Forest Landscape Structure And Forest Quality Change In Qilian Mountains(Middle Section)

Using the landscape ecology principle and methods on the basis of GIS and mathematics, we analyzed the forest landscape spatial pattern of Qilian Mountains(middle section) .The results show that, the study area, Qilian Mountains(middle section) is a high heterogeneous region. The grassland, the forest, the alpine meadow, and the rock-nakedness lands are the main landscape element for their large area and distributing broadly in the study area. There are also other landscape elements with small area, for example, cropland, residential area, factory and diggings area, reservoir or lake, which are distributed fragmentally. The spatial distributions of these landscape elements are affected by the altitude, aspect and slope more of less.Taking the Xishui nature preserve as a case study, we evaluated the fragmentation degree of the forest landscape and the change during the past 10 years (from 1990 to 2000) based on the forest investigation database. The results shows that the forest is the most fragmentized in all the landscape elements, and the following is shrub and grassland, and the bare-land with slight fragmentation. The forest fragmentation has been alleviated from 1990 to 2000, while the others have been aggravated, which enhanced the heterogeneity of whole landscape. The landscape pattern of Xishui nature preserve has no remarkable change from 1999 to 2000. Grassland still is the biggest area landscape element, and the forest still has the most patch number. The area of forest, shrub and cropland increased, while the area of sparse-wood, grassland and bare-land decreased. Furthermore, the variability of the forest age, forest canopy closure and forest growing stock increased during the 10 years, which made the forest structure more complication.