近50年甘肃省张掖市甘州区绿洲时空变化过程

The temporal and spatial change of the oasis in Ganzhou District,Zhangye City of Gansu Province in the recent five decades

人类活动对绿洲自然环境的干预引起了一系列生态环境问题。本文以1963—2009年13个样本年的遥感影像数据为数据源,结合实地调查验证,提取了近50年甘州区绿洲分布情况。计算绿洲单一动态度、双向动态度,对各期绿洲矢量数据做叠置分析和绿洲景观特征指数分析,研究甘州区绿洲在时间序列和空间分布上的变化情况。结果表明:近50年甘州区绿洲总体呈扩张态势,以1986年为界,绿洲变化呈现出前期波动扩张和后期稳定扩张的特点;绿洲变化以主体稳定、外围扩张为主,内部局部退缩、零星波动为辅;稳定绿洲主要集中分布在黑河沿岸以及甘州区各乡镇驻地周围,绿洲的波动、退缩现象主要出现在绿洲边缘。

The intervention of human activities on the oasis natural environment has caused a series of ecological and environmental problems. Combined with fieldwork verification, distribution of the oasis in Ganzhou District was extracted by 13 images which were acquired between 1963 and 2009 in this paper. To get the temporal and spatial change of the oasis, the single dynamic degree and bidirectional dynamic degree of the oasis were calculated. Additionally, 13 vector data about the distribution of the oasis were overlaid and landscape indices of oasis were analyzed successively. The development of oasis in Ganzhou District showed a trend of expansion in recent 50 years. Taking the year 1986 as a cutoff point, oasis development could be divided into two stages which were “wave expansion” in the early stage and “stable expansion” in the late stage. The main phenomenon of oasis change showed body stability and peripheral expansion; the secondary phenomenon was internal partial withdrawal and scattered wave. The stable oases were mainly distributed along the Heihe River and around the residential areas of the towns, while oases in fluctuation and atrophy were distributed at the periphery of stable oasis.