we tested for tree growth stimulation at the high-elevation treeline, where there is overwhelming evidence that low temperature inhibits growth despite an adequate carbon supply. We exposed Larix decidua (European larch) and Pin us mugo ssp. uncinata (mountain pine) to 9 years of free-air CO2 enrichment (FACE) in an in situ experiment at treeline in the Swiss Alps (2180 m a.s.l.). 2. Accounting for pre-treatment vigour of individual trees, tree ring increments throughout the experimental period were larger in Larix growing under elevated CO2 but not in Pinus. The magnitude of the CO2 response in Larix ring width varied over time, with a significant stimulation occurring in treatment years 3-7 (marginal in year 6). 3. After 9 years of treatment, leaf canopy cover, stem basal area and total new shoot production were overall greater in Larix trees growing under elevated CO2, whereas Pinus showed no such cumulative growth response. The Larix ring width response in years 3-7 could have caused the cumulative CO2 effect on tree size even if no further stimulation occurred, so it remains unclear if responsiveness was sustained over the longer term. 4. Larix ring width was stimulated more by elevated CO2 in years with relatively high spring temperatures and an early snowmelt date, suggesting that temperatures were less limiting in these years and greater benefit was gained from extra carbon assimilated under elevated CO2. The magnitude of CO2 stimulation was also larger after relatively high temperatures and high solar radiation in the preceding growing season, perhaps reflecting gains due to larger carbon reserves. 5. Synthesis. Contrasting above-ground growth responses of two treeline tree species to elevated CO2 concentrations suggest that Larix will have a competitive advantage over less responsive species, such as co-occurring Pinus, under future CO2 concentrations. Stimulation of Larix growth might be especially pronounced in a future warmer climate.
DeppongDO, ClineMG ( 2000). Do leaves control episodic shoot growth in woodyplants? The Ohio Journal of Science, 100, 19-23. [本文引用: 1]
DeslauriersA, HuangJG, BalducciL, BeaulieuM, RossiS ( 2016). The contribution of carbon and water in modulating wood formation in black spruce saplings Plant Physiology, 170, 2072-2084. DOI:10.1104/pp.15.01525URLPMID:26850274 [本文引用: 1] Nonstructural carbohydrates (NSCs) play a crucial role in xylem formation and represent, with water, the main constraint to plant growth. We assessed the relationships between xylogenesis and NSCs in order to (1) verify the variance explained by NSCs and (2) determine the influence of intrinsic (tissue supplying carbon) and extrinsic (water availability and temperature) factors. During 2 years, wood formation was monitored in saplings of black spruce (Picea mariana) subjected to a dry period of about 1 month in June and exposed to different temperature treatments in a greenhouse. In parallel, NSC concentrations were determined by extracting the sugar compounds from two tissues (cambium and inner xylem), both potentially supplying carbon for wood formation. A mixed-effect model was used to assess and quantify the potential relationships. Total xylem cells, illustrating meristematic activity, were modeled as a function of water, sucrose, and d-pinitol (conditional r(2) of 0.79). Water availability was ranked as the most important factor explaining total xylem cell production, while the contribution of carbon was lower. Cambium stopped dividing under water deficit, probably to limit the number of cells remaining in differentiation without an adequate amount of water. By contrast, carbon factors were ranked as most important in explaining the variation in living cells (conditional r(2) of 0.49), highlighting the functional needs during xylem development, followed by the tissue supplying the NSCs (cambium) and water availability. This study precisely demonstrates the role of carbon and water in structural growth expressed as meristematic activity and tissue formation.
DietzeMC, SalaAN, CarboneMS, CzimczikCI, MantoothJA, RichardsonAD, VargasR ( 2014). Nonstructural carbon in woody plants Annual Review of Plant Biology, 65, 667-687. DOI:10.1146/annurev-arplant-050213-040054URLPMID:24274032 [本文引用: 1] Nonstructural carbon (NSC) provides the carbon and energy for plant growth and survival. In woody plants, fundamental questions about NSC remain unresolved: Is NSC storage an active or passive process? Do older NSC reserves remain accessible to the plant? How is NSC depletion related to mortality risk? Herein we review conceptual and mathematical models of NSC dynamics, recent observations and experiments at the organismal scale, and advances in plant physiology that have provided a better understanding of the dynamics of woody plant NSC. Plants preferentially use new carbon but can access decade-old carbon when the plant is stressed or physically damaged. In addition to serving as a carbon and energy source, NSC plays important roles in phloem transport, osmoregulation, and cold tolerance, but how plants regulate these competing roles and NSC depletion remains elusive. Moving forward requires greater synthesis of models and data and integration across scales from -omics to ecology.
DolezalJ, KopeckyM, DvorskyM, MacekM, RehakovaK, CapkovaK, BorovecJ, SchweingruberF, LiancourtP, AltmanJ ( 2019). Sink limitation of plant growth determines tree line in the arid Himalayas Functional Ecology, 33, 553-565. DOI:10.1111/fec.2019.33.issue-4URL [本文引用: 1]
DuanH, AmthorJS, DuursmaRA, O’GradyAP, ChoatB, TissueDT ( 2013). Carbon dynamics of eucalypt seedlings exposed to progressive drought in elevated [CO2] and elevated temperature Tree Physiology, 33, 779-792. DOI:10.1093/treephys/tpt061URLPMID:23963410 [本文引用: 1] Elevated [CO2] and temperature may alter the drought responses of tree seedling growth, photosynthesis, respiration and total non-structural carbohydrate (TNC) status depending on drought intensity and duration. Few studies have addressed these important climatic interactions or their consequences. We grew Eucalyptus globulus Labill. seedlings in two [CO2] concentrations (400 and 640 μl l(-1)) and two temperatures (28/17 and 32/21 °C) (day/night) in a sun-lit glasshouse, and grew them in well-watered conditions or exposed them to two drought treatments having undergone different previous water conditions (i.e., rewatered drought and sustained drought). Progressive drought in both drought treatments led to similar limitations in growth, photosynthesis and respiration, but reductions in TNC concentration were not observed. Elevated [CO2] ameliorated the impact of the drought during the moderate drought phase (i.e., Day 63 to Day 79) by increasing photosynthesis and enhancing leaf and whole-plant TNC content. In contrast, elevated temperature exacerbated the impact of the drought during the moderate drought phase by reducing photosynthesis, increasing leaf respiration and decreasing whole-plant TNC content. Extreme drought (i.e., Day 79 to Day 103) eliminated [CO2] and temperature effects on plant growth, photosynthesis and respiration. The combined effects of elevated [CO2] and elevated temperature on moderate drought stressed seedlings were reduced with progressive drought, with no sustained effects on growth despite greater whole-plant TNC content.
EpronD, CabralOMR, LaclauJP, DannouraM, PackerAP, PlainC, Battie-LaclauP, MoreiraMZ, TrivelinPCO, BouilletJP, GérantD, NouvellonY ( 2016). In situ13CO2 pulse labelling of field-grown eucalypt trees revealed the effects of potassium nutrition and throughfall exclusion on phloem transport of photosynthetic carbon Tree Physiology, 36, 6-21. DOI:10.1093/treephys/tpv090URLPMID:26423335 [本文引用: 1] Potassium (K) is an important limiting factor of tree growth, but little is known of the effects of K supply on the long-distance transport of photosynthetic carbon (C) in the phloem and of the interaction between K fertilization and drought. We pulse-labelled 2-year-old Eucalyptus grandis L. trees grown in a field trial combining K fertilization (+K and -K) and throughfall exclusion (+W and -W), and we estimated the velocity of C transfer by comparing time lags between the uptake of (13)CO2 and its recovery in trunk CO2 efflux recorded at different heights. We also analysed the dynamics of the labelled photosynthates recovered in the foliage and in the phloem sap (inner bark extract). The mean residence time of labelled C in the foliage was short (21-31?h). The time series of (13)C in excess in the foliage was affected by the level of fertilization, whereas the effect of throughfall exclusion was not significant. The velocity of C transfer in the trunk (0.20-0.82?m?h(-1)) was twice as high in +K trees than in -K trees, with no significant effect of throughfall exclusion except for one +K?-W tree labelled in the middle of the drought season that was exposed to a more pronounced water stress (midday leaf water potential of -2.2?MPa). Our results suggest that besides reductions in photosynthetic C supply and in C demand by sink organs, the lower velocity under K deficiency is due to a lower cross-sectional area of the sieve tubes, whereas an increase in phloem sap viscosity is more likely limiting phloem transport under drought. In all treatments, 10 times less (13)C was recovered in inner bark extracts at the bottom of the trunk when compared with the base of the crown, suggesting that a large part of the labelled assimilates has been exported out of the phloem and replaced by unlabelled C. This supports the 'leakage-retrieval mechanism' that may play a role in maintaining the pressure gradient between source and sink organs required to sustain high velocity of phloem transport in tall trees.
EvansCG ( 1972). The Quantitative Analysis of Plant Growth Blackwell Scienti?c, Oxford. [本文引用: 1]
FajardoA, PiperFI ( 2014). An experimental approach to explain the southern Andes elevational treeline American Journal of Botany, 101, 788-795. DOI:10.3732/ajb.1400166URLPMID:24812110 [本文引用: 1] ?
FajardoA, PiperFI ( 2017). An assessment of carbon and nutrient limitations in the formation of the southern Andes tree line Journal of Ecology, 105, 517-527. DOI:10.1111/jec.2017.105.issue-2URL [本文引用: 2]
FarquharGD, von CaemmererS, BerryJA ( 1980). A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species Planta, 149, 78-90. DOI:10.1007/BF00386231URLPMID:24306196 [本文引用: 1] Various aspects of the biochemistry of photosynthetic carbon assimilation in C3 plants are integrated into a form compatible with studies of gas exchange in leaves. These aspects include the kinetic properties of ribulose bisphosphate carboxylase-oxygenase; the requirements of the photosynthetic carbon reduction and photorespiratory carbon oxidation cycles for reduced pyridine nucleotides; the dependence of electron transport on photon flux and the presence of a temperature dependent upper limit to electron transport. The measurements of gas exchange with which the model outputs may be compared include those of the temperature and partial pressure of CO2(p(CO2)) dependencies of quantum yield, the variation of compensation point with temperature and partial pressure of O2(p(O2)), the dependence of net CO2 assimilation rate on p(CO2) and irradiance, and the influence of p(CO2) and irradiance on the temperature dependence of assimilation rate.
FatichiS, LeuzingerS, K?rnerC ( 2014). Moving beyond photosynthesis: From carbon source to sink-driven vegetation modeling New Phytologist, 201, 1086-1095. DOI:10.1111/nph.12614URLPMID:24261587 [本文引用: 1]
FatichiS, PappasC, ZscheischlerJ, LeuzingerS ( 2019). Modelling carbon sources and sinks in terrestrial vegetation New Phytologist, 221, 652-668. DOI:10.1111/nph.15451URLPMID:30339280 [本文引用: 1] Contents Summary 652 I. Introduction 652 II. Discrepancy in predicting the effects of rising [CO2 ] on the terrestrial C sink 655 III. Carbon and nutrient storage in plants and its modelling 656 IV. Modelling the source and the sink: a plant perspective 657 V. Plant-scale water and Carbon flux models 660 VI. Challenges for the future 662 Acknowledgements 663 Authors contributions 663 References 663 SUMMARY: The increase in atmospheric CO2 in the future is one of the most certain projections in environmental sciences. Understanding whether vegetation carbon assimilation, growth, and changes in vegetation carbon stocks are affected by higher atmospheric CO2 and translating this understanding in mechanistic vegetation models is of utmost importance. This is highlighted by inconsistencies between global-scale studies that attribute terrestrial carbon sinks to CO2 stimulation of gross and net primary production on the one hand, and forest inventories, tree-scale studies, and plant physiological evidence showing a much less pronounced CO2 fertilization effect on the other hand. Here, we review how plant carbon sources and sinks are currently described in terrestrial biosphere models. We highlight an uneven representation of complexity between the modelling of photosynthesis and other processes, such as plant respiration, direct carbon sinks, and carbon allocation, largely driven by available observations. Despite a general lack of data on carbon sink dynamics to drive model improvements, ways forward toward a mechanistic representation of plant carbon sinks are discussed, leveraging on results obtained from plant-scale models and on observations geared toward model developments.
FeildTS, BrodribbT ( 2001). Stem water transport and freeze-thaw xylem embolism in conifers and angiosperms in a Tasmanian treeline heath Oecologia, 127, 314-320. DOI:10.1007/s004420000603URLPMID:28547101 [本文引用: 1] The effect of freezing on stem xylem hydraulic conductivity and leaf chlorophyll a fluorescence was measured in 12 tree and shrub species from a treeline heath in Tasmania, Australia. Reduction in stem hydraulic conductivity after a single freeze-thaw cycle was minimal in conifers and the vessel-less angiosperm species Tasmannia lanceolata (Winteraceae), whereas mean loss of conductivity in vessel-forming angiosperms fell in the range 17-83%. A positive linear relationship was observed between percentage loss of hydraulic conductivity by freeze-thaw and the average conduit diameter across all 12 species. This supports the hypothesis that large-diameter vascular conduits have a greater likelihood of freeze-thaw cavitation because larger bubbles are produced, which are more likely to expand under tension. Leaf frost tolerances, as measured by a 50% loss of maximum PSII quantum yield, varied from -6 to -13°C, indicating that these species were more frost-sensitive than plants from northern hemisphere temperate forest and treeline communities. There was no evidence of a relationship between frost tolerance of leaves and the resilience of stem water transport to freezing, suggesting that low temperature survival and the resistance of stem water transport to freezing are independently evolving traits. The results of this study bear on the ecological importance of stem freezing in the southern hemisphere treeline zones.
FriendAD, Eckes-ShephardAH, FontiP, RademacherTT, RathgeberCBK, RichardsonAD, TurtonRH ( 2019). On the need to consider wood formation processes in global vegetation models and a suggested approach Annals of Forest Science, 76, 49. DOI:10.1007/s13595-019-0819-xURL [本文引用: 1]
GalianoL, Martínez-VilaltaJ, LloretF ( 2011). Carbon reserves and canopy defoliation determine the recovery of Scots pine 4 yr after a drought episode New Phytologist, 190, 750-759. DOI:10.1111/j.1469-8137.2010.03628.xURLPMID:21261625 [本文引用: 2] ? Severe drought may increase physiological stress on long-lived woody vegetation, occasionally leading to mortality of overstory trees. Little is known about the factors determining tree survival and subsequent recovery after drought. ? We used structural equation modeling to analyse the recovery of Scots pine (Pinus sylvestris) trees 4 yr after an extreme drought episode occurred in 2004-2005 in north-east Spain. Measured variables included the amount of green foliage, carbon reserves in the stem, mistletoe (Viscum album) infection, needle physiological performance and stem radial growth before, during and after the drought event. ? The amount of green leaves and the levels of carbon reserves were related to the impact of drought on radial growth, and mutually correlated. However, our most likely path model indicated that current depletion of carbon reserves was a result of reduced photosynthetic tissue. This relationship potentially constitutes a feedback limiting tree recovery. In addition, mistletoe infection reduced leaf nitrogen content, negatively affecting growth. Finally, successive surveys in 2009-2010 showed a direct association between carbon reserves depletion and drought-induced mortality. ? Severe drought events may induce long-term physiological disorders associated with canopy defoliation and depletion of carbon reserves, leading to prolonged recovery of surviving individuals and, eventually, to delayed tree death.
GalianoL, TimofeevaG, SaurerM, SiegwolfR, Martínez-?VilaltaJ, HommelR, GesslerA ( 2017). The fate of recently fixed carbon after drought release: Towards unravelling C storage regulation in Tilia platyphyllos and Pinus sylvestris. Plant, Cell & Environment, 40, 1711-1724. DOI:10.1111/pce.12972URLPMID:28432768 [本文引用: 2] Carbon reserves are important for maintaining tree function during and after stress. Increasing tree mortality driven by drought globally has renewed the interest in how plants regulate allocation of recently fixed C to reserve formation. Three-year-old seedlings of two species (Tilia platyphyllos and Pinus sylvestris) were exposed to two intensities of experimental drought during ~10?weeks, and 13 C pulse labelling was subsequently applied with rewetting. Tracking the 13 C label across different organs and C compounds (soluble sugars, starch, myo-inositol, lipids and cellulose), together with the monitoring of gas exchange and C mass balances over time, allowed for the identification of variations in C allocation priorities and tree C balances that are associated with drought effects and subsequent drought release. The results demonstrate that soluble sugars accumulated in P.?sylvestris under drought conditions independently of growth trends; thus, non-structural carbohydrates (NSC) formation cannot be simply considered a passive overflow process in this species. Once drought ceased, C allocation to storage was still prioritized at the expense of growth, which suggested the presence of 'drought memory effects', possibly to ensure future growth and survival. On the contrary, NSC and growth dynamics in T.?platyphyllos were consistent with a passive (overflow) view of NSC formation.
GibonY, PylET, SulpiceR, LunnJE, H?hneM, GüntherM, StittM ( 2009). Adjustment of growth, starch turnover, protein content and central metabolism to a decrease of the carbon supply when Arabidopsis is grown in very short photoperiods Plant, Cell & Environment, 32, 859-874. DOI:10.1111/j.1365-3040.2009.01965.xURLPMID:19236606 [本文引用: 3] Arabidopsis was grown in a 12, 8, 4 or 3 h photoperiod to investigate how metabolism and growth adjust to a decreased carbon supply. There was a progressive increase in the rate of starch synthesis, decrease in the rate of starch degradation, decrease of malate and fumarate, decrease of the protein content and decrease of the relative growth rate. Carbohydrate and amino acids levels at the end of the night did not change. Activities of enzymes involved in photosynthesis, starch and sucrose synthesis and inorganic nitrogen assimilation remained high, whereas five of eight enzymes from glycolysis and organic acid metabolism showed a significant decrease of activity on a protein basis. Glutamate dehydrogenase activity increased. In a 2 h photoperiod, the total protein content and most enzyme activities decreased strongly, starch synthesis was inhibited, and sugars and amino acids levels rose at the end of the night and growth was completely inhibited. The rate of starch degradation correlated with the protein content and the relative growth rate across all the photoperiod treatments. It is discussed how a close coordination of starch turnover, the protein content and growth allows Arabidopsis to avoid carbon starvation, even in very short photoperiods.
GreenwoodMS, WardMH, DayME, AdamsSL, BondBJ ( 2008). Age-related trends in red spruce foliar plasticity in relation to declining productivity Tree Physiology, 28, 225-232. DOI:10.1093/treephys/28.2.225URLPMID:18055433 [本文引用: 2] Phenotypic plasticity in needle morphology with increasing tree size and age was investigated by comparing four age classes of red spruce (Picea rubens Sarg.) ranging from juvenile (3-12 years old) to mature (over 100 years old). With increase in tree age there were significant increases in leaf mass per unit area (LMA), mesophyll and vascular bundle area as a percentage of total needle cross-sectional area, and stomatal density. Within the vascular bundle, both xylem cross-sectional area and tracheid lumen area increased significantly, whereas air space as a percentage of total cross-sectional area decreased. These morphological changes were associated with a significant decrease in photosynthetic capacity and stomatal conductance, and an increase in (13)C enrichment. Although both photosynthetic capacity and whole-tree conductance decreased significantly between age classes 3 and 12 years, they did not differ between age classes 53 and 127 years, even though needle (13)C enrichment was significantly greater in the 127-year age class. Thus there appear to be compensatory mechanisms that maintain photosynthetic capacity as trees increase in size and vascular complexity, which in red spruce and other species, may affect leaf hydraulic conductance. Although increased LMA may contribute to reduced photosynthetic capacity in red spruce, similar relationships are not seen in other conifers.
Gri?arJ, ZavadlavS, JyskeT, Lavri?M, LaaksoT, HafnerP, ElerK, VodnikD ( 2019). Effect of soil water availability on intra-annual xylem and phloem formation and non-structural carbohydrate pools in stem of Quercus pubescens. Tree Physiology, 39, 222-233. DOI:10.1093/treephys/tpy101URLPMID:30239939 [本文引用: 1] Non-structural carbohydrates (NSCs, i.e., starch and soluble sugars) are frequently quantified in the context of tree response to stressful events (e.g., drought), because they serve as a carbon reservoir for growth and respiration, as well as providing a critical osmotic function to maintain turgor and vascular transport under different environmental conditions. We investigated the impact of soil water availability on intra-annual leaf phenology, radial growth dynamics and variation in NSC amounts in the stem of pubescent oak (Quercus pubescens Willd.). from a sub-Mediterranean region. For this purpose, trees growing at two nearby plots differing in bedrock and, consequently, soil characteristics (F-eutric cambisol on eocene flysch bedrock and L-rendzic leptosol on paleogenic limestone bedrock) were sampled. Non-structural carbohydrates were analysed in outer xylem and living phloem (separately for non-collapsed and collapsed parts). Results showed that xylem and phloem increments were 41.6% and 21.2%, respectively, wider in trees from F plot due to a higher rate of cell production. In contrast, the amount of NSCs and of soluble sugars significantly differed among the tissue parts and sampling dates but not between the two plots. Starch amounts were the highest in xylem, which could be explained by the abundance of xylem parenchyma cells. Two clear seasonal peaks of the starch amount were detected in all tissues, the first in September-November, in the period of leaf colouring and falling, and the second in March-April, i.e., at the onset of cambial cell production followed by bud development. The amounts of free sugars were highest in inner phloem + cambium, at the sites of active growth. Soil water availability substantially influenced secondary growth in the stem of Q. pubescens, whereas NSC amounts seemed to be less affected. The results show how the intricate relationships between soil properties, such as water availability, and tree performance should be considered when studying the impact of stressful events on the growth and functioning of trees.
HagedornF, JosephJ, PeterM, LusterJ, PritschK, GeppertU, KernerR, MolinierV, EgliS, SchaubM, LiuJF, LiMH, SeverK, WeilerM, SiegwolfRTW, GesslerA, ArendM ( 2016). Recovery of trees from drought depends on belowground sink control Nature Plants, 2, 1-5. DOI:10.1038/nplants.2016.111URLPMID:27428669 [本文引用: 1] Climate projections predict higher precipitation variability with more frequent dry extremes(1). CO2 assimilation of forests decreases during drought, either by stomatal closure(2) or by direct environmental control of sink tissue activities(3). Ultimately, drought effects on forests depend on the ability of forests to recover, but the mechanisms controlling ecosystem resilience are uncertain(4). Here, we have investigated the effects of drought and drought release on the carbon balances in beech trees by combining CO2 flux measurements, metabolomics and (13)CO2 pulse labelling. During drought, net photosynthesis (AN), soil respiration (RS) and the allocation of recent assimilates below ground were reduced. Carbohydrates accumulated in metabolically resting roots but not in leaves, indicating sink control of the tree carbon balance. After drought release, RS recovered faster than AN and CO2 fluxes exceeded those in continuously watered trees for months. This stimulation was related to greater assimilate allocation to and metabolization in the rhizosphere. These findings show that trees prioritize the investment of assimilates below ground, probably to regain root functions after drought. We propose that root restoration plays a key role in ecosystem resilience to drought, in that the increased sink activity controls the recovery of carbon balances.
HandaIT, K?rnerC, H?ttenschwilerS ( 2005). A test of the treeline carbon limitation hypothesis by in situ CO2 enrichment and defoliation. Ecology, 86, 1288-1300. DOI:10.1890/04-0711URL [本文引用: 1]
HararukO, CampbellEM, AntosJA, ParishR ( 2019). Tree rings provide no evidence of a CO2 fertilization effect in old-growth subalpine forests of western Canada Global Change Biology, 25, 1222-1234. DOI:10.1111/gcb.2019.25.issue-4URL [本文引用: 1]
HartmannH, AdamsHD, HammondWM, HochG, Landh?usserSM, WileyE, ZaehleS ( 2018). Identifying differences in carbohydrate dynamics of seedlings and mature trees to improve carbon allocation in models for trees and forests Environmental and Experimental Botany, 152, 7-18. DOI:10.1016/j.envexpbot.2018.03.011URL [本文引用: 1]
HartmannH, McDowellNG, TrumboreS ( 2015). Allocation to carbon storage pools in Norway spruce saplings under drought and low CO2 Tree Physiology, 35, 243-252. DOI:10.1093/treephys/tpv019URLPMID:25769339 [本文引用: 1] Non-structural carbohydrates (NSCs) are critical to maintain plant metabolism under stressful environmental conditions, but we do not fully understand how NSC allocation and utilization from storage varies with stress. While it has become established that storage allocation is unlikely to be a mere overflow process, very little empirical evidence has been produced to support this view, at least not for trees. Here we present the results of an intensively monitored experimental manipulation of whole-tree carbon (C) balance (young Picea abies (L.) H Karst.) using reduced atmospheric [CO2] and drought to reduce C sources. We measured specific C storage pools (glucose, fructose, sucrose, starch) over 21 weeks and converted concentration measurement into fluxes into and out of the storage pool. Continuous labeling ((13)C) allowed us to track C allocation to biomass and non-structural C pools. Net C fluxes into the storage pool occurred mainly when the C balance was positive. Storage pools increased during periods of positive C gain and were reduced under negative C gain. (13)C data showed that C was allocated to storage pools independent of the net flux and even under severe C limitation. Allocation to below-ground tissues was strongest in control trees followed by trees experiencing drought followed by those grown under low [CO2]. Our data suggest that NSC storage has, under the conditions of our experimental manipulation (e.g., strong progressive drought, no above-ground growth), a high allocation priority and cannot be considered an overflow process. While these results also suggest active storage allocation, definitive proof of active plant control of storage in woody plants requires studies involving molecular tools.
HartmannH, TrumboreS ( 2016). Understanding the roles of nonstructural carbohydrates in forest trees—From what we can measure to what we want to know New Phytologist, 211, 386-403. DOI:10.1111/nph.13955URLPMID:27061438 [本文引用: 1] Contents 386 I. 386 II. 388 III. 392 IV. 392 V. 396 VI. 399 399 References 399 SUMMARY: Carbohydrates provide the building blocks for plant structures as well as versatile resources for metabolic processes. The nonstructural carbohydrates (NSC), mainly sugars and starch, fulfil distinct functional roles, including transport, energy metabolism and osmoregulation, and provide substrates for the synthesis of defence compounds or exchange with symbionts involved in nutrient acquisition or defence. At the whole-plant level, NSC storage buffers the asynchrony of supply and demand on diel, seasonal or decadal temporal scales and across plant organs. Despite its central role in plant function and in stand-level carbon cycling, our understanding of storage dynamics, its controls and response to environmental stresses is very limited, even after a century of research. This reflects the fact that often storage is defined by what we can measure, that is, NSC concentrations, and the interpretation of these as a proxy for a single function, storage, rather than the outcome of a range of NSC source and sink functions. New isotopic tools allow direct quantification of timescales involved in NSC dynamics, and show that NSC-C fixed years to decades previously is used to support tree functions. Here we review recent advances, with emphasis on the context of the interactions between NSC, drought and tree mortality.
HesseBD, GoisserM, HartmannH, GramsTEE ( 2019). Repeated summer drought delays sugar export from the leaf and impairs phloem transport in mature beech Tree Physiology, 39, 192-200. DOI:10.1093/treephys/tpy122URLPMID:30388272 [本文引用: 1] Phloem sustains maintenance and growth processes through transport of sugars from source to sink organs. Under low water availability, tree functioning is impaired, i.e., growth/photosynthesis decline and phloem transport may be hindered. In a 3-year throughfall exclusion (TE) experiment on mature European beech (Fagus sylvatica L.) we conducted 13CO2 branch labeling to investigate translocation of recently fixed photoassimilates under experimental drought over 2 years (2015 and 2016). We hypothesized (H1) that mean residence time of photoassimilates in leaves (MRT) increases, whereas (H2) phloem transport velocity (Vphloem) decreases under drought. Transport of carbohydrates in the phloem was assessed via δ13C of CO2 efflux measured at two branch positions following 13CO2 labeling. Pre-dawn water potential (ΨPD) and time-integrated soil water deficit (iSWD) were used to quantify drought stress. The MRT increased by 46% from 32.1 ± 5.4 h in control (CO) to 46.9 ± 12.3 h in TE trees, supporting H1, and positively correlated (P < 0.001) with iSWD. Confirming H2, Vphloem in 2016 decreased by 47% from 20.7 ± 5.8 cm h-1 in CO to 11.0 ± 2.9 cm h-1 in TE trees and positively correlated with ΨPD (P = 0.001). We suggest that the positive correlation between MRT and iSWD is a result of the accumulation of osmolytes maintaining cell turgor in the leaves under longer drought periods. Furthermore, we propose that the positive correlation between Vphloem and ΨPD is due to a lower water uptake of phloem conduits from surrounding tissues under increasing drought leading to a higher phloem sap viscosity and lower Vphloem. The two mechanisms increasing MRT and reducing Vphloem respond differently to low water availability and impair trees' carbon translocation under drought.
HillabrandRM, HackeUG, LieffersVJ ( 2019). Defoliation constrains xylem and phloem functionality Tree Physiology, 39, 1099-1108. DOI:10.1093/treephys/tpz029URLPMID:30901057 [本文引用: 2] Insect defoliation contributes to tree mortality under drought conditions. Defoliation-induced alterations to the vascular transport structure may increase tree vulnerability to drought; however, this has been rarely studied. To evaluate the response of tree vascular function following defoliation, 2-year-old balsam poplar were manually defoliated, and both physiological and anatomical measurements were made after allowing for re-foliation. Hydraulic conductivity measurements showed that defoliated trees had both increased vulnerability to embolism and decreased water transport efficiency, likely due to misshapen xylem vessels. Anatomical measurements revealed novel insights into defoliation-induced alterations to the phloem. Phloem sieve tube diameter was reduced in the stems of defoliated trees, suggesting reduced transport capability. In addition, phloem fibers were absent, or reduced in number, in stems, shoot tips and petioles of new leaves, potentially reducing the stability of the vascular tissue. Results from this study suggest that the defoliation leads to trees with increased risk for vascular dysfunction and drought-induced mortality through alterations in the vascular structure, and highlights a route through which carbon limitation can influence hydraulic dysfunction.
HochG, K?rnerC ( 2009). Growth and carbon relations of tree line forming conifers at constant vs. variable low temperatures Journal of Ecology, 97, 57-66. DOI:10.1111/jec.2009.97.issue-1URL [本文引用: 1]
HochG, PoppM, K?rnerC ( 2002). Altitudinal increase of mobile carbon pools in Pinus cembra suggests sink limitation of growth at the Swiss treeline. Oikos, 98, 361-374. DOI:10.1034/j.1600-0706.2002.980301.xURL [本文引用: 1]
HochG, RichterA, K?rnerC ( 2003). Non-structural carbon compounds in temperate forest trees Plant, Cell and Environment, 26, 1067-1081. DOI:10.1007/s00442-002-1154-7URLPMID:12647099 [本文引用: 1] The carbon charging of pines across the treeline ecotone of three different climatic zones (Mexico 19 degrees N Pinus hartwegii, Swiss Alps 46 degrees N P. cembra and northern Sweden 68 degrees N P. sylvestris) was analyzed, to test whether a low-temperature-driven carbon shortage can explain high-elevation tree limits, and whether the length of the growing season affects the trees' carbon balance. We quantified the concentrations of non-structural carbohydrates (NSC) and lipids (acylglycerols) in all tree organs at three dates during the growing seasons across elevational transects from the upper end of the closed, tall forest (timberline) to the uppermost location where groups of trees > or =3 m in height occur (treeline). Mean ground temperatures during the growing season at the treelines were similar (6.1+/-0.7 degrees C) irrespective of latitude. Across the individual transects, the concentrations of NSC and lipids increased with elevation in all organs. By the end of the growing season, all three species had very similar total mobile carbon (TMC) concentrations at the treeline (ca. 6% TMC in the aboveground dry biomass), suggesting no influence of the length of the growing season on tree carbon charging. At a temperate lowland reference site P. sylvestris reached only ca. 4% TMC in the aboveground dry biomass, with the 2% difference largely explained by higher lipid concentrations of treeline pines. We conclude that carbon availability is unlikely to be the cause of the altitudinal tree limit. It seems rather that low temperatures directly affect sink activity at the treeline, with surplus carbon stored in osmotically inactive compounds.
HsiaoTC, AcevedoE, FereresE, HendersonDW ( 1976). Water stress, growth, and osmotic adjustment Philosophical Transactions of the Royal Society B: Biological Sciences, 273, 479-500. [本文引用: 1]
HuangJB, HammerbacherA, WeinholdA, ReicheltM, GleixnerG, BehrendtT, DamNM, SalaAN, GershenzonJ, TrumboreS, HartmannH ( 2019). Eyes on the future—Evidence for trade-offs between growth, storage and defense in Norway spruce New Phytologist, 222, 144-158. DOI:10.1111/nph.15522URLPMID:30289558 [本文引用: 3] Carbon (C) allocation plays a central role in tree responses to environmental changes. Yet, fundamental questions remain about how trees allocate C to different sinks, for example, growth vs storage and defense. In order to elucidate allocation priorities, we manipulated the whole-tree C balance by modifying atmospheric CO2 concentrations [CO2 ] to create two distinct gradients of declining C availability, and compared how C was allocated among fluxes (respiration and volatile monoterpenes) and biomass C pools (total biomass, nonstructural carbohydrates (NSC) and secondary metabolites (SM)) in well-watered Norway spruce (Picea abies) saplings. Continuous isotope labelling was used to trace the fate of newly-assimilated C. Reducing [CO2 ] to 120?ppm caused an aboveground C compensation point (i.e. net C balance was zero) and resulted in decreases in growth and respiration. By contrast, soluble sugars and SM remained relatively constant in aboveground young organs and were partially maintained with a constant allocation of newly-assimilated C, even at expense of root death from C exhaustion. We conclude that spruce trees have a conservative allocation strategy under source limitation: growth and respiration can be downregulated to maintain 'operational' concentrations of NSC while investing newly-assimilated C into future survival by producing SM.
HuangJG, GuoXL, RossiS, ZhaiLH, YuBY, ZhangSK, ZhangMF ( 2018). Intra-annual wood formation of subtropical Chinese red pine shows better growth in dry season than wet season Tree Physiology, 38, 1225-1236. DOI:10.1093/treephys/tpy046URLPMID:29757427 [本文引用: 1] China's subtropical forests play a vital role in sequestering global carbon; therefore, it is critical to conduct a precise investigation of intra-annual wood formation in these ecosystems to clarify the mechanisms behind this. Two field experiments were established in Chinese subtropical forests to monitor weekly the intra-annual xylem formation of Pinus massoniana Lamb. from January to December 2015, using the recently developed micro-sampling approach. The effects of climate on wood formation were also assessed using linear or mixed models. Results indicate that there is an inactive period that might be semi-dormancy in subtropical pine ecosystems in January compared with the complete dormancy in temperate and boreal ecosystems and the fully active or short-term dormancy in tropical ecosystems. The duration of xylem formation of Chinese red pine in subtropical China in 2015 was 4-6 months longer than temperate and boreal forests. Moreover, trees were found to grow better during the dry season than the wet season, indicating that the Chinese red pine ecosystem is more strongly regulated by net energy than by environmental factors. Our findings indicate that China's subtropical pine forests may benefit from the expected longer dry seasons, possibly leading to better forest growth and improved carbon sequestration under continued climate warming.
IshiiHT, JenningsGM, SillettSC, KochGW ( 2008). Hydrostatic constraints on morphological exploitation of light in tall Sequoia sempervirens trees. Oecologia, 156, 751-763. DOI:10.1007/s00442-008-1032-zURLPMID:18392856 [本文引用: 1] We studied changes in morphological and physiological characteristics of leaves and shoots along a height gradient in Sequoia sempervirens, the tallest tree species on Earth, to investigate whether morphological and physiological acclimation to the vertical light gradient was constrained by hydrostatic limitation in the upper crown. Bulk leaf water potential (Psi) decreased linearly and light availability increased exponentially with increasing height in the crown. During the wet season, Psi was lower in the outer than inner crown. C isotope composition of leaves (delta(13)C) increased with increasing height indicating greater photosynthetic water use efficiency in the upper crown. Leaf and shoot morphology changed continuously with height. In contrast, their relationships with light availability were discontinuous: morphological characteristics did not correspond to increasing light availability above 55-85 m. Mass-based chlorophyll concentration (chl) decreased with increasing height and increasing light availability. In contrast, area-based chl remained constant or increased with increasing height. Mass-based maximum rate of net photosynthesis (P (max)) decreased with increasing height, whereas area-based P (max) reached maximum at 78.4 m and decreased with increasing height thereafter. Mass-based P (max) increased with increasing shoot mass per area (SMA), whereas area-based P (max) was not correlated with SMA in the upper crown. Our results suggest that hydrostatic limitation of morphological development constrains exploitation of light in the upper crown and contributes to reduced photosynthetic rates and, ultimately, reduced height growth at the tops of tall S. sempervirens trees.
JacquetJS, BoscA, O’GradyA, JactelH ( 2014). Combined effects of defoliation and water stress on pine growth and non-structural carbohydrates Tree Physiology, 34, 367-376. DOI:10.1093/treephys/tpu018URLPMID:24736390 [本文引用: 1] Climate change is expected to increase both pest insect damage and the occurrence of severe drought. There is therefore a need to better understand the combined effects of biotic and abiotic damage on tree growth in order to predict the multi-factorial effect of climate change on forest ecosystem productivity. Indeed, the effect of stress interactions on tree growth is an increasingly important topic that greatly lacks experiments and data, and it is unlikely that the impact of combined stresses can be extrapolated from the outcomes of studies that focused on a single stress. We developed an original manipulative study under real field conditions where we applied artificial defoliation and induced water stress on 10-year-old (～10 m high) maritime pine trees (Pinus pinaster Ait.). Tree response to combined stresses was quantitatively assessed following tree secondary growth and carbohydrate pools. Such a design allowed us to address the crucial question of combined stresses on trees under stand conditions, sharing soil supplies with neighboring trees. Our initial hypotheses were that (i) moderate defoliation can limit the impact of water stress on tree growth through reduced transpiration demand by a tree canopy partly defoliated and that (ii) defoliation results in reduced non-structural carbohydrate (NSC) pools, affecting tree tolerance to drought. Our results showed additive effects of defoliation and water stress on tree growth and contradict our initial hypothesis. Indeed, under stand conditions, we found that partial defoliation does not limit the impact of water stress through reduced transpiration. Our study also highlighted that, even if NSC in all organs were affected by defoliation, tree response to water stress was not triggered. We found that stem NSC were maintained or increased during the entire growing season, supporting literature-based hypotheses such as an active maintenance of the hydraulic system or another limiting resource for tree growth under defoliation. We also observed a significant decrease in root carbohydrates, which suggests a shift in the root carbon balance under defoliation. The decrease in carbohydrate supply under defoliation may not counterbalance the carbon use for mineral and water uptakes or a translocation to other tissues.
JensenKH, RioE, HansenR, ClanetC, BohrT ( 2009). Osmotically driven pipe flows and their relation to sugar transport in plants Journal of Fluid Mechanics, 636, 371-396. DOI:10.1017/S002211200900799XURL [本文引用: 1]
JohnsonDM, McCullohKA, WoodruffDR, MeinzerFC ( 2012). Hydraulic safety margins and embolism reversal in stems and leaves: Why are conifers and angiosperms so different? Plant Science, 195, 48-53. DOI:10.1016/j.plantsci.2012.06.010URL [本文引用: 1] Angiosperm and coniferous tree species utilize a continuum of hydraulic strategies. Hydraulic safety margins (defined as differences between naturally occurring xylem pressures and pressures that would cause hydraulic dysfunction, or differences between pressures resulting in loss of hydraulic function in adjacent organs (e.g., stems vs. leaves) tend to be much greater in conifers than angiosperms and serve to prevent stem embolism. However, conifers tend to experience embolism more frequently in leaves and roots than angiosperms. Embolism repair is thought to occur by active transport of sugars into empty conduits followed by passive water movement. The most likely source of sugar for refilling is from nonstructural carbohydrate depolymerization in nearby parenchyma cells. Compared to angiosperms, conifers tend to have little parenchyma or nonstructural carbohydrates in their wood. The ability to rapidly repair embolisms may rely on having nearby parenchyma cells, which could explain the need for greater safety margins in conifer wood as compared to angiosperms. The frequent embolisms that occur in the distal portions of conifers are readily repaired, perhaps due to the abundant parenchyma in leaves and roots, and these distal tissues may act as hydraulic circuit breakers that prevent tension-induced embolisms in the attached stems. Frequent embolisms in conifer leaves may also be due to weaker stomatal response to changes in ambient humidity. Although there is a continuum of hydraulic strategies among woody plants, there appear to be two distinct 'behaviors' at the extremes: (1) embolism prevention and (2) embolism occurrence and subsequent repair. (c) 2012 Elsevier Ireland Ltd.
KiorapostolouN, PetitG ( 2019). Similarities and differences in the balances between leaf, xylem and phloem structures in Fraxinus ornus along an environmental gradient. Tree Physiology, 39, 234-242. DOI:10.1093/treephys/tpy095URLPMID:30189046 The plant carbon balance depends on the coordination between photosynthesis and the long-distance transport of water and sugars. How plants modify the allocation to the different structures affecting this coordination under different environmental conditions has been poorly investigated. In this study, we evaluated the effect of soil water availability on the allocation to leaf, xylem and phloem structures in Fraxinus ornus L. We selected small individuals of F. ornus (height ~2 m) from sites contrasting in soil water availability (wet vs dry). We measured how the leaf (LM) and stem + branch biomass (SBM) are cumulated along the stem. Moreover, we assessed the axial variation in xylem (XA) and phloem tissue area (PA), and in lumen area of xylem vessels (CAxy) and phloem sieve elements (CAph). We found a higher ratio of LM:SBM in the trees growing under drier conditions. The long-distance transport tissues of xylem and phloem followed axial patterns with scaling exponents (b) independent of site conditions. PA scaled isometrically with XA (b ~ 1). While CAxy was only marginally higher at the wet sites, CAph was significantly higher at the drier sites. Our results showed that under reduced soil water availability, F. ornus trees allocate relatively more to the leaf biomass and produce more conductive phloem, which is likely to compensate for the drought-related hydraulic limitations to the leaf gas exchanges and the phloem sap viscosity.
KirschbaumMUF ( 2011). Does enhanced photosynthesis enhance growth? lessons learned from CO2 enrichment studies Plant Physiology, 155, 117-124. DOI:10.1104/pp.110.166819URLPMID:21088226 [本文引用: 1]
KleinT, BaderMKF, LeuzingerS, MildnerM, SchleppiP, SiegwolfRTW, K?rnerC ( 2016). Growth and carbon relations of mature Picea abies trees under 5 years of free-air CO2 enrichment. Journal of Ecology, 104, 1720-1733. DOI:10.1111/jec.2016.104.issue-6URL [本文引用: 1]
K?rnerC ( 2006). Plant CO2 responses: An issue of definition, time and resource supply New Phytologist, 172, 393-411. DOI:10.1111/j.1469-8137.2006.01886.xURLPMID:17083672 [本文引用: 1] In this review I am drawing attention to some constraints and biases in CO2 enrichment experiments and the analysis of data in the literature. Conclusions drawn from experimental works differ when the data are grouped in a way such that the relative frequency of test conditions does not determine the emerging trends, for instance unrealistically strong CO2-'fertilization' effects, which are in conflict with some basic ecological principles. I suggest separating three test conditions: uncoupled systems (plants not depending in a natural nutrient cycle) (I); expanding systems, in which plants are given ample space and time to explore otherwise limited resources (II); and fully coupled systems in which the natural nutrient cycling governs growth at steady-state leaf area index (LAI) and fine root renewal (III). Data for 10 type III experiments yield rather moderate effects of elevated CO2 on plant biomass production, if any. In steady-state grassland, the effects are water-related; in closed tree stands, initial effects decline rapidly with time. Plant-soil coupling (soil conditions) deserves far greater attention than plant-atmosphere coupling (CO2 enrichment technology).
K?rnerC ( 2012). Alpine Treelines: Functional Ecology of the Global High Elevation Tree Limits Springer, Berlin. [本文引用: 1]
K?rnerC ( 2015). Paradigm shift in plant growth control Current Opinion in Plant Biology, 25, 107-114. DOI:10.1016/j.pbi.2015.05.003URLPMID:26037389 [本文引用: 2] For plants to grow they need resources and appropriate conditions that these resources are converted into biomass. While acknowledging the importance of co-drivers, the classical view is still that carbon, that is, photosynthetic CO2 uptake, ranks above any other drivers of plant growth. Hence, theory and modelling of growth traditionally is carbon centric. Here, I suggest that this view is not reflecting reality, but emerged from the availability of methods and process understanding at leaf level. In most cases, poorly understood processes of tissue formation and cell growth are governing carbon demand, and thus, CO2 uptake. Carbon can only be converted into biomass to the extent chemical elements other than carbon, temperature or cell turgor permit.
Landh?usserSM, LieffersVJ ( 2012). Defoliation increases risk of carbon starvation in root systems of mature aspen Trees, 26, 653-661. DOI:10.1007/s00468-011-0633-zURL [本文引用: 1]
LiMH, JiangY, WangA, LiXB, ZhuWZ, YanCF, DuZ, ShiZ, LeiJP, Sch?nbeckL, HeP, YuFH, WangX ( 2018). Active summer carbon storage for winter persistence in trees at the cold alpine treeline Tree Physiology, 38, 1345-1355. DOI:10.1093/treephys/tpy020URLPMID:29538773 [本文引用: 2] The low-temperature limited alpine treeline is one of the most obvious boundaries in mountain landscapes. The question of whether resource limitation is the physiological mechanism for the formation of the alpine treeline is still waiting for conclusive evidence and answers. We therefore examined non-structural carbohydrates (NSC) and nitrogen (N) in treeline trees (TATs) and low-elevation trees (LETs) in both summer and winter in 11 alpine treeline cases ranging from subtropical monsoon to temperate continental climates across Eurasia. We found that tissue N concentration did not decrease with increasing elevation at the individual treeline level, but the mean root N concentration was lower in TATs than in LETs across treelines in summer. The TATs did not have lower tissue NSC concentrations than LETs in summer. However, the present study with multiple tree species across a large geographical scale, for the first time, revealed a common phenomenon that TATs had significantly lower NSC concentration in roots but not in the aboveground tissues than LETs in winter. Compared with LETs, TATs exhibited both a passive NSC storage in aboveground tissues in excess of carbon demand and an active starch storage in roots at the expense of growth reduction during the growing season. This starch accumulation disappeared in winter. Our results highlight some important aspects of the N and carbon physiology in relation to season in trees at their upper limits. Whether or to what extent the disadvantages of winter root NSC and summer root N level of TATs affect the growth of treeline trees and the alpine treeline formation needs to be further studied.
LiMH, XiaoWF, WangSG, ChengGW, CherubiniP, CaiXH, LiuXL, WangXD, ZhuWZ ( 2008). Mobile carbohydrates in Himalayan treeline trees I. Evidence for carbon gain limitation but not for growth limitation Tree Physiology, 28, 1287-1296. DOI:10.1093/treephys/28.8.1287URLPMID:18519260 [本文引用: 2] To test whether the altitudinal distribution of trees is determined by a carbon shortage or an insufficient sugar fraction (sugar:starch ratio) in treeline trees, we studied the status of nonstructural carbohydrates (NSC) and their components (total soluble sugars and starch) in Abies fabri (Mast.) Craib and Picea balfouriana var. hirtella Rehd. et Wils. trees along three elevational gradients, ranging from lower elevations to the alpine treeline, on the eastern edge of the Tibetan Plateau. For comparison, we investigated a low-altitude species (Tsuga yunnanensis (Franch.) Pritz.) which served as a warm-climate reference because it is distributed in closed montane forests below 3100 m a.s.l. in the study area. The carbon status of T. yunnanensis responded to altitude differently from that of the treeline species. At the species level, total NSC was not consistently more abundant in treeline trees than in trees of the same species growing at lower elevations. Thus there was no consistent evidence for carbon limitation of growth in treeline trees. For the three treeline species studied (P. balfouriana and A. fabri in the Kang-Ding Valley and A. fabri in the Mo-Xi Valley), winter NSC concentrations in treeline trees were significantly lower than in lower-elevation trees of the same species, suggesting that, in winter, carbon is limited in treeline trees. However, in no case was there total overwinter depletion of NSC or its components in treeline trees. Treeline and low-altitude species had similar sugar:starch ratios of about three at their upper-elevational limits in April. We conclude that survival and growth of trees at the elevational or latitudinal climate limit depend not only on NSC concentration in perennial tissues, but also on the maintenance of an overwintering sugar:starch ratio greater than three.
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Forest processes and global environmental change: Predicting the effects of individual and multiple stressors 1 2001
... 植物生长使森林生态系统产生巨大而持续的碳汇, 从而可减缓大气CO2浓度([CO2])升高速度(Dymond et al., 2016).森林每年固碳60 Pg, 占陆地总初级生产力的1/2 (Beer et al., 2010).树木生长, 尤其是木质组织的生长能够持续固碳长达数百年.不断加剧的全球变化(大气[CO2]升高、气候暖化、降雨格局改变等)通过影响树木生长、改变森林结构等(Aber et al., 2001), 进而影响森林的碳汇功能(Chapin et al., 2000), 但树木生长对全球变化的响应适应机制尚不明确.因此, 揭示限制树木生长的生理机制, 对评估和预测全球变化情景下森林碳汇功能具有重要意义. ...
Stoichiometry and nutrition of plant growth in natural communities 1 2008
... [CO2]加富实验(FACE)也在一定程度上支持了碳利用限制假说.例如, 在瑞士成熟落叶森林8年的FACE实验发现, 尽管将[CO2]升高到550 μmol·mol-1使叶片净光合速率提升了40% (Bader et al., 2010), 但树木的生物量生产并未持续增加(Bader et al., 2013).在美国田纳西Oak Ridge的10年生Liquidambar styraci?ua幼龄林的一个FACE实验(550 μmol·mol-1 CO2)显示, 最初6年的净初级生产力增加了24%, 但随后5年又下降到对照组水平(Norby et al., 2010).究其原因可能是[CO2]升高促进了植物和微生物生物量增加, 减少了环境中可利用氮, 从而导致渐进性氮限制(Luo et al., 2004).这一现象也符合生态化学计量学原理, 即碳、氮、磷等元素之间具有一定比例, 其中某一种元素的增加, 不一定会影响植物的生长(?gren, 2008).因此, 在养分添加情况下, [CO2]升高可促进欧洲云杉的生长(Sigurdsson et al., 2013).然而, Klein等(2016)报道, 在瑞士西北部的温带针阔混交林中, 虽然土壤不受氮限制, 但5年的[CO2]加富(550 μmol·mol-1 CO2), 110年生欧洲云杉树干径向生长、枝生长和针叶凋落物产量均无显著效应, 这表明还有其他因素限制该树木生长.McCarthy等(2010)发现杜克FACE实验中[CO2]加富10年使得火炬松(Pinus taeda)生物量持续增加是受土壤有效氮和水分共同驱动.然而, 树轮数据分析显示在过去100多年[CO2]升高对热带树木(van der Sleen et al., 2015)和北方亚高山树木(Hararuk et al., 2019)的径向生长均无促进作用.上述研究结果均支持碳利用限制机制; 而且这些****认为: 在当前大气[CO2]下, 树木生长不受碳供给限制, [CO2]升高不会促进或不会持续促进树木生长. ...
The response of photosynthesis and stomatal conductance to rising [CO2]: Mechanisms and environmental interactions 1 2007
Developmental decline in height growth in Douglas-?r 2 2007
... 树木生长碳供给与碳利用限制假说的另一焦点是, 随树高增加, 树木高生长停滞是因为水力限制减少碳同化, 对树木生长造成碳供给限制, 还是水力限制导致树木顶端水分供应不足, 而使树木生长受碳利用限制? Ryan和Yoder (1997)提出了水力限制假说, 即: 随树高增加, 水分传输路径增长、重力势增大, 水分运输阻力增大, 造成水力导度下降; 树木为减少蒸腾失水、维持叶片水势, 其叶片气孔会提前关闭, 进而导致光合速率降低、碳同化量减少、树木生长潜力降低.Ryan等(2006)进一步指出, 随树高增加, 尽管树木在形态、解剖结构、生理机制等方面的调整可在一定程度上缓解树高增加对水力导度的负效应, 但水力限制阻碍气体交换的现象依然十分普遍.Liu等(2018)也报道, 樟子松(Pinus sylvestris var. mongolica)的叶面积与边材面积之比随树高增加而减小, 可在一定程度上缓解大树的水分胁迫, 但同时也可导致碳失衡, 进而限制树木生长.然而, Sala和Hoch (2009)发现, 西黄松(Pinus ponderosa)边材和针叶NSC浓度以及枝条木质部储存的脂质均随树高增加而升高, 而且干旱立地下该趋势比湿润立地下更明显.这说明虽然树高增加可使气孔关闭, 但并未引发碳供给限制, 而是其他因素限制了细胞生长及其对碳的需求(Bond et al., 2007; Greenwood et al., 2008).Piper和Fajardo (2011)报道Nothofagus pumilio的NSC浓度不随树高和树龄增加而降低, 即使夏季干旱导致碳同化减少, 这种格局也没有改变.Bauerle等(1999)指出, 在没有蒸腾的情况下, 树高每增加1 m, 树木木质部水势梯度中的重力势也会增加0.01 MPa; 而蒸腾作用会进一步降低叶片水势.在渗透势不变的情况下, 叶片和顶芽细胞的膨压随着叶片水势的降低而成比例降低, 从而直接影响细胞形成、扩大和代谢等生长过程(Hsiao et al., 1976).当因水分不足而使膨压低于某一阈值时, 细胞扩张和生长将停滞(Steppe et al., 2015).由此推测, 高大树木的顶端细胞生长受限可能是由膨压降低引起的(Bond et al., 2007; Greenwood et al., 2008; Ishii et al., 2008; Meinzer et al., 2008), 即碳利用限制. ...
... ).由此推测, 高大树木的顶端细胞生长受限可能是由膨压降低引起的(Bond et al., 2007; Greenwood et al., 2008; Ishii et al., 2008; Meinzer et al., 2008), 即碳利用限制. ...
Temperate forest trees and stands under severe drought: A review of ecophysiological responses, adaptation processes and long-?term consequences 2 2006
... 在水分胁迫下, 树木为了减少蒸腾失水会关闭气孔, 从而减少气体交换, 降低光合速率(Chaves et al., 2009).当叶片新合成的光合产物无法满足树木对碳的需求时, 由于树木生长、呼吸(Poyatos et al., 2013)、修复、维持(包括水力完整性)、防御(Bréda et al., 2006)等生理活动不断消耗树木储存的碳而可能使其NSC浓度持续降低, 导致树木生长受碳供给限制.然而, 大量研究显示, 干旱条件下, 树木体内NSC浓度可维持不变甚至升高, 其可能原因之一是: 水分胁迫先降低细胞膨压, 后降低气体交换量(Muller et al., 2011; Tardieu et al., 2011), 即水分胁迫对树木碳利用活动的限制早于碳供给活动, 树木生长受碳利用限制, 树木碳利用活动对碳的消耗少于碳的供应, 进而导致NSC积累.例如: Gri?ar等(2019)报道, 土壤可利用水减少显著降低Quercus pubescens次级生长, 但对NSC浓度没有显著影响.Piper等(2017)比较不同水分立地上Pinus contorta和西黄松的生长和NSC浓度发现, 干旱立地上树木径向生长较慢, 但其木质组织NSC浓度较高. ...
... 干旱胁迫使树木NSC浓度不变或升高的第二个原因是: 适应干旱的树木具有“干旱记忆效应” (Galiano et al., 2017).为了避免下一个生长季冠层更严重的枯梢(Bréda et al., 2006)或产生碳饥饿(Galiano et al., 2011), 树木会主动将光合产物优先分配给NSC储存, 从而与生长产生对光合产物的竞争, 最终导致树木生长受碳供给限制.在这种情况下, 干旱虽然降低了树木生长速率, 但其NSC浓度升高(Galiano et al., 2017).例如: von Arx等(2017)在瑞士干旱地区对欧洲赤松(Pinus sylvestris)的10年灌溉试验发现, 灌溉组和对照组均呈现年轮越窄、NSC浓度越高的格局; 这表明树木适应了长期的干旱环境之后, 即使干旱停止, 树木依然会主动储备NSC, 从而减少用于生长的NSC, 使树木生长受碳供给限制.Duan等(2013)研究干旱对不同[CO2]中Eucalyptus globulus幼苗生长、NSC浓度和碳平衡的影响发现, 在中度干旱时, [CO2]升高可同时促进生长和NSC储存.而当干旱加剧时, 这种促进作用消失.这表明树木是否采取这种主动储备NSC的策略可能与干旱的持续时间和强度有关. ...
Carbon source-sink limitations differ between two species with contrasting growth strategies 1 2016
... 树木体内的碳既是其生物量主要组分, 也是其生命活动的能量源泉.植物通过调节碳供给-碳利用活动, 改变其生长速率和光合产物分配, 从而适应不断变化的环境条件(White et al., 2016).因此, 碳供给与碳利用活动是影响树木生长的重要生理机制(Burnett et al., 2016; White et al., 2016), 也是树木生理生态学和全球变化研究的热点和争议焦点之一. ...
Gas exchange and low temperature resistance in two tropical high mountain tree species from the Venezuelan Andes 1 2000
... 植物生长使森林生态系统产生巨大而持续的碳汇, 从而可减缓大气CO2浓度([CO2])升高速度(Dymond et al., 2016).森林每年固碳60 Pg, 占陆地总初级生产力的1/2 (Beer et al., 2010).树木生长, 尤其是木质组织的生长能够持续固碳长达数百年.不断加剧的全球变化(大气[CO2]升高、气候暖化、降雨格局改变等)通过影响树木生长、改变森林结构等(Aber et al., 2001), 进而影响森林的碳汇功能(Chapin et al., 2000), 但树木生长对全球变化的响应适应机制尚不明确.因此, 揭示限制树木生长的生理机制, 对评估和预测全球变化情景下森林碳汇功能具有重要意义. ...
Photosynthesis under drought and salt stress: Regulation mechanisms from whole plant to cell 1 2009
... 在水分胁迫下, 树木为了减少蒸腾失水会关闭气孔, 从而减少气体交换, 降低光合速率(Chaves et al., 2009).当叶片新合成的光合产物无法满足树木对碳的需求时, 由于树木生长、呼吸(Poyatos et al., 2013)、修复、维持(包括水力完整性)、防御(Bréda et al., 2006)等生理活动不断消耗树木储存的碳而可能使其NSC浓度持续降低, 导致树木生长受碳供给限制.然而, 大量研究显示, 干旱条件下, 树木体内NSC浓度可维持不变甚至升高, 其可能原因之一是: 水分胁迫先降低细胞膨压, 后降低气体交换量(Muller et al., 2011; Tardieu et al., 2011), 即水分胁迫对树木碳利用活动的限制早于碳供给活动, 树木生长受碳利用限制, 树木碳利用活动对碳的消耗少于碳的供应, 进而导致NSC积累.例如: Gri?ar等(2019)报道, 土壤可利用水减少显著降低Quercus pubescens次级生长, 但对NSC浓度没有显著影响.Piper等(2017)比较不同水分立地上Pinus contorta和西黄松的生长和NSC浓度发现, 干旱立地上树木径向生长较慢, 但其木质组织NSC浓度较高. ...
Effects of simulated chronic defoliation in summer on growth and survival of blue gum (Eucalyptus globulus Labill.) within young plantations in northern Victoria. 1 2002
... 另外, 树木应对叶损失而产生一种补偿机制, 即叶损失使树木碳供给活动降低, 而碳利用活动维持不变, 重新展叶过程增加对碳的需求会进一步降低树木的碳供给与碳利用比; 为了维持碳供给与碳利用的平衡, 叶片光合速率会加快(Pinkard et al., 2011; Barry & Pinkard, 2013).因而叶损失不一定降低树木生长, 也可能对树木生长影响不显著(Quentin et al., 2012), 甚至促进树木生长(Collett & Neumann, 2002).这与叶损失的程度与叶损失后的恢复时间有关.因而叶损失是否会导致树木生长下降, 在什么条件下、什么阶段、以哪种碳限制机制为主等问题尚需深入研究. ...
The impact of prolonged drought on phloem anatomy and phloem transport in young beech trees 2 2019
... 第三, 干旱降低韧皮部运输速度也会导致NSC积累(Sala et al., 2010).从周围细胞进入韧皮部筛管的水是韧皮部运输的主要驱动因子(Jensen et al., 2009).干旱减少韧皮部的可利用水, 使韧皮部汁液黏性增高(Epron et al., 2016), 运输速度下降.Hesse等(2019)采用13CO2方法发现, 经过3年的控雨处理, 由于从周围组织中吸收的水分减少, Fagus sylvatica韧皮部汁液黏性增高, 运输速度下降.如果干旱发生时间与韧皮部生长同步, 韧皮部解剖结构可能会受到影响(Salmon et al., 2019).Dannoura等(2019)的干旱对8年生Fagus sylvatica碳运输和韧皮部运输能力影响的研究结果也显示, 干旱处理的树木韧皮部筛管直径较小、活跃的韧皮部较窄, 从而使其韧皮部运输能力较低.然而, Kiorapostolou和Petit (2019)研究土壤水对Fraxinus ornus韧皮部的影响发现, 干旱使其产生了更大的管腔面积, 可能是为了抵消其韧皮部汁液黏性的增加, 其韧皮部对干旱表现出一定的适应能力.但该研究没有测定韧皮部的运输速度.总之, 干旱可能会降低韧皮部的运输速度(Dannoura et al., 2019), 阻碍NSC的运输, 使叶片积累的NSC反馈于光合作用(Nikinmaa et al., 2013)和树木生长(Sevanto, 2014), 在严重干旱时甚至可以导致韧皮部失调, 引发碳饥饿, 造成树木死亡(Sala et al., 2010; Hartmann et al., 2018). ...
... 韧皮部的影响发现, 干旱使其产生了更大的管腔面积, 可能是为了抵消其韧皮部汁液黏性的增加, 其韧皮部对干旱表现出一定的适应能力.但该研究没有测定韧皮部的运输速度.总之, 干旱可能会降低韧皮部的运输速度(Dannoura et al., 2019), 阻碍NSC的运输, 使叶片积累的NSC反馈于光合作用(Nikinmaa et al., 2013)和树木生长(Sevanto, 2014), 在严重干旱时甚至可以导致韧皮部失调, 引发碳饥饿, 造成树木死亡(Sala et al., 2010; Hartmann et al., 2018). ...
An alpine treeline in a carbon dioxide-rich world: Synthesis of a nine-year free-air carbon dioxide enrichment study 2 2013
... 低温是中高纬度和高海拔林线树木生长的主要限制因子(Rossi et al., 2007), 但低温限制林线树木生长的生理机制仍存在争议, 主要包括碳供给限制和碳利用限制两个假说(K?rner, 2003; Li et al., 2008; Fajardo & Piper, 2017).碳供给限制假说认为, 气温降低, 光合速率降低或光合季节缩短(Susiluoto et al., 2010), 造成光合产物供应不足(Stevens & Fox, 1991), 表现为树木NSC浓度降低(Li et al., 2008), 生长速率降低(Li & Yang, 2004).例如: Fajardo和Piper (2017)研究发现, 4个不同气候和土壤条件下, 随着海拔升高, 林线Nothofagus pumilio枝条NSC浓度降低, 树干生长降低, 表明其生长受碳供给限制.林线FACE实验也发现, [CO2]增加促进林线欧洲落叶松针叶、芽(Handa et al., 2005)和地上木质组织生长(Dawes et al., 2011, 2013), 进一步证明林线树木生长受碳供给限制. ...
Carbon dynamics of eucalypt seedlings exposed to progressive drought in elevated [CO2] and elevated temperature 1 2013
... 干旱胁迫使树木NSC浓度不变或升高的第二个原因是: 适应干旱的树木具有“干旱记忆效应” (Galiano et al., 2017).为了避免下一个生长季冠层更严重的枯梢(Bréda et al., 2006)或产生碳饥饿(Galiano et al., 2011), 树木会主动将光合产物优先分配给NSC储存, 从而与生长产生对光合产物的竞争, 最终导致树木生长受碳供给限制.在这种情况下, 干旱虽然降低了树木生长速率, 但其NSC浓度升高(Galiano et al., 2017).例如: von Arx等(2017)在瑞士干旱地区对欧洲赤松(Pinus sylvestris)的10年灌溉试验发现, 灌溉组和对照组均呈现年轮越窄、NSC浓度越高的格局; 这表明树木适应了长期的干旱环境之后, 即使干旱停止, 树木依然会主动储备NSC, 从而减少用于生长的NSC, 使树木生长受碳供给限制.Duan等(2013)研究干旱对不同[CO2]中Eucalyptus globulus幼苗生长、NSC浓度和碳平衡的影响发现, 在中度干旱时, [CO2]升高可同时促进生长和NSC储存.而当干旱加剧时, 这种促进作用消失.这表明树木是否采取这种主动储备NSC的策略可能与干旱的持续时间和强度有关. ...
Carbon sequestration in managed temperate coniferous forests under climate change 1 2016
... 植物生长使森林生态系统产生巨大而持续的碳汇, 从而可减缓大气CO2浓度([CO2])升高速度(Dymond et al., 2016).森林每年固碳60 Pg, 占陆地总初级生产力的1/2 (Beer et al., 2010).树木生长, 尤其是木质组织的生长能够持续固碳长达数百年.不断加剧的全球变化(大气[CO2]升高、气候暖化、降雨格局改变等)通过影响树木生长、改变森林结构等(Aber et al., 2001), 进而影响森林的碳汇功能(Chapin et al., 2000), 但树木生长对全球变化的响应适应机制尚不明确.因此, 揭示限制树木生长的生理机制, 对评估和预测全球变化情景下森林碳汇功能具有重要意义. ...
In situ13CO2 pulse labelling of field-grown eucalypt trees revealed the effects of potassium nutrition and throughfall exclusion on phloem transport of photosynthetic carbon 1 2016
... 第三, 干旱降低韧皮部运输速度也会导致NSC积累(Sala et al., 2010).从周围细胞进入韧皮部筛管的水是韧皮部运输的主要驱动因子(Jensen et al., 2009).干旱减少韧皮部的可利用水, 使韧皮部汁液黏性增高(Epron et al., 2016), 运输速度下降.Hesse等(2019)采用13CO2方法发现, 经过3年的控雨处理, 由于从周围组织中吸收的水分减少, Fagus sylvatica韧皮部汁液黏性增高, 运输速度下降.如果干旱发生时间与韧皮部生长同步, 韧皮部解剖结构可能会受到影响(Salmon et al., 2019).Dannoura等(2019)的干旱对8年生Fagus sylvatica碳运输和韧皮部运输能力影响的研究结果也显示, 干旱处理的树木韧皮部筛管直径较小、活跃的韧皮部较窄, 从而使其韧皮部运输能力较低.然而, Kiorapostolou和Petit (2019)研究土壤水对Fraxinus ornus韧皮部的影响发现, 干旱使其产生了更大的管腔面积, 可能是为了抵消其韧皮部汁液黏性的增加, 其韧皮部对干旱表现出一定的适应能力.但该研究没有测定韧皮部的运输速度.总之, 干旱可能会降低韧皮部的运输速度(Dannoura et al., 2019), 阻碍NSC的运输, 使叶片积累的NSC反馈于光合作用(Nikinmaa et al., 2013)和树木生长(Sevanto, 2014), 在严重干旱时甚至可以导致韧皮部失调, 引发碳饥饿, 造成树木死亡(Sala et al., 2010; Hartmann et al., 2018). ...
Adjustment of growth, starch turnover, protein content and central metabolism to a decrease of the carbon supply when Arabidopsis is grown in very short photoperiods 3 2009
... 另外, 树木生长、呼吸、繁殖、储存、防御等不同生命活动过程之间的碳分配格局变化, 通过反馈调节机制可使树木生长受碳供给限制.地下根呼吸对碳的消耗会影响树木地上组织的生长; 同样, 繁殖生长与营养生长对碳的竞争会互相制约(Ryan et al., 2018).例如: Rosati等(2018)对两种油橄榄(Olea europaea)栽培种(速生与慢生)进行摘花处理后发现, 处理之间总生物量差异不显著, 但繁殖组织生物量增加导致营养组织生物量成比例减少.在环境胁迫下, 为提高生存机率, 树木是否会主动降低生长速率增加碳储存, 也引发关注和讨论(Wiley & Helliker, 2012).已有研究证实拟南芥(Arabidopsis spp.)可采取这种保守的碳分配策略(Smith & Stitt, 2007; Gibon et al., 2009; MacNeill et al., 2017).例如: Gibon等(2009)将拟南芥置于不同光照时间下(12、8、4和3 h), 结果显示随光照时间缩短, 拟南芥逐渐抑制生长和淀粉降解, 促进淀粉合成.这表明当碳同化减少时, 植物可以调整碳在储存与生长之间的分配(Smith & Stitt, 2007; Gibon et al., 2009).遮阴、降低大气[CO2]等模拟碳限制的控制实验也显示, 树木亦可改变碳分配策略, 主动降低生长, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系, 以提升在胁迫环境中的生存机率(Huang et al., 2019).例如: Weber等(2019)将10种温带树种置于6%自然光照下3年, 发现遮阴显著降低了树木的生长, 但其NSC浓度表现为先降低后复原的格局.Huang等(2019)测定了生长于低[CO2]中欧洲云杉幼树的生长、气体交换特征、NSC和次生代谢产物浓度, 以及新同化碳的分配, 发现碳限制强烈导致幼树生长速率降低, 但因新同化碳持续供给而使可溶性糖和次生代谢产物的浓度得以稳定.这些研究结果均表明树木通过改变碳分配策略, 减少分配给生长的碳, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系(Huang et al. 2019); Wiley和Helliker (2012)认为这是一种不论是否面对环境胁迫都会频繁发生的保守生存策略.但以上研究均基于控制实验, 判定自然条件下植物是否会采取这种保守的碳分配策略十分困难, 但值得深入研究. ...
... ).例如: Gibon等(2009)将拟南芥置于不同光照时间下(12、8、4和3 h), 结果显示随光照时间缩短, 拟南芥逐渐抑制生长和淀粉降解, 促进淀粉合成.这表明当碳同化减少时, 植物可以调整碳在储存与生长之间的分配(Smith & Stitt, 2007; Gibon et al., 2009).遮阴、降低大气[CO2]等模拟碳限制的控制实验也显示, 树木亦可改变碳分配策略, 主动降低生长, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系, 以提升在胁迫环境中的生存机率(Huang et al., 2019).例如: Weber等(2019)将10种温带树种置于6%自然光照下3年, 发现遮阴显著降低了树木的生长, 但其NSC浓度表现为先降低后复原的格局.Huang等(2019)测定了生长于低[CO2]中欧洲云杉幼树的生长、气体交换特征、NSC和次生代谢产物浓度, 以及新同化碳的分配, 发现碳限制强烈导致幼树生长速率降低, 但因新同化碳持续供给而使可溶性糖和次生代谢产物的浓度得以稳定.这些研究结果均表明树木通过改变碳分配策略, 减少分配给生长的碳, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系(Huang et al. 2019); Wiley和Helliker (2012)认为这是一种不论是否面对环境胁迫都会频繁发生的保守生存策略.但以上研究均基于控制实验, 判定自然条件下植物是否会采取这种保守的碳分配策略十分困难, 但值得深入研究. ...
... ; Gibon et al., 2009).遮阴、降低大气[CO2]等模拟碳限制的控制实验也显示, 树木亦可改变碳分配策略, 主动降低生长, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系, 以提升在胁迫环境中的生存机率(Huang et al., 2019).例如: Weber等(2019)将10种温带树种置于6%自然光照下3年, 发现遮阴显著降低了树木的生长, 但其NSC浓度表现为先降低后复原的格局.Huang等(2019)测定了生长于低[CO2]中欧洲云杉幼树的生长、气体交换特征、NSC和次生代谢产物浓度, 以及新同化碳的分配, 发现碳限制强烈导致幼树生长速率降低, 但因新同化碳持续供给而使可溶性糖和次生代谢产物的浓度得以稳定.这些研究结果均表明树木通过改变碳分配策略, 减少分配给生长的碳, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系(Huang et al. 2019); Wiley和Helliker (2012)认为这是一种不论是否面对环境胁迫都会频繁发生的保守生存策略.但以上研究均基于控制实验, 判定自然条件下植物是否会采取这种保守的碳分配策略十分困难, 但值得深入研究. ...
Age-related trends in red spruce foliar plasticity in relation to declining productivity 2 2008
... 树木生长碳供给与碳利用限制假说的另一焦点是, 随树高增加, 树木高生长停滞是因为水力限制减少碳同化, 对树木生长造成碳供给限制, 还是水力限制导致树木顶端水分供应不足, 而使树木生长受碳利用限制? Ryan和Yoder (1997)提出了水力限制假说, 即: 随树高增加, 水分传输路径增长、重力势增大, 水分运输阻力增大, 造成水力导度下降; 树木为减少蒸腾失水、维持叶片水势, 其叶片气孔会提前关闭, 进而导致光合速率降低、碳同化量减少、树木生长潜力降低.Ryan等(2006)进一步指出, 随树高增加, 尽管树木在形态、解剖结构、生理机制等方面的调整可在一定程度上缓解树高增加对水力导度的负效应, 但水力限制阻碍气体交换的现象依然十分普遍.Liu等(2018)也报道, 樟子松(Pinus sylvestris var. mongolica)的叶面积与边材面积之比随树高增加而减小, 可在一定程度上缓解大树的水分胁迫, 但同时也可导致碳失衡, 进而限制树木生长.然而, Sala和Hoch (2009)发现, 西黄松(Pinus ponderosa)边材和针叶NSC浓度以及枝条木质部储存的脂质均随树高增加而升高, 而且干旱立地下该趋势比湿润立地下更明显.这说明虽然树高增加可使气孔关闭, 但并未引发碳供给限制, 而是其他因素限制了细胞生长及其对碳的需求(Bond et al., 2007; Greenwood et al., 2008).Piper和Fajardo (2011)报道Nothofagus pumilio的NSC浓度不随树高和树龄增加而降低, 即使夏季干旱导致碳同化减少, 这种格局也没有改变.Bauerle等(1999)指出, 在没有蒸腾的情况下, 树高每增加1 m, 树木木质部水势梯度中的重力势也会增加0.01 MPa; 而蒸腾作用会进一步降低叶片水势.在渗透势不变的情况下, 叶片和顶芽细胞的膨压随着叶片水势的降低而成比例降低, 从而直接影响细胞形成、扩大和代谢等生长过程(Hsiao et al., 1976).当因水分不足而使膨压低于某一阈值时, 细胞扩张和生长将停滞(Steppe et al., 2015).由此推测, 高大树木的顶端细胞生长受限可能是由膨压降低引起的(Bond et al., 2007; Greenwood et al., 2008; Ishii et al., 2008; Meinzer et al., 2008), 即碳利用限制. ...
... ; Greenwood et al., 2008; Ishii et al., 2008; Meinzer et al., 2008), 即碳利用限制. ...
Effect of soil water availability on intra-annual xylem and phloem formation and non-structural carbohydrate pools in stem of Quercus pubescens. 1 2019
... 在水分胁迫下, 树木为了减少蒸腾失水会关闭气孔, 从而减少气体交换, 降低光合速率(Chaves et al., 2009).当叶片新合成的光合产物无法满足树木对碳的需求时, 由于树木生长、呼吸(Poyatos et al., 2013)、修复、维持(包括水力完整性)、防御(Bréda et al., 2006)等生理活动不断消耗树木储存的碳而可能使其NSC浓度持续降低, 导致树木生长受碳供给限制.然而, 大量研究显示, 干旱条件下, 树木体内NSC浓度可维持不变甚至升高, 其可能原因之一是: 水分胁迫先降低细胞膨压, 后降低气体交换量(Muller et al., 2011; Tardieu et al., 2011), 即水分胁迫对树木碳利用活动的限制早于碳供给活动, 树木生长受碳利用限制, 树木碳利用活动对碳的消耗少于碳的供应, 进而导致NSC积累.例如: Gri?ar等(2019)报道, 土壤可利用水减少显著降低Quercus pubescens次级生长, 但对NSC浓度没有显著影响.Piper等(2017)比较不同水分立地上Pinus contorta和西黄松的生长和NSC浓度发现, 干旱立地上树木径向生长较慢, 但其木质组织NSC浓度较高. ...
Recovery of trees from drought depends on belowground sink control 1 2016
Hydraulics play an important role in causing low growth rate and dieback of aging Pinus sylvestris var. mongolica trees in plantations of Northeast China. 1 2018
... 树木生长碳供给与碳利用限制假说的另一焦点是, 随树高增加, 树木高生长停滞是因为水力限制减少碳同化, 对树木生长造成碳供给限制, 还是水力限制导致树木顶端水分供应不足, 而使树木生长受碳利用限制? Ryan和Yoder (1997)提出了水力限制假说, 即: 随树高增加, 水分传输路径增长、重力势增大, 水分运输阻力增大, 造成水力导度下降; 树木为减少蒸腾失水、维持叶片水势, 其叶片气孔会提前关闭, 进而导致光合速率降低、碳同化量减少、树木生长潜力降低.Ryan等(2006)进一步指出, 随树高增加, 尽管树木在形态、解剖结构、生理机制等方面的调整可在一定程度上缓解树高增加对水力导度的负效应, 但水力限制阻碍气体交换的现象依然十分普遍.Liu等(2018)也报道, 樟子松(Pinus sylvestris var. mongolica)的叶面积与边材面积之比随树高增加而减小, 可在一定程度上缓解大树的水分胁迫, 但同时也可导致碳失衡, 进而限制树木生长.然而, Sala和Hoch (2009)发现, 西黄松(Pinus ponderosa)边材和针叶NSC浓度以及枝条木质部储存的脂质均随树高增加而升高, 而且干旱立地下该趋势比湿润立地下更明显.这说明虽然树高增加可使气孔关闭, 但并未引发碳供给限制, 而是其他因素限制了细胞生长及其对碳的需求(Bond et al., 2007; Greenwood et al., 2008).Piper和Fajardo (2011)报道Nothofagus pumilio的NSC浓度不随树高和树龄增加而降低, 即使夏季干旱导致碳同化减少, 这种格局也没有改变.Bauerle等(1999)指出, 在没有蒸腾的情况下, 树高每增加1 m, 树木木质部水势梯度中的重力势也会增加0.01 MPa; 而蒸腾作用会进一步降低叶片水势.在渗透势不变的情况下, 叶片和顶芽细胞的膨压随着叶片水势的降低而成比例降低, 从而直接影响细胞形成、扩大和代谢等生长过程(Hsiao et al., 1976).当因水分不足而使膨压低于某一阈值时, 细胞扩张和生长将停滞(Steppe et al., 2015).由此推测, 高大树木的顶端细胞生长受限可能是由膨压降低引起的(Bond et al., 2007; Greenwood et al., 2008; Ishii et al., 2008; Meinzer et al., 2008), 即碳利用限制. ...
Progressive nitrogen limitation of ecosystem responses to rising atmospheric carbon dioxide 1 2004
... [CO2]加富实验(FACE)也在一定程度上支持了碳利用限制假说.例如, 在瑞士成熟落叶森林8年的FACE实验发现, 尽管将[CO2]升高到550 μmol·mol-1使叶片净光合速率提升了40% (Bader et al., 2010), 但树木的生物量生产并未持续增加(Bader et al., 2013).在美国田纳西Oak Ridge的10年生Liquidambar styraci?ua幼龄林的一个FACE实验(550 μmol·mol-1 CO2)显示, 最初6年的净初级生产力增加了24%, 但随后5年又下降到对照组水平(Norby et al., 2010).究其原因可能是[CO2]升高促进了植物和微生物生物量增加, 减少了环境中可利用氮, 从而导致渐进性氮限制(Luo et al., 2004).这一现象也符合生态化学计量学原理, 即碳、氮、磷等元素之间具有一定比例, 其中某一种元素的增加, 不一定会影响植物的生长(?gren, 2008).因此, 在养分添加情况下, [CO2]升高可促进欧洲云杉的生长(Sigurdsson et al., 2013).然而, Klein等(2016)报道, 在瑞士西北部的温带针阔混交林中, 虽然土壤不受氮限制, 但5年的[CO2]加富(550 μmol·mol-1 CO2), 110年生欧洲云杉树干径向生长、枝生长和针叶凋落物产量均无显著效应, 这表明还有其他因素限制该树木生长.McCarthy等(2010)发现杜克FACE实验中[CO2]加富10年使得火炬松(Pinus taeda)生物量持续增加是受土壤有效氮和水分共同驱动.然而, 树轮数据分析显示在过去100多年[CO2]升高对热带树木(van der Sleen et al., 2015)和北方亚高山树木(Hararuk et al., 2019)的径向生长均无促进作用.上述研究结果均支持碳利用限制机制; 而且这些****认为: 在当前大气[CO2]下, 树木生长不受碳供给限制, [CO2]升高不会促进或不会持续促进树木生长. ...
Starch as a source, starch as a sink: The bifunctional role of starch in carbon allocation 2 2017
... 另外, 树木生长、呼吸、繁殖、储存、防御等不同生命活动过程之间的碳分配格局变化, 通过反馈调节机制可使树木生长受碳供给限制.地下根呼吸对碳的消耗会影响树木地上组织的生长; 同样, 繁殖生长与营养生长对碳的竞争会互相制约(Ryan et al., 2018).例如: Rosati等(2018)对两种油橄榄(Olea europaea)栽培种(速生与慢生)进行摘花处理后发现, 处理之间总生物量差异不显著, 但繁殖组织生物量增加导致营养组织生物量成比例减少.在环境胁迫下, 为提高生存机率, 树木是否会主动降低生长速率增加碳储存, 也引发关注和讨论(Wiley & Helliker, 2012).已有研究证实拟南芥(Arabidopsis spp.)可采取这种保守的碳分配策略(Smith & Stitt, 2007; Gibon et al., 2009; MacNeill et al., 2017).例如: Gibon等(2009)将拟南芥置于不同光照时间下(12、8、4和3 h), 结果显示随光照时间缩短, 拟南芥逐渐抑制生长和淀粉降解, 促进淀粉合成.这表明当碳同化减少时, 植物可以调整碳在储存与生长之间的分配(Smith & Stitt, 2007; Gibon et al., 2009).遮阴、降低大气[CO2]等模拟碳限制的控制实验也显示, 树木亦可改变碳分配策略, 主动降低生长, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系, 以提升在胁迫环境中的生存机率(Huang et al., 2019).例如: Weber等(2019)将10种温带树种置于6%自然光照下3年, 发现遮阴显著降低了树木的生长, 但其NSC浓度表现为先降低后复原的格局.Huang等(2019)测定了生长于低[CO2]中欧洲云杉幼树的生长、气体交换特征、NSC和次生代谢产物浓度, 以及新同化碳的分配, 发现碳限制强烈导致幼树生长速率降低, 但因新同化碳持续供给而使可溶性糖和次生代谢产物的浓度得以稳定.这些研究结果均表明树木通过改变碳分配策略, 减少分配给生长的碳, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系(Huang et al. 2019); Wiley和Helliker (2012)认为这是一种不论是否面对环境胁迫都会频繁发生的保守生存策略.但以上研究均基于控制实验, 判定自然条件下植物是否会采取这种保守的碳分配策略十分困难, 但值得深入研究. ...
Adaptive variation in the vulnerability of woody plants to xylem cavitation 1 2004
... 面对低温, 不同树种可能有不同的限制机制.例如: 在智利南部林线(海拔1 300 m)和林线以上(海拔1 350 m), Fajardo和Piper (2014)将Nothofagus pumilio和Pinus contorta幼苗置于离地面2-3 m高处, Nothofagus pumilio生物量和NSC浓度均显著降低(碳供给限制), 但Pinus contorta生物量和NSC浓度均无显著变化.这项研究支持, 不同树种对低温的响应有差异, 该差异可能源于生长以外的其他碳利用活动对碳的利用.通常, 被子植物的抗栓塞能力比裸子植物弱(Field & Brodribb, 2001; Maherali et al., 2004), 其木质部修复会消耗更多的碳(Johnson et al., 2012); 常绿树种枝生长为有限型, 仅在春季进行一次生长(Palacio et al., 2018), 而落叶树种枝生长为无限型, 如果环境条件允许, 其枝条可以在生长季后期不定期生长(Deppong & Cline, 2000), 因而落叶树种需要消耗更多的碳(Dawes et al., 2011). ...
Dynamics of non-structural carbohydrates in terrestrial plants: A global synthesis 1 2016
... 除了光合作用之外, 树木体内NSC的积累与转化也会导致树木生长受碳供给限制.可溶性糖参与植物渗透调节、运输和信号传达, 树木优先将光合产物分配于可溶性糖, 使其浓度维持在一定阈值之上(Sala et al., 2010; Hartmann & Trumbore, 2016; Martínez-Vilalta et al., 2016).正在生长和分化的细胞中糖的多少直接限制木材形成(Michelot et al., 2012; Simard et al., 2013).例如: 欧洲云杉(Picea abies)和欧洲落叶松(Larix decidua)树干形成层可溶性糖浓度变化与木材形成过程存在耦合关系, 即次生壁形成过程和木质化阶段的细胞最多时, 其可溶性糖浓度最高(Simard et al., 2013). ...
Re-assessment of plant carbon dynamics at the Duke free-air CO2 enrichment site: Interactions of atmospheric [CO2] with nitrogen and water availability over stand development 1 2010
... [CO2]加富实验(FACE)也在一定程度上支持了碳利用限制假说.例如, 在瑞士成熟落叶森林8年的FACE实验发现, 尽管将[CO2]升高到550 μmol·mol-1使叶片净光合速率提升了40% (Bader et al., 2010), 但树木的生物量生产并未持续增加(Bader et al., 2013).在美国田纳西Oak Ridge的10年生Liquidambar styraci?ua幼龄林的一个FACE实验(550 μmol·mol-1 CO2)显示, 最初6年的净初级生产力增加了24%, 但随后5年又下降到对照组水平(Norby et al., 2010).究其原因可能是[CO2]升高促进了植物和微生物生物量增加, 减少了环境中可利用氮, 从而导致渐进性氮限制(Luo et al., 2004).这一现象也符合生态化学计量学原理, 即碳、氮、磷等元素之间具有一定比例, 其中某一种元素的增加, 不一定会影响植物的生长(?gren, 2008).因此, 在养分添加情况下, [CO2]升高可促进欧洲云杉的生长(Sigurdsson et al., 2013).然而, Klein等(2016)报道, 在瑞士西北部的温带针阔混交林中, 虽然土壤不受氮限制, 但5年的[CO2]加富(550 μmol·mol-1 CO2), 110年生欧洲云杉树干径向生长、枝生长和针叶凋落物产量均无显著效应, 这表明还有其他因素限制该树木生长.McCarthy等(2010)发现杜克FACE实验中[CO2]加富10年使得火炬松(Pinus taeda)生物量持续增加是受土壤有效氮和水分共同驱动.然而, 树轮数据分析显示在过去100多年[CO2]升高对热带树木(van der Sleen et al., 2015)和北方亚高山树木(Hararuk et al., 2019)的径向生长均无促进作用.上述研究结果均支持碳利用限制机制; 而且这些****认为: 在当前大气[CO2]下, 树木生长不受碳供给限制, [CO2]升高不会促进或不会持续促进树木生长. ...
Biophysical constraints on leaf expansion in a tall conifer 1 2008
... 树木生长碳供给与碳利用限制假说的另一焦点是, 随树高增加, 树木高生长停滞是因为水力限制减少碳同化, 对树木生长造成碳供给限制, 还是水力限制导致树木顶端水分供应不足, 而使树木生长受碳利用限制? Ryan和Yoder (1997)提出了水力限制假说, 即: 随树高增加, 水分传输路径增长、重力势增大, 水分运输阻力增大, 造成水力导度下降; 树木为减少蒸腾失水、维持叶片水势, 其叶片气孔会提前关闭, 进而导致光合速率降低、碳同化量减少、树木生长潜力降低.Ryan等(2006)进一步指出, 随树高增加, 尽管树木在形态、解剖结构、生理机制等方面的调整可在一定程度上缓解树高增加对水力导度的负效应, 但水力限制阻碍气体交换的现象依然十分普遍.Liu等(2018)也报道, 樟子松(Pinus sylvestris var. mongolica)的叶面积与边材面积之比随树高增加而减小, 可在一定程度上缓解大树的水分胁迫, 但同时也可导致碳失衡, 进而限制树木生长.然而, Sala和Hoch (2009)发现, 西黄松(Pinus ponderosa)边材和针叶NSC浓度以及枝条木质部储存的脂质均随树高增加而升高, 而且干旱立地下该趋势比湿润立地下更明显.这说明虽然树高增加可使气孔关闭, 但并未引发碳供给限制, 而是其他因素限制了细胞生长及其对碳的需求(Bond et al., 2007; Greenwood et al., 2008).Piper和Fajardo (2011)报道Nothofagus pumilio的NSC浓度不随树高和树龄增加而降低, 即使夏季干旱导致碳同化减少, 这种格局也没有改变.Bauerle等(1999)指出, 在没有蒸腾的情况下, 树高每增加1 m, 树木木质部水势梯度中的重力势也会增加0.01 MPa; 而蒸腾作用会进一步降低叶片水势.在渗透势不变的情况下, 叶片和顶芽细胞的膨压随着叶片水势的降低而成比例降低, 从而直接影响细胞形成、扩大和代谢等生长过程(Hsiao et al., 1976).当因水分不足而使膨压低于某一阈值时, 细胞扩张和生长将停滞(Steppe et al., 2015).由此推测, 高大树木的顶端细胞生长受限可能是由膨压降低引起的(Bond et al., 2007; Greenwood et al., 2008; Ishii et al., 2008; Meinzer et al., 2008), 即碳利用限制. ...
Comparing the intra-annual wood formation of three European species (Fagus sylvatica, Quercus petraea and Pinus sylvestris) as related to leaf phenology and non-structural carbohydrate dynamics. 1 2012
... 除了光合作用之外, 树木体内NSC的积累与转化也会导致树木生长受碳供给限制.可溶性糖参与植物渗透调节、运输和信号传达, 树木优先将光合产物分配于可溶性糖, 使其浓度维持在一定阈值之上(Sala et al., 2010; Hartmann & Trumbore, 2016; Martínez-Vilalta et al., 2016).正在生长和分化的细胞中糖的多少直接限制木材形成(Michelot et al., 2012; Simard et al., 2013).例如: 欧洲云杉(Picea abies)和欧洲落叶松(Larix decidua)树干形成层可溶性糖浓度变化与木材形成过程存在耦合关系, 即次生壁形成过程和木质化阶段的细胞最多时, 其可溶性糖浓度最高(Simard et al., 2013). ...
Environmental change and carbon limitation in trees: A biochemical, ecophysiological and ecosystem appraisal 1 2007
... 综上所述, 大多数实验证据支持树木碳利用活动对环境变化的响应比碳供给活动更敏感, 在多数情况下树木生长受碳利用限制(Millard et al., 2007; K?rner, 2015; Fatichi et al., 2019).例如: 为适应低温环境, 林线树木叶片能提升其光合能力(Wang et al., 2017), 而组织生长等碳利用活动则不能(Alvarez-Uria & K?rner, 2007; Rossi et al., 2008).尽管目前关于树木碳储存形成是被动或主动的问题仍没有明确答案(Sala et al., 2012).但如果树木能够主动增加碳储存, 减少用于生长的碳, 则这个过程仍可以导致树木生长受碳供给限制.因此, 碳供给与碳利用活动影响树木生长的机制仍需深入探索. ...
Interactive effects of water supply and defoliation on photosynthesis, plant water status and growth of Eucalyptus globulus Labill. 1 2012
... 另外, 树木应对叶损失而产生一种补偿机制, 即叶损失使树木碳供给活动降低, 而碳利用活动维持不变, 重新展叶过程增加对碳的需求会进一步降低树木的碳供给与碳利用比; 为了维持碳供给与碳利用的平衡, 叶片光合速率会加快(Pinkard et al., 2011; Barry & Pinkard, 2013).因而叶损失不一定降低树木生长, 也可能对树木生长影响不显著(Quentin et al., 2012), 甚至促进树木生长(Collett & Neumann, 2002).这与叶损失的程度与叶损失后的恢复时间有关.因而叶损失是否会导致树木生长下降, 在什么条件下、什么阶段、以哪种碳限制机制为主等问题尚需深入研究. ...
Resource investments in reproductive growth proportionately limit investments in whole-tree vegetative growth in young olive trees with varying crop loads 1 2018
... 另外, 树木生长、呼吸、繁殖、储存、防御等不同生命活动过程之间的碳分配格局变化, 通过反馈调节机制可使树木生长受碳供给限制.地下根呼吸对碳的消耗会影响树木地上组织的生长; 同样, 繁殖生长与营养生长对碳的竞争会互相制约(Ryan et al., 2018).例如: Rosati等(2018)对两种油橄榄(Olea europaea)栽培种(速生与慢生)进行摘花处理后发现, 处理之间总生物量差异不显著, 但繁殖组织生物量增加导致营养组织生物量成比例减少.在环境胁迫下, 为提高生存机率, 树木是否会主动降低生长速率增加碳储存, 也引发关注和讨论(Wiley & Helliker, 2012).已有研究证实拟南芥(Arabidopsis spp.)可采取这种保守的碳分配策略(Smith & Stitt, 2007; Gibon et al., 2009; MacNeill et al., 2017).例如: Gibon等(2009)将拟南芥置于不同光照时间下(12、8、4和3 h), 结果显示随光照时间缩短, 拟南芥逐渐抑制生长和淀粉降解, 促进淀粉合成.这表明当碳同化减少时, 植物可以调整碳在储存与生长之间的分配(Smith & Stitt, 2007; Gibon et al., 2009).遮阴、降低大气[CO2]等模拟碳限制的控制实验也显示, 树木亦可改变碳分配策略, 主动降低生长, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系, 以提升在胁迫环境中的生存机率(Huang et al., 2019).例如: Weber等(2019)将10种温带树种置于6%自然光照下3年, 发现遮阴显著降低了树木的生长, 但其NSC浓度表现为先降低后复原的格局.Huang等(2019)测定了生长于低[CO2]中欧洲云杉幼树的生长、气体交换特征、NSC和次生代谢产物浓度, 以及新同化碳的分配, 发现碳限制强烈导致幼树生长速率降低, 但因新同化碳持续供给而使可溶性糖和次生代谢产物的浓度得以稳定.这些研究结果均表明树木通过改变碳分配策略, 减少分配给生长的碳, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系(Huang et al. 2019); Wiley和Helliker (2012)认为这是一种不论是否面对环境胁迫都会频繁发生的保守生存策略.但以上研究均基于控制实验, 判定自然条件下植物是否会采取这种保守的碳分配策略十分困难, 但值得深入研究. ...
Evidence of threshold temperatures for xylogenesis in conifers at high altitudes 1 2007
... 低温是中高纬度和高海拔林线树木生长的主要限制因子(Rossi et al., 2007), 但低温限制林线树木生长的生理机制仍存在争议, 主要包括碳供给限制和碳利用限制两个假说(K?rner, 2003; Li et al., 2008; Fajardo & Piper, 2017).碳供给限制假说认为, 气温降低, 光合速率降低或光合季节缩短(Susiluoto et al., 2010), 造成光合产物供应不足(Stevens & Fox, 1991), 表现为树木NSC浓度降低(Li et al., 2008), 生长速率降低(Li & Yang, 2004).例如: Fajardo和Piper (2017)研究发现, 4个不同气候和土壤条件下, 随着海拔升高, 林线Nothofagus pumilio枝条NSC浓度降低, 树干生长降低, 表明其生长受碳供给限制.林线FACE实验也发现, [CO2]增加促进林线欧洲落叶松针叶、芽(Handa et al., 2005)和地上木质组织生长(Dawes et al., 2011, 2013), 进一步证明林线树木生长受碳供给限制. ...
Critical temperatures for xylogenesis in conifers of cold climates 2 2008
... 综上所述, 大多数实验证据支持树木碳利用活动对环境变化的响应比碳供给活动更敏感, 在多数情况下树木生长受碳利用限制(Millard et al., 2007; K?rner, 2015; Fatichi et al., 2019).例如: 为适应低温环境, 林线树木叶片能提升其光合能力(Wang et al., 2017), 而组织生长等碳利用活动则不能(Alvarez-Uria & K?rner, 2007; Rossi et al., 2008).尽管目前关于树木碳储存形成是被动或主动的问题仍没有明确答案(Sala et al., 2012).但如果树木能够主动增加碳储存, 减少用于生长的碳, 则这个过程仍可以导致树木生长受碳供给限制.因此, 碳供给与碳利用活动影响树木生长的机制仍需深入探索. ...
... 低温是中高纬度和高海拔林线树木生长的主要限制因子(Rossi et al., 2007), 但低温限制林线树木生长的生理机制仍存在争议, 主要包括碳供给限制和碳利用限制两个假说(K?rner, 2003; Li et al., 2008; Fajardo & Piper, 2017).碳供给限制假说认为, 气温降低, 光合速率降低或光合季节缩短(Susiluoto et al., 2010), 造成光合产物供应不足(Stevens & Fox, 1991), 表现为树木NSC浓度降低(Li et al., 2008), 生长速率降低(Li & Yang, 2004).例如: Fajardo和Piper (2017)研究发现, 4个不同气候和土壤条件下, 随着海拔升高, 林线Nothofagus pumilio枝条NSC浓度降低, 树干生长降低, 表明其生长受碳供给限制.林线FACE实验也发现, [CO2]增加促进林线欧洲落叶松针叶、芽(Handa et al., 2005)和地上木质组织生长(Dawes et al., 2011, 2013), 进一步证明林线树木生长受碳供给限制. ...
Quantitative changes in twig growth pattern of young woodland beech (Fagus sylvatica L.) in relation to climate and ozone pollution over 10 years. 1 2002
High carbon storage in carbon-limited trees 1 2019
... 另外, 树木生长、呼吸、繁殖、储存、防御等不同生命活动过程之间的碳分配格局变化, 通过反馈调节机制可使树木生长受碳供给限制.地下根呼吸对碳的消耗会影响树木地上组织的生长; 同样, 繁殖生长与营养生长对碳的竞争会互相制约(Ryan et al., 2018).例如: Rosati等(2018)对两种油橄榄(Olea europaea)栽培种(速生与慢生)进行摘花处理后发现, 处理之间总生物量差异不显著, 但繁殖组织生物量增加导致营养组织生物量成比例减少.在环境胁迫下, 为提高生存机率, 树木是否会主动降低生长速率增加碳储存, 也引发关注和讨论(Wiley & Helliker, 2012).已有研究证实拟南芥(Arabidopsis spp.)可采取这种保守的碳分配策略(Smith & Stitt, 2007; Gibon et al., 2009; MacNeill et al., 2017).例如: Gibon等(2009)将拟南芥置于不同光照时间下(12、8、4和3 h), 结果显示随光照时间缩短, 拟南芥逐渐抑制生长和淀粉降解, 促进淀粉合成.这表明当碳同化减少时, 植物可以调整碳在储存与生长之间的分配(Smith & Stitt, 2007; Gibon et al., 2009).遮阴、降低大气[CO2]等模拟碳限制的控制实验也显示, 树木亦可改变碳分配策略, 主动降低生长, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系, 以提升在胁迫环境中的生存机率(Huang et al., 2019).例如: Weber等(2019)将10种温带树种置于6%自然光照下3年, 发现遮阴显著降低了树木的生长, 但其NSC浓度表现为先降低后复原的格局.Huang等(2019)测定了生长于低[CO2]中欧洲云杉幼树的生长、气体交换特征、NSC和次生代谢产物浓度, 以及新同化碳的分配, 发现碳限制强烈导致幼树生长速率降低, 但因新同化碳持续供给而使可溶性糖和次生代谢产物的浓度得以稳定.这些研究结果均表明树木通过改变碳分配策略, 减少分配给生长的碳, 增加碳储存(Sala et al., 2012), 形成树木生长、碳储存和防御的权衡关系(Huang et al. 2019); Wiley和Helliker (2012)认为这是一种不论是否面对环境胁迫都会频繁发生的保守生存策略.但以上研究均基于控制实验, 判定自然条件下植物是否会采取这种保守的碳分配策略十分困难, 但值得深入研究. ...
How can we make plants grow faster? A source-sink perspective on growth rate 2 2016
... 树木体内的碳既是其生物量主要组分, 也是其生命活动的能量源泉.植物通过调节碳供给-碳利用活动, 改变其生长速率和光合产物分配, 从而适应不断变化的环境条件(White et al., 2016).因此, 碳供给与碳利用活动是影响树木生长的重要生理机制(Burnett et al., 2016; White et al., 2016), 也是树木生理生态学和全球变化研究的热点和争议焦点之一. ...
... ; White et al., 2016), 也是树木生理生态学和全球变化研究的热点和争议焦点之一. ...
Recovery following defoliation involves shifts in allocation that favour storage and reproduction over radial growth in black oak 2 2017
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,*东北林业大学生态研究中心, 哈尔滨 150040; 东北林业大学森林生态系统可持续经营教育部重点实验室, 哈尔滨 150040
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