Abstract: To explore the climate driving factors of the phenological changes of legumes in Alxa Desert, the characteristics of climate change and the temporal evolution trend of the main phenological periods of two typical leguminosae plants(Caraganabrachypoda Pojark. and Oxytropis aciphylla Ledeb.) were studied by using linear trend rate and stepwise regression methods. Based on the observation data of climate elements and vegetation phenology at Alxa Desert monitoring points in recent 40 years, that is from 1981 to 2019. The results showed that: (1)the annual average temperature of the monitoring points in the past 40 years was 8.8℃, and increased significantly with a trend of 0.46℃·10y-1(P<0.01). The average annual hours of sunlight was 3136h, decreasing at a rate of about 98h·10y-1(P<0.01). The average annual precipitation was 159mm, with an increasing trend and a precipitation variation tendency rate of 19.08mm·10y-1(P<0.05). (2) In recent 40 years, the turning green period and flowering period of Caragana microphylla and C. maotouci were significantly advanced, the yellow withered period was slightly delayed, and the whole growth season was extended over the past 40 years. The annual average turning green, the flowering and the yellow withered period from Jan.1of Caraganabrachypoda Pojark were 898, 11610 and 30810 respectively. And these three periods in Oxytropis aciphylla Ledeb 308 ± 10 and 315 ± 10, respectively. (3) From the correlation analysis between vegetation phenology and climate factors, it would be found that the phenological changes of Caraganabrachypoda Pojark and Oxytropis aciphylla Ledeb were mainly limited by air temperature. The sunshine hours had a slight effect on the green returning period of the two plants, and the precipitation only effected the yellowing period of the Caraganabrachypoda Pojark.

Key words: Desert vegetation, Phenological period, Climate change, Influencing factors