Abstract:

The landscape diversity index (LDI) is not only an important indicator in landscape ecology research but also an important component in biodiversity conservation. Based on the land use/cover raster data (30-m resolution), the spatiotemporal variation and scale-dependence characteristics of the LDI of an oasis along the Yellow River in Ningxia, China, have been studied using Neighborhood and Focal tools in ArcMap from 1975 to 2000. The results are as follows: (1) The LDI, which is measured by a square with a side length from 90 m to 6000 m, had obvious spatial scale-dependent characteristics based on five times repeat, and its turning point was 3000 m. (2) The change trend of the LDI had been cyclical in the past decades, with a turning point of 2000. During the study period, the LDI exhibited a decreasing trend from 1975 to 2000, and the analysis of LDI zoning indicated that the main characteristics were as follows: the class area (CA) of the degraded area was the largest, and the CA of the improved area was the smallest, which were 6840 km² and 1332 km², respectively. In contrast, there was an increasing trend for the LDI from 2000 to 2020, mainly characterized by the maximum CA in the impervious area and the minimum CA in the degraded area, which were 7848 km² and 792 km², respectively. Because the initial LDI in 2000 was the lowest in the entire period, its improvement status in the later period did not reach that of the early period. (3) The conversions of the LDI-grading area were mainly characterized by the transfer from the early improved area to the late impervious area (796 km², 60.5% of the improved area) and the transfer from the degraded area to the impervious area (3519 km², 51.5% of the degraded area) and the improved area (3036 km², 44.4% of the degraded area), respectively. (4) The change in the landscape diversity pattern was characterized by a negative correlation between CA and relative splitting index, and this relationship mechanism was universal in different periods and change types. Thus, it is to best understand the landscape diversity change with credible spatiotemporal scales in a regional landscape study. It is necessary to ensure that the research results are not only used for reference and sharing but also used to visualize and analyze regional landscape diversity.

Key words: landscape diversity index, landscape pattern, scale effect, an oasis along the Yellow River in Ningxia