| Elevated atmospheric CO2and increased temperature are the two most important factors in the national list of the impact of climate change on crop yield. The rise in atmospheric CO2has been documented continuously since1958and currently the concentration of CO2in air is about381μmol·mol". The concentration could increase to about550μmol·mol-1by2050, and increased concentrations of atmospheric greenhouse gases will cause global warming of about1.1-6.4℃. Both impacts of rising CO2and elevated temperatures on agriculture are extremely important. Benefits of increased atmospheric CO2to rice production will most likely be limited in a warmer world. China is a large agricultural country, rice and wheat are the staple food of the vast majority of Chinese people, due to rapid population growth and arable land is dwindling, the demands for rice and wheat in the next several decades will continue to increase. Through the establishment of rice and wheat response to temperature and CO2changes in response to database, This study has build a meta-analysis based on the geographical location, replenishment methods, crop varieties, water management, nitrogen fertilizer, temperature and other impact factors of rice and wheat production, and further analysis of the impact factor with rice and wheat yield and biomass quantitative relationship. The purpose of quantitative evaluation of global rice and wheat yield formation and the atmosphere of the quantitative relationship of elevated CO2and temperature, and other impact factors.A meta-analysis was conducted to quantitatively evaluate the effects of increased temperature and atmospheric CO2enrichment on growth and grain yield of rice and wheat. We established a field experimental database by compiling168peer-reviewed studies in Chinese and English books and journals between1985and2010. Major results presented as follows:1. The results suggested that the elevated CO2relative to ambient atmospheric CO2, on average, increased rice and wheat grain yields by19.3%and17.3%, with a number per ear (GNE,11.9%for rice and13.4%for wheat), while the contribution of grain weight was not pronounced. Similarly, the elevated CO2increased the total biomass of rice and wheat by22.1%and15.9%, respectively, of which the increased biomass was more allocated to the belowground than aboveground components.2. Leaf physiological variables such as photosynthetic rates and leaf area index of rice, were increased by8.2%and19.4%due to the elevated CO2, while10.5%and9.4%for wheat, respectively. Gas exchange indicator, GS, of rice and wheat was negativey affected by elevated CO2by-26.5%and-33.3%, respectively. Significant increase was detected by30.9%and30.5%in WUE of rice and wheat, respectively. Among all the tested indicators in this research, WUE was the most responsive one to elevated CO2. As affected by elevated CO2, light use efficiency of rice and wheat was increased by5.3%and11.0%, respectively. However, the N concentration of the crops decreased while more N was absorbed under the increased CO2concentration. The productions of rice and wheat reached a peak value while CO2was provided at660μmol·mol-1. Specifically, the fertilization effect of increased CO2on rice and wheat was the most siginificant one in simulated chamber research, followd by appliances as OTC and FACE. However, many other stress factors, such as gobal warming, drought, and low soil nitrigent level could weaken the fertilization effect of elevated CO2.3. In a meta-analysis of the effect of increased temperature on rice and wheat yield,65individual research paper was analysed. In research on rice, the increased temperature was divided by low intensity (less than4℃higher than ambient temperature) and high intensity (more than4℃higher than ambient temperature). Similarly, in wheat research, increased temperature was devided by the same method but the scale was set as2℃. Overall effect of increased temperatue intensity was studied on rice and wheat yield. The results indicated that, increased temperature decreased the grains per panicle, seed setting rate and yield of rice and wheat significantly. Compared with the ambient temperature, both yield of rice and wheat was decreaed by21.6%and18.7%, respectively, while for rice, grains per panicle, and seed setting rate was decreased by40.8%and33.0%by increased temperature, respectively. But no significant effect was detcetd of higher temperatue on grains per spike and grain weight. Increased temperature expressed inhibiting effect on leaf photosynthethsis of rice while no significant effect was detected on rice plant biomass. Interactive effect of increased temperature and elevated CO2was detected in this research. Compared with the ambient temperature, the fertilization effect of elevated CO2was offseted by an increase in2℃in temperature. The interactive effect between the two factors decreased yield of rice and wheat by10.9%and2.4%, while for rice, grain number and seed setting rate was reduced by16.1%and10.1%, respectively. Both yield and seed setting rate of rice and wheat suffered stressed effect as temperature increased. |
PDF Full Text Request