From plant traits to vegetation structure/Des traits des végétaux à la structure de la végétation

我认为群落集合是一种选择过程，发生在属于不同物种的个体水平上，基于功能特征对主流环境过滤器的适应性适应。这一总体框架在本提案中继续使用了控制条件下的比较实验、操纵性实地实验、沿环境梯度的观测研究和数学建模相结合的方法。我的研究计划的总体目标是回答以下一般性问题：给定一个地区物种库(在一个地区发现的植物物种的列表)，了解这些物种的关键功能特征的价值，以及在该地区的当地社区中发现的环境条件，物种库中的哪些物种将在该地点被发现？这些物种中的哪一种将是优势、次要或稀有的？如果我们沿着重要的环境梯度改变这个地方社区的位置，前两个问题的答案将如何改变？群落内特征值的多变量分布如何影响重要的生态系统特性，如初级生产力、养分循环和凋落物分解？我最近(2010年)出版了我对基于特征的群落集合理解的一般理论模型(《从植物特性到植被结构：生态群落集合中的机会和选择》，剑桥大学出版社)。在接下来的五年计划中，我和我的学生将在五个具体研究项目的基础上测试和扩展这一理解。一位目前在读的博士生(Jessy Loranger)将在法国各地使用一套独特的11个长期田间实验，涉及群落组成、植物特征和环境梯度，以测试我的一般模型(CATS：通过特征选择进行社区组装)。第二名博士生(米夏埃·L·贝洛)将进行一系列对照实验，涉及40个对比鲜明的草本植物双子叶、田间观察和多变量建模，以更好地将叶片经济性状和植物水力结构的多个相关模式与精确测量的水分胁迫水平联系起来。这是目前在草本植物中研究相对较少的逆境。第三位博士生(李元志)将探索一个鲜为人知的基于特征的社区集合的含义，该概念与限制相似性的经典概念有关：如果社区在组合时要求多变量特征空间中有一定的最小重叠，那么社区占据的特征空间的总面积必须随着物种丰富度的增加而扩大。元智将使用现有的长期重复实验来测试这些想法，该实验涉及24个1X1X1立方米的田间中生体，这些中生体最初接受了相同的种子混合物，但土壤肥力水平以及干扰的强度和频率不同。最后两个项目涉及尚未招收的学生。一名硕士学生将通过操纵土壤水分有效性进行田间和中观实验，以测试米夏埃·L·贝洛(博士生)确定的与实际和创建的植物群落的水分胁迫相关的特征综合症是否如预测的那样发生变化。第二名理科硕士学生将在长期的中游实验中测量生态系统反应(初级生产力、养分损失和凋落物分解)，并将这些反应与群落加权性状值及其方差的差异联系起来。这些研究项目将有助于根据可概括的植物特性预测植物群落结构和功能的长期目标。

I view community assembly as a selection process occurring at the level of individuals belonging to different species, based on the adaptive fit of functional traits to prevailing environmental filters. This general framework, continued in this proposal, has been pursued using a combination of comparative experiments under controlled conditions, manipulative field experiments, observational studies along environmental gradients and mathematical modelling. The general goal of my research program is to answer the following general questions: Given a regional species pool (a list of plant species that are found in a region), a knowledge of the values of key functional traits of these species, and the environmental conditions found in a local community within this region, which species from the species pool will be found at this site? Which of these species will be dominant, subdominant or rare? How will the answers to the first two questions change if we were to change the position of this local community along important environmental gradients? How does the multivariate distribution of trait values within a community affect important ecosystem properties like primary productivity, nutrient cycling and litter decomposition? I recently (2010) published the general theoretical model of my understanding of trait-based community assembly (“From plant traits to vegetation structure: Chance and selection in the assembly of ecological communities”, Cambridge U Press). In this next 5-year proposal my students and I will be testing and expanding this understanding based on five specific research projects. A current PhD student (Jessy Loranger) will use a unique set of 11 long-term field experiments throughout France, involving community composition, plant traits and environmental gradients, to test my general model (“CATS: Community Assembly by Trait Selection”). A second PhD student (Michaël Belluau) will conduct a series of controlled experiments involving 40 contrasted herbaceous dicots, field observations, and multivariate modelling to better link multiple correlated patterns in leaf economic traits and plant hydraulic architecture to precisely measured levels of water stress. This is currently a relatively poorly studied stress in herbaceous species. A third PhD student (Yuanzhi Li) will be exploring a little-recognized implication of trait-based community assembly that is linked to the classical notion of limiting similarity: if communities are assembled while requiring a certain minimum amount of overlap in multivariate trait-space, then the total area of trait-space occupied by communities must expand as species richness increases. Yuanzhi will test these ideas using an existing long-term replicated experiment involving 24 1X1X1 m3 field mesocosms that initially received the same seed mixture but that differ in levels of soil fertility as well as the intensity and frequency of disturbance. The last two projects involve students yet to be recruited. One MSc student will conduct field and mesocosm experiments by manipulating soil water availability in order to test whether the trait syndromes related to water stress of actual and created plant communities, identified by Michaël Belluau (PhD student) change as predicted. A second MSc student will measure ecosystem responses (primary productivity, nutrient loss and litter decomposition) in the longterm mesocosm experiment and relate these responses to differences in community weighted trait values and their variance. These research projects will contribute to the longterm goal of predicting plant community structure and functioning from generalizable plant traits.