Dynamic change analysis of landscape pattern in a typical karst watershed:A case study of Xiaojiang watershed of Yunnan Province,China
典型岩溶流域景观格局动态变化——以云南小江流域为例

The landscape maps of Xiaojiang karst watershed, Yunnan province in 1982 and 2003 were obtained by interpreting aerial photo in 1982 and Landsat TM image in 2003. Supported by GIS, and through analyzing the landscape maps, the landscape pattern change maps from 1982 to 2003 were achieved. The dynamic change in spatial pattern of landscape and the driving force of landscape change during the past two decades in Xiaojiang watershed were analyzed. The results indicate: (1) The total landscape transformed area covers 610.12 km~2, of which cultivated land increased by 268.5 km~2 or 132.27%, but unused land decreased by 280.5 km~2 or 54.36% during the past 20 years. (2) The change of landscapes was very rapidin the past 20 years. The overall landscape change percentage was 2.95% in Xiaojiang watershed. Especially, the landscape change percentage for orchard and cultivated land were 34.09% and 10.55% respectively. (3) The amounts of landscape patches increased from 1014 to 1889, but the average area per patch decreased from 1.02 km~2 to 0.55 km~2. The spatial pattern of landscape patches has changed from dominant large and scatter patches mosaic to dominant medium and scatter patches mosaic, and the types of dominating patch have also been changed from unused land and forestland to cultivated land and forest land. (4) When the spatial pattern of landscape was analyzed quantitatively by introducing the diversity index and broken index, a clear picture of the interference degree caused by human activities can be achieved. As the increasing of disturbances from human, the diversity index increased by 4.14%; and the broken index increased by 84.6%. Also, the isolation of unused land landscape and forestland landscape increased by 114.58% and 69.64% respectively, but the isolation of cultivated land landscape decreased by 45.86%. By analyzing the shifting in the centers of unused land, forestland, or cultivated land, the change of landscape spatial pattern was very obvious during the past 20 years in Xiaojiang karst watershed. Centers of different landscape type have changed towards different direction in different speed. The distance in the shift of unused land landscape center was farthest, which is 2.08km from northwest to southeast, and the distance in the center shift of forestland landscape was 1.338km from northeast to southwest; but the distance in the shift of cultivated land landscape center was only 0.222km from southwest to northeast. Finally, through quantitative analysis by introducing social and economic data, it was clarified that the rapid growth of population and the economic development were the main driving forces of cultivated land landscape change, and that the comparative economic benefit and the macro-policies such as ecological and environmental protection were important driving forces of forestland landscape change in Xiaojiang watershed during the past 20 years. So the human driving forces were direct factor of landscape pattern ch