干旱区流域绿洲时空变化及其景观响应

基于1973年的MSS、1980年的航片以及1990年、1999年、2009年的Landsat TM/ETM+等多源遥感影像，结合实地调查进行解译分类和验证，利用GIS、Fragstats和相关统计方法，对北大河流域中下游地区绿洲时空变化和景观响应进行分析。研究表明：① 近40 a来，北大河流域绿洲呈阶段性变化，在整个研究时段绿洲变化表现为扩张与萎缩并存，且以扩张为主。绿洲面积从1973年1 705.55 km² 增长到2009年1 990.60 km²，增长幅度为16.71%。② 绿洲变化在空间和时间尺度上不平衡。绿洲空间变化剧烈区主要集中在流域下游金塔绿洲；绿洲扩张主要表现为绿洲内部“填充式”和边缘“侵吞式”；绿洲萎缩变化主要发生在绿洲-荒漠交错带的生态脆弱区，且区域空间变化不稳定；1973-1990年，绿洲以萎缩为主，1990-2009年绿洲以扩张为主，且在近10 a动态度达到最大值。③ 绿洲面积的增加，促使绿洲景观的不稳定性增强，集中表现为下游和绿洲边缘区绿洲斑块密度、斑块数目和最大斑块指数的不稳定性变化，绿洲破碎化增加，生态脆弱性降低，这不利于维持干旱区内陆河流域生态系统稳定性和可持续发展。

Spatiotemporal Change of Oases and Their Landscape Response in Arid Areas in Northwest China

In this paper, a case study on the spatiotemporal change of the oases and their landscape response in the Beidahe River Basin, a tributary of the Heihe River in an arid area in northwest China, was carried out on the basis of interpretation and analysis of multi source remote sensing images in 1973, 1980, 1990, 1999 and 2009, landscape indices by Frgastats (version 3.3) and related statistical methods. The research results were as follows: ① Both expansion and shrinkage of the oases in the Beidahe River Basin occurred periodically in recent 40 years, but oasis expansion was dominant. The oasis area was enlarged from 1 705.55 km2 in 1973 to 1 990.60 km2 in 2009, and the enlargement rate was 16.71%; ② The oases were changed with an imbalance way at both spatial and temporal scales in the study period. The rapidly changed area was located mainly in the Jinta Oasis in the lower reaches. Oasis expansion was dominated by the oasis internal “filling” and marginal “invasion”, and the oasis shrinkage occurred mainly in the fragile oasis desert ecotone. The oases were gradually shrunk during the period of 1973-1990 and expanded during the period of 1990-2009, and their dynamic degrees were reached to the maximum values in recent 10 years; ③ Enlargement of the oases increased the instable development of oasis landscape, which was characterized by the instable change of oasis PD, NP and LPI in the lower reaches and the marginal zone of the oases in the Beidahe River Basin. The increase of oasis fragmentation and ecological fragility was disadvantageous for maintaining the ecosystem stability and sustainable development in arid area, which needs to be paid more attention in the future.