Dimensions US-China: Collaborative Research: Quantifying the Impact of Eutrophication on the World's Grassland Soil Microbial Biodiversity and Functioning

人类活动正在增加流入各大洲生态系统的生物限制性营养素的数量，如氮(N)和磷(P)，这种增加的养分供应正在造成生物多样性丧失等重大影响。微生物构成了地球上大部分的生物多样性，土壤中微生物的多样性是维持我们生态系统健康的关键一环。然而，我们对全球养分供应的变化如何影响土壤微生物多样性知之甚少。拟议的工作将量化增加的养分供应如何影响土壤微生物多样性，以及这些变化如何影响世界各地草原生态系统的功能。这项研究将利用一个名为营养网络(NutNet)的全球科学家网络，他们正在26个国家的100多个草原地点复制一项相同的营养添加实验。利用这个全球研究平台，该项目将通过计算土壤微生物的同一性(分类学多样性，TD)、它们的进化关系(系统发育多样性，PD)、它们DNA中编码的基因(遗传多样性，GD)以及它们正在做的事情(功能多样性，FD)，来探索不同的土壤微生物‘多样性’。这个研究团队的科学家不仅将确定这些不同维度的多样性如何应对营养变化，而且还将确定它们为什么会发生变化。微生物群落的改变是因为某些微生物可以生长得更好(非生物过滤)，与其他微生物或植物竞争或合作(生物相互作用)，或在迁移方面好或不好(扩散)，或偶然出现(漂移)？该项目将开发新的数学模型，以预测养分未来如何改变不同地区土壤微生物的多样性及其功能。该项目的更广泛影响包括：(I)通过K12教育提高公众对STEM的参与度和识字率，这将惠及4,000多名K-12学生，包括来自服务不足的学校的学生，使用为锡达克里克的教育设立的NutNet地块和在俄克拉荷马州的活动；(Ii)增强NutNet全球合作的研究基础设施，通过公布数据、提供样本和为更多项目提供空间，使更多的研究界受益；以及(Iii)为项目博士后和学生提供国际跨学科合作方面的高级培训，这将产生一支更具竞争力的劳动力，从事农业、环境、生态和气候研究的系统级问题解决。该项目将使用高通量元基因组学技术和综合数学和统计模型来分析土壤草原微生物多样性对全球气候、植物多样性和土壤条件梯度实验富营养化的响应。这项研究将检验土壤微生物对养分供应响应的时空尺度上的理论预测，从而为以下方面提供新的见解：(1)全球土壤微生物多样性(TD、PD、GD、FD)沿气候、植物多样性和土壤条件的广泛梯度；(2)N和P供应对草原土壤微生物群落、养分和土壤C储量的上下文依赖和交互影响；(Iii)植物、微生物和土壤元素化学计量学对于控制微生物生物多样性和功能对养分供应的反应的重要性，以及植物-微生物相互作用在调节植物对养分添加的反应中的作用；(Iv)随机(例如，分散)和确定性(例如，非生物过滤、生物相互作用)过程的相对重要性，这些过程控制着全球环境和地理梯度上微生物生物多样性的每个维度对养分添加的反应；(V)生物多样性和群落组合在控制土壤微生物生态系统功能方面的重要性，以及环境因素(如土壤、植物、气候、地理)的影响；(Vi)草原土壤功能的潜在“生物标志物”(关键分类群或基因)；(Vii)全球模拟草原土壤碳动态的新的元基因组学生态系统模型；以及(Viii)模型推断的营养添加对气候、植物和土壤条件下生物地理梯度土壤碳动态的影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Human activities are increasing the amount of biologically limiting nutrients, such nitrogen (N) and phosphorus (P), flowing into ecosystems on every continent, and this increased nutrient supply is causing dramatic impacts such as biodiversity loss. Microbes comprise most of the biodiversity on earth, and the diversity of microbes in the soil is a critical link in maintaining the health of our ecosystems. However, we have little understanding of how alteration of global nutrient supplies are affecting soil microbial diversity. The proposed work will quantify how increased nutrient supplies affect soil microbial diversity and how these changes affect the functioning of grassland ecosystems around the world. The research will leverage a worldwide network of scientists, the Nutrient Network (NutNet), who are replicationg an identical nutrient-addition experiment at more than 100 grassland sites across 26 countries. Using this global research platform, this project will explore different ‘diversities’ of the soil microbes by counting their idenities (taxonomic diversity, TD), their evolutionary relationships (phylogenetic diversity, PD), the genes encoded in their DNA (genetic diversity, GD), and what they are doing (functional diversity, FD). The scientists on this research team will not only determine how these different dimensions of diversity respond to the nutrient change but also why they are changing. Are microbial communities changing because some microbes can grow better (abiotic filtering), compete or cooperate with other microbes or plants (biotic interactions), or are good or bad at migration (dispersal), or appear by chance (drift)? This project will develop new mathematical models to predict how nutrients change the diversity of soil microbes and their functions in different regions in the future. Broader impacts of this project include (i) increased public engagement and literacy in STEM via K12 education that will reach over 4,000 K-12 students including from under-served schools using NutNet plots set up for education at Cedar Creek and activities at Oklahoma; (ii) enhanced research infrastructure of the global NutNet collaboration, which benefits the greater research community via published data, provision of samples, and space for additional projects; and (iii) advanced training in international cross-disciplinary collaboration for project post-docs and students, that will generate a more competitive workforce to engage in systems-level problem solving for agriculture, environment, ecology and climate research.The project will use high throughput metagenomics technologies and integrative mathematical and statistical modeling to analyze soil grassland microbial diversity responses to experimental eutrophication along global gradients in climate, plant diversity, and edaphic conditions. The research will test theory-based predictions about the responses of soil microbes to nutrient supply across scales of space and time, generating novel insights into: (i) global patterns of soil microbial biodiversity (TD, PD, GD, FD) along broad gradients of climate, plant diversity, and edaphic conditions; (ii) the context-dependence and interactive effects of N and P supply on grassland soil microbial communities, nutrients, and soil C storage; (iii) the importance of plant, microbe and soil elemental stoichiometry for controlling the responses of microbial biodiversity and functioning to nutrient supply, as well as the role of plant-microbe interactions in mediating plant responses to nutrient addition; (iv) the relative importance of stochastic (e.g., dispersal) and deterministic (e.g., abiotic filtering, biotic interactions) processes controlling responses by each of the dimensions of microbial biodiversity to nutrient addition across global environmental and geographic gradients; (v) the importance of biodiversity and community assembly in controlling soil microbial ecosystem functioning, and the influence of environmental factors (e.g., soil, plant, climate, geography); (vi) potential “biomarkers” (key taxa or genes) of grassland soil functions; (vii) novel metagenomics-enabled ecosystem models for global simulation of grassland soil C dynamics; and (viii) model-inferred impacts of nutrient addition on soil C dynamics across biogeographic gradients in climate, plants and edaphic conditions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.