Research On Recent Agricultural Climate Resources And Water Use Efficiency

The warming of the global climate system has significantly increased climate risks in recent years.Due to the unbalanced spatial distribution of agro-climatic resources,there are differences in water and thermal resources on a large scale.Therefore,it is a matter of evaluating the dynamic and spatial characteristics of agricultural climate resources.It is also important to discussing their regional differences,and evaluating the driving factors and response mechanisms of actual evapotranspiration(AET)and water use efficiency in each region,which can improve regions of water resources utilization,the realization of sustainable management of water resources,and provide a scientific basis of the agricultural response to climate change.Therefore,this study takes eight climatic regions in mainland China as the research area,and conducts in-depth discussions on the actual evapotranspiration,hydrothermal resources,and water use efficiency.The main research contents and results of this paper are as follows:(1)In response to the warming hiatus,this study used Terrestrial ET Dataset Across China(TEDAC),applied multiple analysis of tempo-spatial methods,and used Pearson Correlation,sensitivity anlysis and contribution indicators quantify the influence of driving factors.This study focused on the dynamics and causes of AET trend around China’s warming hiatus.The results show that the warming hiatus of eight climate regions exist inconsistent,and the dominant factors of AET change also had temporal and regional differences.By using segmented regression to detect the turning point,the warming hiatus first appeared in the Tibetan Plateau and Northeast China in 2003,and the latest appeared in 2007.There were high correlation relations between AET and solar radiation in southeast areas,and air specific humidity in northwest area.During the global warming period,the leading factors of AET changes were the air specific humidity and temperature,and the biggest contributors to the warming hiatus in some areas shift to shortwave radiation and wind speed.Generally speaking,in the past 30 years,the specific air humidity and temperature have always played an important role in the changes of AET.(2)According to the climate regions,eight dominant crops have been formulated and the base temperature and upper limit temperature suitable for the survival of the corresponding crops have been set.This article mainly studied the climate,thermal resources and water resources during the growing season(GS).The results show that the temperature zones in China had shift northward,both thermal resources and dought risk had increased.During 1961-2018,the lowest temperature(0.23℃/decade,P<0.05)and the highest temperature(0.20℃/decade,P<0.05)increased significantly.The corresponding flue-cured tobacco,alfalfa and summer maize in North Central China,Southwest China,and North China Plains had increased thermal resources,but the risk of extreme high temperature and drought risk also increased.The drought index of summer maize,rice,alfalfa and winter wheat in the corresponding regions of China is higher than 0.1/decade,so the production risk is high.The management of water supply for cotton in the maturity period from September to October in northwest China should be strengthened during GS.Water distribution management are necessary for the winter wheat in Tibetan Plateau from March to June before the winter wheat matures,and the alfalfa in autumn in North Central China.(3)This study based on Gross Primary Production(GPP)and AET data sets,used four meteorological factors(temperature,precipitation,air specific humidity,shortwave radiation),NDVI and soil water as the influencing factors for mainland China from 1982 to 2015.The temporal and spatial changes of WUE in eight climate regions and their driving factors were studied.The results show that annual WUE level in China showed a slight increase(0≤range<0.05),and it is generally more sensitive to NDVI,but there existed differences on the seasonal scale.WUE showed a significant increasing trend in eight regions(P < 0.05).The order of seasonal WUE was autumn>summer>spring>winter,the WUE of cropland ecosystem was higher than that of grassland ecosystem in most areas.The positive high sensitivity level of WUE to NDVI is generally distributed.In most ares of China,annual temperature had a high contribution to WUE change.These results provide considerable evidence for better management of water resources in different regions and seasons in China.