College of Architecture and Urban Planning, Chongqing Jiaotong University, Chongqing, 400074, China.
State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy Sciences, Beijing, 100101, China.
Environ Geochem Health. 2019 Jun;41(3):1583-1597. doi: 10.1007/s10653-018-0236-3. Epub 2019 Jan 8.
Grassland, as an important part of land cover, plays an important role in the global carbon cycle and carbon balance. Net ecosystem productivity (NEP) is a key indicator of the carbon cycle process and an important factor in assessing ecosystem security and maintaining ecosystem balance. In this paper, Boreal Ecosystem Productivity Simulator (BEPS) combining meteorological data, leaf area index, and land cover type data were used to simulate the grassland NEP of China from 1979 to 2008. This model was also used to analyze the responses to changes in climate factors, interannual variation in carbon conversion efficiency, drought stress coefficient, and water use efficiency of grassland in China. Results showed that from 1979 to 2008, the mean annual grassland NEP was 13.6 g C/m with weak carbon sinks. The grassland NEP distribution increased from northwest to southeast across China. Regions with NEP of > 0 (C sink) accounted for 73.1% of the total grassland area of China. The total C sequestration reached 26.6 Tg yearly, and grassland NEP was positive from 1979 to 2008. The annual changing characteristics were analyzed. Grassland NEP was positive with carbon sink from June to September, which was negative with carbon source in the remaining months. The carbon conversion efficiency and water use efficiency of the grassland increased significantly within 30 years. NEP showed positive correlation with precipitation (accounting for 74.2% of the total grassland area was positively correlated) but weakly positive correlation with temperature (50.2% of the case). Furthermore, significant positive correlation was found between grassland NEP and precipitation, especially in northeastern and central Inner Mongolia, northern Tianshan of Xinjiang, southwestern Tibet, and southern Qinghai Lake.
草原作为陆地覆盖的重要组成部分，在全球碳循环和碳平衡中起着重要作用。净生态系统生产力（NEP）是碳循环过程的关键指标，也是评估生态系统安全性和维持生态系统平衡的重要因素。本研究利用气象数据、叶面积指数和土地覆盖类型数据，结合 boreal ecosystem productivity simulator（BEPS）模型，模拟了 1979-2008 年中国草原 NEP 的时空分布特征。并分析了气候因子变化、碳转化效率年际变化、干旱胁迫系数和水分利用效率对中国草原 NEP 的响应。结果表明，1979-2008 年中国草原平均年 NEP 为 13.6 g C/m²，表现为弱碳汇。草原 NEP 从西北向东南呈增加趋势。NEP 为正值（碳汇）的区域占中国草原总面积的 73.1%。每年的碳固存总量达到 26.6Tg，1979-2008 年中国草原 NEP 为正值。分析了其年际变化特征。6-9 月，草原 NEP 为正值，碳汇；其余月份为负值，碳源。30 年来，草原碳转化效率和水分利用效率显著提高。NEP 与降水呈显著正相关（占总草原面积的 74.2%呈正相关），与温度呈弱正相关（占 50.2%呈正相关）。此外，在中国东北部和中部的内蒙古、新疆北部天山、西藏西南部和青海湖南部，NEP 与降水呈显著正相关，特别是在降水丰富的地区。
