| Abstract: | Based on land ecological classification of the source regions of the Yangtze and Yellow Rivers and field investigation, two
phases of TM remote sensing data obtained in 1986 and 2000 were compared. From spatial variations and type transformation
trends, the spatial changes and evolutional patterns of land ecosystem in the source regions of the two rivers were analyzed
using the analytical method of landscape ecological spatial patterns. Results show that middle and high-cover high-cold steppe
areas degraded considerably by 15.82%, high-cover high-cold meadow areas by 5.15%, while high-cold swamp meadow areas decreased
by 24.36%. Lake water area was reduced by 7.5%, especially the lakes in the source region of the Yangtze River. Land desertification
is developing rapidly and the average of desertified land area has increased by 17.11%. Desertified land in the source region
of Yellow River is expanding at an annual rate of 1.83%. Analysis of the evolutional pattern of land ecotypes shows that the
general tendencies of spatial evolution in the regions are coverage reduction and desertification of high-cold steppe, cover
reduction and steppification of high-cold meadows, and desiccation of swamp meadows. As a result, land ecological spatial
distribution pattern in the region is changing and the state of eco-environment declining. |
