Changes in frozen soil caused by global warming are widely expected to have significant effects on ecosystems in cold regions, and the response of the start of the vegetation growing season (SOS) to climate change on the Qinghai-Tibetan Plateau (QTP) has drawn great attention. In this study, we investigated the changes in the freezing/thawing processes and their relationship with the SOS from 2003 to 2015 in the source region of the Yellow River (SRYR) on the northeastern QTP. The results indicate that the soil thaw onset (STO) at a depth of 5 cm advanced significantly in most regions at a rate ranging from 0.09 to 1.47 day · year⁻¹, and the maximum frozen depth decreased in most regions at a rate of 0.007 to 0.031 m · year⁻¹, despite a nonsignificant increase in the spring air temperature. The SOS derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) leaf area index (LAI) data advanced in the regions covered by alpine meadow. The logistic method was shown to be better than the polynomial method in retrieving the SOS using remote sensing indexes. The gray relational analysis suggested that the advance in the STO was the major factor leading to the advance in the SOS of alpine meadow regions. Changes in the LAI during the initial period of the growing season were likely to be primarily influenced by the maximum frozen depth and soil temperature. Furthermore, the substantial effect of frozen soil changes on the SOS in the SRYR necessitates the importance of analyzing frozen soil processes to predict the response of spring vegetation phenology to climate change on the QTP.

人们普遍预计，全球变暖造成的冻土变化将对寒冷地区的生态系统产生重大影响，青藏高原（QTP）对植被生长季节（SOS）的开始对气候变化的反应已引起巨大关注。注意。在这项研究中，我们调查了东北QTP上黄河源区（SRYR）从2003年到2015年冻融过程的变化及其与SOS的关系。结果表明，大多数地区5cm深度处的土壤融化开始（STO）以0.09至1.47天·年- ^1年的速率显着增加，而大多数地区的最大冰冻深度以0.007的速率降低。至0.031 m·年^-1尽管春季空气温度没有明显增加。从中等分辨率成像光谱仪（MODIS）的叶面积指数（LAI）数据得出的SOS在高寒草甸所覆盖的地区更为先进。结果表明，在利用遥感指数检索SOS方面，逻辑方法比多项式方法更好。灰色关联分析表明，STO的升高是导致高寒草甸地区SOS升高的主要因素。在生长期初期，LAI的变化可能主要受最大冻结深度和土壤温度的影响。此外，