The relationship analysis between the meteorological factors and the witheringperiod of gramineous herbage at the HezuoMaqu meadow

Based on the observed data of herbage growing and meteorological factors such as contemporaneous precipitation, atmospheric temperature and sunshine hours of Hezuo and Maqu, the effects of meteorological factors on the herbage withered date were studied in this paper. The results showed that the withered date of gramineous herbage at the HezuoMaqu meadow had an earlier trend with the tendency ratio of 5.5 d/10 a, 2.0 d/10 a; especially after the end of 1990s, the withered date of gramineous herbage at Hezuo showed an obvious earlier trend than before. Heat condition had an important impaction to the withered date of gramineous herbage at the Gannan plateau, the most important factor was the end date of 5 ℃, there was an advancing trend in the end date of 5 ℃ of Hezuo. In addition, the decrease precipitation of summer was another main factor to affect the earlier trend of gramineous herbage withering in Hezuo meadow. The another main factors to affect the earlier trend of the Maqu meadows gramineous herbage withering were increase of the temperature and sunshine hour, the decrease precipitation in September.