近30年来青海省风蚀气候侵蚀力时空差异及驱动力分析

The spatial and temporal differences and driving forces of wind erosion climatic erosivity in Qinghai province from 1984 to 2013

青藏高原气候寒冷、多大风,冻融、风化和风蚀作用强烈,易发生土壤风蚀。气候对土壤风蚀的影响可用风蚀气候因子指数(C)度量。基于联合国粮农组织(FAO)提出的C计算方法,根据1984-2013年间连续完整的青海省气象站地面观测数据,应用地理加权回归模型(GWR)、重心及其转移模型,并结合本文定义的有效敏感性指数、有效影响面积等指标,得到全省风蚀气候侵蚀力及其影响因子的时空分布及其演化规律,并对其驱动力和机理进行了初步分析。结果表明:30年来,全省风蚀气候侵蚀力总体特征是西北高东南低并呈下降趋势,风蚀气候侵蚀力强的区域明显向西南扩展,20世纪80年代是柴达木盆地,90年代扩展到青南高原西北部边缘,21世纪基本涵盖了青南高原的西部;风速是影响风蚀气候侵蚀力的主导因子,其有效敏感区重心从柴达木盆地西南部边缘,移动到海拔较高的青南高原西部地区,这与高原近地面气旋系统中心总体移动趋势相反;其次是气温,其有效敏感区重心从海拔较低的青海省中部地区向海拔较高的青南高原移动,这与青南高原地区的海拔梯度式增温规律有关,即从高原边缘向高原腹地升温,且海拔越高,增温越快;降水主要影响柴达木盆地的侵蚀力,其有效敏感区重心向东南扩展,这可能与高原夏季风进退有关。研究结果可为青藏高原土壤风蚀灾害的预防、评估以及预测提供区域性差异化的技术支持与理论指导,也可为青藏高原乃至全球生源要素(C、N、P、S等)循环的大尺度驱动力研究提供新的研究视角。

The soil erosion is prone to occur in the Qinghai-Tibet Plateau （QTP） where freezing and thawing, weathering and wind erosion are all strong, precipitation is rare, wind is strong and frequent, vegetation is sparse, and the loose ground surface material is susceptible to blowing away by wind. Climate is an important external force for soil erosion and its influence on soil erosion can be described quantitatively by wind erosion climatic factors index （C）. Qinghai province＇s C were calculated based on the method suggested by FAO, using the continuous and complete surface meteorological observation data from meteorological stations in Northwest China＇s Qinghai Province from 1984 to 2013. Applying geographical weighted regression model （GWR）, the gravity center and its transfer model as well as the effective sensitivity index and effective influence area which were defined in this paper, we obtained spatial and temporal distribution and evolution law of wind erosion climatic erosivity （WECE） and its influencing factors, and also analyzed their driving forces and mechanisms. The results showed that WECE in Qinghai province was on the decline and the most severely eroded region has been extending from the Qaidam Basin to the western part of southern Qinghai Plateau during the past 30 years. Wind speed was the dominant factor of WECE, the secondary factor was the temperature and the least impact was the precipitation. The gravity center of wind speed effective sensitive region moved from the edge of the southwest Qaidam Basin to the western part of southern Qinghai Plateau, whose displacement direction was roughly opposite to the direction of cyclone system center of the surface layer over the Qinghai- Tibet Plateau. The gravity center of air temperature effective sensitive region moved from the low-altitude region of central Qinghai to the high-altitude southern Qinghai Plateau. This was related to the law of increasing temperature, namely, temperature was increasing from the edge of the plateau to the plateau hinterland and the higher the altitude was, the faster the temperature increased in the southern Qinghai Plateau. Precipitation mainly affected the WECE in the Qaidam Basin, and its gravity center moved to the southeast, which might be related to the advance and retreat of the Plateau Summer Monsoon. The research of this paper can provide the technical support and theoretical guidance for the prevention, assessment and prediction of soil wind erosion disaster in the QTP. It can also provide a new perspective for the study on large-scale driving force of the biogeochemical cycles （such as C, N and P cycles） in QTP and even in the world.