Above- and belowground plant complementarity

植物多样性的增加增强了生态系统功能的许多方面。生物多样性高的群落绩效的提高被认为源于两类不同的机制：(1)互补性效应和(2)抽样效应，但目前的知识表明，互补性是驱动生物多样性生态系统功能（BEF）关系的主导力量。互补性的检测和量化具有挑战性，特别是在地下。直接的机械方法依赖于使用同位素标记的化合物来测量营养吸收，或依赖于测量地上或地下的空间开采。间接的、相关的方法试图将植物性状作为生态位定义的代理与植物性能联系起来，或比较单一栽培和混合栽培中的物种性能。到目前为止，这些方法主要是单独使用的，结果好坏参半。在这里，我们认为迫切需要对这些方法进行综合和比较，以回答一个长期存在但仍未解决的生态学问题：不同资源的互补利用对BEF关系的相对重要性是什么？我们的目标是整合直接和间接方法的现有证据，首次探索草地生态系统植物资源互补性的全面图景。到目前为止，直接方法的结果支持地面上的光互补，而地下资源互补的证据尚无定论。在工作包1 （WP 1）中，我们的目标是全面综合来自耶拿实验的直接互补性测量的所有证据以及来自其他生物多样性实验的数据。我们将组织一次国际研讨会，对这些数据进行全面回顾和荟萃分析。与直接证据相比，证明互补性驱动BEF关系的间接证据更常见，但主要局限于地上生物量和地上性状。在工作包2 （WP 2）中，我们将为耶拿实验的物种编译最大的可用性状数据集，包括许多根性状，并将其公开。利用该数据集，我们将系统地筛选群落加权均值（与选择效应相关的CWM）或性状功能多样性（与互补效应相关的FD）在资源互补背景下的大量功能的重要性。在最后一步（WP 3）中，我们将结合这些结果，最终分析耶拿实验中通过直接或间接方法测量的地上和地下资源互补性的相对重要性。通过通径分析，第三个WP将揭示资源互补性是否确实是BEF关系的重要机制，以及其重要性是否取决于所研究的生态系统功能。

Increasing plant diversity enhances many aspects of ecosystem functioning. The increased performance of communities with higher diversity is thought to originate from two distinct classes of mechanisms: (1) complementarity effects and (2) sampling effects, but current knowledge suggests that complementarity is the dominating force driving biodiversity ecosystem function (BEF) relationships. The detection and quantification of complementarity is challenging, especially belowground. Direct, mechanistic approaches rely on the use of isotopically labelled compounds to measure nutrient uptake or on measurements of space exploitation above- or belowground. Indirect, correlative approaches attempt to link plant traits as proxies of niche definition to plant performance or compare species performance in monoculture and mixtures. So far, these approaches have mainly been used in isolation and yielded mixed results. Here, we argue that a synthesis and comparison of these approaches is urgently needed to answer a longstanding, but still unanswered question in ecology: what is the relative importance of complementary use of different resources for the BEF relationship? We aim to integrate the existing evidence from direct and indirect approaches and explore, for the first time, a comprehensive picture of resource complementarity in plants of grassland ecosystems. So far, results from direct approaches support aboveground complementarity for light while evidence for belowground resource complementarity is inconclusive. In work package 1 (WP 1) we aim to comprehensively synthesize all evidence for direct complementarity measurements from the Jena Experiment as well as data from other biodiversity experiments. We will organize an international workshop to yield a comprehensive review and a meta-analysis of this data. Indirect evidence for complementarity driving the BEF relationship is more often found than direct evidence, but is limited primarily to aboveground biomass and aboveground traits. In work package 2 (WP 2) we will compile the largest available trait dataset for species of the Jena Experiment, including many root traits, and make it publicly available. With this dataset, we will systematically screen the importance of community weighted means (CWM related to selection effects) or functional diversity of traits (FD related to complementarity effects) for a large number functions in the context of resource complementarity. In a final step (WP 3), we will combine these results to finally analyse the relative importance of above- and belowground resource complementarity measured via direct or indirect approaches in the Jena Experiment. Using path analysis, the third WP will reveal if resource complementarity is indeed an important mechanism of BEF relationships and whether or not its importance depends on the ecosystem function under study.