Analysis of landscape patterns and diversity in the upper reaches of the Shiyang River based on remote sensing and GIS

Abstract

The mountainous ecosystem is important for its unique storage of water and the function of water resources in the northwest mountain-oasis-wilderness ecosystem. Water resources play very important role in the continuous development of economy in the northwest of China. With the use of evaluation indices such as landscape index and landscape diversity, this paper proposes to study on the landscape patterns and biology diversity in the upper reaches of ShiYang River based on remote sensing and GIS, which located in the Qilian mountains . The results show that:1. Landscape in this region shows typical local characteristics and patches were distributed in a ring structure. The main patches were farmland, steppe and shrubbery which were continuous from 2000 to 5000 m and accounted for 74% of the total landscape area. Among these types, the shrubbery and the steppe had very coarse grain size and the highest fractional dimension in this region, displaying high continuity and a dense cluster of larger patches. Compared to the shrubbery and the steppe, the farmland had less patches and finer grain size. Other patches such as the residential land and the impoundment/pond only occupied a very small percentage and are sparsely scattered among the major patch types. 2. Shrubbery, steppe, and farmland changed obviously, but there were some differences in all three types. The shrubbery was mainly transformed to steppe. Steppe was mainly transformed to residential land, and farmland was mainly transformed to bare land/rock. In the past 15 year, the man-made channels had increased.3. There was an increase in fragmentation values in the entire hill-landscape from 1986 to 2000. There was a big difference in the fragmentation in different landscape patches, 0.4637 up to 0.4649 from 1986 to 2000 for farmland, 11.9019 down to 11.7033 for residential land. As the result of invasion of farmland and resident land, the fragmentations of both steppe and forest land went up.4. The order of area of different landscape patches was bare rockland > arboreous forest > shrubbery > farmland > steppe > impoundmentpond > residential land. While the mean patch area of bare landrock and resident land increased in nearly 15 years, they were stable for high-forest and the others decreased. The order of patch dominance was steppe > shrubbery > farmland > residential land > bare rockland > arboreous forest > impoundmentpond. While the patch dominance of impoundmentpond and residential land increased, the others decreased. Steppe and shrubbery were the main landscape patches for nearly 15 years, decreased from 0.4624 to 0.4614, alternatively, shrubbery also decreased from 0.2575 to 0.2568. Their distribution was wide and the area was large. Farmland was the main human landscape, whose dominance indices are 0.1232 and 0.1227, mean patch area of 2.1546km² and 2.1510km². Its spatial distribution centralized and it decreased in the period.