关键词: 生态环境变化, 气候变化, 江河源区, 中国

Abstract: Mountain environments are essential to the survival of the global ecosystem. Mountains provide a large variety of both ecological and physical indicators, whose combined use might serve as a unique chance to observe and detect signals of global environmental change. The Changjiang-Yellow Rivers source region is an important ecological function area for the Qinghai-Tibetan Plateau, and also serious vulnerary for environment. Climate change during 20th century has significantly affected the cryosphere. Under climate scenarios, temperature of the Tibetan Plateau may rise by 2.5～3.6℃ by 2100 or so as compared to that at the end of the 20th century. Permafrost zone will greatly change after climate warming. Their area is expected to decrease and permafrost zone will be moving upward and degrading. The area of extreme stable zone will shrink from 5.59% at present to 0.65% in 2099, stable zone from 16.32% in present to 3.28% in 2099, and substable zone from 25.5% in present to 17.43% in 2099. Area will increase with air temperature rising for transition zone and unstable zone. Area of transition zone will change from 22.85% at present to 31.01% in 2099 and that of unstable zone from 10.8% at present to 27.46% in 2099. Extreme stable zone will transform into stable zone, stable zone into substable zone, substable zone into transition zone, transition zone into unstable zone and unstable zone will be in the stage of degradation. Air temperature rising results in changing of distribution of seasonal snow cover and regime of snowmelt runoff, snowfall increasing due to air temperature rising reaches 7%～10%,the snowmelt period stretches with the shifted advance 10 days. While the discharge increases, the peak of runoff also advances to May. For a warming rate of 0.03 K ·a^-1, without increase in precipitation, almost all less 4 km of glacier length would disappeared and 40% of all glaciers area here would survive until 2100. On the other hand, if the warming rate were to be limited to 0.03 K·a^-1 with an increase in precipitation of 10% per degree warming, the effect of a precipitation change of this magnitude is significant, but by no means enough to compensate for the enhanced melting due to the temperature rise, we predict that overall loss would be restricted to 40% of the 1990 area; the total area of glaciers would decreased from 1168.18 km² at present day to 700 km² until 2001 in the source region of Changjiang River. The area and volume of the glacier will greatly decrease, which will have great impact on the ecological environment of the source region of the Changjiang River. Climate change will affect the water balance, and particularly the amount of runoff and recharge, which in turn determines the water resources available for human and ecosystem uses.

Key words: ecological environmental change, global warming, source region of Changjiang-Yellow Rivers, China