Abstract: Based on the 1982〖KG-*2〗-〖KG-*7〗2006 data of air temperature and of the phen ophase of Populus tomentosa in spring and autumn from 17 phenological observ ation stations in Inner Mongolia, the change trend of the phenophase of P. tom entosa in spring and autumn was studied, and its relations to climate warming were analyzed. The models for predicting the date change of P. tomentosa fir st flowering and defoliating were constructed by stepwise regression method. It was shown that from 1982 to 2006, the air temperature in study area was increase d, and the date of first flowering and defoliating of P. tomentosa was advan ced and postponed, respectively. The first flowering of P. tomentosa was neg atively related to the air temperature in spring and winter, and the main affect ing factor was the air temperature from March to April; while the first defoliat ing 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. A ccording to the national assessment report on climate change, the air temperatur e in Inner Mongolia in spring and autumn would be raised by 15 ℃〖KG-*2〗-〖KG-* 7〗54 ℃ and 12 ℃〖KG-*2〗-〖KG-*7〗44 ℃, and the first flowering and de foliating of P. tomentosa would advance 39〖KG-*2〗-〖KG-*7〗178 days and po stpone 30〖KG-*2〗-〖KG-*7〗124 days, respectively.

Key words: under-mulch partitioning alternate drip irrigation, cotton, dry matter accumulation, nitrogen utilization, coupling effects of water and nitrogen.