Abstract:

Aims Land-use and land-cover changes are important in the study of global change. Our objective is to understand the impact of topography on land use and cover change in Xishuangbanna, Southwest China, from 1976 to 2007.

Methods Based on GIS techniques, we used six periods of Landsat MSS/TM/ETM images and 1:50 000 digital elevation model (DEM) to analyze patterns of land use and cover change and transfer rates as affected by topography.

Important findings The magnitude, pace and spatial reach of land use and cover changes in Xishuangbanna were unprecedented. The most significant changes were a decrease of forest area from 13 193 to 8 336 km²and an expansion of area of rubber plantations from 249 to 2 256 km²at low elevation. Topographic features, especially elevation and slope, exerted significant influence on the distribution pattern, intensity and velocity of land use and cover changes. Changes varied along elevation gradients, slope gradients and aspects. Forest cover continuously decreased below 1 600 m, while the upper limit of rubber plantations increased continuously from 1 000 to 1 400 m and was dominant between 400 and 1 000 m. Farmland was dominant below 600 m and decreased rapidly with increasing elevation. Along all slope gradients, forest cover decreased gradually, while rubber plantation increased, but shrubland and dry land first increased and then decreased. Rubber plantations and farmland were mainly on gentle slopes, while forest occupied the majority of steep slopes. After 1988, rubber plantation cover was unchanged below slopes of 5˚, but continuously expanded above slopes of 5˚. Aspect had large influence on the distribution pattern of cash crops and agricultural land. Rubber plantations on south aspects rapid expanded in comparison to a trend of general increase on north aspects, where forests reached a maximum and dry lands a minimum. Economic interests and population growth lead to excessive deforestation and reclamation in this region. Especially in recent years, the continuous conversion of forests to both rubber plantations and tea gardens has yielded negative effects which have led to further fragmentation affecting the biodiversity and security of natural ecosystems. For local sustainable development, the government must control the expansion of rubber plantations into forest and higher elevations, safeguard relatively intact of tropical ecosystems and manage land sustainably over the long term.

Key words: land use/cover, DEM, elevation, slope, aspect, spatial pattern, rubber plantation, deforestation