广西脆弱岩溶地区是政府植被保护与恢复工作的重点地区。研究气象灾害对植被变化的影响对岩溶地区防灾减灾和生态保护具有重要意义。归一化植被指数(NDVI)作为监测植被生长的工具,对植被有很强的响应性,可以定性和定量地评价植被覆盖度及其生长活力。因此,在这项研究中,分析了植被变化趋势和多种气象灾害的影响,比如干旱,暴雨,高温,低温,利用线性趋势法对广西喀斯特地区的植被,GIS空间分析,和相关分析,利用MODISNDVI和广西岩溶地区2000-2020年的温度和降水信息。结果表明:(1)喀斯特地区NDVI显著增加,32.2%的地区植被明显改善。改善最明显的主要是在研究区的中部,东北和西南部分分散地区植被退化趋势明显。(2)在年际尺度上,NDVI与部分气象灾害指数呈负相关,如相对湿度指数,干旱天数,特大暴雨的数量,大量的暴雨,高温≥35°C的天数,高温35-37°C的天数,高温≥37°C的天数,最低温度,有效积温≤0℃。干旱对植被的明显负效应区主要集中在研究区中部,降雨主要分布在西南部,东北和西北;高温主要分布在西北和东北,低温主要集中在西南和北部。(3)在多年月度规模上,NDVI对干旱的响应,高温和低温灾害指标具有滞后效应,但对降雨灾害指数没有滞后效应。植被对干旱的滞后时间为1个月,高温和低温的滞后时间为3个月。
Fragile karst areas of Guangxi are the key areas of vegetation protection and restoration work of the government. It is of great significance to study the effects of meteorological disasters on vegetation change for disaster prevention and reduction and ecological protection in the karst areas. The Normalized Differential Vegetation Index (NDVI), as a tool for monitoring vegetation growth, has a strong responsiveness to vegetation and can qualitatively and quantitatively evaluate the vegetation cover and its growth vitality. Therefore, in this study, we analyzed the trend of vegetation change and the impacts of multiple meteorological hazards, such as drought, torrential rainfall, high temperature, and low temperature, on the vegetation of the karst region in Guangxi by using the linear trend method, GIS spatial analysis, and correlation analysis, using the MODIS NDVI and temperature and precipitation information from 2000 to 2020 in the karst region of Guangxi. The results show that: (1) NDVI increased significantly in the karst areas, and 32.2% of the areas had significant improvement in vegetation. The improvement was the most obvious mainly in the central part of the study area, while the vegetation degradation trend was obvious in partial scattered areas in northeast and southwest. (2) On the interannual scale, NDVI was negatively correlated with some meteorological disaster indexes, such as relative humidity index, the number of drought days, the amount of extremely heavy rainstorm, the amount of heavy rainstorm, the number of days with high temperature of ≥35 °C, the number of days with high temperature of 35-37 °C, the number of days with high temperature of ≥37 °C, the minimum temperature, and the effective accumulated temperature of ≤0 °C. The obvious negative effect area of drought on vegetation was mainly concentrated in the middle of the study area, and that of rainfall was mainly distributed in the southwest, northeast and northwest; that of high temperature was mainly distributed in the northwest and northeast, and that of low temperature was mainly concentrated in the southwest and north. (3) On the multi-year monthly scale, the responses of NDVI to drought, high temperature and low temperature disaster indexes had a lag effect, but had no lag effect on rainfall disaster indexes. The lag time of vegetation to drought was 1 month, and the lag time to high temperature and low temperature was 3 months.