草地群落多样性和生态系统碳氮循环对氮输入的非线性响应及其机制  

Nonlinear responses of community diversity,carbon and nitrogen cycles of grassland ecosystems to external nitrogen input

作　　者：杨元合[1,2] 张典业 魏斌 刘洋 冯雪徽 毛超 徐玮婕 贺美 王璐 郑志虎 王媛媛 陈蕾伊 彭云峰[1] YANG Yuan-He;ZHANG Dian-Ye;WEI Bin;LIU Yang;FENG Xue-Hui;MAO Chao;XU Wei-Jie;HE Mei;WANG Lu;ZHENG Zhi-Hu;WANG Yuan-Yuan;CHEN Lei-Yi;PENG Yun-Feng(State Key Laboratory of Vegetation and Environmental Change,Institute of Botany,Chinese Academy of Sciences,Beijing 100093,China;University of Chinese Academy of Sciences,Beijing 100049,China;College of Resources and Environmental Science,Hebei Province Key Laboratory for Farmland Eco-Environment,Agricultural University of Hebei,Baoding,Hebei 071000,China;School of Geographical Sciences,Fujian Normal University,Fuzhou 350117,China)

机构地区：[1]中国科学院植物研究所植被与环境变化国家重点实验室,北京100093 [2]中国科学院大学,北京100049 [3]河北农业大学资源与环境科学学院,河北省农田生态环境重点实验室,河北保定071000 [4]福建师范大学地理科学学院,福州350117

出　　处：《植物生态学报》2023年第1期1-24,共24页Chinese Journal of Plant Ecology

基　　金：国家自然科学基金(31825006)。

摘　　要：理解草地生态系统结构和功能对氮富集的响应及其机制有助于准确评估大气氮沉降等外源氮输入的生态效应。全球范围内建立的多水平氮添加实验为认识草地生态系统结构和功能对氮输入的非线性响应机制提供了有效途径。为了反映学术界基于多水平氮添加控制实验取得的主要研究进展,该文综述了草地群落多样性和生态系统碳氮循环过程对外源氮输入的非线性响应特征及其驱动机制。按照目前的研究,氮输入会导致草地植物物种多样性、功能多样性以及土壤细菌多样性下降,但真菌多样性的变化并不明显。地上和地下生产力对氮输入的响应趋势存在差异:地上生产力沿氮添加梯度呈“先上升后饱和”的变化规律,而根系生产量和根冠比呈下降趋势,根系周转速率则呈“先上升后下降”的单峰格局。不同碳分解过程对氮输入的响应也不尽相同:凋落物分解速率沿氮添加梯度表现出“指数衰减、线性增加或无显著变化”的多元响应,而土壤呼吸和CH4吸收速率与施氮量的关系则以“低氮促进、高氮抑制”的单峰趋势为主。类似地,不同土壤碳组分对氮输入的响应存在差异:氮添加总体会导致草地土壤碳库和颗粒态有机碳含量增加,而矿物结合态碳含量随施氮量呈“增加、不变或下降”的多元响应。植物氮吸收量沿氮添加梯度呈“先上升后饱和”的变化特征,但不同土壤氮转化过程沿氮添加梯度呈现差异化响应,且不同草地生态系统中观察到的土壤N_(2)O排放速率与施氮量之间的关系存在差异:温带草地中以指数增加为主,而高寒草地中则出现“先上升后饱和”或者“线性增加”的趋势。未来研究需重点关注根际过程及磷循环对氮输入的非线性响应,并从多维度生物多样性等角度解析多水平氮添加影响草地生物地球化学循环过程的机理。Understanding the response patterns and potential mechanisms of structure and function in grassland ecosystems to nitrogen(N)enrichment is essential to evaluate ecological impacts of external N input.The muti-level N manipulative experiment offers the possibility to explore the nonlinear response patterns and associated mechanisms of structure and function in grassland ecosystems to additional N input.In this review,we summarized the impacts of additional N inputs on community diversity,carbon(C)and N cycling in grassland ecosystems around the world.Numerous studies illustrated that N enrichment induced the decline of plant species diversity,plant functional diversity and soil bacteria richness in grassland ecosystems,yet the change of fungal diversity was not significant.Above-and below-ground plant productivity showed different responses to N input:aboveground plant productivity exhibited initial increasing and subsequent saturation trends,but root productivity and root:shoot ratio showed downward patterns,and root turnover rate appeared a single-peak pattern of first increasing and then decreasing with the continuous increase of N addition rate.Meanwhile,different C decomposition processes responded variously to N enrichment.Specifically,litter decomposition rates exhibited multiple response of“exponential decrease,liner increase or insignificant change with N addition level”.However,the relationship of soil respiration and CH4consumption with N addition was dominated by a single peak trend of increasing at low to medium N levels but declining at high N levels.Likewise,different soil C fractions showed multiple response patterns to N input.N addition generally stimulated soil C storage and particulate organic C accumulation,while the mineral-associated organic C exhibited divergent responses of“increase,unaltered,and decrease”along the N addition gradient.In addition,plant N uptake exhibited initial increasing and subsequent situation trends along N addition gradients,while different soil N transformat

关 键 词：草地生态系统 物种多样性 功能多样性 生态系统生产力 凋落物分解 土壤呼吸 土壤氮转化过程 温室气体通量 

分 类 号：S812[农业科学—草业科学]