,2,*, 曾辉1Variations of root traits in three Xizang grassland communities along a precipitation gradient
ZHOU Wei1, LI Hong-Bo,2,*, ZENG Hui1通讯作者:
收稿日期:2018-06-11接受日期:2018-10-16网络出版日期:2018-11-20
| 基金资助: |
Received:2018-06-11Accepted:2018-10-16Online:2018-11-20
| Fund supported: |
摘要
关键词：
Abstract
Methods In three grassland communities along a precipitation gradient: Nagqu, Baingoin and Nyima from east to west of Xizang Plateau, we collected 22 coexisting plant species and measured three key root traits: 1st-order root diameter, 1st-order lateral root length and root branch intensity.
Important findings The main results showed that: (1) the root of plants in the alpine grassland was generally thin, and the interspecific variation was also small (22.76%); (2) the root diameter of 86% plant species was in the range from 0.073 mm to 0.094 mm. Compared with the thick-root species, thin-root species had a higher root branching intensity, but shorter lateral root length. In addition, at community-level, plants mainly increased root diameter and lateral root length, but reduced root branching intensity to adapt to the decreasing precipitation; while at species-level, the plant species exhibited diverse adaptive strategies along the precipitation gradient.
Keywords：
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周玮, 李洪波, 曾辉. 西藏高寒草原群落植物根系属性在降水梯度下的变异格局. 植物生态学报[J], 2018, 42(11): 1094-1102 doi:10.17521/cjpe.2018.0140
ZHOU Wei, LI Hong-Bo, ZENG Hui.
植物功能属性的种间和种内变异是物种共存和适应环境变化的基础。属性的种间变异能够代表不同物种的生态位空间差异(Díaz et al., 2016), 很多研究基于此分析了各个群落中物种的种间属性变异性, 尤其是针对植物获取土壤资源的根系属性来定义物种的共存策略(Pregitzer et al., 2002; Kong et al., 2014; Liu et al., 2015; Li et al., 2017)。另外, 越来越多的理论和研究表明, 群落的构建过程既要考虑属性的种间变异, 也要考虑环境梯度下属性的种内变异(Jung & Muller, 2010; Messier et al., 2010; Fajardo & Piper, 2011)。因为在环境梯度上, 每一个植物群落中存在最优属性值范围, 故属性值在此范围内的物种可以较易的争夺到有限的资源(Kunstler et al., 2012), 更有利于物种的存活。而根系作为植物获取土壤资源的重要器官, 其属性的种间和种内变化往往能够决定群落的组成和物种的适应策略。
根系属性能够表征植物多样性的资源获取策略。Kong等(2014)发现根系属性可以划分为两个主要的属性维度: 一个是受谱系发育信号约束强烈的根直径、中柱直径等; 另一个则是以适应环境变化为主的根系分支强度和分支比等。这两个维度的根系属性间也存在共变性: 根直径较细的物种具有较高的分支强度和较短的侧根长度, 根较粗的物种则相反。最新的研究表明, 根系属性间的这种共变性或者权衡普遍存在于在亚热带森林、温带森林及温带草原群落中(Eissenstat et al., 2015; Liu et al., 2015; Li et al., 2017)。然而, 这种共变是以物种间根系属性具有巨大的变异为基础的, 尤其是受谱系信号约束最强的根系直径(Valverde-Barrantes et al., 2017)。但在环境胁迫较大时, 物种间的属性往往呈现聚合性或者趋同性, 如北方森林物种的根系直径大小及变异范围要远低于亚热带森林物种(Chen et al., 2013), 这表明环境对物种根系属性的约束作用使得细根物种能更好地适应寒冷的环境。目前, 在环境约束作用极为强烈的西藏高寒草原, 不同物种间根系属性的变异范围及属性间是否存在共变或权衡的研究依然薄弱, 但这对充分理解基于根系属性变异的植物共存策略的普遍性非常重要。
1 材料和方法
1.1 研究区概况
研究区位于青藏高原西北腹地, 为典型的亚寒带气候区, 全年气候干冷, 植物生长季一般为5月中下旬至9月下旬。该区域由于受西南季风及地形因素影响, 降水自东向西逐渐减少(朱桂丽等, 2017)。沿降水梯度由东向西分别选取那曲、班戈和尼玛3个地区的草原群落进行样地设置(表1), 经纬度跨度为31.43°-32.08° N, 86.90°-90.03° E, 且本研究中的3个草原群落均为围栏内未受人为干扰的自然群落。那曲地区的优势植物物种主要是高山嵩草(Kobresia pygmaea)和钉柱委陵菜(Potentilla saundersiana), 其盖度分别是56%和21%; 班戈地区的主要植物物种则是西藏三毛草(Trisetum spicatum subsp. tibeticum)、紫花针茅(Stipa purpurea)和半卧狗娃花(Heteropappus semiprostratus), 其盖度分别是16%、 14%及12%; 尼玛主要分布的植物物种是紫花针茅、纤杆蒿(Artemisia demissa)及小叶棘豆(Oxytropis microphylla), 其盖度分别是28%、26%及24%。Table 1
表1
表1西藏高寒草原群落根系样地基本信息
Table 1
| 地点 Site | 经纬度 Latitude and longitude | 年平均气温 Mean annual temperature (℃) | 年降水量 Mean annual precipitation (mm) | 海拔 Elevation (m) | 土壤氮含量 Soil N (%) | 土壤碳含量 Soil C (%) | 土壤碳氮比 Soil C:N |
|---|---|---|---|---|---|---|---|
| 那曲 Nagqu | 31.65° N, 92.02° E | -2.2 | 445 | 4 600 | 0.193 | 1.965 | 22.97 |
| 班戈 Baingoin | 31.43° N, 90.03° E | -1.2 | 329 | 4 700 | 0.117 | 1.081 | 13.93 |
| 尼玛 Nyima | 32.08° N, 86.90° E | -3.1 | 286 | 4 780 | 0.115 | 2.062 | 18.24 |
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1.2 研究方法
1.2.1 样地设置与样品采集在那曲、班戈和尼玛3个地区分别设置30 m × 30 m的研究区域, 在每个区域内随机选择15个0.5 m × 0.5 m的调查样方, 并记录每个调查样方中物种名称、数量及盖度。在物种调查的基础上分别确定每个地区草原群落的主要物种组成, 并对每个物种选择20株成龄植物进行根系采样(稀有种数量较少则至少保证10株): 用刀切挖出每个物种连同地上部分的土块, 小心去除根周围的土壤, 用去离子水洗净后, 将完整的根系按照不同的物种存放于冰盒内的塑封袋中, 并及时运回实验室, 置于-20 ℃冰箱冷冻保存。
1.2.2 根系属性指标测定
在实验室中用去离子水洗去附着在根上的细小杂质与灰尘, 并将其置于放有去离子水的培养皿中(使根系间不会重叠), 利用扫描仪(Expression 10000XL; Epson, Suwa, Japan)进行扫描, 并使用WINRHIZO软件(Regent Instruments, Quebec, Canada)将获取的图像进行处理分析, 获得一级根直径、一级根长度及分支强度3个指标。其中根系的分级是严格遵循Fitter (1987)、Berntson (1997)及Pregitzer等(2002)所描述的分级方法, 即将最末梢的根系命名为一级根。此外, 对于每一个根系图像, 人工计数每个二级根上的一级根数量, 进而利用一级根数量除以二级根的长度计算出根系分支强度(Kong et al., 2014)。
1.3 数据处理与分析
通过对西藏3个草原群落内22个物种的采样调查, 利用SPSS 22.0 (SPSS, Chicago, USA)统计分析不同物种间根属性的变异情况, 采用单因子方差分析和Tukey检验比较同一根属性在不同水分梯度上的差异。运用Pearson相关分析三个根属性间的相关关系, 同时利用R软件包picante (Kembel et al., 2010)的系统发生独立对比方法(PIC)分析去除系统发育影响后的根属性间关系。为了更好地比较分析群落尺度上根属性的变化, 我们求得物种j在群落h中的重要值Ijh, 其中重要值是各个物种在群落中的相对密度、相对出现频度及相对盖度的平均值。并以此为权重, 计算每个物种根系属性经过群落加权后的属性值(CWM值) (Umaña et al., 2015), 其计算公式如下:式中, Ijh为物种j在草原群落h中的重要值; Djh为物种j在草原群落h的调查样方中所占的总密度; Njh为物种j在草原群落h的调查样方中出现的总频度; Cjh为物种j在草原群落h的调查样方中所占的总盖度。
式中, t为根系属性; tj为物种j的属性值; h为草原群落类型; Ijh为物种j在草原群落h中的重要值;
为了进一步研究不同水分梯度下植物根系属性的变异情况, 我们对3个草原群落中共有种的种内属性进行了对比分析。以该物种出现的降雨量最高的样地中的根系属性作为参数, 计算该物种随水分降低时(其他样地中), 各根系属性的变化百分数。同时, 为了更加清晰的表征出每个物种的适应策略, 我们进一步求得各物种的属性随降雨梯度变化的百分比, 以便能够简明地展现各物种适应策略的差异。
2 结果
2.1 根系属性的种间变异性
在3个草原群落中, 22种高寒草原植物的3个根系属性的种间变异性存在较大的差异(图1)。其中, 物种间一级根直径差异仅有1.96倍, 总变异系数为22.76% (表2)。除了小叶棘豆、半卧狗娃花和海乳草(Glaux maritima)一级根直径大于1 mm, 且种内直径变化范围较大外, 86%的植物种的根的直径主要集中在0.073 mm到0.094 mm, 且物种内直径变化范围较小; 与之相反, 不同物种间一级根长度差异较大, 总变异系数达80.19%, 从一级根长度最短的伊凡薹草(Carex ivanovae, 0.335 mm), 到最长的半卧狗娃花(5.239 mm); 一级根分支强度的变异系数为61.05%, 变异范围从1.119·cm-1到12.041·cm-1。图1
新窗口打开|下载原图ZIP|生成PPT图122种高寒草原植物的谱系发育关系及根系属性的变异。
Fig. 1Variations of phylogeny and traits among the 22 plant species in the alpine grassland.
Table 2
表2
表2西藏高寒草原22种植物的根系属性变异情况
Table 2
| 根属性 Root trait | 最小值 Min. | 最大值 Max. | 平均值 Mean | 变异系数 Coefficient of variation (%) |
|---|---|---|---|---|
| 一级根直径 1st-order root diameter (mm) | 0.073 | 0.142 | 0.088 | 22.76 |
| 一级根长度 1st-order root length (mm) | 0.335 | 5.239 | 1.541 | 80.19 |
| 根系分支强度 Root branching intensity (No.cm-1) | 1.119 | 12.041 | 4.439 | 61.05 |
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2.2 物种间根系属性的相关关系
22个不同植物种间, 一级根直径与一级侧根长度呈显著正相关关系, 而分支强度与一级根直径呈显著负相关关系, 与一级侧根长度也呈显著负相关(表3), 即粗根植物物种具有较大的一级侧根长度, 较低的分支强度, 而细根植物物种则具有高分支强度和低一级侧根长度。但去除种系发生信号后, 仅直径与一级侧根长度仍具有显著正相关关系, 其他根系属性间的这种相关关系不再显著(表3)。Table 3
表3
表3西藏高寒草原22种植物去除种系发生信号(右上)与未去除种系发生信号(左下)时3个根属性间的Pearson相关性
Table 3
| 根属性 Root trait | 一级根直径 1st-order root diameter | 分支强度 Root branching intensity | 一级根长度 1st-order root length |
|---|---|---|---|
| 一级根直径 1st-order root diameter | -0.008ns | 0.672** | |
| 根系分支强度 Root branching intensity | -0.432* | -0.139ns | |
| 一级根长度 1st-order root length | 0.728** | -0.573** |
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2.3 根系属性对水分减少的响应规律
2.3.1 群落尺度上根系属性对水分减少的响应三个根系属性的CWM值随水分的减少具有明显变化, 且变化的程度与方向不同。植物一级根直径和一级侧根长度随水分减少程度的增加而增大, 但一级侧根长度的变化趋势明显大于一级根直径的变化, 根系直径随水分梯度下降增加了9%-30%, 而一级侧根长度则增加了71%-209%; 根系分支强度则随水分减少程度的增加而降低, 变化趋势也较明显, 根系分支强度降低了48%-53% (图2)。说明随着水分的降低, 植物常常通过增加一级根直径, 尤其是增加一级侧根长度, 降低分支强度的方式来适应环境的干旱胁迫。
图2
新窗口打开|下载原图ZIP|生成PPT图2不同降水梯度上的西藏高寒草原3个草原群落加权后的根系属性。
Fig. 2Community-weighted root traits of the three grasslands along the precipitation gradient in Xizang alpine grassland.
2.3.2 物种尺度上根系属性对水分减少的响应
区域常见物种往往分布在不同的草原类型中, 其根系属性对区域水分变化的响应方向及幅度有所差异。结果显示, 随着水分减少, 一级根较粗物种的直径变化要大于一级根较细物种, 但一级根较细物种的其他根系属性变化程度要高于一级根较粗物种(图3)。对于直径来说, 一级根较粗的小叶棘豆和半卧狗娃花随水分减少增加了32%-36%, 而一级根较细物种中只有二裂委陵菜(Potentilla bifurca)随水分减少提高了13%-14%, 其他一级根较细物种直径随水分减少并未有显著变化; 相对于降水较多的班戈地区, 一级根较细物种(弱小火绒草(Leontopodium pusillum))一级侧根长度在降水较少的尼玛地区增长13%-97%, 而一级根较粗物种(半卧狗娃花)则仅增长了8%; 同样, 在水分减少情况下, 一级根较细物种中的弱小火绒草和紫花针茅的根系分支强度降低了45%-69%, 而一级根较粗物种中只有半卧狗娃花的根系分支强度有所变化, 且仅降低了23%, 但纤杆蒿的根分枝强度随水分减少的变化具有特殊性, 呈现了相反的趋势, 其根系分支强度随水分的减少反而增加了123%。
图3
新窗口打开|下载原图ZIP|生成PPT图3西藏高原3个草原类型中7个共有物种(同时出现在两个或三个地区)的根系属性(平均值+标准误差)。Ad, 纤杆蒿; Ts, 西藏三毛草; Lp, 弱小火绒草; Sp, 紫花针茅; Pb, 二裂委陵菜; Om, 小叶棘豆; Hs, 半卧狗娃花。
Fig. 3Root trait mean values of seven regionally common species (appearing in two or three sites at the same time) at three grassland sites (mean + SE) in Xizang alpine grassland. Ad, Artemisia demissa; Ts, Trisetum spicatum; Lp, Leontopodium pusillum; Sp, Stipa purpurea; Pb, Potentilla bifurca; Om, Oxytropis microphylla; Hs, Heteropappus semiprostratus.
进一步的分析表明, 不同物种适应环境水分变化的策略具有多样性(图4)。对于一级根较粗的半卧狗娃花和小叶棘豆, 随水分减少, 其根系直径均有明显的增大, 但前者也同时增加了侧根长度及降低了根系分支强度, 后者则正好相反。然而, 对于其他几个一级根较细的共有物种(二裂委陵菜、紫花针茅、弱小火绒草、西藏三毛草和纤杆蒿), 随水分减少, 根直径相对于其他根系属性变化很小; 根系分支强度则明显降低(纤杆蒿除外); 但侧根长度则呈现不同的变化趋势, 但总体上以增加为主: 纤杆蒿和三毛草的侧根长度随水分减少而降低; 弱小火绒草、紫花针茅和二裂委陵菜的侧根长度则随之增加。
图4
新窗口打开|下载原图ZIP|生成PPT图4西藏高原3个草原类型7个共有物种根系属性随水分变化的平均百分比。Hs, 半卧狗娃花; Om, 小叶棘豆; Pb, 二裂委陵菜; Sp, 紫花针茅; Lp, 弱小火绒草; Ts, 西藏三毛草; Ad, 纤杆蒿。
Fig. 4The average percentage of root traits of seven regionally common species (appearing in two or three sites at the same time) to water stress at three grassland sites in Xizang alpine grassland. Ad, Artemisia demissa; Ts, Trisetum spicatum; Lp, Leontopodium pusillum; Sp, Stipa purpurea; Pb, Potentilla bifurca; Om, Oxytropis microphylla; Hs, Heteropappus semiprostratus.
3 讨论
3.1 根系属性的种间变异性
本研究表明在青藏高原草原群落区域尺度上, 不同物种间根直径变异较小, 而一级侧根长度和根系分支强度变异较大(表2); 并且根系直径较细的物种比直径较粗的物种具有更高的根系分支强度, 以及更短的侧根长度(图1), 而这种属性间的权衡可能是不同物种共存的重要机制之一(Kraft et al., 2015)。Li等(2017)在内蒙古温带草原的研究发现, 细根物种的根系往往能够入侵到粗根物种的根系空间中, 从而使得共存物种可以充分地占据土壤空间及利用有限的土壤资源。同样, 在温带森林及亚热带森林中也发现了木本细根物种与粗根物种间根系分支强度与侧根长度的权衡, 同时结合菌根的侵染, 发现了植物多样性的地下资源获取策略(Eissenstat et al., 2015; Liu et al., 2015)。这些研究与我们的结果说明, 根直径、侧根长度及根系分支强度间的相关关系是普遍存在于高寒草原、温带草原及温带和亚热带森林中的。另外, 我们发现, 在去除了谱系信号影响之后,根系直径和侧根长度的相关性依然紧密(表3), 这说明二者的关系受谱系信号的约束较小。这也可能与植物本身发育的共性有关, 如根系直径和侧根分生组织的比例在不同功能群的植物之间差异很小(Bystrova et al., 2018)。自然环境压力的大小可能决定了植物根系的种间变异。Li等(2017)在内蒙古温带草原的研究发现, 该区物种间的根系直径变异非常大且直径较粗(CV = 50.7%; 0.107-0.459 mm)。但是, 本研究的结果表明, 西藏地区物种间一级根直径的变异性并不大, 且在样地尺度上大部分的物种及区域尺度上分布较广的物种多为较细物种, 物种的直径分布范围仅为0.073-0.142 mm (图1; 表2)。说明环境的筛选可以增加物种功能属性的相似性, 并影响物种的适应性和表现型(Albert et al., 2011; Laughlin et al., 2012)。即在筛选作用较强烈的环境下, 植物的根系属性(如根直径)往往会被约束在特定的范围内, 也就是强烈的环境筛选使得物种间的属性趋同(Valladare et al., 2015; Dwyer & Laughlin, 2017)。根系直径能够反映植物生长的快慢策略(Reich, 2014), 而细根物种具有更快的生长和周转速度(Eissenstat, 1991; McCormack et al., 2012), 且投资成本较低, 故为植物适应严酷的自然环境提供了更高的灵活性(Chen et al., 2013)。因此, 构建较细的根系可能是植物适应西藏较短的生长周期的最佳策略。
3.2 根系属性的种内变异性及植物适应水分减少的策略
群落尺度上的属性CWM值能够反映环境的筛选作用, 代表着当地环境最优适应值(Muscarella & Uriarte, 2016)。而不同群落间, 群落属性值的变化主要源于物种更替(Ackerly & Cornwell, 2007; Corn?well & Ackerly, 2009; Pérez-Ramos et al., 2012)。我们发现在群落尺度上, 一级根直径和一级侧根长度随着样地水分的减少而增大, 根系分支强度则随水分的减少而降低(图2), 说明在区域尺度上, 一级根较粗, 侧根较长, 分支强度较低的植物种更适合生活在水分较少的环境中。另外, 本文结果显示, 侧根长度和分支强度在不同群落间的变异幅度远高于根系直径的变化, 说明侧根长度和分支强度是更容易适应环境变化的根系属性。除了物种间的变化, 不同群落里共有种的属性的种内变异可能也会影响群落CWM值(Violle et al., 2012; Kichenin & Freschet, 2013)。我们的结果显示, 随水分含量降低, 根直径相对于其他根属性来说几乎没有变化, 但侧根长度和分支强度均有所增加, 尤其是分支强度(图4)。另外, 我们也发现, 不同共有种根系属性响应水分变化的规律并不一致(图3)。不同物种的属性种内变异对环境梯度的响应具有较大异质性(Albert et al., 2010; Kichenin & Freschet, 2013)。在区域常见的7个物种中, 半卧狗娃花对水分变化的响应与群落整体尺度上物种的响应一致, 3个根系属性均有所改变; 弱小火绒草主要通过增加侧根长度及降低分枝强度两个属性来适应环境水分的变化; 小叶棘豆、二裂委陵菜、紫花针茅及纤杆蒿则主要通过改变一个属性值的方式来响应水分变化; 而西藏三毛草3个根系属性随环境水分的变化均未有显著变化。以上说明植物的根系属性是会随着环境水分的变化而变化的, 且植物往往是通过改变单一属性或多个属性的方式来适应环境的变化(Nosil et al., 2009), 而物种间这种通过协调不同属性及属性组合间的变异方向及程度来适应水分减少的方式, 体现了不同物种适应环境能力及策略的多样性(Laughlin & Messier, 2015)。
3.3 启示
本研究表明, 与其他生态系统相比, 如森林和温带草原系统(Liu et al., 2015; Li et al., 2017), 虽然西藏高寒草原群落的环境约束作用使得植物的根系直径较细、物种间根系直径变异较小, 但是根系属性间的相关性依然稳固, 如不同物种间根系直径与分支强度呈负相关关系, 与侧根长度呈正相关关系。这种属性间的权衡体现了不同物种的资源获取策略或生态位差异: 一级根较细的物种更依赖于侧根密度的增加获取资源, 而一级根较粗的物种则更可能利用较长的侧根长度获取资源。这说明, 关键的根系属性能够充分地决定植物的资源获取策略, 而这种策略在生态系统中具有普遍性。这为在全球尺度上探究不同物种的生态位空间提供了理论基础。但是, 在个体根属性方面, 除了我们选择的3个属性外, 根毛、其他菌根属性(比如菌根类群、根外菌丝量)、根际分泌物、化学元素浓度等也有一定的功能意义; 在根系特征方面, 整个根系的长度、生物量及在不同土层的分布, 根系的分支特征等也可以提供地下资源捕获策略的信息, 这些也是有待我们进一步研究的方向。本研究对如何来定义植物的属性空间有启发意义: (1)用多少指标, 用什么指标。我们的研究表明地下资源策略似乎通过几个有限的指标就可以得到很好的描述, 但这也有待更多的试验研究的验证。(2)有限的地下策略指标和有限的地上策略指标(Kunstler et al., 2011; Díaz et al., 2016)很有可能定义一个物种, 并认识这个物种在不同环境中的属性值会如何变化。这对预测全球变化下的物种存亡及分布变化以及由此造成的生态系统过程的变化可能有重要意义。(3)本研究也对认识植物如何响应和适应环境条件变化具有一定的价值, 当环境变化时, 物种策略的变化可能包括一个或多个属性指标的变化, 而要认识这种变化方式只有通过更多的实证来研究。
4 结论
在西藏高寒草原, 不同草原植物种间的几个关键根属性间具有显著的权衡: 根直径较细的物种比直径较粗的物种具有更强的分支强度和更短的侧根长度, 这体现了不同物种的生态位差异, 是物种共存的基础。另外, 植物适应水分胁迫的策略在不同尺度上具有较大的差异: 在群落尺度上, 随着水分减少, 根系直径和侧根长度显著增加, 根系分支强度显著降低; 而在物种尺度上, 不同物种往往是通过改变单一或多个属性的方式来适应环境的变化, 且每个根系属性响应水分梯度的变异方向和程度存在差异, 进而表明了不同物种在适应水分变化策略上的多样性。致谢 感谢中国科学院地理科学与资源研究所的 郭大立研究员对实验设计的支持和指导; 感谢马泽清博士在野外采样中给予的帮助及在写作过程中的建议。
参考文献 原文顺序
文献年度倒序
文中引用次数倒序
被引期刊影响因子
DOI:10.1111/j.1461-0248.2006.01006.xURLPMID:17257101 [本文引用: 1]
Plant functional traits vary both along environmental gradients and among species occupying similar conditions, creating a challenge for the synthesis of functional and community ecology. We present a trait-based approach that provides an additive decomposition of species' trait values into alpha and beta components: beta values refer to a species' position along a gradient defined by community-level mean trait values; alpha values are the difference between a species' trait values and the mean of co-occurring taxa. In woody plant communities of coastal California, beta trait values for specific leaf area, leaf size, wood density and maximum height all covary strongly, reflecting species distributions across a gradient of soil moisture availability. Alpha values, on the other hand, are generally not significantly correlated, suggesting several independent axes of differentiation within communities. This trait-based framework provides a novel approach to integrate functional ecology and gradient analysis with community ecology and coexistence theory.
DOI:10.1016/j.ppees.2011.04.003URL [本文引用: 1]
Trait-based studies have become extremely common in plant ecology. Trait-based approaches often rely on the tacit assumption that intraspecific trait variability (ITV) is negligible compared to interspecific variability, so that species can be characterized by mean trait values. Yet, numerous recent studies have challenged this assumption by showing that ITV significantly affects various ecological processes. Accounting for ITV may thus strengthen trait-based approaches, but measuring trait values on a large number of individuals per species and site is not feasible. Therefore, it is important and timely to synthesize existing knowledge on ITV in order to (1) decide critically when ITV should be considered, and (2) establish methods for incorporating this variability. Here we propose a practical set of rules to identify circumstances under which ITV should be accounted for. We formulate a spatial trait variance partitioning hypothesis to highlight the spatial scales at which ITV cannot be ignored in ecological studies. We then refine a set of four consecutive questions on the research question, the spatial scale, the sampling design, and the type of studied traits, to determine case-by-case if a given study should quantify ITV and test its effects. We review methods for quantifying ITV and develop a step-by-step guideline to design and interpret simulation studies that test for the importance of ITV. Even in the absence of quantitative knowledge on ITV, its effects can be assessed by varying trait values within species within realistic bounds around the known mean values. We finish with a discussion of future requirements to further incorporate ITV within trait-based approaches. This paper thus delineates a general framework to account for ITV and suggests a direction towards a more quantitative trait-based ecology.
DOI:10.1111/j.1365-2435.2010.01727.xURL [本文引用: 1]
Summary 1.68Functional traits have been extensively used to describe, group and rank species according to their functions. There is now growing evidence that intraspecific functional variability, as well as interspecific variability, can have significant effects on community dynamics and ecosystem functioning. A core hypothesis for the use of functional traits expressed as species means, that their intraspecific variability is negligible compared with their interspecific variability, has however been too rarely tested empirically. We then addressed four questions: Is intraspecific functional variability across species ranges negligible compared with interspecific variability? Are the major resource economics trade-off and functional strategies robust to individual trait variability? Are species rankings or ordination robust across species ranges once considering intraspecific variability? Can species be discriminated by their leaf traits? 2.68Using an environmentally stratified sampling design within an alpine catchment, we collected five functional traits for 13 common plant species with contrasting life histories and traits. Several populations from a range of environmental conditions were then sampled for each species across their ranges. 3.68With an original combination of single-trait and multi-trait analyses, we highlighted a non-negligible contribution of intraspecific variability to overall functional trait variability (6530%). Although not affecting general and well-known functional trade-offs and strategies, intraspecific functional variability had the potential to alter species ordination and produced a functional continuum rather than a clear-cut species classification. 4.68Deciding whether intraspecific functional variability can be considered as negligible – species being represented by mean trait values –, or not – species being represented by multivariate trait distributions –, is an essential question for multiple ecological issues. However, this decision cannot be generic, but will depend on the studied system and selected traits and species, as well as on study objectives.
DOI:10.1046/j.1469-8137.1997.00687.xURL [本文引用: 1]
Topology is an important component of the architecture of whole root systems. Unfortunately, most commonly applied indices used for characterizing topology are poorly correlated with one another and thus reflect different aspects of topology. In order to understand better how different methods of characterizing topology vary, this paper presents an exploration of several different methods for assigning order within branched root systems on the basis of ( a ) developmental (centrifugal) vs. functional (centripetal) ordering sequences and ( b ) whether orders are assigned to individual links or groups of adjacent links (segments). For each ordering system, patterns of scaling in relation to various aspects of link and segment size are explored using regression analyses. Segment-based ordering systems resulted in better fits for simple scaling relationships with size, but these patterns varied between developmental vs. functional ordering as well as the different size metrics examined. The functional (centripetal), link-based ordering system showed complex, non-linear scaling in relation to numbers of links per order. Using a simple simulation model of root growth, it is demonstrated that this method of characterizing root topology in relation to root size might be a more powerful tool for characterizing root system architecture than in the use of simple, single-index characterizations of topology.
DOI:10.1134/S1062360418020029URL [本文引用: 1]
Primary roots of 98 species from different families of monocotyledonous and dicotyledonous plants and adventitious roots obtained from bulbs and rhizomes of 24 monocot species were studied. Root growth rate, root diameter, length of the meristem and elongation zones, number of meristematic cells in a file of cortical cells, and length of fully elongated cells were evaluated in each species after the onset of steady growth. The mitotic cycle duration and relative cell elongation rate were calculated. In all species, the meristem length was approximately equal to two root diameters. When comparing different species, the rate of root growth increased with a larger root diameter. This was due to an increase in the number of meristematic cells in a row and, to a lesser degree, to a greater length of fully elongated cells. The duration of the mitotic cycle and the relative cell elongation rate did not correlate with the root diameter. It is suggested that the meristem size depends on the level of nutrient inflow from upper tissues, and is thereby controlled during further growth.
DOI:10.1016/j.agrformet.2016.01.010URL
Global warming is anticipated to have profound effects on terrestrial carbon fluxes and thus feed backs to future climate change. Ecosystem respiration (Reco) is one of the dominant components of biosphere CO2fluxes, but the effects of warming onRecoare still unclear. A field warming experiment using open top chambers (OTCs) was conducted in a meadow grassland on the Tibetan Plateau to study the effects of warming on the components ofReco. Warming significantly enhanced above-ground plant respiration (Ragb) and total autotrophic plant respiration (Rplant) by 28.7% and 19.9%, respectively, but reduced heterotrophic respiration (Rh) by 10.4%. These different responses resulted in the insensitive responses ofRecoand soil respiration (Rs) to the experimental warming. The warming treatment also increasedRplant/RecoandRagb/Recoby 8.4% and 17.3%, respectively, while decreasingRh/Recoby 19.0%, suggesting that warming could eventually causeRecoto be dominated byRplant. Enhancements inRplantandRagbwere related to the warming-induced increases in aboveground biomass (AGB) while reducedRhwas closely coupled with warming-induced decrease of microbial biomass carbon. Our results highlight that the differential responses of the components ofRecoto different environmental physics under warming scenarios should be taken into consideration to project the future carbon-climate feed backs.
DOI:10.1111/geb.12048URL [本文引用: 2]
AimPlant roots are crucial for water and nutrient absorption, but large-scale patterns and underlying mechanisms of root trait variation and evolution are poorly understood. Here we quantify the degree of variation in functional traits for the first-order roots across large geographical scales and examine the potential mechanisms underlying these patterns.LocationChina.MethodsWe collected first-order roots (stream-based ordering system) and leaf samples of 65 tree species in six forests from subtropical to temperate zones and determined the key morphological, architectural and chemical traits.ResultsWe found wider variation in root morphology in the subtropical zone, where species with very thick and very thin first-order roots coexisted, in contrast with narrower variation among species in the temperate zone. Inconsistent with the predictions of trait economics spectrum, root nitrogen concentration was uncorrelated with root morphology. Furthermore, average root diameter at the plant family level decreased markedly with their divergence time in both piecewise and phylogenetic independent contrast regression analyses.Main conclusionsHigher variation in root morphology in the subtropical zone appears to result from the coexistence of tree species with thick and thin roots, probably because of a more favourable water supply. Patterns of root evolution towards thinner roots were driven by both phylogeny and possible adaptation of newly diverged species to drier habitats from mid to late Cretaceous. Our findings reveal contrasting selection pressures at the root and leaf level in different climatic zones during plant evolution, and suggest that a single vector of variation linking morphology to resource acquisition or life span ( rait economics ) remains elusive in roots.
DOI:10.1890/07-1134.1URL [本文引用: 1]
Community assembly processes are thought to shape the mean, spread, and spacing of functional trait values within communities. Two broad categories of assembly processes have been proposed: first, a habitat filter that restricts the range of viable strategies and second, a partitioning of microsites and/or resources that leads to a limit to the similarity of coexisting species. The strength of both processes may be dependent on conditions at a particular site and may change along an abiotic gradient. We sampled environmental variables and plant communities in 44 plots across the varied topography of a coastal California landscape. We characterized 14 leaf, stem, and root traits for 54 woody plant species, including detailed intraspecific data for two traits with the goal of understanding the connection between traits and assembly processes in a variety of environmental conditions. We examined the within-community mean, range, variance, kurtosis, and other measures of spacing of trait values. In this landscape, there was a topographically mediated gradient in water availability. Across this gradient we observed strong shifts in both the plot-level mean trait values and the variation in trait values within communities. Trends in trait means with the environment were due largely to species turnover, with intraspecific shifts playing a smaller role. Traits associated with a vertical partitioning of light showed a greater range and variance on the wet soils, while nitrogen per area, which is associated with water use efficiency, showed a greater spread on the dry soils. We found strong nonrandom patterns in the trait distributions consistent with expectations based on trait-mediated community assembly. There was a significant reduction in the range of six out of 11 leaf and stem functional trait values relative to a null model. For specific leaf area (SLA) we found a significant even spacing of trait values relative to the null model. For seed size we found a more platykurtic distribution than expected. These results suggest that both a habitat filter and a limit to the similarity of coexisting species can simultaneously shape the distribution of traits and the assembly of local plant communities.
DOI:10.1038/nature16489URLPMID:26700811 [本文引用: 2]
Abstract Earth is home to a remarkable diversity of plant forms and life histories, yet comparatively few essential trait combinations have proved evolutionarily viable in today's terrestrial biosphere. By analysing worldwide variation in six major traits critical to growth, survival and reproduction within the largest sample of vascular plant species ever compiled, we found that occupancy of six-dimensional trait space is strongly concentrated, indicating coordination and trade-offs. Three-quarters of trait variation is captured in a two-dimensional global spectrum of plant form and function. One major dimension within this plane reflects the size of whole plants and their parts; the other represents the leaf economics spectrum, which balances leaf construction costs against growth potential. The global plant trait spectrum provides a backdrop for elucidating constraints on evolution, for functionally qualifying species and ecosystems, and for improving models that predict future vegetation based on continuous variation in plant form and function.
DOI:10.1111/ele.12781URLPMID:28510261 [本文引用: 1]
Trade-offs maintain diversity and structure communities along environmental gradients. Theory indicates that if covariance among functional traits sets a limit on the number of viable trait combinations in a given environment, then communities with strong multidimensional trait constraints should exhibit low species diversity. We tested this prediction in winter annual plant assemblages along an aridity gradient using multilevel structural equation modelling. Univariate and multivariate functional diversity measures were poorly explained by aridity, and were surprisingly poor predictors of community richness. By contrast, the covariance between maximum height and seed mass strengthened along the aridity gradient, and was strongly associated with richness declines. Community richness had a positive effect on local neighbourhood richness, indicating that climate effects on trait covariance indirectly influence diversity at local scales. We present clear empirical evidence that declines in species richness along gradients of environmental stress can be due to increasing constraints on multidimensional phenotypes.
DOI:10.1111/j.1469-8137.1991.tb00565.xURL [本文引用: 1]
This study tested two hypotheses: (1) species with roots that have a high length to dry mass ratio or specific root length (SRL) also have the potential for high rates of root growth in small volumes of favourable soil and (2) variation in average root diameter fully accounts for variation in SRL. To minimize differences among shoots, the study used 13-year-old 'Valencia' sweet orange [ Citrus sinensis (L.) Osbeck] trees budded to rootstocks representing a range of genotypes. Soil cores 7.4 cm in diameter and 14.2 cm deep were extracted from beneath the canopy, and the soil was sieved free of roots and replaced. Root length, diameter and dry weight of the roots in the disturbed soil and adjacent undisturbed soil were evaluated 5, 10, 19 and 40 weeks following soil replacement. The disturbed soil had a higher water content than the undisturbed soil for the first three sampling dates. Averaged across rootstocks, root length density increased in a linear fashion in the disturbed soil and was comparable to that in the undisturbed soil by 40 weeks. Mean root diameter of the fibrous roots (< 2 mm) declined with age. Rootstocks with the highest SRL had the most rapid rate of root proliferation (cm cm 0908083 wk 0908081 ) ( r = 0.94) and the greatest rate of water extraction at 19 weeks ( r = 0.79). Although variation in root diameter contributed to rootstock variation in SRL, the data also suggested that rootstocks of high SRL had roots with lower tissue density than those of low SRL ( P < 0.05). The potential trade-offs of constructing root systems of high SRL are discussed.
DOI:10.1111/nph.13451URLPMID:25970701 [本文引用: 2]
Abstract The identification of plant functional traits that can be linked to ecosystem processes is of wide interest, especially for predicting vegetational responses to climate change. Root diameter of the finest absorptive roots may be one plant trait that has wide significance. Do species with relatively thick absorptive roots forage in nutrient-rich patches differently from species with relatively fine absorptive roots? We measured traits related to nutrient foraging (root morphology and architecture, root proliferation, and mycorrhizal colonization) across six coexisting arbuscular mycorrhizal (AM) temperate tree species with and without nutrient addition. Root traits such as root diameter and specific root length were highly correlated with root branching intensity, with thin-root species having higher branching intensity than thick-root species. In both fertilized and unfertilized soil, species with thin absorptive roots and high branching intensity showed much greater root length and mass proliferation but lower mycorrhizal colonization than species with thick absorptive roots. Across all species, fertilization led to increased root proliferation and reduced mycorrhizal colonization. These results suggest that thin-root species forage more by root proliferation, whereas thick-root species forage more by mycorrhizal fungi. In mineral nutrient-rich patches, AM trees seem to forage more by proliferating roots than by mycorrhizal fungi. 2015 The Authors. New Phytologist 2015 New Phytologist Trust.
DOI:10.1111/j.1469-8137.2010.03468.xURLPMID:21039558 [本文引用: 1]
The focus of the trait-based approach to study community ecology has mostly been on trait comparisons at the interspecific level. Here we quantified intraspecific variation and covariation of leaf mass per area (LMA) and wood density (WD) in monospecific forests of the widespread tree species Nothofagus pumilio to determine its magnitude and whether it is related to environmental conditions and ontogeny. We also discuss probable mechanisms controlling the trait variation found. We collected leaf and stem woody tissues from 30-50 trees of different ages (ontogeny) from each of four populations at differing elevations (i.e. temperatures) and placed at each of three locations differing in soil moisture. The total variation in LMA (coefficient of variation (CV) = 21.14%) was twice that of WD (CV = 10.52%). The total variation in traits was never less than 23% when compared with interspecific studies. Differences in elevation (temperature) for the most part explained variation in LMA, while differences in soil moisture and ontogeny explained the variation in WD. Traits covaried similarly in the altitudinal gradient only. Functional traits of N. pumilio exhibited nonnegligible variation; LMA varied for the most part with temperature, while WD mostly varied with moisture and ontogeny. We demonstrate that environmental variation can cause important trait variation without species turnover.
DOI:10.1111/j.1469-8137.1987.tb04683.xURL [本文引用: 1]
Although plants devote a large proportion of their resources to roots, we have a poor understanding of the constraints under which root systems function. Roots are much less variable morphologically than leaves and it is likely that root systems rather than individual roots are the focus of natural selection. In other words, architecture is more important than morphology. Existing classifications of root systems, based on the developmental model, have failed to provide much insight into their functioning and an alternative, topological model is outlined, in which the link is the basic unit of classification. Other components of the architecture of root systems, including link lengths, branching angles and diameters, are considered and the ecological implications of variation in each is discussed. Simulation models of transport and space exploration are discussed and it is shown that resource cost, transport efficiency and exploration efficiency cannot be simultaneously minimized and that optimum form may vary with the mobility of the resource. In general, a 'herringbone' structure seems to be the most efficient at exploration of space but the least transport-efficient and the most expensive.
DOI:10.13292/j.1000-4890.201703.033URL
青藏高原是全球变化的敏感区域,过去几十年以来,在全球气候变暖的背景下,藏北高原增温明显。本研究在藏北典型高寒草甸区采用开顶式生长室(OTC)模拟增温的方法,根据OTC的不同高度设置了4个增温梯度(40、60、80和100 cm),分析了植物群落的生长、结构和组成以及生物量对增温的响应。结果表明:不同高度的OTC作用使得年平均空气温度增加了1.13~2.72℃,且OTC的高度越高,其增温效果越明显;伴随着温度的升高,空气湿度以及土壤湿度均有所降低;高山嵩草在所有群落中占有绝对优势,梯度增温作用使得其重要值不断下降;随着温度的升高,莎草类植物的盖度逐渐下降;对整个群落而言,增温幅度较低时,增温对群落的生长和生物量的积累以及多样性都会有明显的促进作用,当温度升高超过一定值,这种促进作用会逐渐减弱甚至变成抑制作用。本研究表明,藏北高寒草甸对增温作用具有敏感而迅速的响应,温度升高使该地区的气候朝着暖干化趋势发展,而一定程度的升温会促进植物群落的生长,但温度升高超过一定幅度时,会导致草地生产力下降,草地退化加剧。
DOI:10.13292/j.1000-4890.201703.033URL
青藏高原是全球变化的敏感区域,过去几十年以来,在全球气候变暖的背景下,藏北高原增温明显。本研究在藏北典型高寒草甸区采用开顶式生长室(OTC)模拟增温的方法,根据OTC的不同高度设置了4个增温梯度(40、60、80和100 cm),分析了植物群落的生长、结构和组成以及生物量对增温的响应。结果表明:不同高度的OTC作用使得年平均空气温度增加了1.13~2.72℃,且OTC的高度越高,其增温效果越明显;伴随着温度的升高,空气湿度以及土壤湿度均有所降低;高山嵩草在所有群落中占有绝对优势,梯度增温作用使得其重要值不断下降;随着温度的升高,莎草类植物的盖度逐渐下降;对整个群落而言,增温幅度较低时,增温对群落的生长和生物量的积累以及多样性都会有明显的促进作用,当温度升高超过一定值,这种促进作用会逐渐减弱甚至变成抑制作用。本研究表明,藏北高寒草甸对增温作用具有敏感而迅速的响应,温度升高使该地区的气候朝着暖干化趋势发展,而一定程度的升温会促进植物群落的生长,但温度升高超过一定幅度时,会导致草地生产力下降,草地退化加剧。
DOI:10.1111/j.1365-2745.2010.01687.xURL [本文引用: 1]
1. Trait-based approaches applied to community ecology have led to a considerable advance in understanding the effect of environmental filters on species assembly. Although plant traits are known to vary both between and within species, little is known about the role of intraspecific trait variability in the non-random assembly mechanisms controlling the coexistence of species, including habitat filtering and niche differentiation.2. We investigate the role of intraspecific variability in three key functional traits – specific leaf area (SLA), leaf dry matter content (LDMC) and height – in structuring grassland communities distributed along a flooding gradient. We quantified the contribution of intraspecific variability relative to interspecific differences in the trait–gradient relationship, and we used a null model approach to detect patterns of habitat filtering and niche differentiation, with and without intraspecific variability.3. Community mean SLA and height varied significantly along the flooding gradient and intraspecific variability accounted for 44% and 32%, respectively, of these trait–gradient relationships. LDMC did not vary along the gradient, with and without accounting for intraspecific variability. Our null model approach revealed significant patterns of habitat filtering and niche differentiation for SLA and height, but not for LDMC. More strikingly, considering intraspecific trait variability greatly increased the detection of habitat filtering and was necessary to detect niche differentiation processes.4. Synthesis. Our study provides evidence for a strong role of intraspecific trait variability in community assembly. Our findings suggest that intraspecific trait variability promotes species coexistence, by enabling species to pass through both abiotic and biotic filters. We argue that community ecology would benefit from more attention to intraspecific variability.
DOI:10.1093/bioinformatics/btq166URLPMID:20395285 [本文引用: 1]
Abstract SUMMARY: Picante is a software package that provides a comprehensive set of tools for analyzing the phylogenetic and trait diversity of ecological communities. The package calculates phylogenetic diversity metrics, performs trait comparative analyses, manipulates phenotypic and phylogenetic data, and performs tests for phylogenetic signal in trait distributions, community structure and species interactions. AVAILABILITY: Picante is a package for the R statistical language and environment written in R and C, released under a GPL v2 open-source license, and freely available on the web (http://picante.r-forge.r-project.org) and from CRAN (http://cran.r-project.org).
DOI:10.1111/1365-2435.12116URL [本文引用: 2]
Despite widespread focus on interspecific variation in trait-based ecology, there is growing evidence that intraspecific trait variability can play a fundamental role in plant community responses to environmental change and community assembly. Here, we quantify the strength and direction of inter- and intraspecific plant community trait responses along a 900m elevation gradient spanning alpine and subalpine plant communities in southern New Zealand. We measured five commonly used leaf traits (i.e. dry matter content, N and P concentrations, leaf area and specific leaf area) on all 31 dominant and subordinate species recorded along the gradient, and examined their species-specific and community-level responses to elevation using both abundance-weighted and nonweighted averages of trait values. By decomposing the variance of community-level measures of these traits across the gradient, we showed that the contribution of interspecific variation to the response of plant assemblages to elevation was stronger than that of intraspecific variation, for all traits except specific leaf area. Further, the relative contributions of interspecific effects were greater when abundance-weighted rather than nonweighted measures were used. We also observed contrasting intraspecific trait responses to the gradient among species (particularly for leaf N and P concentrations), and found both positive and negative covariation between inter- and intraspecific effects on community-level trait values. The weak community-average trait responses to elevation, as found for specific leaf area (SLA) and leaf N and P concentrations, resulted from strong but opposing responses among vs. within species, which are not typically accounted for in species-based measures of plant community responses. For instance, increasing elevation (and associated factors such as a decrease in soil nutrient availability) favoured the dominance of species with relatively high leaf nutrient concentrations while simultaneously triggering an intraspecific decrease in the leaf nutrient concentrations of these species. The context dependency of positive and negative covariation between inter- and intraspecific trait variability, and the species-specific nature of intraspecific shifts in functional trait values, reveal highly complex plastic responses of plants to environmental changes, and highlights the need for greater consideration of the role that intraspecific variation plays in community-level processes. Lay Summary
DOI:10.1111/nph.12842URLPMID:24824672 [本文引用: 3]
SummaryAbsorptive root traits show remarkable cross-species variation, but major root trait dimensions across species have not been defined.We sampled first-order roots and measured 14 root traits for 96 angiosperm woody species from subtropical China, including root diameter, specific root length, stele diameter, cortex thickness, root vessel size and density, mycorrhizal colonization rate, root branching intensity, tissue density, and concentrations of carbon and nitrogen ([N]).Root traits differed in the degree of variation and phylogenetic conservatism, but showed predictable patterns of cross-trait coordination. Root diameter, cortex thickness and stele diameter displayed high variation across species (coefficient of variation (CV)02=020.51–0.69), whereas the stele:root diameter ratio and [N] showed low variation (CV02<020.32). Root diameter, cortex thickness and stele diameter showed a strong phylogenetic signal across species, whereas root branching traits did not, and these two sets of traits were segregated onto two nearly orthogonal (independent) principal component analysis (PCA) axes.Two major dimensions of root trait variation were found: a diameter-related dimension potentially integrating root construction, maintenance, and persistence with mycorrhizal colonization, and a branching architecture dimension expressing root plastic responses to the environment. These two dimensions may offer a promising path for better understanding root trait economics and root ecological strategies world-wide.
DOI:10.1073/pnas.1413650112URLPMID:25561561 [本文引用: 1]
Understanding the processes maintaining species diversity is a central problem in ecology, with implications for the conservation and management of ecosystems. Although biologists often assume that trait differences between competitors promote diversity, empirical evidence connecting functional traits to the niche differences that stabilize species coexistence is rare. Obtaining such evidence is critical because traits also underlie the average fitness differences driving competitive exclusion, and this complicates efforts to infer community dynamics from phenotypic patterns. We coupled field-parameterized mathematical models of competition between 102 pairs of annual plants with detailed sampling of leaf, seed, root, and whole-plant functional traits to relate phenotypic differences to stabilizing niche and average fitness differences. Single functional traits were often well correlated with average fitness differences between species, indicating that competitive dominance was associated with late phenology, deep rooting, and several other traits. In contrast, single functional traits were poorly correlated with the stabilizing niche differences that promote coexistence. Niche differences could only be described by combinations of traits, corresponding to differentiation between species in multiple ecological dimensions. In addition, several traits were associated with both fitness differences and stabilizing niche differences. These complex relationships between phenotypic differences and the dynamics of competing species argue against the simple use of single functional traits to infer community assembly processes but lay the groundwork for a theoretically justified trait-based community ecology.
DOI:10.1038/nature16476URLPMID:26700807 [本文引用: 1]
Abstract Phenotypic traits and their associated trade-offs have been shown to have globally consistent effects on individual plant physiological functions, but how these effects scale up to influence competition, a key driver of community assembly in terrestrial vegetation, has remained unclear. Here we use growth data from more than 3 million trees in over 140,000 plots across the world to show how three key functional traits--wood density, specific leaf area and maximum height--consistently influence competitive interactions. Fast maximum growth of a species was correlated negatively with its wood density in all biomes, and positively with its specific leaf area in most biomes. Low wood density was also correlated with a low ability to tolerate competition and a low competitive effect on neighbours, while high specific leaf area was correlated with a low competitive effect. Thus, traits generate trade-offs between performance with competition versus performance without competition, a fundamental ingredient in the classical hypothesis that the coexistence of plant species is enabled via differentiation in their successional strategies. Competition within species was stronger than between species, but an increase in trait dissimilarity between species had little influence in weakening competition. No benefit of dissimilarity was detected for specific leaf area or wood density, and only a weak benefit for maximum height. Our trait-based approach to modelling competition makes generalization possible across the forest ecosystems of the world and their highly diverse species composition.
DOI:10.1111/j.1461-0248.2012.01803.xURLPMID:22625657 [本文引用: 1]
The relative importance of competition vs. environmental filtering in the assembly of communities is commonly inferred from their functional and phylogenetic structure, on the grounds that similar species compete most strongly for resources and are therefore less likely to coexist locally. This approach ignores the possibility that competitive effects can be determined by relative positions of species on a hierarchy of competitive ability. Using growth data, we estimated 275 interaction coefficients between tree species in the French mountains. We show that interaction strengths are mainly driven by trait hierarchy and not by functional or phylogenetic similarity. On the basis of this result, we thus propose that functional and phylogenetic convergence in local tree community might be due to competition-sorting species with different competitive abilities and not only environmental filtering as commonly assumed. We then show a functional and phylogenetic convergence of forest structure with increasing plot age, which supports this view.
DOI:10.1111/j.1461-0248.2012.01852.xURLPMID:22906233 [本文引用: 1]
Community assembly involves two antagonistic processes that select functional traits in opposite directions. Environmental filtering tends to increase the functional similarity of species within communities leading to trait convergence, whereas competition tends to limit the functional similarity of species within communities leading to trait divergence. Here, we introduce a new hierarchical Bayesian model that incorporates intraspecific trait variation into a predictive framework to unify classic coexistence theory and evolutionary biology with recent trait-based approaches. Model predictions exhibited a significant positive correlation (r = 0.66) with observed relative abundances along a 10 C gradient in mean annual temperature. The model predicted the correct dominant species in half of the plots, and accurately reproduced species' temperature optimums. The framework is generalizable to any ecosystem as it can accommodate any species pool, any set of functional traits and multiple environmental gradients, and it eliminates some of the criticisms associated with recent trait-based community assembly models.
DOI:10.1016/j.tree.2015.06.003URLPMID:26122484 [本文引用: 1]
Phenotypic traits influence species distributions, but ecology lacks established links between multidimensional phenotypes and fitness for predicting species responses to environmental change. The common focus on single traits rather than multiple trait combinations limits our understanding of their adaptive value, and intraspecific trait covariation has been neglected in ecology despite its importance in evolutionary theory and its likely impact on species distributions. Here, we extend the adaptive landscape framework to ecological sorting of multidimensional phenotypes across environments and discuss how two analytical approaches can be used to quantify fitness as a function of the interaction between the phenotype and the environment. We encourage ecologists to consider how phenotypic integration will constrain species responses to environmental change.
DOI:10.1111/nph.14710URLPMID:28758691 [本文引用: 5]
react-text: 461 Background/Question/Methods Fine roots are an important link between plants and soils and account for a significant fraction of net primary production (NPP). At the same time, temporal patterns of root production and activity mediate the capacity of a plant to obtain soil resources across the growing season. However, efforts to accurately describe belowground productivity have been hindered... /react-text react-text: 462 /react-text [Show full abstract]
DOI:10.1111/nph.13434URLPMID:25925733 [本文引用: 4]
Abstract In most cases, both roots and mycorrhizal fungi are needed for plant nutrient foraging. Frequently, the colonization of roots by arbuscular mycorrhizal (AM) fungi seems to be greater in species with thick and sparsely branched roots than in species with thin and densely branched roots. Yet, whether a complementarity exists between roots and mycorrhizal fungi across these two types of root system remains unclear. We measured traits related to nutrient foraging (root morphology, architecture and proliferation, AM colonization and extramatrical hyphal length) across 14 coexisting AM subtropical tree species following root pruning and nutrient addition treatments. After root pruning, species with thinner roots showed more root growth, but lower mycorrhizal colonization, than species with thicker roots. Under multi-nutrient (NPK) addition, root growth increased, but mycorrhizal colonization decreased significantly, whereas no significant changes were found under nitrogen or phosphate additions. Moreover, root length proliferation was mainly achieved by altering root architecture, but not root morphology. Thin-root species seem to forage nutrients mainly via roots, whereas thick-root species rely more on mycorrhizal fungi. In addition, the reliance on mycorrhizal fungi was reduced by nutrient additions across all species. These findings highlight complementary strategies for nutrient foraging across coexisting species with contrasting root traits. 2015 The Authors. New Phytologist 2015 New Phytologist Trust.
DOI:10.1093/aob/mcs293URL
A hypothetical ideotype is presented to optimize water and N acquisition by maize root systems. The overall premise is that soil resource acquisition is optimized by the coincidence of root foraging and resource availability in time and space. Since water and nitrate enter deeper soil strata over time and are initially depleted in surface soil strata, root systems with rapid exploitation of deep soil would optimize water and N capture in most maize production environments.The ideotype Specific phenes that may contribute to rooting depth in maize include (a) a large diameter primary root with few but long laterals and tolerance of cold soil temperatures, (b) many seminal roots with shallow growth angles, small diameter, many laterals, and long root hairs, or as an alternative, an intermediate number of seminal roots with steep growth angles, large diameter, and few laterals coupled with abundant lateral branching of the initial crown roots, (c) an intermediate number of crown roots with steep growth angles, and few but long laterals, (d) one whorl of brace roots of high occupancy, having a growth angle that is slightly shallower than the growth angle for crown roots, with few but long laterals, (e) low cortical respiratory burden created by abundant cortical aerenchyma, large cortical cell size, an optimal number of cells per cortical file, and accelerated cortical senescence, (f) unresponsiveness of lateral branching to localized resource availability, and (g) low K-m and high V-max for nitrate uptake. Some elements of this ideotype have experimental support, others are hypothetical. Despite differences in N distribution between low-input and commercial maize production, this ideotype is applicable to low-input systems because of the importance of deep rooting for water acquisition. Many features of this ideotype are relevant to other cereal root systems and more generally to root systems of dicotyledonous crops.
DOI:10.1111/j.1469-8137.2012.04198.xURLPMID:22686426 [本文引用: 1]
090004Although linkages of leaf and whole-plant traits to leaf lifespan have been rigorously investigated, there is a limited understanding of similar linkages of whole-plant and fine root traits to root lifespan. In comparisons across species, do suites of traits found in leaves also exist for roots, and can these traits be used to predict root lifespan?090004We observed the fine root lifespan of 12 temperate tree species using minirhizotrons in a common garden and compared their median lifespans with fine-root and whole-plant traits. We then determined which set of combined traits would be most useful in predicting patterns of root lifespan.090004Median root lifespan ranged widely among species (95090009336 d). Root diameter, calcium content, and tree wood density were positively related to root lifespan, whereas specific root length, nitrogen (N) : carbon (C) ratio, and plant growth rate were negatively related to root lifespan. Root diameter and plant growth rate, together (R2 = 0.62) or in combination with root N : C ratio (R2 = 0.76), were useful predictors of root lifespan across the 12 species.090004Our results highlight linkages between fine root lifespan in temperate trees and plant functional traits that may reduce uncertainty in predictions of root lifespan or turnover across species at broader spatial scales.
DOI:10.1111/j.1461-0248.2010.01476.xURLPMID:20482582 [本文引用: 1]
Despite the increasing importance of functional traits for the study of plant ecology, we do not know how variation in a given trait changes across ecological scales, which prevents us from assessing potential scale-dependent aspects of trait variation. To address this deficiency, we partitioned the variance in two key functional traits (leaf mass area and leaf dry matter content) across six nested ecological scales (site, plot, species, tree, strata and leaf) in lowland tropical rainforests. In both traits, the plot level shows virtually no variance despite high species turnover among plots and the size of within-species variation (leaf + strata + tree) is comparable with that of species level variation. The lack of variance at the plot level brings substantial support to the idea that trait-based environmental filtering plays a central role in plant community assembly. These results and the finding that the amount of within-species variation is comparable with interspecific variation support a shift of focus from species-based to trait-based ecology.
DOI:10.1098/rspb.2015.2434URLPMID:27030412 [本文引用: 1]
Abstract The notion that relationships between community-weighted mean (CWM) traits (i.e. plot-level trait values weighted by species abundances) and environmental conditions reflect selection towards locally optimal phenotypes is challenged by the large amount of interspecific trait variation typically found within ecological communities. Reconciling these contrasting patterns is a key to advancing predictive theories of functional community ecology. We combined data on geographical distributions and three traits (wood density, leaf mass per area and maximum height) of 173 tree species in Puerto Rico. We tested the hypothesis that species are more likely to occur where their trait values are more similar to the local CWM trait values (the'CWM-optimality' hypothesis) by comparing species occurrence patterns (as a proxy for fitness) with the functional composition of forest plots across a precipitation gradient. While 70% of the species supported CWM-optimality for at least one trait, nearly 25% significantly opposed it for at least one trait, thereby contributing to local functional diversity. The majority (85%) of species that opposed CWM-optimality did so only for one trait and few species opposed CWM-optimality in multivariate trait space. Our study suggests that constraints to local functional variation act more strongly on multivariate phenotypes than on univariate traits. 2016 The Author(s).
DOI:10.1016/j.tree.2008.10.011URLPMID:19185951 [本文引用: 1]
Divergent natural selection has been shown to promote speciation in many taxa. However, although divergent selection often initiates the process of speciation, it often fails to complete it. Several time-based, geographic and genetic factors have been recognized to explain this variability in how far speciation proceeds. We review here recent evidence indicating that variability in the completeness of speciation can also be associated with the nature of divergent selection itself, with speciation being greatly promoted by (i) stronger selection on a given, single trait (the ‘stronger selection’ hypothesis) and (ii) selection on a greater number of traits (the ‘multifarious selection’ hypothesis). However, evidence for each selective hypothesis is still scarce, and further work is required to determine their relative importance.
DOI:10.1111/1365-2745.12000URL [本文引用: 1]
Plant species composition and community functional structure (i.e. trait composition at the community level) result from a hierarchy of environmental filters that constrain which species and traits tend to be dominant in a given habitat.We quantified variation in community functional structure along natural gradients of soil resources using several above- and below-ground parameters and explored links among these attributes to determine whether plant resource economics can be applied at the community level in a Mediterranean rangeland of southern France.Limitation by nitrogen, soil water and soil depth were the main ecological factors driving the functional response at the community level. Most of the community functional parameters considered in this study were more dependent on nitrogen limitation than on the other two factors, mostly related with the acquisition onservation trade-off at both the leaf and the root level.We found a strong coordination between above-ground and below-ground components, with a high level of concordance along the resource gradients explored. As an example, tissue dry matter content both in leaves and roots was positively related to nitrogen limitation. These findings indicate that the leaf economic spectrum paradigm (resource conservation in resource-poor habitats versus resource acquisition in resource-rich habitats) can be extrapolated to the below-ground component and extends to a plant community spectrum.Changes in the functional structure of communities were promoted by two complementary components of variation: (i) the replacement of species with highly contrasting resource-use strategies and, to a lesser extent, (ii) the intraspecific variation in several above-ground traits.Synthesis. This study showed that soil water and nutrient limitations are the main drivers controlling functional community structure in the Mediterranean rangelands studied and that shifts in this structure were mainly due to species turnover. In addition, we provided evidence for a plant community economics spectrum, based on a strong coordination between above- and below-ground components in these resource-limited communities.
DOI:10.2307/3100029URL [本文引用: 2]
The fine roots of trees are concentrated on lateral branches that arise from perennial roots. They are important in the acquisition of water and essential nutrients, and at the ecosystem level, they make a significant contribution to biogeochemical cycling. Fine roots have often been studied according to arbitrary size classes, e.g., all roots less than 1 or 2 mm in diameter. Because of the size class approach, the position of an individual root on the complex lateral branching system has often been ignored, and relationships between the form of the branching root system and its function are poorly understood. The fine roots of both gymnosperms and angiosperms, which formed ectomycorrhizae (EM) and arbuscular mycorrhizae (AM) fungal associations, were sampled in 1998 and 1999. Study sites were chosen to encompass a wide variety of environments in four regions of North America. Intact lateral branches were collected from each species and 18561 individual roots were dissected by order, with distal roots numbered as first-order roots. This scheme is similar to the one commonly used to number the order of streams. Fine root diameter, length, specific root length (SRL; m/g), and nitrogen (N) concentration of nine North American tree species (Acer saccharum, Juniperus monosperma, Liriodendron tulipifera, Picea glauca, Pinus edulis, Pinus elliottii, Pinus resinosa, Populus balsamifera, and Quercus alba) were then compared and contrasted. Lateral roots <0.5 mm in diameter accounted for >75% of the total number and length of individual roots sampled in all species except Liriodendron tulipifera. Both SRL and N concentration decreased with increasing root order in all nine species, and this pattern appears to be universal in all temperate and boreal trees. Nitrogen concentrations ranged from 8.5 to 30.9 g/kg and were highest in the first-order "root tips." On a mass basis, first-order roots are expensive to maintain per unit time (high tissue N concentration). Tissue N appears to be a key factor in understanding the C cost of maintaining first- and second-order roots, which dominate the display of absorbing root length. There were many significant differences among species in diameter, length, SRL, and N concentration. For example, two different species can have similar SRL but very different tissue N concentrations. Our findings run contrary to the common idea that all roots of a given size class function the same way and that a common size class for fine roots works well for all species. Interestingly, fine root lateral branches are apparently deciduous, with a distinct lateral branch scar. The position of an individual root on the branching root system appears to be important in understanding the function of fine roots.
DOI:10.1111/1365-2745.12211URL [本文引用: 1]
ABSTRACT The leaf economics spectrum (LES) provides a useful framework for examining species strategies as shaped by their evolutionary history. However, that spectrum, as originally described, involved only two key resources (carbon and nutrients) and one of three economically important plant organs. Herein, I evaluate whether the economics spectrum idea can be broadly extended to water – the third key resource –stems, roots and entire plants and to individual, community and ecosystem scales. My overarching hypothesis is that strong selection along trait trade-off axes, in tandem with biophysical constraints, results in convergence for any taxon on a uniformly fast, medium or slow strategy (i.e. rates of resource acquisition and processing) for all organs and all resources. Evidence for economic trait spectra exists for stems and roots as well as leaves, and for traits related to water as well as carbon and nutrients. These apply generally within and across scales (within and across communities, climate zones, biomes and lineages). There are linkages across organs and coupling among resources, resulting in an integrated whole-plant economics spectrum. Species capable of moving water rapidly have low tissue density, short tissue life span and high rates of resource acquisition and flux at organ and individual scales. The reverse is true for species with the slow strategy. Different traits may be important in different conditions, but as being fast in one respect generally requires being fast in others, being fast or slow is a general feature of species. Economic traits influence performance and fitness consistent with trait-based theory about underlying adaptive mechanisms. Traits help explain differences in growth and survival across resource gradients and thus help explain the distribution of species and the assembly of communities across light, water and nutrient gradients. Traits scale up – fast traits are associated with faster rates of ecosystem processes such as decomposition or primary productivity, and slow traits with slow process rates. Synthesis. Traits matter. A single ‘fast–slow’ plant economics spectrum that integrates across leaves, stems and roots is a key feature of the plant universe and helps to explain individual ecological strategies, community assembly processes and the functioning of ecosystems.
DOI:10.1111/ele.12527URLPMID:26415689 [本文引用: 1]
Abstract One of the few rules in ecology is that communities are composed of many rare and few common species. Trait-based investigations of abundance distributions have generally focused on species-mean trait values with mixed success. Here, using large tropical tree seedling datasets in China and Puerto Rico, we take an alternative approach that considers the magnitude of intraspecific variation in traits and growth as it relates to species abundance. We find that common species are less variable in their traits and growth. Common species also occupy core positions within community trait space indicating that they are finely tuned for the available conditions. Rare species are functionally peripheral and are likely transients struggling for success in the given environment. The work highlights the importance of considering intraspecific variation in trait-based ecology and demonstrates asymmetry in the magnitude of intraspecific variation among species is critical for understanding of how traits are related to abundance.
DOI:10.3389/fpls.2015.00866URLPMID:4604266 [本文引用: 1]
The consequences of global change for the maintenance of species diversity will depend on the sum of each species responses to the environment and on the interactions among them. A wide ecological literature supports that these species-specific responses can arise from factors related to life strategies, evolutionary history and intraspecific variation, and also from environmental variation in space and time. In the light of recent advances from coexistence theory combined with mechanistic explanations of diversity maintenance, we discuss how global change drivers can influence species coexistence. We revise the importance of both competition and facilitation for understanding coexistence in different ecosystems, address the influence of phylogenetic relatedness, functional traits, phenotypic plasticity and intraspecific variability, and discuss lessons learnt from invasion ecology. While most previous studies have focused their efforts on disentangling the mechanisms that maintain the biological diversity in species-rich ecosystems such as tropical forests, grasslands and coral reefs, we argue that much can be learnt from pauci-specific communities where functional variability within each species, together with demographic and stochastic processes becomes key to understand species interactions and eventually community responses to global change.
DOI:10.1111/nph.14571URL [本文引用: 1]
Abstract Fine-root traits play key roles in ecosystem processes, but the drivers of fine-root trait diversity remain poorly understood. The plant economic spectrum (PES) hypothesis predicts that leaf and root traits evolved in coordination. Mycorrhizal association type, plant growth form and climate may also affect root traits. However, the extent to which these controls are confounded with phylogenetic structuring remains unclear. Here we compiled information about root and leaf traits for > 600 species. Using phylogenetic relatedness, climatic ranges, growth form and mycorrhizal associations, we quantified the importance of these factors in the global distribution of fine-root traits. Phylogenetic structuring accounts for most of the variation for all traits excepting root tissue density, with root diameter and nitrogen concentration showing the strongest phylogenetic signal and specific root length showing intermediate values. Climate was the second most important factor, whereas mycorrhizal type had little effect. Substantial trait coordination occurred between leaves and roots, but the strength varied between growth forms and clades. Our analyses provide evidence that the integration of roots and leaves in the PES requires better accounting of the variation in traits across phylogenetic clades. Inclusion of phylogenetic information provides a powerful framework for predictions of belowground functional traits at global scales.
[本文引用: 1]
DOI:10.11686/cyxb20120303URL
在藏北高原高寒草地样带上对40个围栏内草地群落物种多样性和地上生物量进行测定,探讨了生长季降水对高寒草地生物量和物种多样性分布格局的影响以及地上生物量-物种多样性之间的关系模式。结果表明,降水格局显著地影响藏北高原内部高寒草地群落物种丰富度、多样性和均匀度,群落结构特征与初级生产力关系密切;藏北地区高寒草地地上生物量、物种丰富度、Shannon-Wiener指数和Pielou均匀度指数随生长季累积降水呈指数增加趋势;在高寒草地群落物种丰富度-生产力关系研究中单峰模式的判别系数R2(0.754)略高于线性回归模型(0.743)。沿藏北高原样带高寒草地物种丰富度随地上生物量单调递增,单峰模式的单调递减区间并未出现;然而单峰模型预示着在地上生物量高于121.17g/m2的高寒草地群落物种丰富度可能随生物量单调递减,从而使物种丰富度-地上生物量表现为较为标准的单峰模式;Shannon-Wiener多样性指数和Pielou均匀度指数与地上生物量也均呈单峰模式,但其单调递减区间窄于单调递增区间,峰值分别对应的草地群落地上生物量为71.90和60.90g/m2。
DOI:10.11686/cyxb20120303URL
在藏北高原高寒草地样带上对40个围栏内草地群落物种多样性和地上生物量进行测定,探讨了生长季降水对高寒草地生物量和物种多样性分布格局的影响以及地上生物量-物种多样性之间的关系模式。结果表明,降水格局显著地影响藏北高原内部高寒草地群落物种丰富度、多样性和均匀度,群落结构特征与初级生产力关系密切;藏北地区高寒草地地上生物量、物种丰富度、Shannon-Wiener指数和Pielou均匀度指数随生长季累积降水呈指数增加趋势;在高寒草地群落物种丰富度-生产力关系研究中单峰模式的判别系数R2(0.754)略高于线性回归模型(0.743)。沿藏北高原样带高寒草地物种丰富度随地上生物量单调递增,单峰模式的单调递减区间并未出现;然而单峰模型预示着在地上生物量高于121.17g/m2的高寒草地群落物种丰富度可能随生物量单调递减,从而使物种丰富度-地上生物量表现为较为标准的单峰模式;Shannon-Wiener多样性指数和Pielou均匀度指数与地上生物量也均呈单峰模式,但其单调递减区间窄于单调递增区间,峰值分别对应的草地群落地上生物量为71.90和60.90g/m2。
DOI:10.1104/pp.15.00187URLPMID:26077764
Abstract An emerging paradigm is that root traits that reduce the metabolic costs of soil exploration improve the acquisition of limiting soil resources. Here, we test the hypothesis that reduced lateral root branching density will improve drought tolerance in maize (Zea mays) by reducing the metabolic costs of soil exploration, permitting greater axial root elongation, greater rooting depth, and thereby greater water acquisition from drying soil. Maize recombinant inbred lines with contrasting lateral root number and length (few but long [FL] and many but short [MS]) were grown under water stress in greenhouse mesocosms, in field rainout shelters, and in a second field environment with natural drought. Under water stress in mesocosms, lines with the FL phenotype had substantially less lateral root respiration per unit of axial root length, deeper rooting, greater leaf relative water content, greater stomatal conductance, and 50% greater shoot biomass than lines with the MS phenotype. Under water stress in the two field sites, lines with the FL phenotype had deeper rooting, much lighter stem water isotopic signature, signifying deeper water capture, 51% to 67% greater shoot biomass at flowering, and 144% greater yield than lines with the MS phenotype. These results entirely support the hypothesis that reduced lateral root branching density improves drought tolerance. The FL lateral root phenotype merits consideration as a selection target to improve the drought tolerance of maize and possibly other cereal crops. 2015 American Society of Plant Biologists. All Rights Reserved.
URL [本文引用: 1]
沿昌都到噶尔县的经度梯度,对西藏典型高寒草地植被生产力与植物多样性开展了1 700 km的野外样带调查。实验结果表明:高寒草地的群落结构特征(地上生物量、地下生物量、盖度和密度)与生物多样性(物种丰富度、物种多样性和物种均匀度)均具有明显的经度分布格局。整体而言,这些特征参数均表现出自西向东沿荒漠草原—典型草原—草甸草原呈逐渐递增的趋势;其经度格局主要受降雨量和平均气温所趋动,但降雨量和平均温度的影响在不同指标间存在较大差异;地上生物量由二者共同决定,而物种丰富度受降雨量的影响更大。西藏高寒草地的物种丰富度与地上生物量间存在显著的幂指数关系(y=0.219 7 x~(0.754 9),R~2=0.61,P<0.01)。上述规律的发现,不仅有利于我们更好地理解高寒草地对未来气候变化的响应机制与适应途径,也将帮助我们合理制定放牧策略以实现该地区高寒草地的可持续发展。
URL [本文引用: 1]
沿昌都到噶尔县的经度梯度,对西藏典型高寒草地植被生产力与植物多样性开展了1 700 km的野外样带调查。实验结果表明:高寒草地的群落结构特征(地上生物量、地下生物量、盖度和密度)与生物多样性(物种丰富度、物种多样性和物种均匀度)均具有明显的经度分布格局。整体而言,这些特征参数均表现出自西向东沿荒漠草原—典型草原—草甸草原呈逐渐递增的趋势;其经度格局主要受降雨量和平均气温所趋动,但降雨量和平均温度的影响在不同指标间存在较大差异;地上生物量由二者共同决定,而物种丰富度受降雨量的影响更大。西藏高寒草地的物种丰富度与地上生物量间存在显著的幂指数关系(y=0.219 7 x~(0.754 9),R~2=0.61,P<0.01)。上述规律的发现,不仅有利于我们更好地理解高寒草地对未来气候变化的响应机制与适应途径,也将帮助我们合理制定放牧策略以实现该地区高寒草地的可持续发展。
A trait-based approach to community assembly: Partitioning of species trait values into within-and among-community components
1
2007
... 群落尺度上的属性CWM值能够反映环境的筛选作用, 代表着当地环境最优适应值(
When and how should intraspecific variability be considered in trait-based plant ecology?
1
2011
... 自然环境压力的大小可能决定了植物根系的种间变异.
A multi-trait approach reveals the structure and the relative importance of intraspecific vs. interspecific variability in plant traits
1
2010
... 除了物种间的变化, 不同群落里共有种的属性的种内变异可能也会影响群落CWM值(
Topological scaling and plant root system architecture: Developmental and functional hierarchies
1
1997
... 在实验室中用去离子水洗去附着在根上的细小杂质与灰尘, 并将其置于放有去离子水的培养皿中(使根系间不会重叠), 利用扫描仪(Expression 10000XL; Epson, Suwa, Japan)进行扫描, 并使用WINRHIZO软件(Regent Instruments, Quebec, Canada)将获取的图像进行处理分析, 获得一级根直径、一级根长度及分支强度3个指标.其中根系的分级是严格遵循
Dependence of root cell growth and division on root diameter
1
2018
... 本研究表明在青藏高原草原群落区域尺度上, 不同物种间根直径变异较小, 而一级侧根长度和根系分支强度变异较大(
Differential responses of ecosystem respiration components to experimental warming in a meadow grassland on the Tibetan Plateau
2016
Variation of first-order root traits across climatic gradients and evolutionary trends in geological time
2
2013
... 根系属性能够表征植物多样性的资源获取策略.
... 自然环境压力的大小可能决定了植物根系的种间变异.
Community assembly and shifts in plant trait distributions across an environmental gradient in coastal California
1
2009
... 群落尺度上的属性CWM值能够反映环境的筛选作用, 代表着当地环境最优适应值(
The global spectrum of plant form and function
2
2016
... 植物功能属性的种间和种内变异是物种共存和适应环境变化的基础.属性的种间变异能够代表不同物种的生态位空间差异(
... 本研究对如何来定义植物的属性空间有启发意义: (1)用多少指标, 用什么指标.我们的研究表明地下资源策略似乎通过几个有限的指标就可以得到很好的描述, 但这也有待更多的试验研究的验证.(2)有限的地下策略指标和有限的地上策略指标(
Constraints on trait combinations explain climatic drivers of biodiversity: The importance of trait covariance in community assembly
1
2017
... 自然环境压力的大小可能决定了植物根系的种间变异.
On the relationship between specific root length and the rate of root proliferation: A field study using citrus rootstocks
1
1991
... 自然环境压力的大小可能决定了植物根系的种间变异.
Linking root traits to nutrient foraging in arbuscular mycorrhizal trees in a temperate forest
2
2015
... 根系属性能够表征植物多样性的资源获取策略.
... 本研究表明在青藏高原草原群落区域尺度上, 不同物种间根直径变异较小, 而一级侧根长度和根系分支强度变异较大(
Intraspecific trait variation and covariation in a widespread tree species (Nothofagus pumilio) in southern Chile
1
2011
... 植物功能属性的种间和种内变异是物种共存和适应环境变化的基础.属性的种间变异能够代表不同物种的生态位空间差异(
An architectural approach to the comparative ecology of plant root systems
1
1987
... 在实验室中用去离子水洗去附着在根上的细小杂质与灰尘, 并将其置于放有去离子水的培养皿中(使根系间不会重叠), 利用扫描仪(Expression 10000XL; Epson, Suwa, Japan)进行扫描, 并使用WINRHIZO软件(Regent Instruments, Quebec, Canada)将获取的图像进行处理分析, 获得一级根直径、一级根长度及分支强度3个指标.其中根系的分级是严格遵循
短期增温对藏北高寒草甸植物群落特征的影响
2017
短期增温对藏北高寒草甸植物群落特征的影响
2017
Intraspecific variability and trait- based community assembly
1
2010
... 植物功能属性的种间和种内变异是物种共存和适应环境变化的基础.属性的种间变异能够代表不同物种的生态位空间差异(
Picante: R tools for integrating phylogenies and ecology
1
2010
... 通过对西藏3个草原群落内22个物种的采样调查, 利用SPSS 22.0 (SPSS, Chicago, USA)统计分析不同物种间根属性的变异情况, 采用单因子方差分析和Tukey检验比较同一根属性在不同水分梯度上的差异.运用Pearson相关分析三个根属性间的相关关系, 同时利用R软件包picante (
Contrasting effects of plant inter- and intraspecific variation on community-level trait measures along an environmental gradient
2
2013
... 除了物种间的变化, 不同群落里共有种的属性的种内变异可能也会影响群落CWM值(
... ;
Leading dimensions in absorptive root trait variation across 96 subtropical forest species
3
2014
... 植物功能属性的种间和种内变异是物种共存和适应环境变化的基础.属性的种间变异能够代表不同物种的生态位空间差异(
... 根系属性能够表征植物多样性的资源获取策略.
... 在实验室中用去离子水洗去附着在根上的细小杂质与灰尘, 并将其置于放有去离子水的培养皿中(使根系间不会重叠), 利用扫描仪(Expression 10000XL; Epson, Suwa, Japan)进行扫描, 并使用WINRHIZO软件(Regent Instruments, Quebec, Canada)将获取的图像进行处理分析, 获得一级根直径、一级根长度及分支强度3个指标.其中根系的分级是严格遵循
Plant functional traits and the multidimensional nature of species coexistence
1
2015
... 本研究表明在青藏高原草原群落区域尺度上, 不同物种间根直径变异较小, 而一级侧根长度和根系分支强度变异较大(
Plant functional traits have globally consistent effects on competition
1
2011
... 本研究对如何来定义植物的属性空间有启发意义: (1)用多少指标, 用什么指标.我们的研究表明地下资源策略似乎通过几个有限的指标就可以得到很好的描述, 但这也有待更多的试验研究的验证.(2)有限的地下策略指标和有限的地上策略指标(
Competitive interactions between forest trees are driven by species’ trait hierarchy, not phylogenetic or functional similarity: Implications for forest community assembly
1
2012
... 植物功能属性的种间和种内变异是物种共存和适应环境变化的基础.属性的种间变异能够代表不同物种的生态位空间差异(
A predictive model of community assembly that incorporates intraspecific trait variation
1
2012
... 自然环境压力的大小可能决定了植物根系的种间变异.
Fitness of multidimensional phenotypes in dynamic adaptive landscapes
1
2015
... 除了物种间的变化, 不同群落里共有种的属性的种内变异可能也会影响群落CWM值(
Diverse belowground resource strategies underlie plant species coexistence and spatial distribution in three grasslands along a precipitation gradient
5
2017
... 植物功能属性的种间和种内变异是物种共存和适应环境变化的基础.属性的种间变异能够代表不同物种的生态位空间差异(
... 根系属性能够表征植物多样性的资源获取策略.
... 本研究表明在青藏高原草原群落区域尺度上, 不同物种间根直径变异较小, 而一级侧根长度和根系分支强度变异较大(
... 自然环境压力的大小可能决定了植物根系的种间变异.
... 本研究表明, 与其他生态系统相比, 如森林和温带草原系统(
Complementarity in nutrient foraging strategies of absorptive fine roots and arbuscular mycorrhizal fungi across 14 coexisting subtropical tree species
4
2015
... 植物功能属性的种间和种内变异是物种共存和适应环境变化的基础.属性的种间变异能够代表不同物种的生态位空间差异(
... 根系属性能够表征植物多样性的资源获取策略.
... 本研究表明在青藏高原草原群落区域尺度上, 不同物种间根直径变异较小, 而一级侧根长度和根系分支强度变异较大(
... 本研究表明, 与其他生态系统相比, 如森林和温带草原系统(
Steep, cheap and deep: An ideotype to optimize water and N acquisition by maize root systems
2013
Predicting fine root lifespan from plant functional traits in temperate trees
1
2012
... 自然环境压力的大小可能决定了植物根系的种间变异.
How do traits vary across ecological scales? A case for trait-based ecology
1
2010
... 植物功能属性的种间和种内变异是物种共存和适应环境变化的基础.属性的种间变异能够代表不同物种的生态位空间差异(
Do community-weighted mean functional traits reflect optimal strategies?
1
2016
... 群落尺度上的属性CWM值能够反映环境的筛选作用, 代表着当地环境最优适应值(
Ecological explanations for (incomplete) speciation
1
2009
... 除了物种间的变化, 不同群落里共有种的属性的种内变异可能也会影响群落CWM值(
Evidence for a “plant community economics spectrum” driven by nutrient and water limitations in a mediterranean rangeland of southern France
1
2012
... 群落尺度上的属性CWM值能够反映环境的筛选作用, 代表着当地环境最优适应值(
Fine root architecture of nine North American trees
2
2002
... 植物功能属性的种间和种内变异是物种共存和适应环境变化的基础.属性的种间变异能够代表不同物种的生态位空间差异(
... 在实验室中用去离子水洗去附着在根上的细小杂质与灰尘, 并将其置于放有去离子水的培养皿中(使根系间不会重叠), 利用扫描仪(Expression 10000XL; Epson, Suwa, Japan)进行扫描, 并使用WINRHIZO软件(Regent Instruments, Quebec, Canada)将获取的图像进行处理分析, 获得一级根直径、一级根长度及分支强度3个指标.其中根系的分级是严格遵循
The world-wide “fast-slow” plant economics spectrum: A traits manifesto
1
2014
... 自然环境压力的大小可能决定了植物根系的种间变异.
Commonness, rarity, and intraspecific variation in traits and performance in tropical tree seedlings
1
2015
... 通过对西藏3个草原群落内22个物种的采样调查, 利用SPSS 22.0 (SPSS, Chicago, USA)统计分析不同物种间根属性的变异情况, 采用单因子方差分析和Tukey检验比较同一根属性在不同水分梯度上的差异.运用Pearson相关分析三个根属性间的相关关系, 同时利用R软件包picante (
Species coexistence in a changing world
1
2015
... 自然环境压力的大小可能决定了植物根系的种间变异.
A worldview of root traits: The influence of ancestry, growth form, climate and mycorrhizal association on the functional trait variation of fine-root tissues in seed plants
1
2017
... 根系属性能够表征植物多样性的资源获取策略.
The return of the variance: Intraspecific variability in community ecology
1
2012
... 除了物种间的变化, 不同群落里共有种的属性的种内变异可能也会影响群落CWM值(
藏北高寒草地样带物种多样性沿降水梯度的分布格局
2012
藏北高寒草地样带物种多样性沿降水梯度的分布格局
2012
Reduced lateral root branching density improves drought tolerance in maize
2015
青藏高寒草地植被生产力与生物多样性的经度格局
1
2017
... 研究区位于青藏高原西北腹地, 为典型的亚寒带气候区, 全年气候干冷, 植物生长季一般为5月中下旬至9月下旬.该区域由于受西南季风及地形因素影响, 降水自东向西逐渐减少(
青藏高寒草地植被生产力与生物多样性的经度格局
1
2017
... 研究区位于青藏高原西北腹地, 为典型的亚寒带气候区, 全年气候干冷, 植物生长季一般为5月中下旬至9月下旬.该区域由于受西南季风及地形因素影响, 降水自东向西逐渐减少(
