Graduate Group in Ecology, University of California, Davis, CA 95616;
Department of Physiological Diversity, Helmholtz Center for Environmental Research, 04318 Leipzig, Germany.
Proc Natl Acad Sci U S A. 2020 Mar 31;117(13):7263-7270. doi: 10.1073/pnas.1908117117. Epub 2020 Mar 12.
Spatial heterogeneity in composition and function enables ecosystems to supply diverse services. For soil microbes and the ecosystem functions they catalyze, whether such heterogeneity can be maintained in the face of altered resource inputs is uncertain. In a 50-ha northern California grassland with a mosaic of plant communities generated by different soil types, we tested how spatial variability in microbial composition and function changed in response to nutrient and water addition. Fungal composition lost some of its spatial variability in response to nutrient addition, driven by decreases in mutualistic fungi and increases in antagonistic fungi that were strongest on the least fertile soils, where mutualists were initially most frequent and antagonists initially least frequent. Bacterial and archaeal community composition showed little change in their spatial variability with resource addition. Microbial functions related to nitrogen cycling showed increased spatial variability under nutrient, and sometimes water, additions, driven in part by accelerated nitrification on the initially more-fertile soils. Under anthropogenic changes such as eutrophication and altered rainfall, these findings illustrate the potential for significant changes in ecosystem-level spatial heterogeneity of microbial functions and communities.
组成和功能的空间异质性使生态系统能够提供多种服务。对于土壤微生物及其催化的生态系统功能，在资源输入改变的情况下，这种异质性是否能够得到维持尚不确定。在加利福尼亚州北部一个 50 公顷的草原上，植物群落呈镶嵌状分布，由不同的土壤类型形成，我们测试了微生物组成和功能的空间变异性如何响应养分和水分的添加而变化。在养分添加的作用下，真菌组成失去了一些空间变异性，这是由互惠真菌的减少和拮抗真菌的增加驱动的，而拮抗真菌在最贫瘠的土壤上最为强烈，在这些土壤上，互惠真菌最初最为常见，而拮抗真菌最初最为罕见。细菌和古菌群落组成在资源添加时其空间变异性变化很小。与氮循环有关的微生物功能在养分添加时，有时在水分添加时，表现出更高的空间变异性，部分原因是最初更肥沃的土壤上硝化作用的加速。在人为变化（如富营养化和降雨改变）下，这些发现说明了微生物功能和群落的生态系统水平空间异质性发生重大变化的潜力。
