Li Xuefei, Pei Kequan, Kéry Marc, Niklaus Pascal A, Schmid Bernhard
Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.
Laboratory of Quantitative Vegetation Ecology, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Haidian District, Beijing, P.R. China.
PLoS One. 2017 Apr 18;12(4):e0175727. doi: 10.1371/journal.pone.0175727. eCollection 2017.
Functional traits, properties of organisms correlated with ecological performance, play a central role in plant community assembly and functioning. To some extents, functional traits vary in concert, reflecting fundamental ecological strategies. While "trait syndromes" characteristic of e.g. fast-growing, early-successional vs. competitive, late-successional species are recognized in principle, less is known about the environmental and genetic factors at the source of trait variation and covariation within plant communities. We studied the three leaf traits leaf half-life (LHL), leaf mass per area (LMA) and nitrogen concentration in green leaves (Ngreen) and the wood trait wood density (WD) in 294 individuals belonging to 45 tree or shrub species in a Chinese subtropical forest from September 2006 to January 2009. Using multilevel ANOVA and decomposition of sums of products, we estimated the amount of trait variation and covariation among species (mainly genetic causes), i.e. plant functional type (deciduous vs. evergreen species), growth form (tree vs. shrub species), family/genus/species differences, and within species (mainly environmental causes), i.e. individual and season. For single traits, the variation between functional types and among species within functional types was large, but only LMA and Ngreen varied significantly among families and thus showed phylogenetic signal. Trait variation among individuals within species was small, but large temporal variation due to seasonal effects was found within individuals. We did not find any trait variation related to soil conditions underneath the measured individuals. For pairs of traits, variation between functional types and among species within functional types was large, reflecting a strong evolutionary coordination of the traits, with LMA, LHL and WD being positively correlated among each other and negatively with Ngreen. This integration of traits was consistent with a putative stem-leaf economics spectrum ranging from deciduous species with thin, high-nitrogen leaves and low-density wood to evergreen species with thick, low-nitrogen leaves and dense wood and was not influenced by phylogenetic history. Trait coordination within species was weak, allowing individual trees to deviate from the interspecific trait coordination and thus respond flexibly to environmental heterogeneity. Our findings suggest that within a single woody plant community variation and covariation in functional traits allows a large number of species to co-exist and cover a broad spectrum of multivariate niche space, which in turn may increase total resource extraction by the community and community functioning.
功能性状是与生态表现相关的生物体属性，在植物群落的组装和功能中起着核心作用。在一定程度上，功能性状协同变化，反映了基本的生态策略。虽然原则上已认识到诸如快速生长的早期演替物种与具有竞争力的晚期演替物种等“性状综合征”，但对于植物群落内性状变异和协变根源的环境和遗传因素却知之甚少。2006年9月至2009年1月，我们在中国亚热带森林中对属于45种树或灌木物种的294个个体，研究了三个叶片性状：叶半衰期（LHL）、单位面积叶质量（LMA）和绿叶中的氮浓度（Ngreen）以及木材性状木材密度（WD）。使用多水平方差分析和乘积和分解，我们估计了物种间（主要是遗传原因）即植物功能类型（落叶与常绿物种）、生长形式（乔木与灌木物种）、科/属/种差异的性状变异和协变数量，以及物种内（主要是环境原因）即个体和季节的性状变异和协变数量。对于单个性状，功能类型之间以及功能类型内物种之间的变异很大，但只有LMA和Ngreen在科间差异显著，因此显示出系统发育信号。物种内个体间的性状变异很小，但在个体内发现了由于季节效应导致的较大时间变异。我们没有发现与被测个体下方土壤条件相关的任何性状变异。对于成对性状，功能类型之间以及功能类型内物种之间的变异很大，反映了性状之间强烈的进化协调性，LMA、LHL和WD相互之间呈正相关，与Ngreen呈负相关。这种性状整合与一个假定的茎叶经济谱一致，该谱从具有薄的、高氮叶片和低密度木材的落叶物种到具有厚的、低氮叶片和高密度木材的常绿物种，并且不受系统发育历史的影响。物种内的性状协调性较弱，使得个体树木能够偏离种间性状协调性，从而灵活应对环境异质性。我们的研究结果表明，在单个木本植物群落中，功能性状的变异和协变使得大量物种能够共存并占据广泛的多变量生态位空间，这反过来可能会增加群落的总资源获取量和群落功能。
