近58 a川西北高原的气候变化及其生态效应

Climate Change and Its Ecological Effect in Northwest Sichuan Plateau in Recent 58 Years

川西北高原位于我国一、二级阶梯的过渡地带,是长江、黄河上游的集水区,也是我国五大牧区之一,高寒草甸是其高原面上的典型植被.近年来,草地沙化问题突出,已经威胁到区域生态安全和畜牧业的可持续发展.以过度放牧为主的人为因素和以气候变化为主的自然因素被认为是导致川西北高寒草地沙化的驱动力.着眼于气候因素,研究1961—2018年与草地沙化密切相关的温度、降水、风速、潜在蒸散和气候干燥度的变化特征,在此基础上讨论气候变化的地表覆被效应,结果表明:川西北高原的温度呈显著上升趋势,气候倾向率为0.25℃/Da,受其影响潜在蒸散(potential evapotranspiration,ET_(o))也呈上升趋势,倾向率为4.4 mm/Da.降水量变化表现为平均增加但线性趋势不显著,总体倾向率大于ET_(o),为8.3 mm/Da.因此,气候干燥度呈多年平均变湿润特征,但线性趋势不明显.把各气候因子与地表覆被NDVI进行相关分析发现,单气候因子与NDVI的相关性均不强,说明气候变化对植被影响的复杂性,也证明人类扰动在土地沙化中的作用不可忽略.

Northwest Sichuan Plateau is located in the transitional area of the Tibet Plateau and the Sichuan Basin of China.It is the catchment area of the upper reaches of Yangtze River and the Yellow River,and one of the five pasture areas in China.Alpine meadow is the typical vegetation in this region.However,in recent years,the problem of grassland desertification has been a threat to the regional ecological security and the sustainable development of animal husbandry.The human factors of overgrazing and the natural factors dominated by climate change are considered to be the driving forces of desertification of alpine meadows in northwest Sichuan.In this paper,we focus on the change of climatic factors,including temperature,precipitation,wind speed,potential evapotranspira-tion and climate dryness,which are closely related to grassland desertification from 1961 to 2018.And then the effect of surface cover on climate change is discussed.Results showed that:the temperature of the Northwest Sichuan Plateau showed a significant upward trend,the climatic tendency was 0.25℃/10 a.ET_(o) also showed an increasing trend with a tendency of 4.4 mm/10 a.The trend of precipitation is an average increase but not a linear trend,and the overall trend is larger than ET_(o),with the tendency of 8.3 mm/10 a.Therefore,the climate dryness is characterized by years of average decrease,but the linear trend is not obvious.The correlation analysis of climatic factors and NDVI showed that the correlation between single climatic factors and NDVI was not strong,which indicated the complexity of climate change impact on vegetation,and proved that the role of human disturbance in desertification cannot be neglected.