,1,*1 2
Response of fine roots to precipitation change: A meta-analysis
ZHANG Xin1, XING Ya-Juan1,2, YAN Guo-Yong1, WANG Qing-Gui,1,*1 2
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| 基金资助: |
Online:2018-04-19
| Supported by: | SupportedbytheNationalNaturalScienceFoundationofChina( |
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张鑫, 邢亚娟, 闫国永, 王庆贵. 细根对降水变化响应的meta分析. 植物生态学报, 2018, 42(2): 164-172 doi:10.17521/cjpe.2017.0203
ZHANG Xin, XING Ya-Juan, YAN Guo-Yong, WANG Qing-Gui.
近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(IPCC, 2013)。细根是指直径小于2 mm的根(McCormack et al., 2015), 在植物响应降水变化的过程中起着至关重要的作用。植物可通过调整细根形态、重新分配细根生物量以进行适应性调节, 从而优化资源获取。不同植物生活型(乔木、灌木和草本植物)的细根形态和生物量对降水变化的响应不同, 具体表现为: 1)比根长与根长度密度的变化。比根长和根长度密度从不同角度反映了植物碳分配策略, 即根系经济学层面的理论。生长在不同温度带的乔木细根表现出形态差异(常文静和郭大立, 2008), 不同类型植物根据各自的碳分配策略分别做出相应的形态调整。增加降水导致生长在亚热带和温带的乔木细根根长度密度增加, 而比根长没有显著变化(Coleman, 2007; Herzog et al., 2014), 但de Visser等(1994)研究发现灌溉使北方森林乔木20-40 cm土层的比根长显著增加, 乔木细根对增加降水的响应可能与生长环境有关。增加降水对灌木的细根根长度密度和比根长的影响并不显著(Verburg et al., 2013; Jerbi et al., 2015)。减少降水则导致乔木和灌木细根比根长显著增加(韩艳英等, 2014; 钟波元等, 2016), 钟波元等(2016)对杉木(Cunninghamia lanceolata)幼苗细根进行隔离降水处理时发现细根比根长显著增加, 生长出单位质量更大的细根, 有利于树木在土壤水分短缺时优化收入/产出比。韩艳英等(2014)在研究灌木西藏砂生槐(Sophora moorcroftiana)根系时发现干旱条件下比根长较大, 其养分与水分吸收效率相对较高, 有利于适应干旱环境的生长。2)细根生物量的重新分配。以往对细根生物量受降水影响的研究并没有定论, 增加降水使亚热带和温带乔木细根的生物量显著增加(Coleman, 2007; Chen et al., 2015), Moser等(2010)对热带树种进行短期浇灌实验中并没有发现细根生物量的显著变化, 而Gei和Powers (2015)发现热带雨林中雨季的细根生物量高于干旱季节, 并且土壤水分主要来源于降水, 随土层深度增加而降低, 细根生物量主要集中在水分充足的土壤表层。灌木的细根生物量也随降水增加而增加(Ansley et al., 2014)。在不同持续时间的模拟降水增加实验中, 短期内草地细根生物量增加, 而长期实验中细根生物量减少(Fiala et al., 2012; Kong et al., 2013)。各植物类型细根生物量对降水减少的响应也有所不同, 以往研究发现各温度带的乔木细根生物量在减少降水实验中因细根死亡率高于其生长速率而表现出生物量显著减少(Kon?pka et al., 2012; Moser et al., 2014; 钟波元等, 2016)。Hertel等(2013)研究却发现, 干旱草地的细根生物量在土壤有机层中的比例非但没有减少, 反而增加了。资源最优分配理论则预测植物在干旱及土壤水分亏缺的情况下应该增加吸收水分与蒸发水分的比率, 即水分不足应促进细根的生长、增加生物量和表面积, 从而吸收足够的水分。上述研究结果表明不同植物类型的细根对降水变化的响应存在差异, 可能与细根生长特性、养分资源或实验持续时间有关。
细根的生产力和周转率占全球陆地净初级生产力的22% (McCormack et al., 2015), 以往研究表明增加降水使草地细根生产量和周转率显著增加(Bai et al., 2010; Fiala et al., 2012), 热带、亚热带和北方森林的细根生产量均显著增加(Bai et al., 2010; Olesinski et al., 2011; Ford et al., 2012)。减少草地年降水量导致根生产量减少(Fiala et al., 2009), Yuan和Chen (2010)的meta分析也表明降水减少导致北方森林根系周转率和生产力下降。可见, 降水变化直接影响细根的生产力和周转率, 进而影响土壤碳循环。
土壤微生物是植物营养转化及循环的介质, 细根分解与土壤微生物相互依存, 为土壤微生物提供营养(Zi et al., 2017), 而土壤微生物是细根分解过程中的重要参与者(McClaugherthy et al., 1982; 武志超等, 2012), 已有研究指出土壤水分通过直接影响微生物的活动, 进而间接影响细根分解(Berg & McClaugherty, 2003)。由于土壤微生物对降水变化的响应比植物更敏感(张静茹等, 2014), 同时土壤微生物生物量碳在一定程度上代表了参与细根分解过程的微生物数量和活性(Larsen et al., 2002; Taylor et al., 2002), 本文通过降水变化对土壤微生物生物量碳的影响揭示细根分解对降水变化的响应。Chapin等(2002)指出土壤水分增加导致O2不足, 抑制微生物活性, 从而降低细根分解, 但此观点忽略了厌氧微生物对细根的分解作用。García-Palacios等(2016)在长期(11年)模拟降水变化实验中发现减水导致土壤微生物量减少, 却促进了细根分解。因此, 研究降水变化对土壤微生物的影响, 可以间接评价细根分解对未来全球气候变化的响应。
以往关于细根响应降水变化的研究都是针对同类型植物, 缺少对各植物类型细根应对降水变化的比较。因此, 本文应用meta分析的方法, 从48篇已发表的国内外论文中搜集到202组数据, 探究以下问题: 不同植物类型细根生物量、生产量、周转率、根长度密度、比根长和细根分解对降水变化的响应如何? 是否存在土层空间异质性? 是否因降水变化量或实验持续时间的不同而发生变化? 本研究可为降水变化对全球不同植物类型细根动态及碳循环的影响提供数据支持。
1 研究方法
1.1 文献选择及数据库建立
本文研究以细根、降水、水分等关键词检索Web of Science、Springer-Link Journals、EBSCO、CNKI和ResearchGate等中英文期刊数据库, 收集发表在2007-2017年的所有满足条件且可获取的论文用于meta分析。结合本研究目的, 所筛选的论文必须满足以下条件: (1)实验必须设有对照组和处理组。(2)同一实验中的对照组和处理组必须设置于相同气候、土壤、植物类型下。(3)实验样地除降水处理外无温度、矿质养分变化等其他因素处理。(4)从论文中直接提取或用GetData v2.22从图片中提取到细根相关参数的平均值、标准偏差、标准误差、置信区间和样本容量。通过筛选, 本研究利用搜集的48篇实验性文献(附录I)建立细根对降水变化响应的数据库, 包括作者、发表年限以及实验的相关背景数据。其中, 背景数据包括实验地点、植物类型、降水变化量、实验持续时间、采样季节、采样土层深度。细根参数包括细根生物量、生产量、周转率、根长度密度(RLD)、比根长(SRL)、土壤微生物量碳(MBC)(附录II)。1.2 数据分组及分析方法
首先, 根据实验目的进行数据分组。将植物类型划分为热带乔木、亚热带乔木、温带乔木、北方乔木、灌木和草本植物。按实验持续时间划分为短期(<1年)、中期(1-3年)和长期实验(>3年)。本文将增加和减少的降水变化量划分为: <50%、50%-100%、100%-200%、>200% 4个区间, 并根据Jerbi等(2015)的研究结果, 按土层深度0-10 cm、10-20 cm、20-40 cm分组, 进行亚组分析。其次, 计算响应比(RR)并进行对数转换, 用于评估增加或减少降水对细根各指标的影响效应, 计算公式为:lnRR = ln(Xt / XC) (1)
其中Xt为处理组平均值, XC为对照组平均值(Hedges et al., 2008)。
运用Metawin 2.1软件(Sinauer Associates, Sunderland, USA)中的随机模型计算平均加权响应比(RR++)和95%置信区间, RR++为正值则为正效应, 负值则为负效应。如果95%置信区间不包括0, 表示细根指标对降水变化响应显著; 反之, 则响应不显著。
2 结果和分析
2.1 不同类型植物细根对增加或减少降水的响应
由图1A可知, 增加降水条件下, 各类型植物细根生物量中只有灌木变化显著(响应比0.06, 95%置信区间(以下简称CI) 0.04, 0.08)。增加降水使草地细根根长度密度显著增加(响应比0.90, 95% CI 0.03, 1.77), 而对亚热带乔木、温带乔木和灌木影响不显著, 对北方森林乔木细根比根长的影响呈显著正效应(响应比0.07, 95% CI 0.01, 0.13)。减少降水对亚热带乔木(响应比-0.58, 95% CI -0.93, -0.23)、温带乔木(响应比-0.28, 95% CI -0.51, -0.05)和灌木(响应比-1.72, 95% CI -2.95, -0.49)细根生物量的影响均表现为显著负效应, 而对热带乔木细根生物量的影响不显著(图1B)。图1
新窗口打开|下载原图ZIP|生成PPT图1不同类型植物细根和土壤微生物生物量碳对增加(A)或减少(B)降水的加权响应比。括号内数字代表样本量, 误差线代
Fig. 1Weighted response ratio of increasing (A) or reducing (B) precipitation on fine root of different plant type and soil microbial biomass carbon. The variables are categorized into different groups depending on plant types. The number in parentheses represents the sample size for each variable. Error bars represent 95% confidence intervals. MBC, soil microbial biomass carbon; RLD, root length density; SRL, specific root length.
2.2 不同土层细根对降水变化的响应
由图2A和2B可知, 细根生长对降水变化量为50%的响应最显著, 而且不同土层的细根对降水变化的响应程度不同, 可见细根对降水变化的响应存在空间异质性。降水增加量小于50%时(图2A), 显著增加20-40 cm土层的细根生物量(响应比0.23, 95% CI 0.04, 0.42)和10-20 cm的细根比根长(响应比0.07, 95% CI 0.01, 0.13)。降水增加量为50%-100%时, 显著增加10-20 cm土层的细根生物量(响应比0.18,95% CI 0.01, 0.35)。降水增加量大于200%时, 显著增加0-10 cm土层的细根生物量(响应比0.26, 95% CI 0.05, 0.47), 细根生物量和比根长对增加降水的响应强于减少降水。降水减少量少于50%时(图2B), 显著减少20-40 cm土层细根生产量(响应比-0.79, 95% CI -1.30, -0.28), 显著增加0-10 cm土层细根根长度密度(响应比0.95, 95% CI 0.10, 1.80)。降水量减少50%-200%对细根没有显著影响, 细根生产量和细根根长度密度对减少降水的响应强于增加降水。图2
新窗口打开|下载原图ZIP|生成PPT图2各土层细根指标对不同增加(A)或减少(B)降水量的加权响应比。括号内数字代表样本量, 误差线代
Fig. 2Weighted response ratio (RR++) of different increasing (A) or reducing (B) precipitation amount on each soil layer fine root. The variables are categorized into different groups depending on duration. The number in parentheses represents the sample size for each variable. Error bars represent 95% confidence intervals. RLD, root length density; SRL, specific root length.
2.3 细根对不同降水变化实验持续时间的响应
细根对不同降水变化实验持续时间的响应主要表现为生物量、根长度密度的变化。不同持续时间的降水变化实验中, 细根生物量只在3年以上的长期减少降水实验中表现出显著负效应(响应比-0.28, 95% CI -0.48, -0.08)(图3B), 在3年以内的实验中变化不显著。细根根长度密度只在1年以内的短期增加降水实验中表现出显著正效应(响应比0.26, 95% CI 0.01, 0.51)(图3A), 而在1年以上的实验中变化不显著, 表明长期降水变化实验显著影响地下碳分配, 而短期实验中细根通过形态适应对降水变化做出应对。细根的比根长、周转率与生产量对降水变化的响应不受实验时长的影响。图3
新窗口打开|下载原图ZIP|生成PPT图3不同实验持续时间下细根和土壤微生物生物量碳对增加(A)或减少(B)降水的加权响应比。括号内数字代表样本量, 误差线代
Fig. 3Weighted response ratio (RR++) of increasing (A) or reducing (B) precipitation on fine root and soil microbial biomass carbon under different duration of experiment . The variables are categorized into different groups depending on duration. The number in parentheses represents the sample size for each variable. Error bars represent 95% confidence intervals. MBC, soil microbial biomass carbon; RLD, root length density; SRL, specific root length.
2.4 土壤微生物生物量碳对降水变化的响应
增加降水使土壤微生物生物量碳显著增加(总响应比0.29, 95% CI 0.07, 0.51), 且各植物类型下的土壤微生物生物量碳响应均显著, 热带乔木、北方乔木、灌木对增加降水的响应比分别为1.01 (95% CI 0.84, 1.18)、0.24 (95% CI 0.07, 0.41)和0.13 (95% CI 0.10, 0.16)(图1A)。减少降水导致土壤微生物生物量碳显著降低(总响应比-0.53, 95% CI -0.83, -0.23)。热带乔木和亚热带乔木植被下的土壤微生物生物量在降水减少的条件下均显著降低, 响应比分别为-0.81 (95% CI -0.99, -0.63)、-0.41 (95% CI -0.74, -0.18)(图1B)。由此可见, 各类型植物的细根分解易受降水变化的影响。土壤微生物生物量碳对不同降水变化实验时长的响应均显著, 短于3年的增加降水实验中, 土壤微生物生物量碳显著增加(1年以内的响应比0.13, 95% CI 0.10, 0.16; 1-3年的响应比0.45, 95% CI 0.31, 0.59)(图3A)。长于1年的减少降水实验中, 土壤微生物生物量碳显著减少(1-3年的响应比-0.81, 95% CI -1.00, -0.63; 3年以上的响应比-0.41, 95% CI -0.74, -0.08)(图3B)。因此, 土壤微生物对土壤环境变化十分敏感, 细根分解对降水变化的显著响应或与实验持续时间无关。3 讨论
3.1 不同类型植物细根对降水变化的响应差异
不同植物对营养的需求和碳分配策略均有所不同, 导致细根在响应降水变化时表现出差异性(陈明涛和赵忠, 2011)。本研究发现灌木对降水格局变化的响应强于乔木, Starr和Oberbauer (2008)指出在非乔木植物中, 根系大多分布在浅土层且木质化较少, 如草本和灌木在响应积雪厚度变化时表现出比乔木更强的可塑性。灌木表现出较强的可塑性可能与灌木浅层根系为细根型群落根系(反J型根系生态位径级分布)有关(董宾芳, 2015), 灌木的表层土壤根系主体为细根(≤1 mm), 而乔木林地浅层根系为细-粗混合型群落根系, 表层土壤根系同时包括细根(≤1 mm)和粗根(≥10 mm)(胡建忠等, 2005)。细根对降水变化的响应强于粗根, 降水变化导致土壤水分条件改变, 增加降水有利于更多的碳分配于构建根系, 进而导致细根生物量增加, 根长度密度减小, 提高水分运输率。减少降水则导致土壤水分短缺, 细根因生长变慢导致其生物量降低。Yuan和Chen (2010)在相关的meta分析中发现, 年降水量每增加100 mm, 北方森林乔木细根生物量以0.43 Mg·hm-2的速率显著增加, 而本文研究只发现了北方森林乔木比根长显著增加。导致本研究和以往研究存在差异的原因可能是, 细根生物量的变化并不能完全由降水变化解释, 也可能与树种或其他外界环境因素(比如氮沉降、温度升高等)有关。Liu等(2017)也在温带森林中发现单因素降水对乔木细根生物量的影响并不显著。Yuan和Chen (2010)对北方森林的研究从气候、物种、土壤性质以及林龄等4个方面进行, 本文仅从单因素降水变化分析北方森林乔木细根的变化, 可能因此产生差异。本研究中减少降水导致亚热带乔木、温带乔木和灌木细根生物量显著减少(图1B), 这与资源最优分配理论相悖, Hertel等(2013)指出水分亏缺对细根生物量的影响可能取决于植物碳水化合物的供给是否充足, 当水分限制导致碳源受限时, 资源最优分配理论中的现象可能不会发生。水分胁迫限制了新生根的生长, Chen等(2013)也指出干旱胁迫下的杉木幼苗会受到异速生长的抑制, 因此降水减少导致细根生物量的减少。而热带乔木细根生物量并没有受到降水减少的显著影响, 可能因为热带地区常年高温高湿, 部分抵消了降水减少的影响。3.2 不同土层细根对降水变化的响应
土壤水分含量直接影响细根的垂直分布, 表现出生态位分离(Imada et al., 2013), 细根生物量、比根长和根长度密度的分布表现出空间异质性(Jiang et al., 2016)。本研究表明细根各指标对降水变化的响应也存在空间异质性, 20-40 cm土层的细根生物量对降水变化响应最显著, 可能因为该土层土壤养分和水分相对于0-20 cm的土层较贫瘠, 导致细根对降水的响应更加敏感(图2A)。本研究还发现增加或减少50%的降水时细根响应最强烈, 其中减少50%的降水使20-40 cm细根生产量显著减少, 而细根生产量降低非常不利于植物的生存。已有研究表明细根面临水分胁迫时采取的适应策略不一定完全表现在增加细根生物量或生产量, 可能依靠细根形态做出适应性变化(钟波元等, 2016), 本文研究结果与之一致, 即减少50%的降水显著增加了0-10 cm土层的根长度密度, 从而增大植物吸水表面, 减小土壤输水距离, 最大限度地获取水资源, 这可能是土壤表层细根为应对深层细根生产量减少而做出的形态调整策略, 因此分布在不同土层的细根对降水变化的响应可能存在形态或生理上的互补作用。因此, 研究细根对降水变化的响应时, 不但要研究细根形态和生理的响应, 而且要研究细根不同土层对降水变化的响应是否有互补作用。3.3 细根对降水变化实验持续时间长短的响应
在增加降水实验中, 短期(≤1年)根长度密度显著增加, 而1年以上的中期和长期根长度密度变化不显著(图3A), 原因可能是短期实验中细根需要一定的适应稳定时间, 细根通过提高密度以更多地吸收土壤中充足的水分,这有利于植物的正常生长。中、长期增水实验会导致土壤水分富足或过剩, 细根不需要额外增加密度就可以吸收足够的水分以维持植物的生长。在长期减少降水实验中, 细根生物量表现为显著下降, 表明植物重新调整了地下碳分配策略, 这与以往研究结果(Fiala et al., 2012; Moser et al., 2014)一致。本文长期降水变化显著影响细根生物量分配的结果表明: 未来几十年或者更长时间内, 降水变化对细根的影响会引起地下碳库的显著变化, 进而影响全球碳循环。因此, 探索细根对降水变化的响应时应更加注重长期实验, 积极倡导长期定位观测, 以增加控制实验的客观性和可信度。3.4 降水变化对细根养分归还的影响
细根分解对土壤碳输入的年均贡献量高达50% (Vogt et al., 1996), 是一个有土壤微生物参与的复杂过程。Li等(2013)在降水增加实验中发现土壤微生物生物量碳显著增加, 表现出较高的微生物分解能力, 表明增加降水可提高土壤微生物活性, 促进细根分解。有研究表明细根生物量对土壤微生物生物量碳质量分数的总贡献最大, 土壤中绝大多数微生物菌群量受地下细根生物量的显著影响(林宇等, 2017; 罗达等, 2017)。增加降水既增加了细根生物量, 又提高了土壤溶质的可用性, 为土壤微生物提供了充足的底物资源, 进而提高了土壤微生物对细根的分解能力, 促使细根养分归还土壤。早期研究中也证明底物资源有效性直接影响土壤微生物活性, 从而影响细根分解速度(Bloomfield & Vogt, 1993)。然而减少降水影响细根分解的机制还不确定, Martin等(2004)和Ostertag等(2008)都认为, 降低土壤水分使微生物活性受限和底物转化能力降低而减弱根降解。但García-Palacios等(2016)认为减少降水导致土壤微生物生物量的减少, 反而促进细根分解。虽然本文减少降水导致土壤微生物生物量碳显著降低, 但细根周转的变化并不显著, 因此不能确定减少降水就增强或减弱了细根养分归还能力。4 结论
(1)不同类型植物细根对降水变化的响应存在差异, 灌木细根的响应强于乔木, 缘于灌木浅层根系中细根所占比例高于乔木。(2)增加或减少50%的降水时细根响应最显著, 细根各指标对降水变化的响应存在空间异质性, 不同土层细根对降水变化的响应可能存在形态或生理上的互补作用。(3)长期(≥3年)降水变化显著影响细根生物量, 而短期实验中细根通过形态适应以应对降水变化。(4)增加降水促进细根分解, 加快细根养分归还进程, 而减少降水对细根养分归还的影响尚未明确。细根是土壤养分资源的重要来源, 因此, 研究降水变化对细根分解的影响为揭示生态系统养分循环对全球气候变化的响应具有重要意义。
致谢 长白山科学研究院开放基金(2016001)支持。
参考文献 原文顺序
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DOI:10.2111/REM-D-13-00119.1URL [本文引用: 1]
Expansion of woody plants in North American grasslands and savannas is facilitated in part by root system adaptation to climatic extremes. Climatic extremes are predicted to become more common with global climate change and, as such, may accelerate woody expansion and/or infilling rates. We quantified root biomass and distribution patterns of the invasive woody legume, honey mesquite (Prosopis glandulosa), and associated grasses following a long-term rainfall manipulation experiment in a mixed grass savanna in the southern Great Plains (United States). Root systems of mature trees were containerized with vertical barriers installed to a depth of 270 cm, and soil moisture was manipulated with irrigation (Irrigated) or rainout shelters (Rainout). Other treatments included containerized, precipitation-only (Control) and noncontainerized, precipitation-only (Natural) trees. After 4 yr of treatment, soil cores to 270 cm depth were obtained, and mesquite root length density (RLD) and root mass, and grass root mass were quantified. Mesquite in the Rainout treatment increased coarse-root (66&spigt;662 mm diameter) RLD and root mass at soil depths between 90 cm and 270 cm. In contrast, mesquite in the Irrigated treatment increased fine-root (66&spilt;662 mm diameter) RLD and root mass between 30 cm and 270 cm depths, but did not increase total root mass (fine66+66coarse) compared to the Control. Mesquite root-to-shoot mass ratio was 2.8 to 4.6 times greater in Rainout than the other treatments. Leaf water stress was greatest in the Rainout treatment in the first year, but not in subsequent years, possibly the result of increased root growth. Leaf water use efficiency was lowest in the Irrigated treatment. The increase in coarse root growth during extended drought substantially increased mesquite belowground biomass and suggests an important mechanism by which woody plant encroachment into grasslands may alter below ground carbon stocks under climate change scenarios predicted for this region.
DOI:10.1111/j.1365-2486.2009.02019.xURL [本文引用: 2]
Fine root production and turnover play important roles in regulating carbon (C) cycling in terrestrial ecosystems. In order to examine effects of climate change on root production and turnover, a field experiment with increased temperature and precipitation had been conducted in a semiarid temperate steppe in northern China since April 2005. Experimental warming decreased annual root production, mortality, and mean standing crop by 10.3%, 12.1%, 7.0%, respectively, while root turnover was not affected in 2006 and 2007 by the warming. Annual root production and turnover was 5.9% and 10.3% greater in the elevated than ambient precipitation plots. Changes in root production and mortality in response to increased temperature and precipitation could be largely attributed to the changes in gross ecosystem productivity (GEP) and belowground/aboveground C allocation. There were significant interactive effects of warming and increased precipitation on root productivity, mortality, and standing crop. Experimental warming had positive and negative effects on the three root variables (root production, mortality, standing crop) under ambient and increased precipitation, respectively. Increased precipitation stimulated and suppressed the three root variables in the unwarmed and warmed subplots, respectively. The positive dependence of soil respiration and ecosystem respiration upon root productivity and mortality highlights the important role of root dynamics in ecosystem C cycling. The nonadditive effects of increased temperature and precipitation on root productivity, mortality, and standing crop observed in this study are critical for model projections of climate-ecosystem feedbacks. These findings indicate that carbon allocation is a focal point for future research and that results from single factor experiments should be treated with caution because of factor interactions.
[本文引用: 1]
DOI:10.1007/BF00013020URL [本文引用: 1]
DOI:10.3773/j.issn.1005-264x.2008.06.005URL [本文引用: 1]
细根在发挥植物功能以及生态系统碳和养分循环过程中起着重要作 用.为了解我国不同森林生态系统细根直径变化规律,提供建立根系模型的基础,该文研究了我国温带、亚热带和热带45个常见树种1～5级根直径的变异以及直 径与根序的关系.结果表明:1)在所有树种中,1级根直径最细,5级根直径最粗,直径随根序的增加而增加.此外,同一根序的直径在不同树种间变异较大,在 不同生态系统中,各树种1级根的总体平均直径呈现温带<亚热带<热带的格局.2)不同生态系统树种同一根序平均直径变异程度不同,各个根序都 是温带最小,亚热带次之,热带最大.3)细根内部各个根序的平均直径变异的52%～q根序解释,33%由树种解释,生态系统类型和生活型分别解释7%和2 %.不同系统不同树种直径的变异说明无法用统一的直径级来研究根的功能,也无法用统一的根序和直径间的关系来建立根系形态模型.今后的研究需要进一步认识 根序和直径在不同树种中如何与根的功能相联系.
DOI:10.3773/j.issn.1005-264x.2008.06.005URL [本文引用: 1]
细根在发挥植物功能以及生态系统碳和养分循环过程中起着重要作 用.为了解我国不同森林生态系统细根直径变化规律,提供建立根系模型的基础,该文研究了我国温带、亚热带和热带45个常见树种1～5级根直径的变异以及直 径与根序的关系.结果表明:1)在所有树种中,1级根直径最细,5级根直径最粗,直径随根序的增加而增加.此外,同一根序的直径在不同树种间变异较大,在 不同生态系统中,各树种1级根的总体平均直径呈现温带<亚热带<热带的格局.2)不同生态系统树种同一根序平均直径变异程度不同,各个根序都 是温带最小,亚热带次之,热带最大.3)细根内部各个根序的平均直径变异的52%～q根序解释,33%由树种解释,生态系统类型和生活型分别解释7%和2 %.不同系统不同树种直径的变异说明无法用统一的直径级来研究根的功能,也无法用统一的根序和直径间的关系来建立根系形态模型.今后的研究需要进一步认识 根序和直径在不同树种中如何与根的功能相联系.
DOI:10.1111/nph.12426URLPMID:23902539
Abstract Understanding the allocation of gross primary production (GPP) and its response to climate is essential for improving terrestrial carbon (C) modelling. Here, we synthesize data on component GPP fluxes from a worldwide forest database to determine the allocation patterns of GPP across global gradients in climate and nitrogen deposition (Ndep ). Our results reveal that allocation of GPP is governed in an integrated way by allometric constraints and by three trade-offs among GPP components: wood production (NPPwood ) vs fine-root production (NPPfroot ), NPPwood vs foliage production (NPPfoliage ), and autotrophic respiration (Ra ) vs all biomass production components. Component fluxes were explained more by allometry, while partitioning to components was related more closely to the trade-offs. Elevated temperature and Ndep benefit long-term woody biomass C sequestration by stimulating allometric partitioning to wood. Ndep can also enhance forest C use efficiency by its effects on the Ra vs biomass production trade-off. Greater precipitation affects C allocation by driving the NPPwood vs NPPfoliage trade-off toward the latter component. These results advance our understanding about the global constraints on GPP allocation in forest ecosystems and its climatic responses, and are therefore valuable for simulations and projections of ecosystem C sequestration. 2013 The Authors. New Phytologist 2013 New Phytologist Trust.
URL [本文引用: 1]
为了系统研究干旱对黄土高原主要造林树种根系特征及各部分物质分配的影响,通过人为控制土壤水分,按土壤田间持水量的70%、50%、35%设干旱处理水平(各水平均设7、14和21d),观测2年生油松、刺槐、侧柏、沙棘苗木根生物量、地上部分生物量及细根(直径2mm)指标(表面积、根长、根尖数)。结果表明:1)随着干旱胁迫程度和处理时间的增加,油松根生物量和细根指标值显著增加;刺槐根生物量总体上有增加,细根指标值保持稳定;侧柏根系生物量在中度干旱时增加,重度干旱时减少,两水平处理随着处理时间的延长有减少的趋势,细根指标值仅在重度干旱(21d)明显减少;沙棘根生物量、细根指标值在中度干旱条件下明显增加,但随着处理时间的延长,增加量逐渐减少,在重度干旱条件下不能存活。2)干旱条件下,根、茎、叶的物质分配格局发生了变化,树种之间差异很大。
URL [本文引用: 1]
为了系统研究干旱对黄土高原主要造林树种根系特征及各部分物质分配的影响,通过人为控制土壤水分,按土壤田间持水量的70%、50%、35%设干旱处理水平(各水平均设7、14和21d),观测2年生油松、刺槐、侧柏、沙棘苗木根生物量、地上部分生物量及细根(直径2mm)指标(表面积、根长、根尖数)。结果表明:1)随着干旱胁迫程度和处理时间的增加,油松根生物量和细根指标值显著增加;刺槐根生物量总体上有增加,细根指标值保持稳定;侧柏根系生物量在中度干旱时增加,重度干旱时减少,两水平处理随着处理时间的延长有减少的趋势,细根指标值仅在重度干旱(21d)明显减少;沙棘根生物量、细根指标值在中度干旱条件下明显增加,但随着处理时间的延长,增加量逐渐减少,在重度干旱条件下不能存活。2)干旱条件下,根、茎、叶的物质分配格局发生了变化,树种之间差异很大。
[本文引用: 1]
DOI:10.1007/s11104-007-9375-5URL [本文引用: 2]
In forest trees, roots mediate such significant carbon fluxes as primary production and soil CO 2 efflux. Despite the central role of roots in these critical processes, information on root distribution during stand establishment is limited, yet must be described to accurately predict how various forest types, which are growing with a range of resource limitations, might respond to environmental change. This study reports root length density and biomass development in young stands of eastern cottonwood ( Populus deltoidies Bartr.) and American sycamore ( Platanus occidentalis L.) that have narrow, high resource site requirements, and compares them with sweetgum (Liquidambar styraciflua L.) and loblolly pine ( Pinus taeda L.), which have more robust site requirements. Fine roots (5mm) were sampled to determine spatial distribution in response to fertilizer and irrigation treatments delivered through drip irrigation tubes. Root length density and biomass were predominately controlled by stand development, depth and proximity to drip tubes. After accounting for this spatial and temporal variation, there was a significant increase in RLD with fertilization and irrigation for all genotypes. The response to fertilization was greater than that of irrigation. Both fine and coarse roots responded positively to resources delivered through the drip tube, indicating a whole-root-system response to resource enrichment and not just a feeder root response. The plastic response to drip tube water and nutrient enrichment demonstrate the capability of root systems to respond to supply heterogeneity by increasing acquisition surface. Fine-root biomass, root density and specific root length were greater for broadleaved species than pine. Roots of all genotypes explored the rooting volume within 2years, but this occurred faster and to higher root length densities in broadleaved species, indicating they had greater initial opportunity for resource acquisition than pine. Sweetgum鈥檚 root characteristics and its response to resource availability were similar to the other broadleaved species, despite its functional resemblance to pine regarding robust site requirements. It was concluded that genotypes, irrigation and fertilization significantly influenced tree root system development, which varied spatially in response to resource-supply heterogeneity created by drip tubes. Knowledge of spatial and temporal patterns of root distribution in these stands will be used to interpret nutrient acquisition and soil respiration measurements.
DOI:10.1016/0378-1127(94)90134-1URL
ABSTRACT In five coniferous forest ecosystems in Europe, water and nutrient supply, as well as atmospheric loads, were manipulated for 3 or 4 years. Water supply was optimised and nutrients were added according to tree demand in optimal proportions relative to the ambient N supply. Tree growth was strongly enhanced by optimal water supply but not further enhanced by nutrient additions. The nutritional balance in trees was improved for P and K. The increased water and nutrient supply retarded needle shedding in autumn and diminished root production. To date, the manipulated decrease in N input to the soil has decreased the N content in needles in one stand. Water additions tended to lower N contents at two sites. Large applications of N increased N content in needles even though the N nutrition was already optimal. Liming with dolomite stimulated tree growth only in the nutrient-poor stand, but has generally increased Ca content in needles. The number of species and cover of understorey vegetation has increased considerably by liming and, in some cases, by water addition.Ecosystem manipulation experiments have been shown to be a useful tool for the quantification of the growth effects of traditionally limiting factors. Additionally they give indications of the effects on forest ecosystem processes of future changes in atmospheric loads.
DOI:10.14079/j.cnki.cn42-1745/tv.2015.04.011URL [本文引用: 1]
植被根系在黄土丘陵区水土流失防治中发挥重要作用。采用分层挖掘法获取陕北黄土丘陵区三种林地根系,仿照群落生态学研究方法,利用根系生态位指数分析该区三种林地根系的分布特征,结果表明:三种林地根系生态位指数随深度的增加呈现较明显的下降趋势,但也有明显的差别,山杨林地中,根系生态位指数最大值是1.37,为最小值的6.95倍,而油松林地中最大值是1.07,为最小值的2.41倍,灌木林地中最大值是0.76,为最小值的2.75倍,三种林地中,相同深度的根系生态位表现为:山杨林油松林灌木林。山杨林地和油松林地根系生态位径级分布呈明显的不等高U型特征,林地根系为细-粗混合型,灌木林地为明显的反J型,为细根型群落根系。就群落根系生态位指数来看,山杨林地为5.40,油松林为4.41,灌木林为3.09。
DOI:10.14079/j.cnki.cn42-1745/tv.2015.04.011URL [本文引用: 1]
植被根系在黄土丘陵区水土流失防治中发挥重要作用。采用分层挖掘法获取陕北黄土丘陵区三种林地根系,仿照群落生态学研究方法,利用根系生态位指数分析该区三种林地根系的分布特征,结果表明:三种林地根系生态位指数随深度的增加呈现较明显的下降趋势,但也有明显的差别,山杨林地中,根系生态位指数最大值是1.37,为最小值的6.95倍,而油松林地中最大值是1.07,为最小值的2.41倍,灌木林地中最大值是0.76,为最小值的2.75倍,三种林地中,相同深度的根系生态位表现为:山杨林油松林灌木林。山杨林地和油松林地根系生态位径级分布呈明显的不等高U型特征,林地根系为细-粗混合型,灌木林地为明显的反J型,为细根型群落根系。就群落根系生态位指数来看,山杨林地为5.40,油松林为4.41,灌木林为3.09。
DOI:10.1007/s10021-009-9264-2URL [本文引用: 1]
A field experiment was established to quantify the effects of different amounts of rainfall on root growth and dry mass of belowground plant parts in three types of grassland ecosystems. Mountain ( Nardus grassland), highland (wet Cirsium grassland), and lowland grassland (dry Festuca grassland) ecosystems were studied in 2006 and 2007. Roofs constructed above the canopy of grass stands and gravity irrigation systems simulated three climate scenarios: (1) rainfall reduced by 50%, (2) rainfall enhanced by 50%, and (3) the full natural rainfall of the current growing season. Experimentally reduced amounts of precipitation significantly affected both yearly root increments and total root dry mass in the highland grassland. Dry conditions in 2007 resulted in considerable reduction of total belowground dry mass in highland and mountain grasslands. Although not all differences in root biomass of studied grasslands were statistically significantly, some also showed a decrease in root increment and in the amount of belowground dry mass in dry conditions.
DOI:10.1100/2012/805298URLPMID:3353563 [本文引用: 3]
The effect of different amounts of rainfall on the below-ground plant biomass was studied in three grassland ecosystems. Responses of the lowland (dry Festuca grassland), highland (wet Cirsium grassland), and mountain (Nardus grassland) grasslands were studied during five years (2006???2010). A field experiment based on rainout shelters and gravity irrigation simulated three climate scenarios: rainfall reduced by 50% (dry), rainfall increased by 50% (wet), and the natural rainfall of the current growing season (ambient). The interannual variation in root increment and total below-ground biomass reflected the experimentally manipulated amount of precipitation and also the amount of current rainfall of individual years. The effect of year on these below-ground parameters was found significant in all studied grasslands. In comparison with dry Festuca grassland, better adapted to drought, submontane wet Cirsium grassland was more sensitive to the different water inputs forming rather lower amount of below-ground plant matter at reduced precipitation.
DOI:10.1016/j.agrformet.2011.12.008URL [本文引用: 1]
Soil CO2 efflux (Esoil), the main pathway of C movement from the biosphere to the atmosphere, is critical to the terrestrial C cycle but how precipitation and soil moisture influence Esoil remains poorly understood. Here, we irrigated a longleaf pine wiregrass savanna for six years; this increased soil moisture by 41.2%. We tested how an altered precipitation regime affected total belowground carbon allocation (TBCA), root growth, soil carbon, and Esoil. We used two methods to quantify Esoil: daytime biweekly manual measurements and automated continuous measurements for one year. We hypothesized that the low-frequency manual method would miss both short- and long-term (i.e., subdaily to annual, respectively) effects of soil moisture on Esoil while the high-frequency data from the automated method would allow the effects of soil moisture to be discerned. Root growth was significantly higher in irrigated plots, particularly at 0–20cm depth. Irrigated annual Esoil was significantly greater than that of the control when estimated with the continuous measurements but not when estimated from biweekly measurements. The difference in annual Esoil estimates is likely due to (1) the delayed increase in Esoil following irrigation pulses of soil moisture (i.e., variation that the biweekly manual measurements missed) and (2) the diel timing of biweekly manual measurements (they were completed early to mid-day before peak efflux). With irrigation, estimates of TBCA increased almost two-fold with automated measurements but only 36% with intermittent measurements. Relative to controls, irrigated treatments stored almost 2MgCha611year611 more in soils and 0.26MgCha611year611 more in roots. High-frequency measurements of Esoil were essential to estimate total belowground carbon allocation. With irrigation, soil carbon pools were not at steady-state, so shifts in soil carbon storage must be considered in TBCA estimates.
DOI:10.1007/s10021-015-9946-xURL
Climate change-induced rainfall reductions in Mediterranean forests negatively affect the decomposition of plant litter through decreased soil moisture. However, the indirect effects of reduced...
DOI:10.1007/s11104-014-2324-1URL
Background Fine roots comprise a dynamic carbon pool in forests. Legumes, widespread in the tropics, have a specialized strategy of nitrogen acquisition. However, the belowground dynamics of this...
DOI:10.3969/j.issn.1000-5382.2014.02.010URL [本文引用: 1]
采用分层挖掘法对西藏特有灌木砂生槐（ Sophora moorcroftian）天然灌丛幼林根系进行取样，研究不同径级根系生物量、比根长和根长密度及垂直分布状况。研究结果表明：砂生槐总根系生物量为12．77 g · m-2，其中粗根（5 mm＜d≤20 mm）所占的比例最高，为46．22％，其次为小根（2 mm＜d≤5 mm），所占比例为37．67％，细根（0＜d≤2 mm）生物量所占比例最小为16．11％。细根的比根长为1．91 m· g-1，明显大于小根0．34 m· g-1和粗根0．05 m· g-1。细根的根长密度最大为4．01 m· m-2，明显大于小根和粗根。不同径级砂生槐根系生物量、比根长和根长密度在各土层中的分布差异显著。
DOI:10.3969/j.issn.1000-5382.2014.02.010URL [本文引用: 1]
采用分层挖掘法对西藏特有灌木砂生槐（ Sophora moorcroftian）天然灌丛幼林根系进行取样，研究不同径级根系生物量、比根长和根长密度及垂直分布状况。研究结果表明：砂生槐总根系生物量为12．77 g · m-2，其中粗根（5 mm＜d≤20 mm）所占的比例最高，为46．22％，其次为小根（2 mm＜d≤5 mm），所占比例为37．67％，细根（0＜d≤2 mm）生物量所占比例最小为16．11％。细根的比根长为1．91 m· g-1，明显大于小根0．34 m· g-1和粗根0．05 m· g-1。细根的根长密度最大为4．01 m· m-2，明显大于小根和粗根。不同径级砂生槐根系生物量、比根长和根长密度在各土层中的分布差异显著。
DOI:10.2307/177062URL [本文引用: 1]
Meta-analysis provides formal statistical techniques for summarizing the results of independent experiments and is increasingly being used in ecology. The response ratio (the ratio of mean outcome in the experimental group to that in the control group) and closely related measures of proportionate change are often used as measures of effect magnitude in ecology. Using these metrics for meta-analysis requires knowledge of their statistical properties, but these have not been previously derived. We give the approximate sampling distribution of the log response ratio, discuss why it is a particularly useful metric for many applications in ecology, and demonstrate how to use it in meta-analysis. The meta-analysis of response-ratio data is illustrated using experimental data on the effects of increased atmospheric CO2 on plant biomass responses.
DOI:10.1371/journal.pone.0096321URLPMID:4011741 [本文引用: 1]
Scots pines (Pinus sylvestris L.) in the inner-Alpine dry valleys of Switzerland have suffered from increased mortality during the past decades, which has been caused by longer and more frequent dry periods. In addition, a proceeding replacement of Scots pines by pubescent oaks (Quercus pubescens Willd.) has been observed. In 2003, an irrigation experiment was performed to track changes by reducing drought pressure on the natural pine forest. After nine years of irrigation, we observed major adaptations in the vegetation and shifts in Scots pine fine root abundance and structure. Irrigation permitted new plant species to assemble and promote canopy closure with a subsequent loss of herb and moss coverage. Fine root dry weight increased under irrigation and fine roots had a tendency to elongate. Structural composition of fine roots remained unaffected by irrigation, expressing preserved proportions of cellulose, lignin and phenolic substances. A shift to a more negative 13C signal in the fine root C indicates an increased photosynthetic activity in irrigated pine trees. Using radiocarbon (14C) measurement, a reduced mean age of the fine roots in irrigated plots was revealed. The reason for this is either an increase in newly produced fine roots, supported by the increase in fine root biomass, or a reduced lifespan of fine roots which corresponds to an enhanced turnover rate. Overall, the responses belowground to irrigation are less conspicuous than the more rapid adaptations aboveground. Lagged and conservative adaptations of tree roots with decadal lifespans are challenging to detect, hence demanding for long-term surveys. Investigations concerning fine root turnover rate and degradation processes under a changing climate are crucial for a complete understanding of C cycling.
DOI:10.1111/1365-2745.12124URL
Optimal resource partitioning theory predicts that plants should increase the ratio between water absorbing and transpiring surfaces under short water supply. An increase in fine root mass and surface area relative to leaf area has frequently been found in herbaceous plants, but supporting evidence from mature trees is scarce and several results are contradictory.In 12 mature Fagus sylvatica forests across a precipitation gradient (820-540 mm yr-1), we tested several predictions of the theory by analysing the dependence of standing fine root biomass, fine root production and fine root morphology on mean annual precipitation (MAP), the precipitation of the study year, and stand structural and edaphic variables. The water storage capacity of the soil (WSC) was included as a covariable by comparing pairs of stands on sandy (lower WSC) and loam-richer soils (higher WSC).Fine root biomass, total fine root surface area, fine root production and the fine root : leaf biomass production ratio markedly increased with reduced MAP and precipitation in the study year, while WSC was only a secondary factor and stand structure had no effect.The precipitation effect on fine root biomass and production was more pronounced in stands on sandy soil with lower WSC, which had, at equal precipitation, a higher fine root biomass and productivity than stands on loam-richer soil.The high degree of allocational plasticity in mature F. sylvatica trees contrasts with a low morphological plasticity of the fine roots. On the more extreme sandy soils, a significant decrease in mean fine root diameter and increase in specific root area with decreasing precipitation were found; a similar effect was absent on the loam-richer soils.Synthesis. In support of optimal partitioning theory, mature Fagus sylvatica trees showed a remarkable allocational plasticity as a long-term response to significant precipitation reduction with a large increase in the size and productivity of the fine root system, while only minor adaptive modifications occurred in root morphology. More severe summer droughts in a future warmer climate may substantially alter the above-/below-ground C partitioning of this tree species with major implications for the forest C cycle.
DOI:10.3321/j.issn:1000-0933.2005.03.015URL [本文引用: 1]
根系生态位研究是全面掌握植物群落特性、种间搭配以及生态功能的重要科学问题,其测度方式、分布特征、影响因素等方面内容,对于合理指导退耕还林还草工程十分必要.将植物群落根系视为'标准地',分布于每个土体层次的每个径级根系视为'植物种',根量、根长、根数作为'植物种'的观测变量,仿照群落生态学方法,提出了一种综合计算根系生态位指数的方法.即将整个研究区域作为一个系统,将这一系统中所有植物群落,统一选用指标最大值,在纵向(即相对于指标维的不同指标)用上限效果测度公式统一进行归一化处理,然后在横向(土层、径级间,简称层径级)进行合并运算,得出层径级根系参数,这一参数定义为层径级根系生态位指数;而将某一群落各层径级生态位指数之和,定义为植物群落根系生态位指数,从而使区域内所有植物群落间具有可比性.使用这一方法,对国家退耕还林还草科技试验县--青海省大通县退耕地人工植物群落根系进行了系统研究.研究结果表明,根系生态位垂直空间分布大多数为典型的表层聚积型,表土层0～20cm根系生态位指数明显高于其它层次.植物群落根系比单一种群或纯林根系具有更高的生态位指数.根系生态位径级分布包括J型、反J型、S型和U型.J型多为粗根-深根型植物群落根系,反J型为细根-浅根型植物群落根系,S型和U型为上述2种类型之间的过渡型.根系生态位指数与植物群落地上部分鲜重生物量、根系丰富度呈显著正相关.退耕地植物群落根系的生态位指数较为接近天然植被,明显高于农作物根系.青海云杉+中国沙棘、中国沙棘、青海云杉等3种植物配置模式更有利于退耕地植物根系生态位的恢复.实施退耕还林还草工程是有效增加根系生态位、提高根系多方面功能的重要途径.
DOI:10.3321/j.issn:1000-0933.2005.03.015URL [本文引用: 1]
根系生态位研究是全面掌握植物群落特性、种间搭配以及生态功能的重要科学问题,其测度方式、分布特征、影响因素等方面内容,对于合理指导退耕还林还草工程十分必要.将植物群落根系视为'标准地',分布于每个土体层次的每个径级根系视为'植物种',根量、根长、根数作为'植物种'的观测变量,仿照群落生态学方法,提出了一种综合计算根系生态位指数的方法.即将整个研究区域作为一个系统,将这一系统中所有植物群落,统一选用指标最大值,在纵向(即相对于指标维的不同指标)用上限效果测度公式统一进行归一化处理,然后在横向(土层、径级间,简称层径级)进行合并运算,得出层径级根系参数,这一参数定义为层径级根系生态位指数;而将某一群落各层径级生态位指数之和,定义为植物群落根系生态位指数,从而使区域内所有植物群落间具有可比性.使用这一方法,对国家退耕还林还草科技试验县--青海省大通县退耕地人工植物群落根系进行了系统研究.研究结果表明,根系生态位垂直空间分布大多数为典型的表层聚积型,表土层0～20cm根系生态位指数明显高于其它层次.植物群落根系比单一种群或纯林根系具有更高的生态位指数.根系生态位径级分布包括J型、反J型、S型和U型.J型多为粗根-深根型植物群落根系,反J型为细根-浅根型植物群落根系,S型和U型为上述2种类型之间的过渡型.根系生态位指数与植物群落地上部分鲜重生物量、根系丰富度呈显著正相关.退耕地植物群落根系的生态位指数较为接近天然植被,明显高于农作物根系.青海云杉+中国沙棘、中国沙棘、青海云杉等3种植物配置模式更有利于退耕地植物根系生态位的恢复.实施退耕还林还草工程是有效增加根系生态位、提高根系多方面功能的重要途径.
[本文引用: 1]
[本文引用: 2]
DOI:10.1007/s12155-014-9550-5URL [本文引用: 2]
Determining the appropriate wastewater dose to supply nutrients while avoiding overirrigation is essential for achieving more balanced above- and belowground development of the plants, thereby ensuring high filtering functionality of a willow vegetation filter system. Aboveground biomass and root development of a 3-year-old willow vegetation filter in response to three increasing doses of secondary-treated urban wastewater under both fertilized and unfertilized conditions were evaluated. Fine, coarse and total root biomass, fine root length density (FRLD), specific fine root length (SFRL) and specific root area (SRA) were assessed in soil core samples collected at four different depths (0–20, 20–40, 40–60 and 60–8002cm) in all treatments. While aboveground biomass increased as wastewater amounts and fertilization increased (from 23.8902Mg02hain non-irrigated condition to 47.0702Mg02hain the highest wastewater dose, from 31.502Mg02hain unfertilized plots to 40.102Mg02hain the fertilized), total and fine root biomass decreased when willow was irrigated with the highest wastewater dose (i.e. total root biomass is 2.5402Mg02hain non-irrigated condition—1.3602Mg02hain the highest wastewater dose). The root biomass did not follow the same development pattern, and a significant decrease in fine root biomass was observed when the highest irrigation dose was applied. In these circumstances, we believe that the supply in water and nutrient is sufficient to the development of the willows which react by diminishing the amount of roots proportionally to the aboveground parts. This may lead to a higher transpiration rate and allow willows to avoid a surplus of water in the soil.
DOI:10.1016/j.ecoleng.2015.11.020URL [本文引用: 1]
In order to study the spatial and seasonal variation characteristics of fine roots in a salinization area, we examined three configuration modes through soil samples collected via soil drilling. Fine roots biomass (FRB) showed significant differences among the different modes. Significant differences of FRB were observed at a soil depth of 0–6002cm in the three modes ( p 02<020.05). More than 60% of FRB were concentrated in the soil depth range between 0 and 2002cm, and decreased exponentially as soil depth increased. Specific root length (SRL) and fine root length density (FRLD) showed a similar vertical distribution pattern to the FRB. In all three modes, FRB showed significant seasonal differences ( p 02<020.05). FRB was highest in July, and showed the bimodal variation, while monthly variation of FRB in the root diameter range of Φ 02≤02202mm and 202mm02<02 Φ 02≤02502mm showed significant positive correlations ( p 02<020.05). Total FRB was highest in the tree-shrub stand model (TSSM). Due to the effect of salinity, FRB showed significant differences in different soil depths and resulted in FRB spatial niche separation. We found that high salt content salt had an obvious inhibitory effect on the distribution of FRB. Therefore, salinity should be below 1.502mS/cm, which was conducive the growth of plant roots. The results indicated that TSSM had the highest FRB, SRL, and FRLD, and may have the strongest effect on salt suppression and salt control in saline-alkali land.
DOI:10.5194/bg-10-8129-2013URL [本文引用: 1]
Water availability has profound effects on plant growth and productivity in temperate and semiarid grasslands. However, it remains unclear how variation of inter-annual precipitation by extreme rainfall events will alter the aboveground and belowground responses of plants, and how these responses may be contingent on N availability. In this study, we examined the interactive effects of inter-annual precipitation variation and N addition on aboveground and live fine root biomass of a semiarid grassland in northern China for two consecutive years (2007 and 2008). Inter-annual variation in precipitation resulting mainly from the occurrence of extreme rainfall events in 2008 significantly affected above-and belowground plant biomass responses to water addition. In addition, variation of inter-annual precipitation by this extreme rainfall event suppressed plant responses to nitrogen addition and reduced the interaction effects between water and nitrogen addition. These effects of inter-annual precipitation fluctuation could be attributed to the negative influence of the extreme rainfall event on soil N and water availability, ultimately reducing plant rainfall use efficiency and nitrogen use efficiency. In conclusion, our results suggest ecosystem responses to water and N enrichment could be altered by inter-annual variation of precipitation regime caused by the naturally occurring extreme rainfall events.
DOI:10.1111/efp.12005URL [本文引用: 1]
Summary A rain shelter experiment was conducted in a 90-year-old Norway spruce stand, in the Kysucké Beskydy Mts (Slovakia). Three rain shelters were constructed in the stand to prevent the rainfall from reaching the soil and to reduce water availability in the rhizosphere. Fine root biomass and necromass were repeatedly measured throughout a growing season by soil coring. We established the quantities of fine root biomass (live) and necromass (dead) at soil depths of 0–5, 5–15, 15–25 and 25–35cm. Significant differences in soil moisture contents between control and drought plots were found in the top 15cm of soil after 20weeks of rainfall manipulation (lasting from early June to late October). Our observations show that even relatively light drought decreased total fine root biomass from 272.0 to 242.8gm 612 and increased the amount of necromass from 79.2 to 101.2gm 612 in the top 35cm of soil. Very fine roots (VFR), that is, those with diameter up to 1mm, were more affected than total fine roots defined as 0–2mm. The effect of reduced water availability was depth-specific; as a result, we observed a modification of vertical distribution of fine roots. More roots in drought treatment were produced in the wetter soil horizons at 25–35cm depth than at the surface. We conclude that fine and VFR systems of Norway spruce have the capacity to re-allocate resources to roots at different depths in response to environmental signals, resulting in changes in necromass to biomass ratio.
DOI:10.1016/S0929-1393(02)00093-8URL
Mesocosms from two subarctic heaths from high and low altitudes, respectively, and differing in the composition of vegetation were experimentally subjected to 18 diurnal freeze–thaw cycles fluctuating between day temperatures of +2 °C and night temperatures of –4 °C. Mesocosm respiration was consistently lower and higher in cycled mesocosms compared to mesocosms kept unfrozen (+2 °C) and frozen (–4 °C) , respectively. When extrapolated to the entire non-growing season, our data suggest a non-growing season carbon (C) loss in the order of 20–30 g C m 612, which is substantial compared with a likely annual incorporation of plant biomass C of 150–200 g C m 612 per year. The results support the hypothesis that winter carbon fluxes must be included in annual carbon budgets for arctic ecosystems. Microbial biomass C decreased only in cycled mesocosms, indicating that while microbial activity is mainly controlled by temperature, microbial biomass is strongly affected by temperature fluctuations around the freezing point. In contrast to microbial C, microbial biomass nitrogen (N) mass did not change in cycled mesocosms, leading to decreased microbial C to N ratio. Second, soil inorganic N concentration declined in the soils subjected to the cycles, showing that microbes surviving the freeze–thaw cycles had a high potential for sequestering soil N and N that presumably was released from dead microbes. The two sets of mesocosms responded very similarly to the freeze–thaw cycles, indicating that the observed responses to multiple diurnal freeze–thaw cycles are common for both ecosystem types despite the differences in plant species composition and climate.
DOI:10.1371/journal.pone.0081359URLPMID:24244738 [本文引用: 1]
Natural forest succession often affects soil physical and chemical properties. Selected physical and chemical soil properties were studied in an old-growth forest across a forest successional series in Dinghushan Nature Reserve, Southern China.The aim was to assess the effects of forest succession change on soil properties. Soil samples (0-20 cm depth) were collected from three forest types at different succession stages, namely pine (Pinus massoniana) forest (PMF), mixed pine and broadleaf forest (PBMF) and monsoon evergreen broadleaf forest (MEBF), representing early, middle and advanced successional stages respectively. The soil samples were analyzed for soil water storage (SWS), soil organic matter (SOM), soil microbial biomass carbon (SMBC), pH, NH4 (+)-N, available potassium (K), available phosphorus (P) and microelements (available copper (Cu), available zinc (Zn), available iron (Fe) and available boron (B)) between 1999 and 2009. The results showed that SWS, SOM, SMBC, Cu, Zn, Fe and B concentrations were higher in the advanced successional stage (MEBF stage). Conversely, P and pH were lower in the MEBF but higher in the PMF (early successional stage). pH, NH4 (+)-N, P and K declined while SOM, Zn, Cu, Fe and B increased with increasing forest age. Soil pH was lower than 4.5 in the three forest types, indicating that the surface soil was acidic, a stable trend in Dinghushan.These findings demonstrated significant impacts of natural succession in an old-growth forest on the surface soil nutrient properties and organic matter. Changes in soil properties along the forest succession gradient may be a useful index for evaluating the successional stages of the subtropical forests. We caution that our inferences are drawn from a pseudo-replicated chronosequence, as true replicates were difficult to find. Further studies are needed to draw rigorous conclusions regarding on nutrient dynamics in different successional stages of forest.
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为探究福建东南沿海不同人工林砂质土壤微生物生物量碳(MBC)和生物量氮(MBN)及其影响因子,以肯氏相思(Acaica cunninghamia)、纹荚相思(Acacia aulacocarpa)和木麻黄(Casuarina equisetifolia)人工林为对象,采用通径分析模型,分析土壤微生物量对土壤理化性质、凋落物和细根生物量的响应。结果显示:3种人工林土壤MBC和MBN质量分数分别为42.60~51.56和5.38~6.88 mg·kg~(-1),且木麻黄的MBC和MBN质量分数均显著高于纹荚相思和肯氏相思(P0.05)。土壤w(MBC)∶w(MBN)为7.49~7.98;微生物碳熵(w(MBC)∶w(SOC))和氮熵(w(MBN)∶w(TN))的变化范围分别为1.09%~1.17%和1.34%~1.50%。Pearson相关分析表明,MBC、MBN质量分数与DOC、SOC、TN、凋落物生物量和细根生物量呈极显著正相关(P0.01)。通径分析表明,影响土壤MBC最重要的因子是细根生物量,其次是SOC;影响土壤MBN最重要的因素是细根生物量,其次是凋落物生物量。3种人工林的MBC和MBN质量分数、微生物碳氮熵与国内多数森林土壤相比均处于较低水平。
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为探究福建东南沿海不同人工林砂质土壤微生物生物量碳(MBC)和生物量氮(MBN)及其影响因子,以肯氏相思(Acaica cunninghamia)、纹荚相思(Acacia aulacocarpa)和木麻黄(Casuarina equisetifolia)人工林为对象,采用通径分析模型,分析土壤微生物量对土壤理化性质、凋落物和细根生物量的响应。结果显示:3种人工林土壤MBC和MBN质量分数分别为42.60~51.56和5.38~6.88 mg·kg~(-1),且木麻黄的MBC和MBN质量分数均显著高于纹荚相思和肯氏相思(P0.05)。土壤w(MBC)∶w(MBN)为7.49~7.98;微生物碳熵(w(MBC)∶w(SOC))和氮熵(w(MBN)∶w(TN))的变化范围分别为1.09%~1.17%和1.34%~1.50%。Pearson相关分析表明,MBC、MBN质量分数与DOC、SOC、TN、凋落物生物量和细根生物量呈极显著正相关(P0.01)。通径分析表明,影响土壤MBC最重要的因子是细根生物量,其次是SOC;影响土壤MBN最重要的因素是细根生物量,其次是凋落物生物量。3种人工林的MBC和MBN质量分数、微生物碳氮熵与国内多数森林土壤相比均处于较低水平。
DOI:10.1016/j.scitotenv.2016.08.116URLPMID:27693152 [本文引用: 1]
61We measured fine root biomass and decomposition using combined experiment of simulated drought and warming.61Effects of throughfall reduction on fine root biomass and decomposition depended on soil temperature.61Fine root biomass and decomposition increased under single climate treatment.61Under simultaneous soil warming, fine root biomass and fine root decomposition were suppressed by throughfall reduction.
DOI:10.13287/j.1001-9332.201702.028URL
以川西亚高山云杉人工林林地土壤为对象,采用磷脂脂肪酸（PLFA）法研究了4种不同林龄（50、38、27和20年）的人工林土壤微生物多样性和群落结构特征。结果表明：随着林龄的增加,土壤有机碳和全氮含量逐步增加;土壤微生物Shannon多样性和Pielou均匀度则呈现先增后减的趋势。土壤微生物总PLFAs量、细菌PLFAs量、真菌PLFAs量、放线菌PLFAs量以及丛枝菌根真菌PLFAs量均表现为随林龄的增加而增加。主成分分析（PCA）表明,不同林龄人工林的土壤微生物群落结构之间存在显著差异,其中,第1主成分（PC1）和第2主成分（PC2）共同解释了土壤微生物群落结构总变异的66.8%。冗余分析（RDA）表明,对土壤微生物群落结构产生显著影响的环境因子分别为土壤有机碳、全氮、全钾以及细根生物量。随着人工造林时间的延长,土壤肥力和微生物生物量得以增加,森林生态系统的恢复进程稳定。
DOI:10.13287/j.1001-9332.201702.028URL
以川西亚高山云杉人工林林地土壤为对象,采用磷脂脂肪酸（PLFA）法研究了4种不同林龄（50、38、27和20年）的人工林土壤微生物多样性和群落结构特征。结果表明：随着林龄的增加,土壤有机碳和全氮含量逐步增加;土壤微生物Shannon多样性和Pielou均匀度则呈现先增后减的趋势。土壤微生物总PLFAs量、细菌PLFAs量、真菌PLFAs量、放线菌PLFAs量以及丛枝菌根真菌PLFAs量均表现为随林龄的增加而增加。主成分分析（PCA）表明,不同林龄人工林的土壤微生物群落结构之间存在显著差异,其中,第1主成分（PC1）和第2主成分（PC2）共同解释了土壤微生物群落结构总变异的66.8%。冗余分析（RDA）表明,对土壤微生物群落结构产生显著影响的环境因子分别为土壤有机碳、全氮、全钾以及细根生物量。随着人工造林时间的延长,土壤肥力和微生物生物量得以增加,森林生态系统的恢复进程稳定。
DOI:10.1111/j.1744-7429.2004.tb00322.xURL [本文引用: 1]
Interest in tropical secondary forests has grown as large areas of agriculture have been abandoned in recent decades; yet, there are few long-term studies of post-agriculture vegetation recovery in the tropics. In this study, we compared the vegetation structure and floristic composition of old-growth and 40-year-old secondary riparian forests in the Cordillera Central, Dominican Republic. Canopy height and stem density of woody plants were similar between forest types, but basal area of trees was 27 percent lower in secondary forests. Introduced tree species comprised 20 percent of the basal area and dominated the understory of secondary forests. Life-form diversity was higher in old-growth forests as arborescent ferns, the palm species, and epiphytic bromeliads, orchids, and bryophytes were much more abundant. The number of species of epiphytic orchids and bromeliads, ground ferns, and herbaceous plants was also significantly higher in old-growth forests. The species density of woody plants and vines, however, was comparable between forest types, and vine abundance was significantly higher in secondary forests. The high importance of introduced tree species and the delayed recovery of several plant life-forms have important implications for the conservation of plant diversity in secondary forests in the tropics. The robust regeneration of woody structure despite the long land tenure (ca 60 yr) by farmers is probably due to the nutrient-rich alluvial soils and low-intensity agriculture. This study revealed the potential for the rapid recovery of woody plant diversity and structure in fertile secondary forests adjacent to mature forest seed sources and the more delayed recovery of nonwoody plant diversity and abundance. RESUMEN El inter0108s por los bosques tropicales secundarios ha crecido debido a que grandes extensiones de 0103reas agricolas han sido abandonadas en las 0102ltimas d0108cadas. Aun asi, en los tr0106picos hay pocos estudios a largo plazo sobre la recuperaci0106n de la vegetati0106n de zonas agricolas abandonadas. En nuestro estudio, comparamos la estructura de la vegetaci0106n y la composici0106n floristica de bosques ribere01±os maduros y bosques de 40 a01±os de edad en la Cordillera Central de Rep0102blics Dominicana. La altura del dosel y la densidad de tallos de plantas le01±osas fueron similares en los distintos tipos de bosque, pero el 0103rea basal de los 0103rboles fue 27 por ciento m0103s baja en los bosques secundarios. Las especies arb6reas introducidas representaron 20 por ciento del 0103rea basal y dominaron el sotobosque de los bosques secundarios. La diversidad de formas de vida fue m0103s alta en los bosques maduros, debido a que los helechos arborescentes, las palmas, bromelias, orquideas, y musgos epifitos fueron mucho m0103s abundantes. El numero de especies de orquideas y bromelias epifitas, helechos de tierra y de plantas herb0103ceas fue significativamente m0103s alta en los bosques maduros. Sin embargo, el n0102meros de especies le01±osas y de bejucos fue comparable en los dos tipos de bosque, mientras que la abundancia de bejucos fue significativamente mayor en los bosques secundarios. La gran importancia de las especies arb0106reas ex0106ticas y la lenta recuperati0106n de varias formas de vida vegetal, llevan implicaciones importantes para la conservati0106n de la diversidad de plantas en bosques tropicales secundarios. La regenerati0106n vigorosa de la estructura le01±osa, a pesar de la larga ocupaci0106n de estas tierras por los granjeros ( ca 60 a01±os) se debe, probablemente, a la riqueza de nutrientes del suelo en los terrenos aluviales y a la agricultura de baja intensidad que se practicaba en la zona. Este estudio demuestra el potential para una recuperaci0106n r0103pida de la diversidad y estructura de la vegetaci0106n le01±osa en bosques secundarios f0108rtiles que colindan con fuentes de semilla ubicadas en bosques maduros, y la recuperaci0106n m0103s lenta de la diversidad y abundancia de plantas no le01±osas.
DOI:10.2307/1938874URL [本文引用: 2]
Standing crop, rates of production, mortality, decomposition, and nitrogen dynamics of two size classes of fine roots (0-05 mm and 0.5-3.0 mm diameter) were estimated for 1 yr in a 53-yr-old red pine (Pinus resinosa Ait.) plantation and in an adjacent 80-yr-old mixed hardwood stand in north-central Massachusetts. Dry matter of live fine roots was higher in the hardwoods (mean = 6.1 Mg/ha; annual range 3.6-8.6 Mg/ha) than in the plantation (mean = 5.1 Mg/ha; annual range 2.5-7.8 Mg/ha.) Dead root mass was similar in the hardwoods (mean = 4.4 Mg/ha) and the plantation (mean = 4.0 Mg/ha). Nitrogen standing crop of live roots in the hardwoods was higher than in the plantation (mean = 65 kg/ha and 42 kg/ha, respectively). Net fine root production was estimated from changes in standing crop. Production estimates ranged from 4.1 to 11.4 Mg in the hardwoods and from 3.2 to 10.9 1 in the plantation, depending on the assumptions made in the calculations. Concurrent estimates of total nitrogen requirement for this production ranged from 73 to 184 kg@?ha^-^1@?yr^-^1 in the hardwoods and from 44 to 122 kg@?ha^-^1@?yr^-^1 in the plantation. Decomposition, measured as mass loss from buried cloth bags, was @?20% in 0.4-mm mesh bags and as high as 47% in 3-mm mesh bags after 1 yr. Integrating production and nitrogen requirements with estimates of decomposition rates and nitrogen mineralization for these ecosystems suggested that the lower estimates of production are more accurate.
DOI:10.1111/nph.13363URLPMID:25756288
Fine roots acquire essential soil resources and mediate biogeochemical cycling in terrestrial ecosystems. Estimates of carbon and nutrient allocation to build and maintain these structures remain uncertain because of the challenges of consistently measuring and interpreting fine-root systems. Traditionally, fine roots have been defined as all roots 2 mm in diameter, yet it is now recognized that this approach fails to capture the diversity of form and function observed among fine-root orders. Here, we demonstrate how order-based and functional classification frameworks improve our understanding of dynamic root processes in ecosystems dominated by perennial plants. In these frameworks, fine roots are either separated into individual root orders or functionally defined into a shorter-lived absorptive pool and a longer-lived transport fine-root pool. Using these frameworks, we estimate that fine-root production and turnover represent 22% of terrestrial net primary production globally - a c. 30% reduction from previous estimates assuming a single fine-root pool. Future work developing tools to rapidly differentiate functional fine-root classes, explicit incorporation of mycorrhizal fungi into fine-root studies, and wider adoption of a two-pool approach to model fine roots provide opportunities to better understand below-ground processes in the terrestrial biosphere.
DOI:10.1007/s10457-010-9303-1URL [本文引用: 2]
In South-east Asia, ENSO-related droughts represent irregularly occurring hazards for agroforestry systems containing cocoa which are predicted to increase in severity with expected climate warming. To characterize the drought response of mature cocoa trees, we conducted the Sulawesi Throughfall Displacement Experiment in a shaded ( Gliricidia sepium ) cocoa agroforestry system in Central Sulawesi, Indonesia. Three large sub-canopy roofs were installed to reduce throughfall by about 80% over a 13-month period to test the hypotheses that (i) cocoa trees are sensitive to drought due to their shallow fine root system, and (ii) bean yield is more sensitive to drought than leaf or stem growth. As 83% of fine root (diameter 2mm) was located in the upper 40cm of the soil, the cocoa trees examined had a very shallow root system. Cocoa and Gliricidia differed in their vertical rooting patterns, thereby reducing competition for water. Despite being exposed for several months to soil water contents close to the conventional wilting point, cocoa trees showed no significant decreases in leaf biomass, stem and branch wood production or fine root biomass. Possible causes are active osmotic adjustment in roots, mitigation of drought stress by shading from Gliricidia or other factors. By contrast, production of cocoa beans was significantly reduced in the roof plots, supporting reports of substantial reductions in bean yields during ENSO-related drought events in the region. We conclude that cocoa possesses traits related to drought tolerance which enable it to maintain biomass production during extended dry periods, whereas bean yield appears to be particularly drought sensitive.
DOI:10.1111/gcb.12424URLPMID:24115242 [本文引用: 1]
Climate change scenarios predict increases in the frequency and duration of ENSO-related droughts for parts of South-East Asia until the end of this century exposing the remaining rainforests to increasing drought risk. A pan-tropical review of recorded drought-related tree mortalities in more than 100 monitoring plots before, during and after drought events suggested a higher drought-vulnerability of trees in South-East Asian than in Amazonian forests. Here, we present the results of a replicated (n = 3 plots) throughfall exclusion experiment in a perhumid tropical rainforest in Sulawesi, Indonesia. In this first large-scale roof experiment outside semihumid eastern Amazonia, 60% of the throughfall was displaced during the first 8 months and 80% during the subsequent 17 months, exposing the forest to severe soil desiccation for about 17 months. In the experiment's second year, wood production decreased on average by 40% with largely different responses of the tree families (ranging from 100 to +100% change). Most sensitive were trees with high radial growth rates under moist conditions. In contrast, tree height was only a secondary factor and wood specific gravity had no influence on growth sensitivity. Fine root biomass was reduced by 35% after 25 months of soil desiccation while fine root necromass increased by 250% indicating elevated fine root mortality. Cumulative aboveground litter production was not significantly reduced in this period. The trees from this Indonesian perhumid rainforest revealed similar responses of wood and litter production and root dynamics as those in two semihumid Amazonian forests subjected to experimental drought. We conclude that trees from paleo- or neotropical forests growing in semihumid or perhumid climates may not differ systematically in their growth sensitivity and vitality under sublethal drought stress. Drought vulnerability may depend more on stem cambial activity in moist periods than on tree height or wood specific gravity.
DOI:10.1007/s10021-008-9152-1URL
Secondary forests are becoming increasingly widespread in the tropics, but our understanding of how secondary succession affects carbon (C) cycling and C sequestration in these ecosystems is limited. We used a well-replicated 80-year pasture to forest successional chronosequence and primary forest in Puerto Rico to explore the relationships among litterfall, litter quality, decomposition, and soil C pools. Litterfall rates recovered rapidly during early secondary succession and averaged 10.5 (± 0.1 SE) Mg/ha/y among all sites over a 2-year period. Although forest plant community composition and plant life form dominance changed during succession, litter chemistry as evaluated by sequential C fractions and by 0106C-nuclear magnetic resonance spectroscopy did not change significantly with forest age, nor did leaf decomposition rates. Root decomposition was slower than leaves and was fastest in the 60-year-old sites and slowest in the 10-and 30-year-old sites. Common litter and common site experiments suggested that site conditions were more important controls than litter quality in this chronosequence. Bulk soil C content was positively correlated with hydrophobic leaf compounds, suggesting that there is greater soil C accumulation if leaf litter contains more tannins and waxy compounds relative to more labile compounds. Our results suggest that most key C fluxes associated with litter production and decomposition re-establish rapidly:— within a decade or two— during tropical secondary succession. Therefore, recovery of leaf litter C cycling processes after pasture use are faster than aboveground woody biomass and species accumulation, indicating that these young secondary forests have the potential to recover litter cycling functions and provide some of the same ecosystem services of primary forests.
DOI:10.1890/02-3154URL [本文引用: 1]
Vascular plants are generally assumed to have no photosynthetic activity under the snow because of the severity of the subnivean environment. In the arctic tundra, snow cover persists into the spring after air temperatures and light increase to levels suitable for photosynthesis of vascular plants in the absence of snow cover. We found significant photosynthetic activity in four arctic evergreen species under springtime snow. This activity was facilitated by favorable conditions in the subnivean environment, where CO2 concentrations are elevated, temperatures are often above freezing, and light levels are sufficient to drive photosynthesis. Diurnal changes in CO2 concentration under the snow and light responses of snow-covered ecosystem CO2 fluxes provide supporting evidence of carbon gain at the ecosystem level. This activity allows evergreens to rapidly increase photosynthesis upon snowmelt and reduces wintertime losses of carbon from arctic ecosystems. The loss of these species under predicted scenarios of climate change could have serious implications for tundra carbon balance, potentially increasing carbon losses.
DOI:10.1016/S0038-0717(01)00199-7URL [本文引用: 1]
Knowledge of microbial numbers and activity in subsoils is essential for understanding the transformation and downward movement of natural and synthetic organics. Soil cores were taken from two soil profiles (surface textures: silty clay loam and loamy sand), and samples extracted from the 0–30 cm (surface), 1.0–1.3 m (mid) and 2.7–3.0 m (deep; clay) and 3.9–4.2 m (deep; sand) layers. A variety of soil biotic (microbial numbers, microbial biomass, enzyme activities) and abiotic properties (pH, organic C, texture, CEC) were measured. Bacterial numbers decreased with depth as indicated by viable counts and by calculations based upon biomass carbon and extracted DNA. Direct microscopic counts were the most sensitive method of enumeration and gave bacterial numbers between 37 and 442× greater than colony forming units and those calculated from DNA extracted from soil. DNA extracted from soil ranged from 1.23 (sand surface) and 1.34 (clay surface) μg g 611 d wt soil to 0.02 (sand deep) and 0.01 (clay deep) μg g 611 d wt soil. Bacterial numbers, estimated from biomass-C measurements, were comparable to direct counts. Large numbers of bacteria were recorded in the subsoils (direct counts: 5.6×10 8 sand, 4.5×10 8 clay) even though this was equivalent to only 4.7 and 1.7% of those in the surface soils. Fungi were isolated from surface and mid-depth layers of both soils but were absent from the deep soil samples. Enzymatic activities (arylsulphatase, β-glucosidase, phosphomonoesterases, urease, dehydrogenase, FDA hydrolysis), assayed with or without buffers, also decreased with depth. The exception was urease activity in the clay soil where no difference was seen between mid and deep in non-buffered assays but a 2.9-fold greater activity was exhibited in the mid than in the surface soil when buffered. Strong positive correlations ( R>0.95) were observed between all enzyme activities (except with urease activity in clay soil and non-buffered phosphatase activity in sand soil) and between all methods of estimating bacterial abundance. Strong positive correlations ( R>0.90) were also found between bacterial abundance and enzyme activities and between enzyme activities and organic matter content.
DOI:10.1111/gcb.12082URLPMID:23504850 [本文引用: 1]
Climate change is expected to impact the amount and distribution of precipitation in the arid southwestern United States. In addition, nitrogen (N) deposition is increasing in these regions due to increased urbanization. Responses of belowground plant activity to increases in soil water content and N have shown inconsistent patterns between biomes. In arid lands, plant productivity is limited by water and N availability so it is expected that changes in these factors will affect fine root dynamics. The objectives of this study were to quantify the effects of increased summer precipitation and N deposition on fine root dynamics in a Mojave Desert ecosystem during a 2-year field experiment using minirhizotron measurements. Root length density, production, and mortality were measured in field plots in the Mojave Desert receiving three 25 mm summer rain events and/or 40 kg N ha1. Increased summer precipitation and N additions did not have an overall significant effect on any of the measured root parameters. However, differences in winter precipitation resulting from interannual variability in rainfall appeared to affect root parameters with root production and turnover increasing following a wet winter most likely due to stimulation of annual grasses. In addition, roots were distributed more deeply in the soil following the wet winter. Root length density was initially higher under canopies compared to canopy interspaces, but converged toward the end of the study. In addition, roots tended to be distributed more deeply into the soil in canopy interspace areas. Results from this study indicated that increased summer precipitation and N deposition in response to climate change and urbanization are not likely to affect fine root dynamics in these Mojave Desert ecosystems, despite studies showing aboveground plant physiological responses to these environmental perturbations. However, changes in the amount and possibly distribution of winter precipitation may affect fine root dynamics.
URL [本文引用: 1]
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DOI:10.1080/07352689.2010.483579URL [本文引用: 1]
Fine roots <2 mm in diameter play a key role in regulating the biogeochemical cycles of ecosystems and are important to our understanding of ecosystem responses to global climate changes. Given the sensitivity of fine roots, especially in boreal region, to climate changes, it is important to assess whether and to what extent fine roots in this region change with climates. Here, in this synthesis, a data set of 218 root studies were complied to examine fine root patterns in the boreal forest in relation to site and climatic factors. The mean fine root biomass in the boreal forest was 5.28 Mg ha611, and the production of fine roots was 2.82 Mg ha611 yr611, accounting for 32% of annual net primary production of the boreal forest. Fine roots in the boreal forest on average turned over 1.07 times per year. Fine roots contained 50.9 kg ha611 of nitrogen (N) and 3.63 kg ha611 of phosphorous (P). In total, fine roots in the boreal forest ecosystems contain 6.1 × 107 Mg N and 4.4×106Mg P pools, respectively, about 10% of the global nutrients of fine roots. Fine root biomass, production, and turnover rate generally increased with increasing mean annual temperature and precipitation. Fine root biomass in the boreal forest decreased significantly with soil N and P availability. With increasing stand age, fine root biomass increased until about 100 years old for forest stands and then leveled off or decreased thereafter. These results of meta analysis suggest that environmental factors strongly influence fine root biomass, production, and turnover in boreal forest, and future studies should place a particular emphasis on the root-environment relationships.
DOI:10.13348/j.cnki.sjlyyj.2014.04.002URL [本文引用: 3]
未来气候变化预示着降雨时间和数量的变化。降雨是干旱半干旱地区最重要的水分来源，降雨格局的变化将直接影响该区域生态系统的稳定性，而土壤微生物作为敏感指标多用来监测生态系统的稳定性。文中综述了降雨对干旱半干旱地区土壤微生物生物量、多样性的直接影响，以及其通过改变土壤水分、土壤空气和植被生长等对土壤微生物产生的间接影响，其中还可能伴随着其他因素的干扰，如土地利用方式、温度、海拔等。通过了解降雨格局变化对干旱半干旱地区土壤微生物的影响，可以更好地预测未来气候变化对该地区生态稳定性的影响。指出了降雨对干旱半干旱地区土壤微生物影响研究中存在的问题，并对未来研究进行了展望。
DOI:10.13348/j.cnki.sjlyyj.2014.04.002URL [本文引用: 3]
未来气候变化预示着降雨时间和数量的变化。降雨是干旱半干旱地区最重要的水分来源，降雨格局的变化将直接影响该区域生态系统的稳定性，而土壤微生物作为敏感指标多用来监测生态系统的稳定性。文中综述了降雨对干旱半干旱地区土壤微生物生物量、多样性的直接影响，以及其通过改变土壤水分、土壤空气和植被生长等对土壤微生物产生的间接影响，其中还可能伴随着其他因素的干扰，如土地利用方式、温度、海拔等。通过了解降雨格局变化对干旱半干旱地区土壤微生物的影响，可以更好地预测未来气候变化对该地区生态稳定性的影响。指出了降雨对干旱半干旱地区土壤微生物影响研究中存在的问题，并对未来研究进行了展望。
DOI:10.13287/j.1001-9332.201609.023URL [本文引用: 1]
在福建三明陈大国有采育场杉木幼苗小区,采用土钻法和内生长环法,以非隔离降水为对照,对隔离降水50%处理一年的杉木幼苗细根生物量和形态、化学计量学、比根呼吸、非结构性碳水化合物等功能特征进行研究.结果表明：与对照相比,隔离降水处理0～1 mm细根生物量显著降低,1～2 mm细根生物量差异不显著;隔离降水导致细根在形态上发生了适应性变化,0～1 mm和1～2 mm细根比根长分别增加21.1%和30.5%,0～1 mm细根组织密度显著降低,而比表面积显著增加.隔离降水导致细根氮的富集,但限制了对磷的吸收,氮磷比升高,导致营养失衡;隔离降水没有显著改变细根比根呼吸和非结构性碳水化合物含量,但导致1～2 mm细根可溶性糖、糖淀比显著降低,淀粉含量增加33.3%,表明其通过增加非结构性碳水化合物贮存比例以应对降水减少.
DOI:10.13287/j.1001-9332.201609.023URL [本文引用: 1]
在福建三明陈大国有采育场杉木幼苗小区,采用土钻法和内生长环法,以非隔离降水为对照,对隔离降水50%处理一年的杉木幼苗细根生物量和形态、化学计量学、比根呼吸、非结构性碳水化合物等功能特征进行研究.结果表明：与对照相比,隔离降水处理0～1 mm细根生物量显著降低,1～2 mm细根生物量差异不显著;隔离降水导致细根在形态上发生了适应性变化,0～1 mm和1～2 mm细根比根长分别增加21.1%和30.5%,0～1 mm细根组织密度显著降低,而比表面积显著增加.隔离降水导致细根氮的富集,但限制了对磷的吸收,氮磷比升高,导致营养失衡;隔离降水没有显著改变细根比根呼吸和非结构性碳水化合物含量,但导致1～2 mm细根可溶性糖、糖淀比显著降低,淀粉含量增加33.3%,表明其通过增加非结构性碳水化合物贮存比例以应对降水减少.
URL
【Objective】Seven natural stand types were investigated to understand the soil microbial community. The main forest species were Picea crassifolia,Betula platyphylla,Larix gmelinii,Populus davidiana. The purpose of this study was to improve management and evaluation strategies of the forest by adjusting the structure and restoring the degraded forest. 【Method 】The 7 stand types were Datong Picea crassifolia(A),Datong Betula platyphylla(B),Huangzhong Picea crassifolia + Betula platyphylla(C),Ledu Larix gmelinii + Betula platyphylla(D),Minhe Populus davidiana(E),Xunhua Populus davidiana + Betula platyphylla(F),and Jianzha Picea crassifolia(G) in Qinghai Province. The soil physical-chemical properties and soil microbial community composition were investigated by conventional laboratory analysis and phospholipid fatty acids(PLFAs) analysis. Changes of individual PLFA signatures and correlations between soil properties and soil microbial group of PLFA indicators were analyzed by principal components analysis(PCA) and redundancy analysis(RDA),respectively. 【Result】A total of 17 different PLFAs with different types of biomarkers were detected in the soil samples among different stand types. The stand types A and B exhibited alarger number PLFAs compared with other stand types. The lowest number of PLFAs was found in stand type G. The PLFAs biomarker was variable in different stand soils. The highest content was 16: 0. The highest richness of PLFAs was saturated fatty acid. The highest total content of PLFAs biomarkers was found in stand B,and the lowest in stand G. The contents of bacteria and fungus PLFAs displayed the following order: broad-leaved stand mixed broadleaf-conifer stand conifer stand. The Simpson index,Shannon-Wiener index of stands F and G were significantly lower than those of the other stand types. McIntosh index were holistically higher in stand types A,B and D than in the other types. Principal Component Analysis(PCA) showed that generalized bacteria and Gram positive bacteria were the main soil microbial group. Redundancy analysis(RDA) indicated that the effects of pH,soil moisture and fine root biomass on soil microbial community were higher than those of soil organic carbon,bulk density and litter standing crop. 【Conclusion 】Soil microbial community composition and impact factors were significantly different among different stand types. Therefore,the management and utilization of forest ecosystem should consider the change of soil microbial community characteristics,in order to improve forest management practices.
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... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
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... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
... id="C4">细根的生产力和周转率占全球陆地净初级生产力的22% (
... id="C18">在增加降水实验中, 短期(≤1年)根长度密度显著增加, 而1年以上的中期和长期根长度密度变化不显著(
Long- and short-term precipitation effects on soil CO2 efflux and total belowground carbon allocation
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... id="C4">细根的生产力和周转率占全球陆地净初级生产力的22% (
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The influence of seasonality and species effects on surface fine roots and nodulation in tropical legume tree plantations
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... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
西藏砂生槐根系生物量、比根长和根长密度
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... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
The meta-analysis of response ratios in experimental ecology
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... id="C10">其中Xt为处理组平均值, XC为对照组平均值(
Nine years of irrigation cause vegetation and fine root shifts in a water-limited pine forest
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... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
Fine root biomass and dynamics in beech forests across a precipitation gradient—Is optimal resource partitioning theory applicable to water-limited mature trees?
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退耕地人工植物群落根系生态位及其分布特征
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... id="C16">不同植物对营养的需求和碳分配策略均有所不同, 导致细根在响应降水变化时表现出差异性(
退耕地人工植物群落根系生态位及其分布特征
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... id="C16">不同植物对营养的需求和碳分配策略均有所不同, 导致细根在响应降水变化时表现出差异性(
Vertical distribution of fine roots of
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... id="C17">土壤水分含量直接影响细根的垂直分布, 表现出生态位分离(
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... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
... ;
Willow root development and morphology changes under different irrigation and fertilization regimes in a vegetation filter
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... id="C8">首先, 根据实验目的进行数据分组.将植物类型划分为热带乔木、亚热带乔木、温带乔木、北方乔木、灌木和草本植物.按实验持续时间划分为短期(<1年)、中期(1-3年)和长期实验(>3年).本文将增加和减少的降水变化量划分为: <50%、50%-100%、100%-200%、>200% 4个区间,
... id="C17">土壤水分含量直接影响细根的垂直分布, 表现出生态位分离(
The spatial and seasonal variation characteristics of fine roots in different plant configuration modes in new reclamation saline soil of humid climate in China
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... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
Extreme rainfall events can alter inter-annual biomass responses to water and N enrichment
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... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
Moderate drought alters biomass and depth distribution of fine roots in Norway spruce
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2012
... id="C5">土壤微生物是植物营养转化及循环的介质, 细根分解与土壤微生物相互依存, 为土壤微生物提供营养(
Repeated freeze thaw cycles and their effects on biological processes in two arctic ecosystem types
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Changes in forest soil properties in different successional stages in lower tropical China
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... id="C19">细根分解对土壤碳输入的年均贡献量高达50% (
滨海沙地3种人工林表层土壤微生物量及其影响因素
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滨海沙地3种人工林表层土壤微生物量及其影响因素
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Effects of experimental throughfall reduction and soil warming on fine root biomass and its decomposition in a warm temperate oak forest
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2017
... id="C19">细根分解对土壤碳输入的年均贡献量高达50% (
川西亚高山不同林龄云杉人工林土壤微生物群落结构
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川西亚高山不同林龄云杉人工林土壤微生物群落结构
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Forty years of tropical forest recovery from agriculture: Structure and floristics of secondary and old-growth riparian forests in the Dominican Republic
1
2004
... id="C5">土壤微生物是植物营养转化及循环的介质, 细根分解与土壤微生物相互依存, 为土壤微生物提供营养(
The role of fine roots in the organic matter and nitrogen budgets of two forested ecosystems
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1982
... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
... id="C4">细根的生产力和周转率占全球陆地净初级生产力的22% (
Redefining fine roots improves understanding of below-ground contributions to terrestrial biosphere processes
2015
Response of cocoa trees ( Theobroma cacao) to a 13-month desiccation period in Sulawesi, Indonesia.
2
2010
... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
... id="C18">在增加降水实验中, 短期(≤1年)根长度密度显著增加, 而1年以上的中期和长期根长度密度变化不显著(
Replicated throughfall exclusion experiment in an Indonesian perhumid rainforest: Wood production, litter fall and fine root growth under simulated drought
1
2014
... id="C4">细根的生产力和周转率占全球陆地净初级生产力的22% (
Effects of soil moisture manipulations on fine root dynamics in a mature balsam fir (
2011
Litterfall and decomposition in relation to soil carbon pools along a secondary forest chronosequence in Puerto Rico
2008
Photosynthesis of Arctic evergreens under snow implications for tundra ecosystem carbon balance
1
2008
... id="C5">土壤微生物是植物营养转化及循环的介质, 细根分解与土壤微生物相互依存, 为土壤微生物提供营养(
Comparison of microbial numbers and enzymatic activities in surface soils and subsoils using various techniques
1
2002
... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
Do increased summer precipitation and N deposition alter fine root dynamics in a Mojave Desert ecosystem?
1
2013
... id="C19">细根分解对土壤碳输入的年均贡献量高达50% (
Review of root dynamics in forest ecosystems grouped by climate, climatic forest type, and species
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1996
... id="C5">土壤微生物是植物营养转化及循环的介质, 细根分解与土壤微生物相互依存, 为土壤微生物提供营养(
高山森林三种细根分解初期微生物生物量动态
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高山森林三种细根分解初期微生物生物量动态
2012
Fine root biomass, production, turnover rates, and nutrient contents in boreal forest ecosystems in relation to species, climate, fertility, and stand age: Literature review and meta-analyses
1
2010
... id="C5">土壤微生物是植物营养转化及循环的介质, 细根分解与土壤微生物相互依存, 为土壤微生物提供营养(
降雨对干旱半干旱地区土壤微生物影响研究进展
3
2014
... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
... ;
... id="C17">土壤水分含量直接影响细根的垂直分布, 表现出生态位分离(
降雨对干旱半干旱地区土壤微生物影响研究进展
3
2014
... id="C3">近年来, 干旱、洪水、风暴等极端气候事件的普遍发生导致降水格局改变(
... ;
... id="C17">土壤水分含量直接影响细根的垂直分布, 表现出生态位分离(
隔离降水对杉木幼苗细根生物量和功能特征的影响
1
2016
... id="C5">土壤微生物是植物营养转化及循环的介质, 细根分解与土壤微生物相互依存, 为土壤微生物提供营养(
隔离降水对杉木幼苗细根生物量和功能特征的影响
1
2016
... id="C5">土壤微生物是植物营养转化及循环的介质, 细根分解与土壤微生物相互依存, 为土壤微生物提供营养(
Profile of soil microbial community under different stand types in Qinghai Province
2017
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