| Global climate is wanning at an unprecedented speed and the trend will continue in predictable future. This opinion has become a common agreement for most scientists. Acute climate change will affect various aspects of human life, such as society, economy and ecology etc., among which agriculture is the first to be affected. So, it is significantly important to evaluate the impacts of climate change on agriculture.There were three sections in the thesis. All of them aimed to assess the effects of climate change on winter wheat production in the Huang-Huai- Hai Plain of China.In the first section, the characteristics of warmed climate during the wheat growing season in the past 40 years were analyzed using the BASELINE daily weather data (1961-2000) at 10 representative sites in the studied region. And the impacts of climate change occurred on the wheat production were evaluated.in the second section, three (2 CO2) scenarios only considering climate change alone (C scenario) were generated first, using outputs of the GISS, GFDL and UKMO GCMs, combined with the BASELINE. Then, climate change scenarios including change in climate variability (C+V scenario) were produced, based on 3 hypotheses and the Weather Generator (WGEN) in DSSAT. Finally, the CERES-Wheat Model was run under both the (C+V) scenarios and the BASELINE, and the combined effects of climate change and its variability with doubled CO2 on whiter wheat production in the studied region were assessed, based on the results simulated comparison.In the third section, the emphasis was put on evaluation of the gradual effects of climate change in future 50 years. All the three sections drew an outline of global climate change affecting the whiter wheat production at present and in future in the studied region.In the third section, the gradual climate change scenarios considering both climate and its variability in future 50 years (i.e., 2010, 2030 and 2050) were generated, using outputs of the GISS Transient Run and the BASELINE, adopting the same method described in the second section mentioned above. Then the combined gradual effects of climate change and its variability on whiter wheat production in the studied region were analyzed, based on the results simulated by CERES-Wheat and all the results at the representative sites were displayed graphically using the GIS technology.The main conclusions of this study were as the follows:1. The temperature has increased during the wheat growing season since the late of 1960s in the Huang-Huai-Hai Plain and, it became more evident after the end of 1980s. With the increase of temperature, the solar radiation decreased gradually. However, the temperature variability increased. Although precipitation had no significant change, its variability had the trend to increase after 1980s and its instability was larger than that of the temperature variability. The change in climate and its variability occurred had unfavorable effects on wheat production in thestudied region.2. Under the (2 CO2) scenarios, the growth duration of winter wheat at all the sites would be shortened evidently due to the increased temperature, which would bring harmful effects for wheat production. However, CO2 elevation and change in the climate variability had almost no any influence on the growth duration. When considering the combined impacts of climate change and the direct effects of CO2 (CC+PE), the simulated yields for irrigated wheat would increase at most sites. This was because the beneficial effects of CO2 elevation might offset in a great extent the unfavorable effects due to shortening of the growth duration. With increase of the climate variability, the amplitude of increased yield simulated would be reduced. And the variation coefficient (VC) of the simulated yields and their instability would also increase. For the rainfed wheat, the simulated results seemed to be similar to the irrigated wheat in general, but the change scope of the simulated yield between the sites was larger and its yield stability was... |
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