Microorganisms mediate nutrient cycling in soils, and thus it is assumed that they largely control responses of terrestrial ecosystems to anthropogenic nutrient inputs. Therefore, it is important to understand how increased nitrogen (N) and phosphorus (P) availabilities, first, affect soil prokaryotic and fungal community composition and second, if and how changes in the community composition affect soil element cycling. We measured soil microbial communities and soil element cycling processes along a nine-year old experimental N-addition gradient partially crossed with a P-addition treatment in a temperate grassland. Nitrogen addition affected microbial community composition, and prokaryotic communities were less sensitive to N addition than fungal communities. P addition only marginally affected microbial community composition, indicating that P is less selective than N for microbial taxa in this grassland. Soil pH and total organic carbon (C) concentration were the main factors associated with prokaryotic community composition, while the dissolved organic C-to-dissolved N ratio was the predominant driver of fungal community composition. Against our expectation, plant biomass and plant community structure only explained a small proportion of the microbial community composition. Although microbial community composition changed with nutrient addition, microbial biomass concentrations and respiration rates did not change, indicating functional redundancy of the microbial community. Microbial respiration, net N mineralization, and non-symbiotic N₂ fixation were more strongly controlled by abiotic factors than by plant biomass, plant community structure or microbial community, showing that community shifts under increasing nutrient inputs may not necessarily be reflected in element cycling rates. This study suggests that atmospheric N deposition may impact the composition of fungi more than of prokaryotes and that nutrient inputs act directly on element-cycling rates as opposed to being mediated through shifts in plant or microbial community composition.

微生物介导土壤中的养分循环，因此可以认为它们在很大程度上控制了陆地生态系统对人为养分输入的响应。因此，重要的是要了解增加的氮（N）和磷（P）的利用率如何首先影响土壤原核和真菌群落组成，其次，群落组成的变化是否以及如何影响土壤元素循环。我们在温带草原沿9年的实验N-添加梯度与P-添加处理部分交叉的土壤微生物群落和土壤元素循环过程进行了测量。氮的添加会影响微生物群落的组成，而原核生物群落对氮的敏感性不如真菌群落。除磷外，对微生物群落组成的影响很小，表明在该草原上，P对微生物类群的选择性不如N。土壤pH和总有机碳（C）浓度是与原核生物群落组成有关的主要因素，而溶解有机碳与溶解氮的比例是真菌群落组成的主要驱动力。与我们的预期不同，植物生物量和植物群落结构仅解释了微生物群落组成的一小部分。尽管微生物群落组成随养分的添加而变化，但微生物生物量浓度和呼吸速率没有改变，表明微生物群落功能上的冗余。微生物呼吸，净氮矿化和非共生氮 土壤pH和总有机碳（C）浓度是与原核生物群落组成有关的主要因素，而溶解有机碳与溶解氮的比例是真菌群落组成的主要驱动力。与我们的预期不同，植物生物量和植物群落结构仅解释了微生物群落组成的一小部分。尽管微生物群落组成随养分的添加而变化，但微生物生物量浓度和呼吸速率没有改变，表明微生物群落功能上的冗余。微生物呼吸，净氮矿化和非共生氮 土壤pH和总有机碳（C）浓度是与原核生物群落组成有关的主要因素，而溶解有机碳与溶解氮的比例是真菌群落组成的主要驱动力。与我们的预期不同，植物生物量和植物群落结构仅解释了微生物群落组成的一小部分。尽管微生物群落组成随养分的添加而变化，但微生物生物量浓度和呼吸速率没有改变，表明微生物群落功能上的冗余。微生物呼吸，净氮矿化和非共生氮 植物生物量和植物群落结构仅解释了微生物群落组成的一小部分。尽管微生物群落组成随养分的添加而变化，但微生物生物量浓度和呼吸速率没有改变，表明微生物群落功能上的冗余。微生物呼吸，净氮矿化和非共生氮 植物生物量和植物群落结构仅解释了微生物群落组成的一小部分。尽管微生物群落组成随养分的添加而变化，但微生物生物量浓度和呼吸速率没有改变，表明微生物群落功能上的冗余。微生物呼吸，净氮矿化和非共生氮_2种固着作用受非生物因素的控制要强于植物生物量，植物群落结构或微生物群落的控制，这表明在增加养分输入下的群落转移不一定反映在元素循环速率上。这项研究表明，大气中氮的沉积可能比原核生物对真菌的组成影响更大，而且养分输入直接作用于元素循环速率，而不是通过植物或微生物群落组成的变化来介导。