Enhancing the relationship between biodiversity and ecosystem functioning under multiple anthropogenic stressors

生物多样性是生态系统健康运作和造福人类的基石，生物多样性越高，功能越好。这些生物多样性-生态系统功能（BEF）关系已经被反复观察到，然而，我们实际上对人为压力源和生态系统改变如何影响BEF关系知之甚少。在人类主导的景观中，压力源影响生态系统的基本非生物成分，如养分供应、水流、温度波动、土壤肥力、土壤和水的pH值和盐度。这些人为影响还包括生物成分，如非本地物种的存在和传播，以及大型和长寿生物的排除。虽然这些新的生态系统不可否认地为人类提供了重要的功能和利益，但目前尚不清楚这些系统中增加生物多样性是否能提供与自然生态系统相同的回报。人为压力源可以协同或拮抗地影响生物多样性关系，因为它们可以以多种方式影响单个物种，从而改变物种的共存和适应性。在植物生态系统中，这些压力源有三种主要影响：1)直接降低物种的适应性——从而降低它们的竞争能力；2)生态位空间的改变使物种能够共存；3)物种特异性相互作用的破坏，如授粉相互作用或土壤病原体。为了了解人为压力源对生物多样性关系的影响，我将开展一系列研究，考察物种表现、共存、群落多样性和生态系统功能，然后将这些与压力源的组合进行比较。观察性研究将利用城市化、物种入侵、化学和道路盐污染以及土壤肥力等现实世界的压力源梯度来评估城市环境中的BEF关系。模拟将具体评估关于压力源对物种的直接和间接影响的假设，以及增加的多样性如何影响竞争和共存的功能。这项工作将重点关注胁迫源对地下植物-土壤反馈的影响，以及胁迫源如何改变相互关联，以及这些关联如何影响植物的适应性和共存。来自观察性研究的材料将用于启动实验，例如作为盆栽实验中受压力影响的土壤微生物池。实验将使用生长箱和田间地块对丰富度和应激源处理进行因子组合，以测试应激源数量的增加是否会降低BEF关系的强度，或者多样性是否对在多种应激源下维持功能越来越重要。

Biodiversity is the cornerstone of healthy ecosystem functioning and the delivery of benefits to human populations, and higher biodiversity has been shown to result in greater functioning. These biodiversity-ecosystem function (BEF) relationships have been repeatedly observed, yet, we actually have very little understanding about how anthropogenic stressors and ecosystem modifications influence BEF relationships. In human-dominated landscapes, stressors influence fundamental abiotic components of an ecosystem, such as nutrient availability, the flow of water, temperature fluctuations, soil fertility, the pH and salinity of soil and water. These anthropogenic influences also include the biotic components like the presence and spread of non-indigenous species, as well as the exclusion of large-bodied and long-lived organisms. While these novel ecosystems undeniably supply important functions and benefits to people, it remains unclear if increasing biodiversity in these systems provides the same return as in natural ecosystems. Anthropogenic stressors can act synergistically or antagonistically in influencing BEF relationships because they can impact individual species in a multitude of ways that can alter species coexistence and fitness. In plant ecosystems, these stressors can have three main effects: 1) a direct reduction of species fitness -thus reducing their competitive abilities; 2) an alteration of niche spaces that allow species to coexist; and 3) a disruption of species-specific interactions like pollination mutualisms or soil pathogens. To understand the impacts of anthropogenic stressors on BEF relationships, I will carry out a number of studies examining species performance, coexistence, community diversity and ecosystem function and then compare these to combinations of stressors. Observational studies will use real-world stressor gradients of urbanization, species invasion, chemical and road salt pollution, and soil fertility to evaluate BEF relationships in urban settings. Simulations will specifically assess assumptions about direct and indirect impacts of stressors on species and how increasing diversity influences functioning as competition and coexistence are impacted. This work will focus on the prevalence of stressor impacts on belowground plant-soil feedbacks and how stressors alter mutualistic associations, and further how these associations influence plant fitness and coexistence. Material from the observational studies will be used to initiate experiments, for example as stressor-influenced pools of soil microbes for pot experiments. Experiments will use growth chambers and field plots to factorially combine richness and stressor treatments to test whether increasing numbers of stressors reduce the strength of BEF relationships or whether diversity is increasingly important for maintaining function under multiple stressors.