基于SPCA和遥感指数的干旱内陆河流域生态脆弱性时空演变及动因分析——以石羊河流域为例

以石羊河流域为研究区,基于干旱内陆河流域生态特征和遥感数据快速、客观、大面积观测的特点,采用遥感模型计算湿度、绿度、干度和热度等指标,并构建石羊河流域生态脆弱性评价指标体系,在此基础上运用空间主成分分析法(SPCA)对石羊河流域2000和2016年生态脆弱性时空演变及动因进行了分析。研究结果表明:(1)从各遥感指数空间分布来看,湿度和绿度指标均值在17年间呈增长趋势,证明该流域水源涵养能力变好,植被覆盖率变大;干度指标均值有所下降,表明该流域地表裸露程度有所降低;而与植被和水资源关系密切的地表温度均值呈逐年上升趋势,说明该流域水热平衡差异进一步增加,对未来生态脆弱性影响显著;(2)从全流域生态脆弱性时空演变特征来看,该流域主要以强度和中度脆弱为主,17年间生态脆弱性整体上呈缓慢降低趋势;(3)从不同的海拔生态脆弱性分布来看,中山区(1000—2000m)最高,高中山区(2000—3000m)次之,高山区(3000m)最低,17年间中山区生态脆弱性有所下降,而高中山区与高山区却呈上升的趋势;(4)从不同的行政区划生态脆弱性来看,金川区、凉州区、永昌县、民勤县和古浪县整体上处于中度和强度脆弱水平,而天祝县和肃南县处于轻度和微度脆弱水平;(5)从生态脆弱性的演变动因来看,4个指标对石羊河流域生态脆弱性影响均为显著。2000年生态脆弱性的主导影响因子依次为热度湿度绿度干度,而2016年为热度干度绿度湿度。总的来看,石羊河流域生态脆弱程度近年来有所降低,但综合治理工作仍任重道远。本文的遥感方法和分析思路对该流域生态脆弱性保护及治理提供一定的理论基础和决策依据。

Spatio-Temporal evolution and motivation analysis of ecological vulnerability in Arid Inland River Basin based on SPCA and remote sensing index: A case study on the Shiyang River Basin

With Shiyang River Basin as the study area, this paper used a remote sensing model to calculate indicators such as greenness, dryness, wetness and heat to construct ecological vulnerability assessment indicators based on the ecological characteristics of Arid Inland River Basin and the characteristics of rapid, objective, and large-area observational remote sensing, which was analyzed the spatio-temporal evolution and motivation of ecological vulnerability by Spatial Principal Component Analysis (SPCA) in 2000 and 2016 in Shiyang River Basin. The research showed that (1) From the spatial distribution of each remote sensing index, the mean of wetness and greenness showed an increasing trend in 17 years, which proved that the water conservation capacity was better and the vegetation coverage was larger in the basin. The mean of dryness had decreased, indicating that the degree of surface exposure of the basin had reduced. The mean of surface temperature closely related to vegetation and water resources was increasing year by year, which indicated that the differences of water and heat balance were further increasing in the basin, which had a significant effect on ecological vulnerability in the future. (2) From the spatio-temporal evolution of ecological vulnerability in the whole basin, the basin was mainly dominated by strong vulnerability and moderate vulnerability, and the ecological vulnerability had been slowly decreasing in 17 years. (3) From the ecological vulnerability distribution at different elevations, the highest in medium mountain area (1000-2000m), the medium in high-medium mountain area (2000-3000m), and the lowest in high mountain area (> 3000m). During 17 years of change, the ecological vulnerability of medium mountain area had decreased, while the high-medium mountain area and high mountain area were on the rise. (4) From the ecological vulnerability of different administrative divisions, Jinchuan, Liangzhou, Yongchang, Minqin and Gulang as a whole were at the level of moderate vulnerability and strong vulnerability, while Tianzhu and Sunan were at the level of slight vulnerability and light vulnerability. (5) From the motivation of ecological vulnerability, the four indicators had significant effects on the ecological vulnerability of Shiyang River Basin. The main influencing factors of ecological vulnerability were heat > wetness > greenness > dryness in 2000, and the main influencing factors of ecological vulnerability were heat > dryness > greenness > wetness in 2016. Overall, the ecological vulnerability of Shiyang River Basin had decreased in recent years, however the comprehensive management still has a long way to go. The remote sensing methods and analysis ideas of this paper provided theoretical basis and decision-making foundation for the ecological vulnerability protection and management in this basin.