| In this paper EPIC model and RegCM3 model were evaluated using experimental field data and measured metrological data. The climate change and the response of cropping system on it were analyzed using the simulation results of EPIC model and RegCM3 model as well as the observed results from experiment fields and meteorology stations. After this analysis, we pointed out some agricultural measurements to adapt the climate change and provided some suggestions for farmers to develop agriculture sustainably on the Loess Plateau.Evaluation results of the EPIC model showed: 1) similar results were founded in winter wheat field, spring maize field and grain-alfalfa rotation land. The variation of soil moisture in different soil layers, different months and different years all were simulated well by EPIC model in these three cropping systems on the Loess Plateau. More precision of simulated results were found in the 0.5-2 m soil layer than that in 0-0.5 m soil layer. Soil moisture was simulated better in rainy years, dry years and normal years than that in extreme rainfall years. 2) The EPIC model simulated the variation of soil organic carbon content among different years well in 0-0.5 m soil. The correlation index between simulated and observed soil organic carbon content were 0.90, 0.82 and 0.86 for alfalfa land, winter wheat field and grain-legume rotation field respectively. Correlation between simulated and observed NO3-N content was significant (P<0.05) in irrigated winter wheat/summer maize field. The changing trend of NO3-N content in different soil layers were simulated well with a Relative Root Mean Square Error (RRMSE) of 7.5%. 3) The difference between simulated and observed crop yield of winter wheat, spring maize and grain-alfalfa rotation cropping system was not significant with the Root Mean Square Error (RMSE) value of 0.291, 0.286 and 0.241 t/hm~2 respectively. The similar value of determination coefficients (R~2) and Model Efficiency (ME) indicated the variation of crop yield in different years was simulated well by EPIC model.Evaluation results of the RegCM3 model indicated, 1) variation of precipitation and temperature in different years were simulated well by RegCM3 model on the Loess Plateau, with the RRMSE value of 3.0% and 2.0% respectively. 2) Comparing with observed value, simulated value of precipitation was slightly higher in spring, summer, autumn and winter; simulated value of temperature was slightly higher in spring and winter and slightly lower in summer. A good agreement was founded between simulated and observed both for rainfall and temperature, however, some difference was found, at the same time, in part place on the Loess Plateau. Simulation results of more than 5 mm rainfall affaires were better than that of lower than 5 mm rainfall affairs.Results of the analysis for climate change on the Loess Plateau showed, 1) comparing with that during 2001-2010, precipitation decreased and temperature increased during 2021-2030 in the northwest region on the Loess Plateau. In the southeast region, precipitation increased and temperature decreased during 2021-2030, comparing with that during 2001-2010. 2) Precipitation decreased and temperature increased in the northwest region during 2041-2050, comparing with that during 2001-2010. In the southeast regions on the Loess Plateau, precipitation increased and temperature increased during 2041-2050, comparing with that during 2001-2010.Its crop yield decreased for winter wheat, spring wheat and benne, and increased for spring maize, potato, broom corn millet and foxtail millet during 2001-2050, comparing with that during 1961-2000 in the arid and semi-arid regions on the Loess Plateau. Available soil water in 0-10 m soil reduced in winter wheat field, spring wheat field and benne field, and increased in spring maize field, potato field, foxtail millet field and broomcorn millet field during 2001-2050, comparing with that during 1961-2000. Soil organic carbon content in 0-0.5 m soil increased in spring wheat field, potato field, foxtail millet field and broomcorn millet field, however, this increasing trend was not significant during 2001-2005, comparing with that during 1961-2000. Considering on the sustainable development of agriculture in the arid and semi-arid regions on the Loess Plateau,it was better to enlarge the cultivation areas of potato and foxtail millet and to compress the cultivation areas of winter wheat.Crop yield increased for winter wheat, spring maize and cole-seed and decreased for spring wheat during 2001-2050, comparing with that during 1961-2000 in the semi-humid regions on the Loess Plateau. Available soil water in 0-10 m soil reduced in winter wheat field and cole-seed field, and increased in spring maize and spring wheat field during 2001-2050, comparing with that during 1961-2000. Soil organic carbon in 0-0.5 m soil decreased in winter wheat field, spring maize field, cole-seed field and spring wheat field during 2001-2050, comparing with that during 1961-2000. Considering the effects of climate change on crop production and the sustainable development of agriculture, it was better to enlarge cultivating areas of spring maize and to compress cultivating areas of spring wheat and cole-seed in the semi-humid regions on the Loess Plateau.Results of this study showed, a higher soil desiccation rate and soil water restoration rate appeared in the earlier rotation stage and a lower rate appeared in the later rotation stage,both in the process of formation of desiccation layer during alfalfa growth period and soil water restoration during alfalfa-grain crop rotation period. It was difficult to restore the soil water in 8-10 m soil. Considering the sustainable use of soil water for alfalfa-grain cropping system, optimum stand age for alfalfa were 6-8 years and 4-6 years in the semi-arid regions and in the semi-arid and drought-prone regions respectively on the Loess Plateau. Optimum cultivation years for grain crop on desiccated alfalfa grasslands were 16-20 years and 32-33 years respectively.Farmers can get more incomings and can make the soil water used sustainably, through foxtail millet-potato cropping system (FP) in the Northern Shaanxi regions. Farmers can take FP and MPFP (its rotation sequence was spring maize, potato, foxtail millet and potato) cropping system, when the price of potato was relative higher than other crops. MFP (its rotation sequence was spring maize, foxtail millet and potato) and MFMP (its rotation sequence was spring maize, foxtail millet, spring maize and potato) cropping system were the better when potato price was relative lower. |
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