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.
Ying Yong Sheng Tai Xue Bao. 2021 Aug;32(8):2783-2790. doi: 10.13287/j.1001-9332.202108.005.
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 (., 0, 2, 5, 10, 20 and 50 g·m·a) and two levels of mowing (., 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 , plant community, litter and ecosystem. Mowing significantly increased the N content of leaf and litter, but reduced N pools of , 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·a. 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.
大气氮（N）沉降增加对生态系统的物种多样性、生产力和稳定性有很大影响。因此，了解草地氮库如何响应大气氮沉降增加至关重要。本研究在中国内蒙古额尔古纳的一个草甸草原进行。设置了六个氮添加水平（即0、2、5、10、20和50 g·m⁻²·a⁻¹）和两个刈割水平（即刈割和不刈割）。在处理后的第七年采集优势植物地上组织、根系、地上凋落物以及100 cm深度土壤的样本。测定氮含量并计算氮库。结果表明，添加氮显著增加了地上植物组织和凋落物的氮含量，以及植物群落、凋落物和生态系统的氮库。刈割显著增加了叶片和凋落物的氮含量，但降低了植物群落和凋落物的氮库，且不影响它们对氮添加的响应。刈割和氮添加对植物群落氮库有显著的交互作用。不刈割处理下高氮添加水平导致更多氮储存在凋落物库中，植物群落氮库的饱和阈值出现在10 g·m⁻²·a⁻¹。在刈割处理下，植物群落氮库随氮添加增加而增加，刈割后更多氮储存在植物群落氮库中。刈割可以减轻氮沉降增加对生物多样性和生态系统稳定性的负面影响，并延缓因氮沉降增加导致的生态系统氮饱和的发生。
