Characteristics of Grassland and Ecological Changes of Vegetations in the Source Regions of Yangtze and Yellow Rivers

Based on the grassland survey and remote sensing technology, the ecological types and their spatial distribution of grassland, the features of grassland resources and their utilization statues in the source regions of Yangtze and Yellow rivers were studied. The production capacity of the grassland was estimated. By the regional eco-environment investigation and three periods' remote sensing information, the eco-environmental changes of the grassland in recent 40 years were analyzed. Those results showed: (l) The types of grassland in the study area were mainly the high-cold meadow and the high--cold steppe. The high-cold meadow was one of the most important grassland types in the study area, could be divided into four sub-types: high-cold typical meadow, high-cold swamp, high-cold steppe meadow and high-cold shrub meadow. The high-cold meadow area was about 53.78% of the whole study area. (2) The coarse protein contents of the main forage grass were over 10%, and the coarse fat contents over 2%, and the energy reserves over 9.34 kJ. g-1. (3) Since 1970s, because of the rapidly improvement of livestock husbandry the grazing over the cold season pastureland was very heavy with the l-5 fold larger than the theoretical carry capacity. The most of the warm pasturelands were over grazing too. Those resulted in the seripusly degradation of grassland with the annual degredating rate of 6.64% -34.45%. Rodent damages also play an important role in the ecological degradation. It was the most urgent need in the source regions of the Yangtze and Yellow rivers to rationally utilize the grassland resources and to study possible rehabilitation measures for the eec-environment of the regions so as to ensure a sustainable development.