Arid Zone Research ›› 2015, Vol. 32 ›› Issue (5): 1039-1045.doi: 10.13866/j.azr.2015.05.29

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On the Net Ecosystem Productivity in the Upper Reaches Area of Shiyang River

XU Chun-hua1, ZHANG Hua1,2, MA Rui-fen1   

  1. 1. College of Geographic and Environmental Sciences, Northwest Normal University, Lanzhou 730070, Gansu, China;
    2. State Key Laboratory of Grassland Agro-ecosystems, Lanzhou University, Lanzhou 730070, Gansu, China
  • Received:2014-05-07 Revised:2014-10-01 Online:2015-09-15 Published:2015-10-14

Abstract: By using MODIS data,combining with CASA (Carnegie Ames Stanford that CASA) model and soil respiration fitting equation,this paper simulated the Net Ecosystem Productivity (NEP) of different vegetation types in the upper reaches area of Shiyang River in 2012. The result shows that: ① The NEP is 126.96 g·m-2·a-1 and the total annual NEP is 1.38 × 1010 t·a-1 from 2003 to 2012,and it has been a marked increase in recent 10 years. ② The NEP shows a spatial pattern,becoming lower in turns from the central to the north and south. Overall,it acts as a carbon sink,only a small part of the desert acts as a carbon source. There are larger differences between different ecosystems to the NEP. This is correlated to hydrothermal conditions and the different distribution of vegetation types in the study area. ③ Interannual variation of the NEP was positively related to the temperature and precipitation,the precipitation has a larger influence on NEP,and complementary in the space.

Key words: NEP, MODIS, CASA model, carbon source/sink, upper reaches area of Shiyang river