喀斯特关键带植被时空变化及其驱动因素

中国南方喀斯特地区广泛面临着生态问题,植被的保护与恢复倍受关注,对这一区域植被覆盖的进行监测和预测是非常必要的。以MODIS-NDVI为数据源,分析2000—2016年间,研究区不同地质背景,多种土地覆被类型的NDVI时空变化特征及驱动因素。结果表明:(1)从2000—2016年间,研究区植被覆盖整体呈增长趋势;其中喀斯特区域增长情况略优于非喀斯特区域。植被覆盖在空间上呈现东高西低;其中林地的NDVI值最高,耕地次之,依次草地,居民用地,水域,未利用地最低;在林地和耕地中,非喀斯特区域的NDVI值比喀斯特高,其余的土地覆被类型中都比喀斯特区域低。(2)研究区植被覆盖改善的地区占60.19%,退化地区占17.06%;草地,耕地区改善明显,退化主要在水域和建设用地; Hurst指数显示在研究区持续性改善的NDVI大于持续性退化;相比非喀斯特区域,喀斯特区域改善及持续性改善情况更佳。(3)整体而言,海拔对NDVI的空间分布影响力最大,温度次之,依次为降雨,夜间灯光指数;相比而言,非喀斯特区域NDVI空间分布更易受地形因子影响;喀斯特区域NDVI空间分布更易受气候差异及人类活动影响。(4)研究区分别有49%,45%,61%的NDVI与气温,降雨,日照的相关系数通过a=0.05的显著性检验;相比非喀斯特而言,喀斯特区域植被生长更易受气候变化的影响。

Determinants and spatial-temporal evolution of vegetation coverage in the karst critical zone of South China

Ecological conservation and restoration in the karst critical zone of South China have recently gained considerable attention, thereby requiring the monitoring and forecasting of vegetation coverage in the district. In the present study, the moderate-resolution imaging spectroradiometer(MODIS) satellite time series (2000-2016), the Hurst exponent index, and a geographical detector were used to analyze the determinants and spatial-temporal evolution of vegetation coverage in different geologic areas (karst and non-karst) and under different types of land use. (1) The regional vegetation of south China increased from 2000 to 2016, and the growth rate of the karst areas was slightly higher than that of non-karst areas. Vegetation coverage increased from east to west presents the distribution pattern of the east high and west low in space. Forest land yielded the highest Normal Difference Vegetation Index(NDVI) value, followed by cultivated field, grassland, construction land, and water. Non-karst areas yielded higher NDVI values than did karst areas, except for areas classified as forest land or cultivated fields. (2) The results also suggest that 60.19% of the vegetation was maintained throughout the study period, whereas 17.06% of the vegetation degraded. In particular, the vegetation of grassland and cultivated fields ameliorated significantly, whereas that of areas classified as water or construction land degraded. According to the Hurst exponent index, the NDVI for sustainable maintenance is greater than that of sustainable degeneration. The proportion of sustainable maintenance was greater in karst areas than in non-karst areas. (3) Overall, Digital Elevation Model(DEM) exerted the greatest influence on the spatial distribution of NDVI, followed by temperature, precipitation, and the night-time light index, and the spatial distribution of NDVI was more strongly affected by topographic factors in the non-karst areas than in the karst areas. (4) NDVI was significantly correlated with temperature, precipitation, and sunshine (coefficients:49%, 45%, and 61%, respectively).