Land Use and Regional Climate in Eastern China over the Past 300 Years

Abstract:

Historical documents of Qing Dynasty to present from 15-17provinces in the eastern China are used to reconstruction of historical crop cover in eastern China and the crop ratio at years of 1724,1784,1820,1873,1887,1893,1913,1933,1986,and 1995 by comparing with present crop land types and crop ratio. Then they are Interpolated from the political unit ( counties) to the grid in 0.5°×0.5° horizontal resolution in the area of 19°N to 45°N and 103°E to126°E. Based on and compared with modern vegetation distribution, the Chinese Natural Resources Database, historical documents, and local chronicles , the historical vegetation in eastern China are reconstructed.

Furthermore, RegCM3 is sued to do sensitive simulation of climatic effect of land cover change in the eastern China by using reconstructed vegetation in this study and those from GLCC (USGS) data for area out off the study area. According to simulation results and temperature anomalies data from Wang et al. (19 98), and Ge et al. (2003), the possible effects of land use change on regional climate are discussed. From this study we found that

(1)The crop land cover and ratio changed significantly since 1724, and the fast increasing periods are 1724-1820 and 1933-1980. the average highest ratios are at 1887 and around 1980 in the eastern China.(2) With the crop land extending the vegetation type were changed in the most part of eastern China: some primary forest (coniferous and rainforest) are replaced by plantation (broadleaf forest) in the last 50 years in eastern China.(3) Urbanization caused decrease of crop land in the past 20 years in the developed area, such as lower reaches of Yangtze River. Current urban area is about 10% compared with 0.05% in Qing Dynasty in eastern China.(4)The simulation results show that in the centennial time scale, the trend of precipitation change during the past 300 years is ‘more-less-more’ in the part of North China. The difference of precipitation between 1995 and 1724 shows that increase in broadleaf forest area might increase the precipitation while the extending of crop land will result in decrease in precipitation.(5)Land use change has significant effect on the surface air temperature. Vegetation degradation causes decrease in temperature in the most area of eastern China.