J Plant Ecol ›› 2022, Vol. 15 ›› Issue (1): 168-179 .DOI: 10.1093/jpe/rtab081

• Research Articles • Previous Articles     Next Articles

The interactive effects of nitrogen addition and increased precipitation on gross ecosystem productivity in an alpine meadow

Ruo-Nan Shen1,2, Yang-Jian Zhang1, Jun-Tao Zhu1,3,*, Ning Chen4, Yao Chen1,2, Guang Zhao1, Yi-Xuan Zhu1,2, Ze Tang1,2 and Wen-Yu Li1,2   

  1. 1 Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China, 2 University of Chinese Academy of Sciences, Beijing 100049, China, 3 Lhasa Plateau Ecosystem Research Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China, 4 Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China

    *Corresponding author. E-mail: zhujt@igsnrr.ac.cn
  • Received:2021-03-02 Revised:2021-04-17 Accepted:2021-06-25 Online:2021-08-02 Published:2022-02-01

Abstract:

The ecological consequences of precipitation change and increased atmospheric nitrogen (N) deposition have profound impacts on ecosystem CO2 exchange in grassland ecosystems. Water and N can largely influence grassland productivity, community composition and ecosystem functions. However, the influences of water and N addition on the ecosystem CO2 exchange of alpine grassland ecosystems remain unclear. A field manipulative experiment with water and N additions was conducted in an alpine meadow on the Tibetan Plateau over 4 years with contrasting precipitation patterns. There were four treatments: control (Ctrl), N addition (N), water addition (W) and N and water addition (NW), each replicated three times. N addition, but not water addition, increased gross ecosystem productivity (GEP), plant biomass, community cover and community-weighted mean height. The responses of ecosystem CO2 exchange to water and N addition varied between the wet and dry years. Water addition had a positive effect on net ecosystem carbon exchange (NEE) due to a larger increase in GEP than in ecosystem respiration (ER) only in the dry year. On the contrary, N addition significantly enhanced ecosystem CO2 exchange only in the wet year. The increased GEP in N addition was attributed to the larger increase in NEE than ER. Moreover, N addition stimulated NEE mainly through increasing the cover of dominant species. Our observations highlight the important roles of precipitation and dominant species in regulating ecosystem CO2 exchange response to global environmental change in alpine grasslands.

Key words: ecosystem CO2 exchange, water addition, nitrogen addition, plant functional groups, alpine grassland

摘要:

氮水添加对高寒草甸生态系统生产力的影响

降水变化和大气氮沉降增加对草原生态系统碳交换具有重要的影响,进而影响草地生产力、群落组成和生态系统功能。然而,氮水添加对高寒草甸生态系统碳交换的影响目前尚不清楚。因此,本研究在青藏高原高寒草甸布设氮水添加试验,设置4种不同处理:对照、 加氮、加水和同时添加氮水,对生态系统碳交换过程进行了连续4年的原位观测。研究结果发现,氮添加可以增加总生态系统生产力(GEP)、植物地上生物量、群落盖度和群落加权平均高度(CWMh),而水分添加没有显著影响。生态系统碳交换对氮水添加的响应在干湿年存在显著差异。水分添加仅在干旱年对净生态系统碳交换(NEE)具有显著影响,原因是GEP的增加量大于生态系统呼吸(ER)。相反,氮添加仅在湿润年显著提高了生态系统碳交换,其中GEP的增加归因于NEE的增加量大于ER。结构方程结果表明,氮添加主要通过增加优势种的盖度从而提高NEE。本研究强调了降水和优势物种在调节高寒草甸生态系统响应环境变化中的重要作用。

关键词: 生态系统碳交换, 水添加, 氮添加, 植物功能群, 高寒草地