The Influence of Climate Change on Suitability of Shaanxi Apple Growth

Based on the meteorological data from 1961 and phenological observations data from 2001 of the northern part of Shaanxi Province, the main meteorological factors that influence apple production and quality, the features of frosts over the apple blooming periods and the average days of high temperature as well as the impact of climate change on apple growth during the past 50 years are analyzed, using the methods of time series analysis and agricultural climatic indices and grade criterion for apple planting demarcation of China. The results suggest that among the factors affecting apple planting, the annual mean temperature is in a rising trend. The rate of rising trend is about 0.23—0.37℃/10 a across Yan'an and the north area of it, and is about 0.14—0.24℃/10 a in Guanzhong and Weibei apple planting areas. The minimum mean temperature from June to August is in a smaller rising trend, too. The mean relative humidity in the same period doesn't change much. The mean annual precipitation is in a decreasing trend. In the recent 30 years (1979—2008), the mean annual precipitation becomes obviously less than the average from 1961 to 1990.Analysis on apple growth during the three periods of 1961 to 1990, 1971 to 2000 and 1979 to 2008 show that the grades of climatic suitability of apple growth remains in former climatic suitability range. Due to the rising of annual mean temperature, the grade of the west Guanzhong apple planting area decreases, but the grade of the north apple planting area increases. Due to the minimum mean temperature of summer rising, the years of grades are not in suitable range in Huanghe River bank and Guanzhong areas are increasing years. Precipitation change results in the grades decreasing in part of Guanzhong and the east of other apple planting areas. That is to say, in some regions the rising of the annual average temperature and the declining of the mean annual precipitation have resulted in the grades change of climate suitability for apple growth. Increasing frost frequency, especially in the second ten days of April in recent years since 1961, increases the possibility of frost damage on apple flowering in Yan'an and the west of Weibei apple planting areas where the date of apple flower is ahead of before. Since the 1990s, the increasing high temperature days have caused growing damage on apple production and should be noticed.