永昌县绿洲时空变化过程

Spatio-temporal process of oasis in Yongchang County

通过对永昌县1986-2015年的7期LandsatTM/OLI影像数据解译得到7个样本年的绿洲分布情况,分别用绿洲动态度模型、格网化绿洲变化率和叠置分析3种方法分析绿洲变化的时空特征.结果表明:近30 a永昌县绿洲面积增加了166.37 km^2,增幅为17%.绿洲以扩张为主,且绿洲与非绿洲间转化剧烈,呈现出平衡-非平衡-平衡的波动状态.永昌县绿洲的变化在空间上具有明显的地域差异性,清河绿洲以扩张为主,西大河绿洲退缩较剧烈,金川河绿洲和东大河绿洲变化相对稳定.稳定型绿洲是永昌县绿洲的主体,呈片状分布在地势平坦、水源充足、交通便利的各乡镇驻地周围.变化型绿洲分布在稳定型绿洲的内部或外围,主要由耕地的开垦、弃耕、复垦的多次反复所导致.

Based on the Landsat TM/OLI image data from 1986 to 2015 in Yongchang County, the distribution of oasis in seven sample years was obtained. The temporal and spatial characteristics of oasis changes were described from three aspects： oasis dynamic model, grid-based oasis rate of change and overlay analysis. The results showed that, in the past 30 years, the area of Yongchang Oasis had increased by 166.37 km^2, increased rate was 17%. The expansion of the Yongchang Oasis was dominant, the changes between oasis and non-oasis were highly frequent, showing a fluctuating and unbalanced-equilibrium fluctuating state. The spatial distribution of Yongchang Oasis presented obvious regional differences.The Qinghe Oasis mainly was expanded, that of Xida River Dasis became worse, the oases of the Jinchuan River and the Dongda River were relatively stable. Stable oasis was the main feature in Yongchang County, with a flaky distribution in the flat, water-abundant, transportation-convenient areas around the towns. Variable oasis distributed inside or outside of the stable oasis,were mainly the results of repeated reclamation, abandonment and reclamation of cultivated land.