Climate Change&Its Impact On Agriculture In Hebei Province During Last50Years

The climate of Hebei province has been changed notably under the global warming background. With the temperature increasing, rainfall decreasing and drought intensifies, it has a great impact on local economic development and agricultural environment in last decade. It is very important to understand the climate changing pattern and to grasp the variation characteristics of weather and climate and drought, floods and freezing hazards and their effects on crops during crop growing season for guiding local agricultural production, enhancing capabilities of hazards prevention and reducing, and promoting agriculture sustainable development in Hebei province.Based on the daily climatic data of72weather stations (1961-2010), crop development stages data of30agricultural meteorological stations, and crop (winter wheat, spring and summer maize) yields of119counties of Hebei province, the climate change and its impact on crops in Hebei province during last50years was analyzed by methods including linear trend, EOF (Empirical Orthogonal Function) analysis and wavelet. The results showed that annual mean air temperature has increased by0.1----0.5℃/10a, and the value is higher in the north part than in the south part of Hebei, especially it was greater than0.3℃/10a in the north-west part of Hebei. Annual precipitation has a decreased trend in Hebei, but with different trends in different seasons, i.e. increased in spring, decreased obviously in summer, but no clear trend in autumn and winter. Rainfall also has some periodic variability, and the cycle scale is different during different time interval. Sunshine hours has a decreased trend in the crop growing seasons, and it declined range is more bigger in north and middle parts than that in northeast and south parts of Hebei. From north to south, the accumulated temperature (AT) for crop growth has increased, including AT>0℃of winter wheat before and after winter time and whole growing season, AT>0℃and AT>10℃of maize during whole season. The most increased AT of winter wheat before and after winter time was in the northeast and north parts, the least of it was in the middle part of Hebei. The most increased AT>0℃and AT>10℃of maize was in the northeast part, and the least in south part of Hebei.Drought-flood has some phase variation in Hebei province. It was less rainfall during1980S and the later of1990S, and light drought occurred mainly in1980S, but heavy drought has appeared frequently since the later of1990S. It was much precipitation in1970S and the early1990S. The coefficient of variation drought-flood is the largest in the later of1990S and the least in the1980S. The flood-drought variation feature is not the same in the different seasons. During the last10years (2001-2010), continuous drought was mainly in summer, and light drought in autumn, but a most variation of drought in winter. There are four patterns of drought-flood in spatial distribution, i.e. the consistency in the whole areas, the opposite between south and south, the opposite between east and west, and the opposite between middle and south-north, and the mainly is the first one. The frequency of different grade droughts happens different during winter wheat each development stage. During the whole growing season, middle drought frequency occurred was the most, and heavy drought the lowest. During the sowing-seedling stages, heavy drought frequency occurred was the most, and middle drought the least. During elongation-heading stages, middle drought frequency occurred was the most, and light drought the least. During the milking-ripening stages, heavy drought frequency occurred was the most, and then was light drought.Different grades of drought have a decreased trend for winter wheat in each development stages. The heavy drought has decreased notably, but others have little variation during the whole growing season and elongation and heading stages for winter wheat. The droughts have no obvious change in seeding and ripening stages, and have little impact on wheat production in the future. It is favourable to wheat during elongation and heading stages because of reducing in heavy and middle droughts.The freezing hazards occurred mostly in the north and little in the south of Hebei province, and it has a decreased trend in the winter wheat areas, especially in the north part of Hebei province. A contrary correlation was found between the freezing disaster frequency and winter wheat yield. The frequency of late spring coldness for winter wheat was42%, and its annual mean area was12%of the wheat planted acreage, and the most of it happened in the1990S.