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

更广泛的研究背景：营养物质是跨越营养水平和营养网络的重要纽带。树木多样性已被证明影响营养水平之间的营养循环。然而，每个层次固有的复杂性和营养层次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，这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：在这里，我们建议研究侵蚀对养分的再分配，以及土壤微生物(消费者)和植物(初级生产者)之间与养分相关的相互作用，沿着BEF-中国的树木多样性梯度。我们的中心假设是：(1)侵蚀沿坡面重新分配养分，并区分土壤中可供土壤微生物和树木使用的养分模式。侵蚀部分表现出较低的养分利用率，促进了养分循环，而沉积区则以养分超产为主。(2)土壤微生物在不同树种的土壤中都能更有效地循环利用养分(养分超产)，而养分超产是土壤养分超产的主要过程。(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，但循环更重要。因此，任何一个过程的优势导致营养水平对树木多样性的化学计量学响应的差异。方法：我们将使用化学计量学方法，从营养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泥沙通量测量、土壤、植物和动物的营养分析以及磷酸盐中氧同位素特征的测定来实现我们的目标。此外，该项目将包括完整的土壤数据基线(所有主要养分和土壤属性)，以示对参与研究小组的所有项目的礼貌。创新：我们将继续对土壤属性进行独特的长期监测。我们将研究树木多样性对侵蚀引起的横向物质运输的影响，包括养分和其他地上表面成分的重新分配，如凋落物、花粉、植物碎片和生物，这是生物多样性研究中被广泛忽视的机制。此外，我们的目标是解决较高的营养水平，例如消耗树木凋落物的土壤微生物，是否与较低的营养水平对树木多样性的反应相同。主要研究人员参与：该项目将由图宾根大学的Yvonne Oelmann(PI)、Steffen Seitz和Thomas Scholten(Co-Pis)进行，并与我们的中国合作伙伴於亮(中国科学院)和Naili Zhang(北京林业大学)合作进行。

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).