青藏高原冻融荒漠化退化区分布及影响因素

目的]青藏高原由于其高海拔、气温低、冻融侵蚀强烈的特点,是冻融荒漠化的主要发生区。探究青藏高原冻融退化区分布及其原因,对该区水土保持工作和生态环境保护具有重要参考意义。方法]选择植被覆盖度、冻融循环次数、土壤温度日较差、土壤含水量、年降水量和坡度作为冻融侵蚀因子,对2000—2019年青藏高原冻融侵蚀敏感性进行了评价,结合研究期内青藏高原荒漠化趋势,构建了一种判定冻融荒漠化退化区域的方法。结果]2000—2019年青藏高原冻融侵蚀区总面积为1.531×10⁶ km²,中度及以上敏感性区域面积为9.131×10⁵ km²,占青藏高原总面积的35.92%。青藏高原冻融荒漠化退化区域面积约为1.113×10⁵ km²,主要分布于高原西南部,退化程度以中度退化为主,面积占比为44.35%。结论]气温上升、湿润指数下降和净太阳辐射增强是青藏高原冻融荒漠化发生的主要自然驱动因素,高原南部部分地区由于气候条件的差异,三者发挥了相反的作用。

Distribution and Influencing Factors of Freeze-thaw Desertification Degradation in Qinghai-Tibet Plateau

Objective]The Qinghai-Tibet Plateau(QTP)is the main distribution area of freeze-thaw desertification in China due to its high altitude, low temperature, and intense freeze-thaw erosion. To explore the distribution and causes of freeze-thaw degradation areas on the QTP has important reference significance for soil and water conservation and ecological environment protection in this area. Methods] Six main factors affecting freeze-thaw erosion were selected in this study to evaluate the freeze-thaw erosion sensitivity in the QTP: vegetation coverage, days of freeze-thaw cycle, daily range of soil temperature, soil moisture content, annual precipitation and slope. Combined with the desertification trend of the QTP during the study period, a method was established to determine the degraded zones of freeze-thaw desertification. Results] In 2000—2019, the total area of freeze-thaw erosion area was 1.531×10⁶ km², and the area of moderate and above sensitivity was 9.131×10⁵ km², accounting for 35.92% of the total area of the QTP. The area of freeze-thaw desertification degradation zones in the QTP was 1.113×10⁵ km², mainly distributed in the southwest of the plateau, and the degradation degree was mainly moderate, accounting for 44.35%. Conclusion] In general, the increase of annual average temperature, the decrease of moisture index and the increase of net solar radiation are the main natural driving factors for freeze-thaw desertification in the QTP, while in some parts of the south plateau, the three factors play the opposite roles due to different environmental conditions.