Change of vegetation coverage and its response to climatic factors in the Guanling-Zhenfeng demonstration area for reduction and control of rock desertification

This paper studies the variation of vegetation coverage and the effect of climatic factors on the vegetation coverage in a demonstration area for reduction and control of karst rocky desertification. Based on the 30 m(16 d) resolution Landsat images during 2006-2015, using the method of maximum value composite (MVC), normalized difference vegetation index (NDVI), and correlation and partial correlation analyses, we systematically examine the spatial and temporal variation characteristics and the trend of vegetation index of the demonstration area and its relationship with climate factors. The results show that, (1) the annual maximum average value of NDVI between 2006 and 2015 is 0.39, which is higher in the north and south boundary regions of the demonstration area and lower in the south bank of the Huajiang river; (2) Since 2006, the places with extremely low(-1.210), low(-0.669) and moderate(-0.729) NDVI values exhibited a falling trend, those with high(1.359) and extremely high(1.247) increased overall significantly; (3) On the monthly scale, the NDVI of this month and the rainfall and temperature of this month, last month and month before the last one all pass the correlation coefficient test(P<0.05), and the correlation between NDVI and rainfall this month is higher than that between NDVI and temperature(RNDVI rainfall =0.782), the correlation between NDVI of this month and temperature of last month is higher than that between NDVI of this month and rainfall of last month(RNDVI temperature =0.771). (4) The vegetation growth of the demonstration area has no lag phase to rainfall, but a month lag to air temperature.