A PRELIMINARY MODELLING OF EFFECTS OF CLIMATE CHANGE ON WINTER WHEAT YXELD ON THE PLAIN OF YELLOW-HUAI-HAI RIVER BASINS

The relationship between winter wheat yield and temperature and precipitalion in various decades during the growing season is analysed respectively,and different kinds of curves of temperature and precipitation partial regression coefficient aj(t) are given.On the basis of this the effects of temperature increase and comprehensive effects of temperature and precipitation in various seasons on the yield Ire modelled.The results show that the effects are different in various parts and different seasons:in northern and central parts of the plain the higher temperature in autumn and winter will be in favour of yield increase and in spring will result in a reduction of yield; in contrast,in southern parts the increase of temprature in autumn and spring will result in yield reduction but warmer winter will be favourable to yield increase.The enhanced precipitation has different overlaping influence on the yield effect,of warmer climate:in the northern and central parts of plain the enhanced precipitation in autumn and winter is favourable to yield increase and in spring has moderation effects on yield reduction; but in southern parts too much precipitation in each season will cause reduction of yield.In general,in most area the higher temperature and enhanced precipitation during the whole growing season of wheat will be in favour of yield increase,but in southern parts more precipitation will give negative influence.