近25年延河流域土地利用/覆盖变化的时空特征

基于1980年和2005年两期土地利用矢量数据,选取土地利用转移矩阵、土地利用动态度和重心转移3种方法对延河流域土地利用/覆盖时空变化特征进行了定量研究。结果表明:(1)在近25a,延河流域森林和农田面积在数量上发生了大幅度的变化,以农田流向森林为主,然而草地和农田始终是流域主要的土地利用类型,二者所占比重之和在两个时期均在87%以上,加上森林三者所占比重达99%以上;(2)25a内,延河流域仅有3.89%的土地资源发生了利用方式的变化,但聚落用地面积增加迅速,年均增加速率为4.10%,主要靠占用农田和草地来实现;(3)区域之间以及区域和整个流域之间的土地利用变化方向和变化速度不一致,其中安塞地区的各土地利用类型变化速度均大于全流域,这与安塞地区的社会经济活动比较活跃,土地利用变化总体较为剧烈息息相关;(4)25a内,各种土地利用类型在空间上分布比较均匀,其中森林在空间上不断向上游、高海拔方向转移,而流域内水体的重心向流域下游迁移。

Spatio-temporal Characteristics of Land Use/Land Cover Change(LUCC) over the Past 25 Years in the Yan River Basin

Based on the two vector maps of land use and cover of 1980 and 2005 of Yan River Basin in the middle reaches of the Yellow River,the spatio-temporal land use and cover change(LUCC) was analyzed with methods of transition matrix,land use dynamic degree and barycenter transfer.The results showed as followings:(1) the areas of forests and cropland had significantly changed within the certain 25 years,and mainly from farmland to forestry,but the grassland and cropland were still the major part,accounting for 87% or more of the area.The areas of these three types of lands were more than 99% of that in the Yan River Basin;(2) only 3.89% of the total land changed,but the settlement land use area increased rapidly with an annual increase rate of 4.10%,of which mainly came from cropland and grassland;(3) the regional differences of LUCC were clear that the changing rate was greater in Ansai County than other counties induced by its active socio-economic activities;(4) the spatial characters of LUCC was quite even in the target region that the forests was shifted to the upper reaches and highland,and the barycenter of water bodies transferred to the lower reaches.