Above- and belowground plant complementarity

不断增加的植物多样性增强了生态系统功能的许多方面。具有较高多样性的群落性能的提高被认为源于两类不同的机制：(1)互补效应和(2)采样效应，但目前的知识表明，互补性是推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，尤其是在地下。直接的机械方法依赖于使用同位素标记的化合物来测量养分的吸收，或者依赖于对地上或地下空间开发的测量。间接的、相关的方法试图将植物性状作为生态位定义的替代品与植物表现联系起来，或者在单一栽培和混合栽培中比较物种表现。到目前为止，这些方法主要是孤立使用的，结果喜忧参半。在这里，我们认为迫切需要对这些方法进行综合和比较，以回答生态学中一个长期存在但仍未得到回答的问题：不同资源的互补使用对BEF关系的相对重要性是什么？我们的目标是整合来自直接和间接方法的现有证据，并首次探索草原生态系统植物资源互补的全面图景。到目前为止，直接方法的结果支持光的地上互补，而地下资源互补的证据尚不确定。在工作包1(WP 1)中，我们的目标是全面综合耶拿实验的直接互补性测量的所有证据以及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审查和综合分析。驱动BEF关系的互补性的间接证据比直接证据更多，但主要限于地上生物量和地上性状。在工作包2(WP2)中，我们将汇编耶拿实验物种的最大可用特征数据库集，包括许多根特征，并将其公开提供。利用这个数据集，我们将系统地筛选社区加权平均值(与选择效应相关的CWM)或特征功能多样性(与互补效应相关的功能多样性)在资源互补背景下对大量功能的重要性。在最后一步(WP 3)，我们将结合这些结果，最终分析在耶拿实验中通过直接或间接方法衡量的地上和地下资源互补性的相对重要性。利用通径分析，第三个WP将揭示资源互补是否确实是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.