长期氮添加对草甸草原生态系统氮库的影响  

Effects of long-term nitrogen addition on the nitrogen pools in a meadow steppe ecosystem

作　　者：耿倩倩 王银柳 牛国祥 王楠楠 哈斯木其尔[1,2] 李昂 黄建辉[1,2] GENG Qian-qian;WANG Yin-liu;NIU Guo-xiang;WANG Nan-nan;HASI Muqier;LI Ang;HUANG Jian-hui(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;Key Laboratory of Wetland Ecology and Environment,Northeast Institute of Geography and Agroecology,Chinese Academy of Sciences,Changchun 130102,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]中国科学院东北地理与农业生态研究所湿地生态与环境重点实验室,长春130102

出　　处：《应用生态学报》2021年第8期2783-2790,共8页Chinese Journal of Applied Ecology

基　　金：国家自然科学基金项目(32071562)资助。

摘　　要：大气氮沉降增加深刻影响生态系统物种多样性、生产力及其稳定性,研究草原生态系统N库如何响应不断增加的大气氮沉降至关重要。本研究在内蒙古额尔古纳草甸草原开展刈割和不同水平外源氮添加试验,设置6个氮添加水平:0、2、5、10、20和50 g·m^(-2)·a^(-1),同时设置刈割处理,分为刈割和不刈割2个水平。在连续处理的第7年,采集群落中优势植物地上部分、群落根、地表凋落物和0~100 cm分层土壤样品,测定N含量并计算N库储量。结果表明:氮添加显著增加植物地上部分和凋落物N含量,以及羊草、植物群落和凋落物的N库及生态系统N库总量。刈割处理显著增加羊草叶片和凋落物N含量,降低羊草、植物群落和凋落物N库,但并不改变它们对氮添加的响应格局。此外,刈割和氮添加对植物群落N库存在显著的交互作用。在不刈割处理下,高水平氮添加使更多的氮储存在凋落物中等待分解,植物群落N库的饱和阈值出现在10 g·m^(-2)·a^(-1);在刈割处理下,植物群落N库表现为随氮添加量增加而不断增加,并且在相同水平氮添加条件下刈割后进入到植物群落N库中的氮更多。刈割可以缓解氮沉降不断增加对生物多样性和生态系统稳定性造成的不利影响,并可以在一定程度上推迟氮沉降增加引起的生态系统氮饱和的发生。Increasing atmospheric nitrogen(N) deposition greatly affects species diversity, productivity, and stability of ecosystems. It is thus of the great importance to understand how grassland N pools respond to the increased atmospheric N deposition. This study was conducted in a meadow steppe in Erguna, Inner Mongolia, China. There were six levels of N addition(i.e., 0, 2, 5, 10, 20 and 50 g·m^(-2)·a^(-1)) and two levels of mowing(i.e., mowing and unmown). Samples of aboveground tissues of dominant plant, root, aboveground litter, and soil to the depth of 100 cm were collected in the seventh year after treatments. The N content was measured and the N pool was calculated. The results showed that N addition significantly increased the N content of aboveground plant tissues and litter, as well as N pools of Leymus chinensis, plant community, litter and ecosystem. Mowing significantly increased the N content of L. chinensis leaf and litter, but reduced N pools of L. chinensis, plant community and litter, and did not affect their responses to N addition. There was a significant interactive effect between mowing and N addition on plant community N pool. High levels of N addition in the unmown treatment led to more N stored in the litter pool, with the saturation threshold for the plant community N pool occurred at 10 g·m^(-2)·a^(-1). Under mowing treatment, the plant community N pool increased with the increasing N addition, and more N stored in plant community N pool after mowing. Mowing could alleviate the negative impacts of increasing N deposition on biodiversity and ecosystem stability, and extended postponing the occurrence of ecosystem N saturation induced by increasing N deposition.

关 键 词：氮添加 刈割 氮含量 氮库 草甸草原 氮饱和 

分 类 号：S812[农业科学—草业科学]