Determining the effects of climate on winter wheat yield in Northern China via yield gap analysis-A case study of Luancheng County, Hebei Province

In order to determine the effect of climate on winter wheat yield in the North China Plain, potential wheat productivity (Y_mp) was simulated using daily dynamic crop growth model and agro-climate data from the Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences. Yield gap (YG) was calculated as the difference between Y_mp and the actual yield under sufficient irrigation (Y_h). A correlative stepwise regression analysis was used to determine the relationship between climate factors at different growth stages and YG. The same analysis was used to determine the relationship between climate factors and Y_h. Before heading, sunshine hours and temperature factors (mean air temperature, maximum air temperature, minimum air temperature and daily temperature-range) were positively related with YG. After heading, however, both sunshine hours and daily temperature-range tended to be negatively correlated with YG. The results suggested that higher light and temperature increased production potential in the early growth stage. At the late stage, however, sufficient sunshine and large daily temperature-range benefited actual yield by enhancing vigorous growth. For actual yield, sunshine hours and daily temperature-range were positively correlated with Y_h at most growth stages. This suggested that high sunshine and daily temperature-range were favored actual yield. While precipitation was negatively correlated to YG for almost the whole growth period, it was not significantly correlated with Y_h. This suggested that precipitation influenced yield gap by reducing production potential. Only at the late ripening stage (about ten days before harvest) was precipitation positively correlated with YG and slightly negatively related with Y_h. It implied that at late ripening stage, winter wheat yield did not benefit from precipitation.