Identifying key landscape pattern indices influencing the ecological security of inland river basin: The middle and lower reaches of Shule River Basin as an example.

Landscape pattern evolution leads to changes of landscape spatial structure, which are intuitively reflected in the changes of ecosystem structure and composition and finally affect ecological security. In this paper, we assessed the spatiotemporal variation of the ecological security and landscape pattern of the middle and lower reaches of Shule River Basin in 1987-2015. Further, we analyzed the correlation between the ecological security and landscape pattern of the study region and correlation coefficients were calculated. On this basis, the key landscape pattern indices influencing the ecological security of the study region were identified. This may provide useful information for ecological regulation and design. The results show that: (1) From 1987 to 2015, the ecological security in the middle and lower reaches of the Shule River Basin was of medium or low level, showing periodic "U" shaped fluctuations, and the fluctuation period was gradually shortened. In addition, there was an overall spatial pattern of "high ecological security in the west, middle and south and low ecological security in the east". (2) The landscape pattern showed clear stage characteristics. The complexity of landscape pattern increased from 1987 to 1996 and decreased after 1996. (3) Landscape size, shape, quantity, type and spatial configuration had important impacts on ecological security and showed significant temporal variation. In a period when the influence of human activities was weak, ecological security was mainly related to landscape area indices. With increase in human activities, landscape shape, fragmentation and connectivity changed greatly, which led to changes in the structure and composition of ecosystem, thus finally affecting ecological security.