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Spatiotemporal dynamics of China’s grassland NPP and its driving factors.

LIU Yang-yang1, ZHANG Zhao-ying2, TONG Lin-jing1, WANG Qian1, ZHOU Wei3, WANG Zhen-qian4, LI Jian-long1*   

  1. (1Department of Ecology, School of Life Science, Nanjing University, Nanjing 210023, China; 2International Institute for Earth System Science, Nanjing University, Nanjing 210023, China; 3College of Architecture and Urban Planning, Chongqing Jiaotong University, Chongqing 400074, China; 4School of Earth Sciences, Lanzhou University, Lanzhou 730000, China).
  • Online:2020-02-10 Published:2020-02-10

Abstract: Grassland NPP in China from 2000 to 2015 was simulated based on the CASA model, incorporated with MODIS and meteorological data. Trend analysis, coefficient of variation and Hurst index were used to examine the temporal and spatial dynamics, stability and persistence of grassland NPP. The main influencing factors of grassland NPP change in China were identified. The results showed that grassland NPP increased significantly from 2000 to 2015, with an average change rate of 1.53 g C·m-2·a-1. Grassland NPP changed abruptly after 2011, with an obvious increase trend. Grassland NPP showed spatial heterogeneity, being lower in Northwest and higher in Southeast China. Areas with low NPP value were concentrated in most areas of Tibet Plateau and central Inner Mongolia. The area with increased grassland NPP accounted for 81.21% of the total grassland area, mainly distributed in the central region of Tibet Plateau and most areas of Loess Plateau. The regions with stable grassland NPP were mainly concentrated in Gannan region of Gansu Province and most of eastern Qinghai Province, while the unstable regions were mainly distributed in most areas of Tibet Plateau, central part and Hulunbuir of Inner Mongolia. The result of Hurst index analysis showed that grassland NPP in northern Xinjiang and most regions of Loess Plateau would continue to increase or decrease, while the future change of grassland NPP in southern Qinghai, central Inner Mongolia and Heilongjiang would be antisustainable. The average NPP values of alpine and subalpine meadow and meadow were 578.8 and 565.31 g C·m-2·a-1, respectively, while that of desert grassland was 122.61 g C·m-2·a-1. The increase in grassland NPP in most areas of China is mainly controlled by precipitation, while the increased temperature has a certain inhibition on grassland NPP. Human activities such as the reduction of overgrazing and the implementation of returning farmland to grassland exert important influence over the increases of grassland NPP.

Key words: topsoil salinity, spatial heterogeneity., GWR model