Characterizing landscape dynamics of a small catchment under ecological rehabilitation interventions in Northwestern China

摘要

This study compared both pre- and post-landscape structures of Tongziba Catchment (with an ecological rehabilitation program) with a control catchment (Haichaoba, without such a program), and analyzed landscape dynamics in the key ecological conservation zone of Tongziba Catchment from 1987 to 2005 by using landscape metrics method. We used FRAGSTATS software to calculate landscape matrices and characterize landscape structures. Results showed that prior to the 2000 ecological rehabilitation program, the Tongziba Catchment shared with Haichaoba Catchment much of the land-use history and landscape fragmentation, the treated catchment did not have much more sound landscape features than the untreated one when the program was completed in 2005. During the study period, the landscape dynamics of the key ecological conservation zone of Tongziba Catchment were characterized by significant landscape type conversions from a mixture of sparse and dense, to moderately dense, grassland; landscapes became more fragmented and heterogeneous, patch shapes tended to become regular and simplified, and the landscape diversity was decreasing. The ecological rehabilitation program implemented during 2000-2005, however, transformed sparse and moderately dense grassland, riverbed and floodplain in the area to dense grassland. With the rehabilitation interventions, then, the fragmentation was moderated and the spatial properties of landscape patches tended toward complexity. The conservation program did not exert so evident influence on the landscape dynamics at catchment scale, but positive influences on the landscape dynamics of the key ecological conservation zone really did exist.