| Climate change is an increasingly important aspect for agriculture production, economic development and environment protection. This issue has gained universal recognition by the scholars as well as by the governments. Climate change leads to the global warming, temperature increasing and precipitation decreasing in some parts of the world, which is vital to food production and food supply. Meanwhile, it has been becoming more and more concerned for the resarcheres. While,the food shortage countries lie in the arid and semi-arid area, some global main food production countries are also located in the arid and semi-arid area. Therefore, it is strategically significant to do the study of climate change impacts on crop yield in the arid and semi-arid area under future climate scenarios.This thesis mainly discusses the climate change impacts on maize growth with and without irrigation under A2 (regional resources scenario) and B2 (regional sustainable development scenario) climate scenarios in 2020, 2050 and 2080 in Murray Darling Basin, Australia and different subarea in Loess Plateau, China, without considering the impacts of CO2 concentration. Meanwhile, the maize yield, water balance components and water use efficiency during maize growth period are analysed with SWAP and SWAGMAN? Destiny. The main results of this thesis are as follows:(1) Two crop growth and water management models, SWAP and SWAGMAN? Destiny, are validated in Finley and Yangling with the experimental data. The result shows that both models can be used to simulate the soil water content tendency and water balance components in arid and semi-arid area. The calibrating results of soil water content show that both models can reflect the tendency of soil water content variation in the soil profiles. Relatively, the soil water content simulated by SWAP are much closer to the measured data than that by SWAGMAN? Destiny. The simulation results of water balance components show that the simulation errors by both models is less than 10%. Therefore, the simulation results can be used to provide the information about crop water requirements and water consumptions, aiming to precisely evaluate water use efficiency.(2) Based on the analysis of historical climate data in Murray Darling Basin, Australia, both temperature and rainfall during maize growth period are projected by ECHAM5, HadGEM1 and CSIRO Mk3.0 global climate models in 2020, 2050 and 2080. The prediction results indicated that the amplification of rainfall will increase conspicuously while the increase rate will gradually decrease, which is 51.72%, 49.27%, 46.39% in 2020, 2050 and 2080 respectively compared with the baseline data. The future temperature will increase little by little,the temperature in 2020 is nearly the same as beseline, while the mean increase rates in 2050 and 2080 are 0.92℃,2.01℃. Therefore, the climate models which are chosen in the thesis can be used to well project the future climate scenarios.(3) Although there are some differences in the simulation results of water balance components, maize yield and water use efficiency under A2 and B2 scenarios with and without irrigation by SWAP and SWAGMAN? Destiny models, while the variation tendency are consistent and the changing extent are similar. What's more, the altering scales of each variable are presented in this thesis. Compared with baseline, the evapotranspiration under rainfed condition will increase evidently in 2020,2050 and2080, and the augment rates are 56.08%, 61.69% and 68.13%, while maize yield and water use efficiency will decrease, the rates are 4.43%, 9.44%, 16.08% and 37.48%, 42.79%, 49.18% respectively. Both the evapotranspiration, crop yield and irrigation efficiency, total water efficiency will increase under A2 scenario and irrigation condition. The amplification of above variables are be in 11.70%, 17.65% and 22.75%; 10.91%, 17.24%, 20.53%; 8.49%, 11.49%, 14.19% and 2.04%, 5.47%, 8.70% respectively. The prediction results under B2 scenario is similar but the variable extent is less than that of A2. The changing extent differences of most indices under A2 and B2 scenarios are in 5% but no one exceed 15%.(4) On the basis of the future temperature and rainfall preditions under A2 and B2 scenarios in Loess Plateau, water balance components, maize yield and water use indices in different subarea are predicted and analyzed by SWAP and SWAGMAN? Destiny models under rainfed condition. The prediction results without irrigation show that the variation tendencies are consistent and the variable extent are similar by both models. In 2020,2050 and 2080, the augment rate of evapotranspiration in different subarea is 9.98%, 16.49%, 24.51% in loam-2, 3.47%, 8.31%, 13.82% in loam-1, 1.28%, 2.08%, 5.85% in lighter Soil,and 7.49%, 11.67%, 20.31% in sandy soil. The decrease rates of crop yield and crop water use efficiency are 4.18%, 5.58%, 8.01% and 13.02%, 20.02%, 27.09% in loam-2, 0.79%, 1.48%, 2.69% and 2.63%, 6.73%, 12.59% in loam-1, 11.65%, 11.65%, 13.40% and 9.44%, 13.43%, 17.42% in lighter soil, 33.01%, 36.22%, 37.34% and 34.41%, 38.99%, 43.37% in sandy soil respectively. Especially, the decrease rate of crop yield and crop water use efficiency are more obviously in lighter and sandy soil. The prediction results under B2 scenario is similar but the variable extent is less than that of A2. The changing extent differnces of most indices under A2 and B2 scenarios are in 5% but no one exceed 12%.(5) Maize yield and water use efficiency under irrigation condition are predicted by SWAP and SWAGMAN? Destiny models in the different subarea of Loess Plateau based on the future climate predictions. The results shows that the evapotranspiration will increase in 2020, 2050 and 2080 under A2 scenarios and the increase rate is 10.07%, 17.76%, 29.07% in loam-2, 5.05%, 9.65%, 12.07% in loam-1, 0.60%, 1.77%, 4.04% in lighter soil, 3.79%, 7.01%, 9.78% in sandy soil. The water use efficiency will decrease and decrease percentage is 6.64%, 14.30%, 19.10% in loam-2, 2.98%, 5.49%, 8.07% in loam-1, 2.13%, 8.04%, 11.38% in lighter soil and 11.38%, 16.48%, 19.52% in sandy soil respectively. The crop yield will increase in Loam-2 and Loam-1, and the increase rate are 3.76%, 3.95%, 5.12% in loam-2 and 0.58%, 2.22%, 3.88% in loam-1. The crop yield will decrease in lighter and sany soil, and the variable rate are 1.29%, 6.00%, 7.38% in lighter soil and 10.63%, 13.98%, 15.23% in sandy soil respectively. The prediction results under B2 scenario is similar but the variable extent is less than that of A2. The changing extent differences of most indices under A2 and B2 scenarios are in 5% but no one exceed 10%.(6) Compared with baseline, the prediction results in both research area under A2 and B2 scenarios presented that the variable scale of water balance components, maize yield and water use indices under A2 scenario will be entirely greater than that under B2 scenario while the changing tendency is similar and most changeable tendency differences are in 5%. Therefore, climate change impacts extent and tendency on the above variables under both scenarios are consistent.The thesis ensembly provided the variable tendency of maize yield and water use efficiency under future climate scenarios in both study area. The research results can not only provide scientific evidences for agriculture production and water resources management in above area, but also be refenrences for similar result in other area. However, the study in this thesis is dependent on the present irrigation method and tillage condition. Therefore, it is necessary to validate the models under the temperature increasing condition, while this may overevaluate climate change impacts on crop growth. The changing tendency of crop yield and water use efficiency need to be further studied with the development of agriculture condition, irrigation technique and deficit irrigation in the future. Furthermore, it is necessary to carry out the studies of climate impacts on agriculture related with CO2 concentration and crop growth state.
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