摘要:近年来，高速的城市化和工业化建设导致全球大气氮沉降量逐年递增，其中热带亚热带地区氮沉降量显著高于全球平均水平，而大部分热带亚热带森林土壤趋近氮饱和状态，氮沉降增加将持续向土壤输入外源活性氮，极易导致土壤氮过剩，进而破环整个森林生态系统氮循环的平衡。我国热带亚热带地区经济发展快速，氮沉降增加导致的土壤养分失衡和林地退化等生态问题日益凸显，森林土壤氮循环对大气氮沉降的响应及适应机制已引起了学术界的广泛关注。研究表明氮循环各环节均由特定的功能微生物驱动完成，明确氮沉降增加对热带亚热带森林土壤氮循环功能微生物及其介导的关键过程的影响，对评价未来氮沉降增加背景下全球森林土壤氮循环的响应及驱动机制有重要作用，可为促进我国热带亚热带地区森林修复、生态环境的改善与提升提供科学支撑。鉴于此，本文综述了热带亚热带森林土壤氮循环主要过程（如固氮、硝化、反硝化、厌氧氨氧化等）及其功能微生物群落丰度、活性、组成等对氮沉降增加的响应，同时分析了这些功能微生物的群落特征与主要环境因子（如NH₄⁺、NO₃^-、有机碳、pH、含水量等）的关联性。在此基础上探讨了氮沉降增加下功能微生物对热带亚热带森林土壤氮循环的调控作用，重点探讨了功能微生物如何通过改变丰度与群落组成而影响氮循环过程，并对目前研究中存在的主要问题与未来研究重点进行了简要剖析。



Abstract:The rapid urbanization and industrialization have increased global atmosphere nitrogen (N) deposition year by year, and the N deposition amount in tropical and subtropical areas is higher than the global average value. However, majority of the soil from tropical and subtropical forests is almost N saturation. The elevated N deposition will continuously enhance the input of active N into soil, which would easily induce soil N excess and further destroy N cycling balance of the entire forest ecosystem. The tropical and subtropical areas in our country are characterized by rapid economic development, and the increase of N deposition has caused the ecological problems such as soil nutrients imbalance as well as forest degradation. Therefore, the responses and adaptive mechanisms of forest soil N cycling to N atmosphere deposition have attracted lots of attentions in academia. According to previous researches, each step in N cycling pathway is driven by specifically functional microorganisms. Thus, clarifying the effects of elevated N deposition on functional microorganisms in tropical and subtropical soil is important for the assessment on soil N cycling and the driving mechanisms in forests under global N deposition. Moreover, the study results can provide scientific bases for the forest restoration and environmental improvement of the tropical and subtropical areas in our country. Therefore, this research reviewed the responses of soil N cycling processes (e.g., N-fixation, nitrification, denitrification and anammox) and functional microbial abundance, activity and composition to the increased N deposition in tropical and subtropical forests. The correlations between functional microbial attributes and environmental factors (e.g., NH₄⁺, NO₃^-, organic carbon, pH and soil water content) were summarized and discussed. Based on the review, we discussed the regulations of functional microorganisms on soil N cycling under N deposition, highlighted the effects of functional microorganisms on N cycling processes through altering microbial community abundance and composition, afterwards proposed the main defects of the existing studies as well as the key points in future studies.





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