Coastal Ecosystems Research Station of Yangtze River Estuary, Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, The Institute of Biodiversity Science, Fudan University, 220 Handan Road, Shanghai, 200433, China.
Glob Chang Biol. 2014 Jul;20(7):2332-43. doi: 10.1111/gcb.12490. Epub 2014 Apr 26.
Anthropogenic activities have increased nitrogen (N) deposition by threefold to fivefold over the last century, which may considerably affect soil respiration (Rs). Although numerous individual studies and a few meta-analyses have been conducted, it remains controversial as to how N addition affects Rs and its components [i.e., autotrophic (Ra) and heterotrophic respiration (Rh)]. To reconcile the difference, we conducted a comprehensive meta-analysis of 295 published studies to examine the responses of Rs and its components to N addition in terrestrial ecosystems. We also assessed variations in their responses in relation to ecosystem types, environmental conditions, and experimental duration (DUR). Our results show that N addition significantly increased Rs by 2.0% across all biomes but decreased by 1.44% in forests and increased by 7.84% and 12.4% in grasslands and croplands, respectively (P < 0.05). The differences may largely result from diverse responses of Ra to N addition among biomes with more stimulation of Ra in croplands and grasslands compared with no significant change in forests. Rh exhibited a similar negative response to N addition among biomes except that in croplands, tropical and boreal forests. Methods of partitioning Rs did not induce significant differences in the responses of Ra or Rh to N addition, except that Ra from root exclusion and component integration methods exhibited the opposite responses in temperate forests. The response ratios (RR) of Rs to N addition were positively correlated with mean annual temperature (MAT), with being more significant when MAT was less than 15 °C, but negatively with DUR. In addition, the responses of Rs and its components to N addition largely resulted from the changes in root and microbial biomass and soil C content as indicated by correlation analysis. The response patterns of Rs to N addition as revealed in this study can be benchmarks for future modeling and experimental studies.
人为活动导致过去一个世纪氮（N）沉积增加了两倍至五倍，这可能会极大地影响土壤呼吸（Rs）。尽管已经进行了许多单独的研究和少数几项荟萃分析，但关于 N 添加如何影响 Rs 及其组成部分[即自养（Ra）和异养呼吸（Rh）]仍然存在争议。为了解决这一分歧，我们对 295 项已发表的研究进行了综合荟萃分析，以研究 Rs 及其组成部分对陆地生态系统中 N 添加的响应。我们还评估了它们的响应在生态系统类型、环境条件和实验持续时间（DUR）方面的差异。我们的研究结果表明，N 添加在所有生物群系中均显著增加了 Rs，增幅为 2.0%，但在森林中降低了 1.44%，在草地和农田中分别增加了 7.84%和 12.4%（P < 0.05）。这些差异可能主要是由于生物群系之间 Ra 对 N 添加的反应不同，与森林相比，农田和草地中 Ra 的刺激更大。除了农田、热带和北方森林外，Rh 对 N 添加的反应在生物群系中也呈现出相似的负响应。Rs 的分区方法并未导致 Ra 或 Rh 对 N 添加的响应产生显著差异，除了根排除和成分整合方法中的 Ra 呈现出相反的响应外，在温带森林中也是如此。Rs 对 N 添加的响应比（RR）与年平均温度（MAT）呈正相关，当 MAT 小于 15°C 时更为显著，但与 DUR 呈负相关。此外，如相关分析所示，Rs 及其组成部分对 N 添加的响应主要是由于根和微生物生物量以及土壤 C 含量的变化所致。本研究中揭示的 Rs 对 N 添加的响应模式可以作为未来建模和实验研究的基准。
