1990-2015年长江中游地区耕地利用转型时空特征

Spatiotemporal characteristics of cultivated land use transition in the Middle Yangtze River from 1990 to 2015

依据土地利用转型理论内涵,尝试性地从显性形态视角构建耕地利用转型特征识别框架,基于1990-2015年间6期Landsat TM影像解译数据,定量刻画长江中游地区县域耕地利用形态时空特征,揭示不同时段耕地利用转型分异规律。结果表明:(1)1990-2015年间长江中游地区耕地利用显性形态经历了剧烈而非均衡的转型过程,耕地转换减少8075 km^2,且耕地转换量累积率在前20%的县域占总耕地转换量的66.9%;(2)25年间数量形态经历了"先减后增"的变化过程,且长江中游地区耕地利用转型均衡度呈现"阶段下降,快速上升,平稳降低"的变化趋势;(3)耕地空间形态整体呈现以武汉、长沙、南昌为中心向外扩散的分布特征,其中耕地转换量高值区主要呈现出明显的梯度分布特征,转型幅度高值区主要呈现"大聚集小分散"分布特征,转型速度高值区则主要呈现出"条带式"分布特征;(4)从地形起伏度上看,耕地利用转型整体呈现随地形起伏度上升而逐级降低的趋势,在1~2级地形起伏度上的县域耕地利用转型呈现无序状态,而在3~5级地形起伏度上的县域主要以低转型幅度和低转型速度为主。研究框架及结果对区域耕地利用转型识别和适度调整耕地利用和经营模式等具有积极意义。

Based on the theory of land use transition, quantity and spatial forms are external representations as well as research basis of the cultivated land quality and structure. However,on different geographic locations, socio-economy, and institution, the degree and speed of cultivated land use reduction significantly differ. In this perspective, the single land use dynamic amplitude index refers to the construction of cultivated land transition velocity model in order to fully describe the characteristics of speed and regional imbalance. Within the means of the ＂3S＂, the spatial visualization is described by the quantity and spatiotemporal variation characteristic of cultivated land use transition. What＇s more, the Lorenz index curve, the Gini coefficient, and variation coefficient are quoted to describe the equilibrium degree of cultivated land use transition at county level. In addition, to explore the spatiotemporal distribution of the cultivated land use transition in the natural geographic conditions, a county level terrain model is adopted to examine cultivated land quantity and spatial transformation of different topographic gradients. Therefore, the spatiotemporal variations of cultivated land use transition are quantitatively used to interpret the data retrieved from the Landsat TM in the Middle Yangtze River from 1990 to 2015. Results show that there was an unbalanced and drastic transition in this region during the study period. The cultivated land area decreased to 8075 km^2. Meanwhile, the first 20% of the accumulation rate of cultivated land conversion area accounted for 66.9% of the total cultivated land conversion. During the study period, the quantity of the cultivated land use transition experienced the process of ＂first reduced and then increased＂ and shows a trend of ＂decline, rapid increase, and steady reduction＂ in the study area. On the other hand, the spatial form of the cultivated land use transition spread outside from Wuhan, Changsha, Nanchang as the center, what＇s more, the high value area of cultivated land conversion is mainly characterized by the gradient distribution. The high value zone of transition presents a distribution pattern of large aggregation and small dispersion, and the high value area of transformation is mainly characterized by a ＂strip type＂. In terms of the topographic relief, transformation of cultivated land use shows a tendency of gradual reduction with the rise of the terrain as a whole, and 1-2 level terrain fluctuation degrees of the county cultivated land use transition are in disorder, but the 3-5 level terrain fluctuation degrees of the county are mainly in low transition amplitude and low transition speed.