[Impact of climate warming on phenophase of Populus tomentosa in Inner Mongolia]

Based on the 1982-2006 data of air temperature and of the phenophase of Populus tomentosa in spring and autumn from 17 phenological observation stations in Inner Mongolia, the change trend of the phenophase of P. tomentosa in spring and autumn was studied, and its relations to climate warming were analyzed. The models for predicting the date change of P. tomentosa first flowering and defoliating were constructed by stepwise regression method. It was shown that from 1982 to 2006, the air temperature in study area was increased, and the date of first flowering and defoliating of P. tomentosa was advanced and postponed, respectively. The first flowering of P. tomentosa was negatively related to the air temperature in spring and winter, and the main affecting factor was the air temperature from March to April; while the first defoliating of P. tomentosa was positively related to the air temperature in autumn, and the main affecting factor was the air temperature from August to October. According to the national assessment report on climate change, the air temperature in Inner Mongolia in spring and autumn would be raised by 1.5 degrees C-5.4 degrees C and 1.2 degrees C-4.4 degrees C, and the first flowering and defoliating of P. tomentosa would advance 3.9-17.8 days and postpone 3.0-12.4 days, respectively.