Mutualism theory predicts how legumes influence biodiversity-ecosystem function relationships under global change

互利共生理论预测全球变化下豆科植物如何影响生物多样性-生态系统功能关系

• 批准号: 1457508
• 负责人: Ellen Simms
• 金额: $ 79.94万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-15 至 2021-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1457508&HistoricalAwards=false
• 关键词: Mutualism; theory; predicts; how; legumes

Primary productivity, the conversion of solar energy to plant biomass via photosynthesis, is a particularly important ecosystem service that supports most global ecosystems and is positively related to plant biodiversity. This project will increase mechanistic understanding of the biodiversity-productivity relationship to better explain how environmental conditions influence ecosystem services. Ecological theory predicts that differences among plant species underlie variation in the biodiversity-productivity relationship. However, the mechanisms underlying this variation among plant species are rarely experimentally quantified, leaving causal connections between plant variation and the biodiversity-productivity relationship elusive. Plants in the legume (bean) family are infected by beneficial soil bacteria called rhizobia, which fix atmospheric nitrogen (N) in exchange for carbon (C) from their plant hosts. As most plants obtain N from soil, access to atmospheric N via this mutualism can differentiate legumes from non-legumes, thus influencing the productivity-diversity relationship. This project will experimentally examine biotic processes that differentiate legume species from each other and from non-legumes to understand how these differences cause variation in patterns of primary productivity within a long-term biodiversity, CO2, and N manipulation experiment in Minnesota, USA--BioCON. To promote public understanding of science, middle school students will grow and observe legume seeds inoculated with local bacteria under two N treatments to test if bacteria from regions with high soil N are less beneficial than those from regions with low soil N. Undergraduates will be trained in relevant techniques and develop independent projects within the scope of this work. The research and outreach projects will inform management of ecosystem function under current and future global change scenarios, with important implications for human well-being.Niche differences (ND) and relative fitness differences (RFD) among legume species will be assessed by determining the composition and density of, and plant benefit from, the species-specific nodulating rhizobial community (NRC) in soil samples from the ambient condition BioCON biodiversity plots. Structural equation models will relate ND and RFD, and their underlying mechanisms, to relative yield totals calculated from each diversity treatment, to test the hypothesis that higher ND between legumes and non-legumes produces stronger richness-productivity relationships and higher RFD weakens the richness-productivity relationship. Evolution of the NRC in response to enhanced CO2 and/or N, and its consequences for the richness-productivity relationship, will be assessed by determining the composition and density of, and plant benefit derived from, the NRC of each BioCON diversity, CO2, and N treatment combination. Finally, variation among legume species in how CO2- and/or N-availability shifts enforcement of rhizobial cooperation (partner choice and sanctions), and the consequences of this variation for the richness-productivity relationship, will be examined through mixed-inoculation experiments.

初级生产力，即通过光合作用将太阳能转化为植物生物质，是一项特别重要的生态系统服务，支持大多数全球生态系统，并与植物生物多样性呈正相关。该项目将增进对生物多样性与生产力关系的机制理解，以更好地解释环境条件如何影响生态系统服务。生态理论预测，植物物种之间的差异是生物多样性与生产力关系变化的基础。然而，植物物种之间这种差异的机制很少通过实验进行量化，使得植物变异与生物多样性-生产力关系之间的因果关系难以捉摸。豆科植物受到称为根瘤菌的有益土壤细菌的感染，这种细菌固定大气中的氮 (N)，以换取植物宿主的碳 (C)。由于大多数植物从土壤中获取氮，通过这种互利共生获取大气中的氮可以将豆科植物与非豆科植物区分开来，从而影响生产力与多样性的关系。该项目将通过实验研究区分豆科植物物种和非豆科植物物种的生物过程，以了解这些差异如何在美国明尼苏达州 BioCON 的长期生物多样性、二氧化碳和氮操纵实验中导致初级生产力模式的变化。为了促进公众对科学的理解，中学生将种植并观察在两次氮处理下接种当地细菌的豆类种子，以测试来自高土壤氮地区的细菌是否不如来自低土壤氮地区的细菌有益。本科生将接受相关技术培训，并在这项工作范围内开发独立项目。研究和推广项目将为当前和未来全球变化情景下的生态系统功能管理提供信息，对人类福祉具有重要影响。将通过确定来自环境条件BioCON生物多样性地块的土壤样本中物种特异性结瘤根瘤菌群落（NRC）的组成和密度以及植物从中获得的益处来评估豆科植物物种之间的生态位差异（ND）和相对适应度差异（RFD）。结构方程模型将 ND 和 RFD 及其基本机制与根据每种多样性处理计算出的相对产量总量联系起来，以检验豆类和非豆类之间较高的 ND 会产生更强的丰富度-生产率关系，而较高的 RFD 会削弱丰富度-生产率关系的假设。将通过确定每种 BioCON 多样性、CO2 和 N 处理组合的 NRC 的组成和密度以及源自 NRC 的植物效益来评估 NRC 响应 CO2 和/或 N 增加的演变及其对丰富度-生产力关系的影响。最后，将通过混合接种实验来研究豆科植物物种之间在二氧化碳和/或氮可用性如何改变根瘤菌合作执行（伙伴选择和制裁）方面的变化，以及这种变化对丰富度-生产力关系的影响。