Two Ultraviolet Radiation Datasets that Cover China

Ultraviolet（UV） radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization＇s measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes.

Much Improved Irrigation Use Efficiency in an Intensive Wheat-Maize Double Cropping System in the North China Plain

Crop yield and water use efficiency （WUE） in a wheat-maize double cropping system are influenced by short and uneven rainfalls in the North China Plain （NCP）, A 2-year experiment was conducted to investigate the effects of irrigation on soil water balance, crop yield and WUE to improve irrigation use efficiency in the cropping system, Soil water depletion （~SWS） by crop generally decreased with the increase of irrigation and rainfall, while ASWS for the whole rotation was relatively stable among these irrigation treatments, High irrigations in wheat season increased initial soil moisture and ASWS for subsequent maize especially in the drought season, Initial soil water influenced mainly by the irrigation and rainfall in the previous crop season, is essential to high yield in such cropping systems, Grain yield decreased prior to evapotranspiraUon （ET） when ET reached about 300mm for wheat, while maize showed various WUEs with similar seasonal ET, For whole rotation, WUE declined when ET exceeded about 650 mm, These results indicate great potential for improving irrigation use efficiency in such wheat-maize cropping system in the NCP, Based on the present results, reasonable irrigation schedules according to different annual rainfall conditions are presented for such a cropping system.

Fertilization regulates the response of wheat yield to interannual temperature variation in North China

Aims understanding the effect of long-term fertilization on the sensitivity of grain yield to temperature changes is critical for accurately assess-ing the impact of global warming on crop production.In this study,we aim to assess the impacts of temperature changes on grain yields of winter wheat(Triticum aestivum l.)under different fertilization treatments in a long-term manipulative experiment in North China.Methods We measured grain yields of winter wheat under four fertilization treatments at the Yucheng Comprehensive Experimental station each year from 1993 to 2012.We also measured air temperature at 0200,0800,1400 and 2000 h each day since 1 January 1980.We then used the first-difference method and simple linear regres-sion models to examine the relationship of crop yield changes to mean air temperature,mean daytime and nighttime air temperature in crop growing seasons.Important Findings We found that increases in mean daily temperature,mean day-time temperature and mean nighttime temperature each had a positive impact on the grain yield of winter wheat.grain yield increased by 16.7-85.6%for winter wheat in response to a 1°C increase in growing season mean daily temperature.Winter wheat yield was more sensitive to variations of nighttime temperature than to that of daytime temperature.The observed temperature impacts also varied across different fertilization treatments.balanced fertilization significantly enhanced grain yields for winter wheat under a warming climate.Wheat plots treated with nitrogen and phosphorous balanced fertilization(NPK-and NP-treated plots)were more responsive to temperature changes than those without.This report provides direct evidence of how temperature change impacts grain yields under different fertiliza-tion treatments,which is useful for crop management in a chang-ing global climate.