Intra-annual stability of spatial and temporal niche complementarity in temperate grasslands

在子项目植物水关系(SP8)中，我们将讨论互补资源利用，这是解释生物多样性-生态系统功能关系的潜在机制之一。我们将把重点放在水和光的利用上，因为在这方面仍然存在重大的知识差距，尽管这两种资源与植物表现相关。我们的目标是在物种水平上确定水分来源的时间生态位，并首次在主要实验(块2)中沿着多样性梯度量化植物水分关系，以补充正在进行的划分生态系统水通量的努力(任务1)。我们将确定光和水利用方面的生态生理机制，这是任何时空资源互补的基础(在示踪剂和Ecotron实验中)(任务2)。此外，我们将在新的物种特定性状实验(任务3)中评估光和水利用生态位的时间发展、它们的生化基础以及与C和N分配的相关性。我们基于植物生态生理学(如叶片水势、叶片气体交换率)的测量将得到与水和光有关的植物特性(如叶片形态、碳分配、叶片绿度)、冠层光剖面以及植物木质部和土壤水的稳定氧和氢同位素分析的补充。基于这些不同的方法，我们将收集关于光，特别是水使用的独特数据集，以量化生态位互补性及其随时间的发展，并确定潜在的生态生理机制。

Within Subproject Plant Water Relations (SP8), we will address complementary resource use, one of the potential mechanisms explaining biodiversity-ecosystem functioning relationships. We will focus on water and light use, since here major gaps in knowledge still exist, despite the relevance of both resources for plant performance. We aim to identify temporal niches for water sourcing at the species level and for the first time quantify plant water relations along a diversity gradient in the main experiment (block 2), complementing on-going efforts to partition ecosystem water fluxes (task 1). We will determine the ecophysiological mechanisms in terms of light and water use that are the basis for any spatio-temporal resource complementarity (in the tracer and Ecotron experiments) (task 2). In addition, we will assess the temporal development of light and water use niches, their biochemical basis and relevance for C and N allocation in the new species-specific trait experiment (task 3). Our measurements based on plant ecophysiology (e.g., leaf water potentials, leaf gas exchange rates) will be complemented by the assessment of water- and light-related plant traits (e.g., leaf morphology, carbon allocation, leaf greenness), canopy light profiles as well as stable oxygen and hydrogen isotope analyses of plant xylem and soil water. Based on these different approaches, we will collect a unique dataset on light, and in particular, on water use, to quantify niche complementarity and its development over time as well as to identify the underlying ecophysiological mechanisms.