Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, 210037, China.
Faculty of Natural Resources Management, Lakehead University, 955 Oliver Road, Thunder Bay, ON, P7B 5E1, Canada.
ISME J. 2018 Jun;12(7):1817-1825. doi: 10.1038/s41396-018-0096-y. Epub 2018 Mar 27.
Soil microbes comprise a large portion of the genetic diversity on Earth and influence a large number of important ecosystem processes. Increasing atmospheric nitrogen (N) deposition represents a major global change driver; however, it is still debated whether the impacts of N deposition on soil microbial biomass and respiration are ecosystem-type dependent. Moreover, the extent of N deposition impacts on microbial composition remains unclear. Here we conduct a global meta-analysis using 1408 paired observations from 151 studies to evaluate the responses of soil microbial biomass, composition, and function to N addition. We show that nitrogen addition reduced total microbial biomass, bacterial biomass, fungal biomass, biomass carbon, and microbial respiration. Importantly, these negative effects increased with N application rate and experimental duration. Nitrogen addition reduced the fungi to bacteria ratio and the relative abundances of arbuscular mycorrhizal fungi and gram-negative bacteria and increased gram-positive bacteria. Our structural equation modeling showed that the negative effects of N application on soil microbial abundance and composition led to reduced microbial respiration. The effects of N addition were consistent across global terrestrial ecosystems. Our results suggest that atmospheric N deposition negatively affects soil microbial growth, composition, and function across all terrestrial ecosystems, with more pronounced effects with increasing N deposition rate and duration.
土壤微生物构成了地球上大部分的遗传多样性，并影响着许多重要的生态系统过程。大气氮（N）沉降的增加代表了主要的全球变化驱动因素；然而，氮沉降对土壤微生物生物量和呼吸作用的影响是否依赖于生态系统类型仍存在争议。此外，氮沉降对微生物组成的影响程度尚不清楚。在这里，我们使用来自 151 项研究的 1408 对配对观测值进行了全球荟萃分析，以评估氮添加对土壤微生物生物量、组成和功能的响应。我们表明，氮添加减少了总微生物生物量、细菌生物量、真菌生物量、生物量碳和微生物呼吸。重要的是，这些负面影响随着氮施用量和实验持续时间的增加而增加。氮添加降低了真菌与细菌的比例以及菌根真菌和革兰氏阴性细菌的相对丰度，增加了革兰氏阳性细菌的相对丰度。我们的结构方程模型表明，氮施用量对土壤微生物丰度和组成的负面影响导致微生物呼吸减少。氮添加的影响在全球陆地生态系统中是一致的。我们的结果表明，大气氮沉降对所有陆地生态系统的土壤微生物生长、组成和功能都有负面影响，随着氮沉降速率和持续时间的增加，影响更为明显。
