滇北区域土地利用类型及植被覆盖度的时空动态变化

Spatiotemporal Dynamic Changes of Land Use and Vegetation Coverage in Northern Yunnan

以位于云南省北部的昆明市、曲靖市、昭通市、楚雄彝族自治州为研究区域,依据土地利用数据和中分辨率成像光谱仪归一化植被指数数据(MODIS-NDVI),应用像元二分模型提取滇北2000—2020年植被覆盖度;采用核密度分析、土地利用动态度、土地利用转移矩阵、像元二分模型、泰尔森中位数和曼-肯德尔(Sen+MK)趋势分析法,分析滇北不同土地利用类型的时空变化,结合植被覆盖度分析耕地、草地、林地近21 a的空间变化趋势。结果表明:滇北区域整体以林地为主,近21 a,耕地和草地有一定减少,建设用地大面积增加。耕地主要分布特征由“个体式”演变为“组团式”,其中高密度主要分布在昭通市、曲靖市北部地区;草地主要分布在曲靖市、昆明市东北部区域,整体上曲靖市草地存在一定退化;林地主要集中在楚雄市、昭通市,呈“连片式”向周围扩展;建筑用地高密度集中在各州市核心区域。近21 a,综合土地利用动态度为0.08%,说明滇北的土地利用类型相互转化比较平稳,但内部转换频繁。近21 a,草地、耕地、林地植被覆盖度(F_(VC)),分别以0.77%/a、0.29%/a、0.52%/a的速率呈现上升趋势,3种不同土地利用类型的植被覆盖度均以改善趋势为主,草地改善趋势最明显。

Taking Kunming City,Qujing City,Zhaotong City and Chuxiong Yi Autonomous Prefecture located in the north of Yunnan Province as the research area,with the land use data and MODIS-normalized vegetation index data,the pixel dichotomy model was used to extract the vegetation coverage in northern Yunnan from 2000 to 2020.The kernel density analysis,land use dynamic degree,land use transfer matrix,pixel dichotomy model,Theilson median and Mann-Kendall trend analysis were used to analyze the spatial and temporal changes of different land use types in northern Yunnan.The whole area of northern Yunnan is dominated by forest land.In the past 21 a,cultivated land and grassland have decreased to a certain extent,and construction land has increased in a large area.The main distribution characteristics of cultivated land changed from“individual type”to“group type”,and the high density was mainly distributed in Zhaotong City and the northern part of Qujing City.The grassland is mainly distributed in Qujing City and the northeastern part of Kunming City.On the whole,the grassland in Qujing City has some degradation.Forest land is mainly concentrated in Chuxiong City,Zhaotong City,contiguous to the surrounding expansion;the high density of construction land is concentrated in the core areas of the cities.In recent 21 a,the comprehensive land use dynamic degree is 0.08%,which indicates that the mutual transformation of land use types in north Yunnan is stable,but the internal transformation is frequent.In the past 21 a,the vegetation coverage of grassland,cultivated land and forest land showed an upward trend at the rate of 0.77%/a,0.29%/a and 0.52%/a,respectively.The vegetation coverage of three different land use types was mainly improved,and the improvement trend of grassland was the most obvious.