Trophic-interaction, tree-diversity and soil-erosion effects on soil-plant stoichiometry

更广泛的研究背景：营养物质是营养水平和网络之间的重要联系。树木多样性已被证明可以影响营养水平上的营养循环。然而，每个营养水平的内在复杂性和营养水平之间的相互作用限制了我们对树木多样性对养分循环的影响的理解，而养分循环是预测森林生态系统对前所未有的生物多样性丧失速度的反应所必需的。假设：在此，我们建议研究土壤养分通过侵蚀的再分配以及土壤微生物（消费者）与植物（初级生产者）之间养分相关的相互作用。我们的中心假设是：(1)侵蚀沿着斜坡重新分配养分，并区分土壤中土壤微生物和树木可利用的养分模式。侵蚀区养分有效性较低，有利于养分循环，而沉积区则以养分过剩为主。(2)土壤微生物在不同树木混合土壤中更有效地循环和吸收养分（“养分过剩”），而养分过剩是主要的基础过程。(3)在不同的树木混合物中，树木也能更有效地回收和吸收养分，但回收更为重要。因此，任何一个过程的优势都会导致营养水平对树木多样性的化学计量反应的差异。方法：我们将使用化学计量学方法，从养分循环的角度评估树木多样性对营养相互作用的影响。我们将结合最先进的基于径流图的沉积物通量测量，土壤，植物和动物的营养分析以及磷酸盐氧同位素特征的测定来实现我们的目标。此外，该项目将包括一个完整的土壤数据基线（所有主要养分和土壤属性），作为对研究小组参与的所有项目的礼貌。创新：我们将继续独特的长期监测土壤性质。我们将研究树木多样性对侵蚀侧向物质运输的影响，包括养分和其他地上表面成分（如凋落物、花粉、植物碎屑和生物）的再分配，这是生物多样性研究中一个被广泛忽视的机制。此外，我们的目标是解决是否更高营养水平，例如消耗凋落物的土壤微生物，对树木多样性的反应与较低营养水平相同。主要研究人员：该项目将由德国<s:1>宾根大学的Yvonne Oelmann （PI）、Steffen Seitz和Thomas Scholten （co -PI）主持，并与我们的中方合作伙伴Liang Yu（中国科学院）和Naili Zhang（北京林业大学）合作。

Wider research context: Nutrients are an essential link across trophic levels and networks. Tree diversity has been shown to influence nutrient cycles across trophic levels. However, the complexity inherent in each of the levels and interactions among trophic levels constrain our understanding of tree diversity effects on nutrient cycling that is required to predict the response of forest ecosystems to unprecedented rates of biodiversity loss. Hypotheses: Here we propose to study the redistribution of nutrients via erosion and the nutrient-related interactions between soil microorganisms (consumers) and plants (primary producers) along the tree diversity gradient of BEF-China. Our central hypotheses are: (1) Erosion redistributes nutrients along slopes and differentiates the nutrient pattern in soils available to soil microorganisms and trees. Eroded parts show lower nutrient availability and foster nutrient recycling while deposition areas are dominated by nutrient overyielding. (2) Soil microorganisms both recycle and take up nutrients more efficiently (‘nutrient overyielding’) in soil of diverse tree mixtures while nutrient overyielding dominates as the underlying process. (3) Trees also both recycle and take up nutrients more efficiently in diverse tree mixtures but recycling is more important. Consequently, the dominance of either one of the processes results in a divergence of stoichiometric responses of trophic levels to tree diversity.Methods: We will use a stoichiometric approach and assess tree diversity effects on trophic interactions in terms of nutrient cycling. We will combine state-of-the-art runoff-plot based sediment flux measurements, nutrient analyses in soil, plants, and animals and the determination of oxygen isotope signatures in phosphate to reach our aims. In addition, the project will comprise a full soil data baseline (all major nutrients and soil properties) as a courtesy to all projects involved in the research group.Innovation: We will continue the unique long-term monitoring of soil properties. We will study the influence of tree diversity on lateral matter transport by erosion including the redistribution of nutrients and other aboveground surface components like litter, pollen, plant debris, and organisms, which is a widely neglected mechanism in biodiversity research. Furthermore, we aim to resolve whether higher trophic levels, for example soil microorganisms that consume tree litter, share the same responses to tree diversity as lower trophic levels.Primary researchers involved: This project will be conducted by Yvonne Oelmann (PI), Steffen Seitz and Thomas Scholten (Co-PIs) (University of Tübingen) and in collaboration with our Chinese partners Yu Liang (Chinese Academy of Sciences) and Naili Zhang (Beijing Forestry University).