Abstract:

Aims For sustainable watershed development planning, this study explores how ecological carrying capacity varies with changes in land use type and population.
Methods Based on interpretation and analysis of five Landsat TM remote sensing images for 1989, 1994, 1999, 2004, and 2009, respectively, we examined the spatio-temporal patterns of land use change in the upper, middle, and lower reaches of Dongjiang watershed, using the total rate of change and single and integrated degree of land use dynamics as indicators. We calculated the total and per capita eco-capacity for the watershed in different years based on the population data, equivalence factors, and yield factors, in addition to the data of land use and land cover change, and further analyzed the factors determining the direction of changes in the eco-capacity.
Important findings The results showed that: (1) there were apparent changes in the area for various land use types between 1989 and 2009. Despite the urban development, the coverage of forest vegetation increased, indicating lack of trade-off between urbanization and vegetation coverage. However, there were different patterns of change in land use among the upper, middle, and lower reaches. The land use type mainly varied from garden fields to forests in the upper and middle reaches of the watershed, while in the lower reach a change from arable land to build-up area dominated. (2) With the population growth along the Dongjiang watershed over the past two decades, although the per capita eco-capacity indicated a downward trend, its rate of decline lagged behind the population growth rate, and the total eco-capacity still showed a trend of increase, implying an optimization of land use types during the 20-year period. With respect to the temporal patterns, in the decade (1994-2004) after the end of the “10-year greening of Guangdong Province”, per capita eco-capacity tended to be relatively stable under the pressure of population growth, while it declined quickly in the periods of 1989-1994 and 2004-2009. The former period was probably associated with the development of reform and opening up policy, and the latter seemed to have less possibility on spatial optimization of land use types. The total eco-capacity showed different trends among the three regions; the upper and middle reaches exhibited an unstable trend (i.e., from decreasing to increasing), while the lower reach indicated a pattern of increasing-decreasing-stable trend. In conclusion, the increasing population demand for urbanization did not lead to deterioration of the forest resources in the watershed. To some extent, we could thus achieve the coordinated development in both aspects. In spite of increasing demand on ecological resources with population growth, we could establish a better strategy in land use to improve ecological services, and to reduce the downward trend in the per capita eco-capacity.

Key words: degree of land use dynamics, Dongjiang watershed, ecological carrying capacity, Landsat TM, land use change