| Research on changes of net primary productivity of grassland vegetation in Gannan pastoral area over the past 10 years |
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| DOI：10.7606/j.issn.1000-7601.2011.01.47 |
| Key Words: improved CASA model change of grassland NPP correlation Gannan pastoral area |
| Author Name | Affiliation | | YANG Donghui | College of Geographic and Environmental Science, Northwest Normal University, Lanzhou, Gansu 730070, China | | ZHAO Jun | College of Geographic and Environmental Science, Northwest Normal University, Lanzhou, Gansu 730070, China | | ZHANG Zhihui | Institute of Cold and Arid Regions Environmental and Engineering, Chinese Academy of Sciences, Lanzhou, Gansu 730000, China | | FU Peng | College of Geographic and Environmental Science, Northwest Normal University, Lanzhou, Gansu 730070, China | | LIU Chunyu | College of Geographic and Environmental Science, Northwest Normal University, Lanzhou, Gansu 730070, China |
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| Abstract: |
| An improved CASA model with MODIS NDVI along with meteorological data was used to estimate the net primary productivity (NPP) of grassland vegetation in pasture season in July each year in 2000, 2005 and 2008, and to analyse its spatial and temporal dynamics. The results showed that: (1) The fundamental spatial pattern of annual NPP in Gannan pastoral was characterized by low NPP levels distributed in the west-southwest and northwest corners, then the NPP levels increased gradually from the two corners into the arid inland regions. This distribution was bound up with different hydrothermal conditions and variation of zonal of vegetation. In addition, it was significantly different between the average NPP of grassland vegetation in July and the total NPP of grassland vegetation in
July, which was closely related to each county area. The sequence of the value of average NPP of grassland vegetation in July in each county was Luqu>Maqu>Hezuo>Xiahe, while the sequence of the value of total NPP of grassland vegetation in July in each county was Maqu>Xiahe>Luqu>Hezuo. (2) The value of NPP of grassland vegetation in July of 2008 was much smaller than that of 2000. From 2000～2008, the NPP of grassland vegetation of the entire study area in July increased first, and then decreased. The main reason was the changes of temperatur
e, precipitation and wettability, while wettability change was a major limiting factor to affect the growth of pasture in Gannan plateau. |
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