Direct and indirect effects of nitrogen enrichment on soil organisms and carbon and nitrogen mineralization in a semi‐arid grassland

1. Semi-arid grasslands on the Mongolian Plateau are expected to experience high inputs of anthropogenic reactive nitrogen in this century. It remains unclear, however, how soil organisms and nutrient cycling are directly affected by N enrichment (i.e., without mediation by plant input to soil) vs. indirectly affected via changes in plant-related inputs to soils resulting from N enrichment. 2. To test the direct and indirect effects of N enrichment on soil organisms (bacteria, fungi, and nematodes) and their associated C and N mineralization, in 2010 we designated two subplots (with plants and without plants) in every plot of a six-level N-enrichment experiment established in 1999 in a semi-arid grassland. 3. In 2014, 4 years after subplots with and without plant were established, N enrichment had substantially altered the soil bacterial, fungal, and nematode community structures due to declines in biomass or abundance whether plants had been removed or not. N enrichment also reduced th...

1. 蒙古高原的半干旱草原预计在本世纪将面临人为活性氮(anthropogenic reactive nitrogen)的大量输入。然而目前仍不清楚，氮富集(N enrichment)是通过何种途径直接影响土壤生物与养分循环（即不经过植物向土壤输入的介导作用），还是经由氮富集引发的植物相关土壤输入变化产生间接影响。2. 为探究氮富集对土壤生物（细菌、真菌与线虫）及其介导的碳(C)、氮(N)矿化过程的直接与间接效应，研究团队于2010年在1999年于半干旱草原建立的6级氮富集野外试验的每个样地内，设置了两个亚样地：保留原生植被亚样地与移除植被亚样地。3. 2014年，即亚样地设置完成4年后，无论植被是否被移除，氮富集均通过降低生物量或种群丰度，显著改变了土壤细菌、真菌与线虫的群落结构；氮富集同时还降低了……