Spatio-temporal change analysis of leaf area index in the Loess Plateau during 2000-2014
WANG Zhihui, YAO Wenyi, TANG Qiuhong, YANG Er, KONG Xiangbing, WANG Lingling, XIAO Peiqing
1. Yellow River Institute of Hydraulic Research, Yellow River Conservancy Commission, 450003, Zhengzhou, China; 2. Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 100101, Beijing, China
Abstract:[Background] Vegetation structural characteristic is an important factor determining soil and water conservation effect of vegetation, and leaf area index (LAI) is one of the most important vegetation structural characteristics. Remote sensing technology is the most effective tool to monitor LAI dynamics at regional scale. [Methods] In this paper, the spatio-temporal variation characteristics of LAI, including changed area percentage, absolute change rate and relative change rate, at regional scale and pixel scale were investigated respectively using Mann-Kendall trend analysis and Sen-slope analysis based on MOD15A2H product. And variation characteristics of LAI for different sub-basins, slopes, aspects and vegetation types were analyzed and compared. In addition, the reason of variation of LAI was explored using linear regression method and partial relation analysis based on MOD44B product. [Results] 1) The change trend of LAI during 2000-2014 in the Loess Plateau increased significantly, and the absolute change rate and relative change rate of LAI were 0.042/Year and 2.71%/Year respectively. 2) For the spatial distribution of variation characteristics of LAI, areas with a significant increase trend of LAI accounted for 58.6% in the Loess Plateau, and areas with a significant decrease trend of LAI accounted for 0.9% in the Loess Plateau. The variation extent of LAI in the regions between Hekou and Longmen, including Huangfuchuan, Kuyehe, Wudinghe and Yanhe were tremendous. The change rate and area percentage of changed regions for LAI in the area where slope was between 15° and 25° were the highest. There was no significant difference for LAI in different aspects. The change rate and area percentage of changed regions for LAI in cropland and grassland were the highest. 3) In the Loess Plateau, the increase of tree coverage was the main reason for increase of vegetation LAI, and there were no significant relationship between LAI and vegetation fractional coverage. [Conclusions] The change trend of LAI during 2000-2014 in the Loess Plateau is significantly positive. Compared with absolute change rate, relative change rate is more able to illustrate the variation extent of LAI. According to statistical analysis, compared with total vegetation fractional coverage, LAI is more related to the vegetation vertical structure in the Loess Plateau, and the increase of tree coverage caused by "Grain to Green" project carried out across the Loess Plateau could be one of the important reasons for improvement of vegetation vertical structure.
王志慧1,2, 姚文艺1, 汤秋鸿2, 杨二1, 孔祥兵1, 王玲玲1, 肖培青1. 2000—2014年黄土高原植被叶面积指数时空变化特征[J]. 中国水土保持科学, 2017, 15(1): 71-80.
WANG Zhihui, YAO Wenyi, TANG Qiuhong, YANG Er, KONG Xiangbing, WANG Lingling, XIAO Peiqing. Spatio-temporal change analysis of leaf area index in the Loess Plateau during 2000-2014. SSWC, 2017, 15(1): 71-80.
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