[Landscape stability and its pattern transition in Jinghe watershed].
Based on remote sensing and GIS, this paper analyzed the landscape change patterns in the Jinghe watershed of northwest Loess Plateau, one of the areas most suffered from soil and water erosion. The results indicated that the landscape structure in the watershed did not change very much over the past 15 years, and was dominated by grassland and arable land, which occupied 85% of total watershed area. Forest and other land use accounted for 10% and 5% of total area, respectively. A transition of landscape patterns occurred at large-scale watershed level. During 1986- 2000, the inter-transitions between different landscape types were very complicated, mainly occurred among woodland, grassland and arable land. The self-stableness of dominant landscape patterns was > 89%, and only 11% of them transferred into other types. Among landscape types, the one sharing small percentage of the total had a high speed of vanishing or transferring into other types. A significant transition was found between sub-patterns of a large landscape pattern, e. g., the transition of medium- into low-coverage grassland during 1986 - 1995 and the reverse during 1995 - 2000 was occurred, implying a situation of grassland degradation and improvement over the decades. The spatial-temporal changes of landscape features were observed in the watershed. In terms of spatial change, the dominance index and contagion index of the landscape showed an increasing trend, fractal dimension index showed a decreasing trend, while patch density showed an increasing trend, followed by a decreasing trend from upper to down streams. For temporal change, both landscape dominance and contagion decreased to a certain extent, fractal index remained stable, while patch density increased, showing a fragmentation direction of the landscape in the watershed. The NDVI value changed since the implementation of the policy of conversing farmland into grassland and forest in 2000, which was from 7.4% to 0.8% in low value class, from 29.8% to 25.1% in high value class, from 18.3% to 25.7% in higher value class, and from 2.3% to 5.5% in the highest class, showing an improving trend in landscape quality.
Xie
Gaodi
G
Institute of Geographical Sciences and Natural Resources Reseach, Chinese Academy of Sciences, Beijing 100101, China. xiegd@igsnrr.ac.cn
Zhen
Lin
L
Yang
Li
L
Guo
Guangmeng
G
D002681:China; D003247:Conservation of Natural Resources; D017753:Ecosystem; D040362:Geographic Information Systems; D006802:Human Activities; D063245:Plant Development; D045483:Rivers; D017215:Satellite Communications; D012987:Soil / Q000032:analysis*; D014867:Water / Q000032:analysis
D012987:Soil; D014867:Water