[Responses of subalpine meadow Poa botryoides to climate change]

Based on the field plot observation and related meteorological data, the effects of climate change in 1985-2005 on the growth and development of subalpine meadow Poa botryoides in Maqu County of Gansu Province were analyzed. The results showed that during study period, the annual precipitation in the Maqu County had a decreasing trend, with a rate of -9.895 mm x (10 a)(-1) and a cycle of 3 years, while the annual air temperature had an increasing trend, with a rate of 0.341 degrees C x (10 a)(-1). The aridity index of P. botryoides in growth season had an obvious increasing trend, with a rate of 0.036 x (10 a)(-1), and the tendency was more markedly from the beginning of the 1990s to 2005. The period from reviving to ripeness of P. botryoides was 140-150 d, and the requirements of accumulated temperature above 0 degree C, precipitation, and sunshine duration in this period were 1000 degrees C-1200 degrees C, 400-450 mm, and 1000-1100 h, respectively. The growth rate of P. botryoides turned to higher at 54 d after reviving, reached the highest at 80 d after reviving, and became lower at 104 d after reviving. Under the effects of climate warming, the phenophase of P. botryoides was advanced by 15 d x (10 a)(-1) at heading stage, 7-8 d x (10 a)(-1) at flowering stage, 8-9 d x (10 a)(-1) at ripeness stage, and 3 d x (10 a)(-1) at withering stage. Climate change made the P. botryoides yield in study area have greater variation and higher unsteadiness.