The Impacts Of Climate Change On Surface Dry-Wet Status And Growing Season From 1960 To 2005 In Three Provinces Of Northeast China

Climatic resources are the foundation of agriculture and forestry.Any change on climate will lead to the alteration of water and energy conditions,and impact on the development of agriculture and forestry.The three provinces of Helongjiang,Jilin and Liaoning in northeast China are the main production area of the country,and the climate change in this region is very significantly as well.To investigate the impact of climate change on agriculture and forestry of this area,the alteration of surface dry-wet status and growing season were analyzed in this study.The analysis of surface dry-wet status was based on the meteorological datasets from 1960 to 2005 in 72 stations of the three provinces.Potential-evapotranspiration was computed by using Penman-Monteith model with these meteorological datasets.The aridity index was defined as a ratio of potential-evapotranspiration to precipitation.Upscaling was completed by Kriging interpolation to address the spatial characters of potential-evapotranspiration and aridity index.Results indicated that there was a variation in the dry-wet status with significant spatiotemporal characteristics in this region.Higher values of the aridity index occurred in the period from 1960 to 1979 and increased generally.The increase in the aridity index was attributed to a reduction in precipitation and an increase in potential-evapotranspiration which was induced by an augment in vaper pressure difference.By contrast,the surface in most of this region,particularly in Heilongjiang Province and the east part of Jilin Province,tended to be wetting during the period from 1980 to 2005 due to an increase in precipitation and a reduction in potential-evapotranspiration.The reduction in potential-evapotranspiration can be explained by a decline of wind speed and net radiation.As a whole,climate change did not aggravate surface aridity in three provinces of northeast China over the last several decades.Three main crops of maize,bean and rice were chosen to examine the variations and tendency of growing season which was determined by the temperature conditions of the safe sowing time and mature time of each crop.The adopted analysis method was as same as the aridity index.Results showed the growing season of each crop also behaved differently during two periods.There was no obviously tendency in growing season from 1960 to 1985,but after 1986 it extended year by year because of the earlier of safe sowing time and the later of mature time.Between these two reasons,the later of mature time played a more important role.Compared the average growing season between two periods from 1960 to 1965 and 2000 to 2005,the growing season of the three provinces obviously came earlier and ended later,in a word,it has been extended among 40 years.