Impacts Of Climate Change On Rice Production In Fujian Province Based On Self-adaption

Food security is an important part of national security, and food safety guarantee function is·also main function of agricultural multifunctionality. Among a good many factors affecting food security, the impact of climate change is the most direct to rice yield. Therefore, the ability to predict the abnormal changes of climate and the impact of these changes has become a major problem needed to be solved urgently. Fujian Province has a large population with relatively little land and lives on rice, for this reason, rice abundant or poor harvest has played a significant impact on food security. So it has an important theoretical and practical significance to research the impact of climate change on rice production and yield in Fujian province.Based on Special Report on Emission Scenario (SRES) A2, B2, A1B scenarios of IPCC, meteorological database of the period during1961-1990and2011-2050of17sites in Fujian Province from the PRECIS was established, and further corrected future scenarios by using observed daily weather data to analysis the temporal and spatial distribution and the annual fluctuation law of meteorological elements in rice growth period based on all scenarios. Fujian Province was divided into three rice regions based on the topographic features and rice cultivation patterns, which were double cropping rice region in Southeastern Fujian, double cropping rice region in Northwestern Fujian, single rice regions in the mountain areas of Northwestern Fujian.3representative rice species from the different cropping systems were studied. Daily meteorological data in2006to2007and regional test yield data of this period were used to initialize and determine CERES-Rice module parameters. Based on Emission Scenario Special Report (SRES) A1B scenario of IPCC, data from the PRECIS were integrated with CERES-Rice model, adopting rain-fed and irrigation, considering the direct gain effects brought by the increasing CO2and related agricultural climate index, this paper simulated and accessed the impact of climate change on rice production in Fujian Province in the2020s and2040s. According to the start date and accumulated temperature over10℃, the start date and the length of rice growth season and the variation in accumulated temperature during the period of rice growth season were calculated for the baseline and all future scenarios to furthermore analysis the possible changes of rice planting layouts on all sampling point in the future. Further, the probable adjustment of cultivation modes such as cropping system, variety combination and sowing date, and the change of rice yields, stability and overall output of rice by using adaptive countermeasures were analyzed under3climate change scenarios in the research area. The main results were as follows:(l)The temperature of rice growth stages will rise in Fujian Province and the temperature increment will be larger as time goes on in the future. Calculation results shows that the average temperature increment is more prominent in single rice growth stage, the temperature would rise by0.3-2.4℃in the2020s and1.5-3.4℃in the2040s, while there would be relatively small on the temperature increment of early rice growth stage (0.2-0.9℃for2020s,0.7-1.7℃for2040s). The temperature increment in late rice growth stage lies between early rice and single rice,which would be0.3-2.1℃and0.5-3.6℃for2020s and2040s,irespectively. The annual fluctuation of daily average temperature is the largest in late rice growth stage. The precipitation would increase in most of the sites and it increases10%-40%in early rice growth stage, which is greater than single rice with10%-30%and late rice with10%-20%. In Southeastern Fujian, the annual precipitation variability is the largest in early growth stage. Total solar radiation in rice growth stage likely would reduce in future and it would lessen about10%-20%average for2020s and2040s; even it would reduce by40%with the largest fluctuation annually for early rice in Northwestern Fujian. So it is summarized that the frequency of late rice growth duration encountering with high temperature and extreme weather will increases in Fujian Province in the future, and the early rice growth would be affected mainly by cloudy and drizzly weather.(2) In future, the accumulated temperature above10℃would increase and the rice growing season would lengthen due to the climatic warming. The safety sowing time of early rice would be in advance over10days average on A2and B2scenarios and12days on A1B scenario, while≥10℃accumulated temperature (10≤T≤22℃) would be higher690℃yearly on the former two scenarios and910.8℃on A1B scenario. So it is possible that late season variety with characteristics of longer growth period and higher yield would be selected to replace early-middle maturing variety with inverse characteristics of shorter growth period and lower yield, and single crop rice planting region can also plant double cropping rice.(3) Irrespective of rain-fed or irrigated rice, rice growth durations would shorten under scenarios in the future. The growth duration of single rice shortened the most (over20days) under the2040s scenario. Yields for rain-fed late rice in double cropping rice region in Northwestern Fujian dropped the most by6.9%and10.2%compared with yields under the baseline weather conditions on A2and B2scenarios in the2020s respectively, and even the reductions of output increased by14.1%and15.6%under the2040s scenario. Yield reductions of early rice in all ecological regions are close to that of single rice in the mountain climate of Fujian northwestern. When fully irrigation, the decreased rice yield amplitude would drop in most of all rice regions and it is more noticeable for the yield changes of late rice. The production status of late rice would be more optimistic on2scenarios in Southeastern Fujian rice region, and even that yield increase slightly by2.3%and3.1%under A2and B2scenarios respectively in the2020s, and yield turn into decreasing by2.8%on A2scenario and compared with the present, it would remain basically the same (0.5%) on B2scenario in the2040s. Future yields for single rice and early rice showed reduced under A1B scenario. In double cropping rice region of Southeastern Fujian, the rate of decreased output for rain-fed and irrigated early rice was over12.4%and11.3%, respectively; while in double cropping rice region of Northwestern Fujian, it was smaller under the2020s scenario. Because of the negative contributions of mid-maturing varieties, yields for rain-fed and irrigated single rice region in mountain regions of Northwestern Fujian dropped by7.1%and2.1%respectively on A1B scenario. The decreased rice yield amplitude showed increased gradually in the2040s. On the contrary, yields of late rice over the same period were increased under A1B scenario. Under the simulated2020s scenario, the increased amplitude of late rice for irrigated double cropping rice region in Northwestern Fujian was21%, and only10.6%in southeastern Fujian, while the yields of rain-fed late rice increases slightly under A IB scenario. In all rice regions, the increased amplitude of late rice yield would drop in the2040s.(4) The result showed that under A2and B2scenarios or A1B scenario, the yield stability of late rice was worse than that of early rice in all double cropping rice region, and single rice yield stability lies between early rice and late rice. With the increase of temperature, the instability of grain yield will increase. If irrigation were satisfied, the yield stability would improve in most of rice regions. Therefore fully irrigation can alleviate the fluctuation of rice yield induced by hyperthermia to some extent. During the rice growth season, the soil moisture condition in the research area would be less than today, while irrigation demands would increase in all rice crop regions. (5) In fact, with continuous change of climate and improvement of science and technology, the farmers in future would adopt different productive patterns and managements from the present. For example, they would use new varieties with longer growth durations and high temperature-resistant to adapt the hot climate, increase the local multiple cropping index to fully utilize the heat resources and, adopt more advanced cultivation technologies to get a higher yields. Phenomenon like these essentially belongs to the self adaption of agriculture. It means agriculture could automatically regulate its productive patterns and managements to adapt to the new environmental change. Therefore, it seems scientific and reasonable to consider the self adaption of food production in climate impact assessment studies. The results indicated that the simulated yields of early rice in the Double Rice Region in Southeasternern Fujian under A2, B2and A1B scenarios increase by15.9%,18.0%and19.2%and that of late rice increase respectively by9.2%,7.4%and7.4%when the self-adaption adjustment was considered, compared without consideration. In the Double Rice Region in Northwesternern Fujian, the simulated yields of early rice increase by21.2%,20.5%,18.9%and that of late rice increase respectively by14.7%,14.8%,7.2%under the3climate change scenarios when the self-adaption was considered, compared without consideration Similar results could be obtained in the Single Rice Region in the mountain areas of Northwesternern Fujian. The simulated yields of single rice increase respectively by4.9%,5.0%,2.9%under the3scenarios, comparing the two case with and without consideration of self-adaption. In this rice region, double rice might be grown in future in the site of Changting under the A1and B2scenarios. When the self-adaption adjustment was considered, the overall output of rice crop in Fujian Province under the3climate change scenarios would increase by5.9%,5.2%and5.1%respectively. It is concluded that more optimistic results could be obtained when self-adaption ability of food production was taken into consideration.