Abstract: Based on the meteorological data and the data of the growth period of winter wheat from 30 agrometeorological stations of Henan Province, the effective precipitation was calculated by using the U.S. Department of Agriculture Soil Conservation method. Meanwhile, the water requirement (ET_c) of winter wheat in the whole growing period during 1981-2010 in Henan Province was estimated by using FAO PenmanMonteith equation and crop coefficient method recommended by Food and Agriculture Organization. The spatialtemporal distribution characteristics of ET_c and water deficit (WD) and their major climatic impact factors were analyzed using the mathematical statistics. The results showed that the Penman-Monteith model well simulated the ET₀ of winter wheat during the whole growing period in Henan Province in the past 30 years, with a correlation coefficient of 0.85 (P<0.01) between the modeled ET₀ and the observed 20 cm pan evaporation during the same period in same stations. The mean precipitation and effective precipitation of the 30 years during the whole growing period of winter wheat were 244.0 and 114.9 mm, respectively. The mean ET_c and WD for the study area were 408.0 and 293.1 mm for the whole growth period during the past 30 years, respectively. Spatially, precipitation and effective precipitation decreased gradually from south to north, which was opposite to the distribution characteristics of ET_c and WD. The differences in precipitation and effective precipitation among different regions increased during 1981-2010, while the differences in ET_c and WD among different regions decreased. Temporally, ET_c and WD of Henan Province showed downward trends which were not significant. The variations of ET_c and WD differed spatially. The ET_c and WD increased in west and north of Henan Province, but reduced in the rest areas. Partial correlation analysis indicated that wind speed reduction during the past 30 years was the main cause of decreased ET_c, however, the WD had the closest relationship with precipitation. Stepwise regression analysis suggested that the changes of ET_c and WD had close relationships with meteorological factors and growth stages of winter wheat as a whole, and the contribution of each factor to ET_c and WD differed, among them, the whole growing days and precipitation were the biggest one, respectively.

Key words: soil nutrient, soil enzyme activity, soil respiration, subalpine forest, naphthalene