Drought and Flood Analysis and Impact on Food Production in Fushun

Based on monthly precipitation data during 1961-2008 in 50 stations in Fushun,drought and flood indicators of three counties were calculated with Z index method. The geographical and seasonal distribution characteristics of Fushun were analyzed,and so was the impact of droughts and floods on food production. It shows that,since 1961,there are 7 poor harvest years in Fushun,with quadrennial caused by continuous seasonal floods or droughts,two years by year drought,one year by summer flood.

The Limiting Effect of Deep Soil Water on Evapotranspiration of a Subtropical Coniferous Plantation Subjected to Seasonal Drought

Seasonal drought is a common occurrence in humid climates.The year 2003 was the driest year during the period 1985-2011 in southeastern China.The objective of this study was to elucidate the impact of the exceptional drought in 2003,compared with eddy flux measurements during 2004-11,on the dynamics of evapotranspiration （ET） and related factors,as well as their underlying mechanisms,in a subtropical coniferous plantation in southeastern China.It was found that daily ET decreased from 5.34 to 1.84 mm during the intensive drought period and recovered to 4.80 mm during the subsquent recovering drought period.Path analysis indicated that ET was mainly determined by canopy conductance and deep soil water content （50 cm） during the intensive drought and recovering drought periods,respectively.The canopy conductance offset the positive effect of air vapor pressure deficit on ET when suffering drought stress,while the canopy conductance enhanced the positive effect of air temperature on ET during the late growing season.Because the fine roots of this plantation are mainly distributed in shallow soil,and the soil water in the upper 40 cm did not satisfy the demand for ET,stomatal closure and defoliation were evident as physiological responses to drought stress.

Identification of quantitative trait loci for four morphologic traits under water stress in rice (Oryza sativa L.)

Late season drought coinciding with the rice booting to heading stage affects the development of plant height, panicle exserfion, and flag leaf size, and causes significant yield loss. In this study, a recombinant inbred line population derived from a cross between paddy and upland cultivars was used for data collection of the morphologic traits under well water and drought stress conditions. Drought stress was applied at the stage of panicle initiation in the field in 2002 and at the booting stage in PVC pipes in 2003. The data from stress conditions and their ratios （trait measured under stress condition/trait measured under well water condition） or differences （trait measured under stress condition minus trait measured under well water condition） were used for QTL analysis. Totally, 17 and 36 QTLs for these traits were identified in 2002 and 2003, respectively, which explained a range of 2.58%-29.82% of the phenotypic variation. Among them, six QTLs were commonly identified in the two years, suggesting that the drought stress in the two years was different. The genetic basis of these traits will provide useful information for improving rice late season drought resistance, and their application as indirect indices in rice late season drought resistance screening was also discussed.

Impact of extreme seasonal drought on ecosystem carbon-water coupling across China

Water use effciency(WUE)is a critical evaluation indicator of ecosystem responses to climate change and its extremes.However,the influence of the timing of extreme drought on the variation of ecosystem WUE under severe water stress has not been studied extensively.In particular,the modulation of drought impacts on WUE under regional hydro-climatic conditions and biome types is poorly understood.Considering observation-based ecosystem flux and drought index datasets,this study examined the impact of extreme seasonal drought on WUE in China and attempted to reveal the underlying drivers of seasonal variations in drought impacts.Results showed that the direction and magnitude of drought impacts on WUE depend on the occurrence time of extreme drought and the seasonal dynamics of regional ecological and climatic conditions.Across the vegetated regions in China,the most widespread reduction in WUE under extreme drought conditions was observed in summer,whereas approximately 60%of the study area showed positive changes in WUE under extreme drought conditions in spring.Furthermore,the co-regulation of drought characteristics and background environmental conditions in determining the impacts of extreme seasonal drought on ecosystem WUE is highlighted.Classification and regression tree analysis results illustrate that leaf area index(LAI)and drought timing dominated ecosystem WUE variation in response to extreme drought in China.Regions with lower LAI experienced more serious reductions in WUE under extreme drought.These findings indicate the importance of accounting for the interaction between drought seasonality and biome features in assessing drought impacts,thus contributing to improving the modelling of terrestrial ecosystem responses to climate extremes under global warming.

Seasonal drought effects on carbon sequestration of a mid-subtropical planted forest of southeastern China

Continuous measurement of carbon dioxide exchange using the eddy covariance (EC) technique is made at the Qianyanzhou mid-subtropical planted forest as part of the ChinaFLUX network. Qianyanzhou planted forest is affected by typical subtropical continental monsoon climate. It has plentiful water and heat resource but is in inconsistency of its seasonal distribution in the mid-subtropical region, thus seasonal drought frequently occurs in this planted forest. In this study, seasonal drought effect on ecosystem carbon sequestration was analyzed based on net ecosystem productivity (NEP), ecosystem respiration (RE) and gross ecosystem productivity (GEP) at the month scale in 2003 and 2004. In this drought-stressed planted forest, ecosystem carbon sequestration showed a clear seasonality, with low rates during seasonal drought and in winter. The declining degree of ecosystem carbon sequestration under the seasonal drought condition was determined by the accumulation of soil moisture deficits and a co-occurrence of high temperatures. Different drought effects are expected for RE and GEP. The net effect of ecosystem carbon balance depends on how these two quantities are affected relatively to each other. Summer drought and heat wave are two aspects of weather that likely play an important part in the annual NEP of forest in this region.

Rice re-cultivation in southern China： An option for enhanced climate change resilience in rice production

Rice planted in southern China accounts for 94% of the total in sown acreage and 88% of the total in production, which matters a lot to Chinese food security. However, due to the prolonged conflict between water availability and rice growth in spatial/temporal distribu- tion, rice production suffers from seasonal drought at acreage of 16%-22%, which compro- mises food production capacity and food security. Focusing on the spatial distribution of seasonal drought with rice and the practices to adapt to it, and based on an analysis of bal- anced water supply for and demand by rice at a growing season scale during 1981-2030, this paper assesses the changing seasonal drought in the process of rice production under the changing climate in the future, and identifies general rice re-cultivation options for climate change adaptation. Some conclusions can be drawn as follows. （1） Rice suggests a decline in seasonal drought, with early season rice （early rice hereafter） by 12,500 km2, middle season rice （middle rice） by 80,000 km2, and in particular late season rice （late rice） by 25,000 km2, which accounts for almost 20% of its cultivated acreage. It is indicated that due to climate change, seasonal drought in major rice producing areas tends to alleviate in general, late season rice in particular. （2） Future climate change brings about a significant impact on the spatial/temporal distribution of water resources in rice producing areas in China. Based on ＇pre-designed＇ adaptation actions for rice-re-cultivation, the rice cultivation pattern undergoes a significant alteration between 1981-2000 and 2001-2030. In eastern Guizhou and western Hunan, the pattern of single early plus single dry farming is changed into double cropping. In eastern Hunan, the pattern of dry cropping is changed into single early plus single dry farming In northern Anhui, the pattern of dry farming cropping is changed into middle rice. All this is aimed at a potential adequate availability of water for rice production in the future. （3） Rice re-cultivation patterns developed in this paper help re-balance water demand and supply for rice growth using the spatial analysis tool to adapt rice growth to the changing water avail- ability from spatial perspective, and come up with rice producer-friendly re-cultivation options in response to climate change.