Responses Of Yield And Photo-temperature Potential Productivity Of Highland Barley To Climate Change In The Tibetan Plateau

The continuous increase of world population exerts enormous pressure on the limited global food supply.Impacts of climate change on food production and food security widely concerned governments,scientists and other stakeholders.Accurate quantification of crop response and sensitivity to climate change is fundamental for understanding and predicting the spatial-temporal patterns of climate change and the implications for agricultural production and food security.The influences of climate change on the phenology and yield of highland barley(Hordeum vulgare L.var.nudum Hook.f.)during the growing season were investigated on the Tibetan Plateau from 1977 to 2017.This study also analyzed the sensitivity of highland barley to different climatic variables.The CERES-Barley model in the DSSAT(Decision Support System for Agrotechnology Transfer)software was validated with statistical and field observation data,and then applied to simulate the potential yield of highland barley on the Tibetan Plateau.Then yield gaps were calculated based on observed and simulated yields.Finally,we analyzed the impacts of climate change on highland barley production and yield gaps through several statistical methods.Some main results were obtained as follows.(1)Temperature and precipitation during the growing season of highland barley remarkably increased on the Tibetan Plateau over the past 40 years,whereas solar radiation decreased but only decreased at the Linzhi station.(2)Due to climate change on the Tibetan Plateau,the growing season of highland barley obviously decreased at most stations.The growth stages of emergence to anthesis and anthesis to maturity were shortened.However,the growth stage of anthesis to maturity was shortened even more because the advancing of maturity date was greater than that of anthesis date.Since the growth date of anthesis to maturity was just the grain-filling stage of highland barley,the reduction of growing days had negative effects on the formation of final yield.(3)The growing season of highland barley remarkably decreased if with the same variety and the fixed sowing date.The decrease of growing season in high-altitude areas was mainly caused by the increase of average maximum temperature,however,in low-altitude areas,which were mainly caused by the increase of effective accumulated temperature during the whole growing season due to rising mean temperature.(4)The potential yield of highland barley was limited by the altitude and more sensitive to solar radiation at the high-altitude stations.It was large and stable at the high-altitude stations with an altitude of 3500 m.The average potential yield of the Shannan Station approached to 12000 kg·hm-2,while it was only 6000 kg·hm-2 at low-altitude stations around 3000 m.(5)The climatic warming in the Tibet Plateau had little effect on the actual yield of highland barley in the past 30 years.The main effects on the yield of highland barley were due to the change of the minimum temperature from anthesis to maturity.The increase of minimum temperature from anthesis to maturity had a positive effect on the yield of highland barley at the Gannan Station,while the increase of the minimum temperature in the Guinan Station reduced the yield of highland barley.Due to the negative correlation between rainfall and radiation,the areas with more rainfall often had less radiation.So the rainfall in different growth stages was negatively correlated with highland barley yield in most areas of the Tibetan Plateau.(6)The yield gaps of highland barley in the Tibetan Plateau decreased from 58.2% to 34.5% due to the increase of actual production in the past 30 years.And the decreasing rate of yield gaps decelerated in recent decade.The yield gaps in Lasa and Shigatse were the least during 2007-2017,which were less than 25%.The yield gaps in the Tibetan Plateau gradually decreased over the past 30 years because of the increase of actual yield,which was caused by the improvement of varieties and cultivation management.However,the yield gaps were still large except for Lasa and Shigatse.Therefore,there was great potential to increase crop production in the future.