Above- and belowground phenological complementarity as drivers of biodiversity-ecosystem functioning relationships in experimental tree plantations

高度的生物多样性往往会增强生态系统的功能。对于草原和社区的短命生物，这些积极的关系可以解释为选择效应，促进，负密度效应和/或资源利用的互补性。虽然也有关于森林生态系统的积极效应的报道，但在这些长寿命系统中，对生物多样性生态系统功能关系的机制理解相当差。我们的研究旨在填补这一空白，通过调查时间互补性是否增强了物种丰富的人工林与单种林相比的养分吸收。本研究拟参加国际多样性公约的两个实验地点树木实验网络（IDENT）是全球树木生物多样性实验网络TreeDivNet的一部分。主要地点将在弗赖堡，分析的一个子集也将在加拿大的一个地点进行，以测试我们的结果的一般性。在三个工作包中，我们计划研究i）物种特异性营养示踪剂吸收速率和功能性状，ii）营养吸收的物候学，营养状况和树叶营养含量沿着树木功能多样性和物种丰富度的梯度，（3）植物展叶和落叶的物候期，以及叶面积指数与植物物种丰富度和功能多样性的关系，加深了对植物养分吸收与功能性状关系的认识。此外，我们将能够测试更多物种丰富的种植园是否随着时间的推移表现出更大的营养吸收连续性，以及这是否会导致更好的营养状况和更高的营养吸收率。此外，我们将调查是否有更大的连续性冠层发展导致地上时间的互补性，在光截获更高的多样性。在最后一步中，我们将把地上物候学与养分吸收的物候学联系起来。该项目计划为期三年，主要由一名博士候选人执行，他将被整合到IDENT和TreeDivNet网络中。

High biodiversity often results in enhanced ecosystem functioning. For grasslands and communities of short lived organisms these positive relationships can be explained by selection effects, facilitation, negative density effects and/or complementarity in resource use. Although positive effects have also been reported for forest ecosystems the mechanistic understanding of biodiversity ecosystem functioning relationships is rather poor in these long lived systems.Our study aims at filling part of this gap by investigating whether temporal complementarity enhances the nutrient uptake in species rich tree plantations compared to monospecific stands.The study is supposed to take part at two experimental sites of the International Diversity Experiment Network with Trees (IDENT), which is part of the global network of tree biodiversity experiments TreeDivNet. The main site will be in Freiburg and a subset of analyses will also take place at a site in Canada to test for the generality of our results.In three work packages we plan to study i) species specific nutrient-tracer uptake rates and functional traits, ii) phenology of nutrient uptake, nutrient status and foliage nutrient content along gradients of tree functional diversity and species richness, and iii) phenology of leaf expansion and abscission, and leaf area index as a function of species richness and functional diversity.Our study should deepen our understanding of the relationship between nutrient uptake and functional traits. Further we will be able to test whether more species rich plantations show a greater continuity of nutrient uptake over time and whether this leads to better nutrient status with higher nutrient uptake rates. Additionally we will investigate whether a greater continuity of canopy development leads to aboveground temporal complementarity in light interception with higher diversity. In a last step we will link aboveground phenology to the phenology of nutrient uptake.The project is planned for three years and should mainly be carried out by a PhD candidate, who will be integrated in the IDENT and TreeDivNet networks.