| Henan Province is an important grain production base in China.Its grain output ranks in the forefront of the country for a long time,which effectively ensures the national food security.In history,various meteorological disasters in Henan Province have been very frequent,among which drought disasters have the highest frequency and the greatest harm,which seriously hindered the development of agricultural production and social economy.As the second largest grain crop in Henan Province,maize occupies an important position in its agricultural production,and drought during the growth period of maize will lead to unstable maize yield.Soil moisture plays an important role in the atmospheric water cycle.It is not only the basic condition for crop growth and development,but also one of the important indicators to evaluate drought.Therefore,the quantitative study on the temporal and spatial variation characteristics of soil moisture and its impact on maize yield in Henan Province has important theoretical and practical significance for agricultural production and economic development in this region.In this paper,the EVI and LST data provided by MODIS sensor were used to construct the EVI-Ts double parabola space,and the soil moisture information of Henan Province from 2000 to 2019 were retrieved based on TVDI;The linear trend method,correlation analysis and twoway fixed effect model were used to explore the temporal and spatial variation characteristics and influencing factors of soil moisture in Henan Province from the aspects of terrain,land use type and meteorological factors.In the final step,the maize growth period was divided into different growth stages,and discussed the impact of Dryland Soil moisture change on Maize Yield in each growth stage.The main conclusions are as follows:(1)The TVDI index calculated based on EVI-Ts double parabola space showed a significant negative correlation between the monitoring data of 0～10cm soil relative humidity in different seasons,which can be used to reflect the soil moisture status in Henan Province.The annual average TVDI value of Henan Province was 0.42,which was generally wet;Spatially,Funiu Mountains in western Henan,Southern and Eastern Henan were wetter than western Henan hilly area,Northern and central Henan,among which southern Henan was the wettest and Western Henan hilly area was the driest.(2)From 2000 to 2019,the soil moisture in Henan Province decreased slowly,showing a trend of aridity,and the drought area expanded to the southeast.2012 was the time node for the obvious change of soil moisture.Spatially,most areas of the eastern Henan plain and Nanyang basin have become significantly dry,while the mountainous areas in western Henan and southern Henan have become slightly wet;Under different land use types,the drought trend of cultivated land was obvious,and the forest land and grassland showed a good trend.The soil moisture in Henan Province was the highest in August and the lowest in October;The spatial variation of soil moisture had the characteristics of East-West transfer with time.From January to August,the drought shifted from the mountain area of western Henan to the hilly area,and the degree and scope decreased;From September to October,the drought in the western mountainous area basically disappeared,and the drought in Nanyang basin developed to the whole eastern Henan Plain;From November to December,the drought in the eastern Henan Plain disappeared,the drought in Nanyang Basin weakened,and the drought in the western mountainous area reappeared.(3)Soil moisture was positively correlated with altitude and slope in Henan Province;The change of land use would lead to the change of soil moisture,and the overall trend showed that the soil moisture of paddy field,forest land,grassland and dryland decreased in turn;Among meteorological factors,precipitation and sunshine hours played a role in promoting soil moisture,while temperature,evapotranspiration and soil moisture were negatively correlated.The effect of air temperature on soil moisture was higher than that of other factors.(4)During the study period,the maize yield in Henan Province increased year by year,while the meteorological yield showed a decreasing trend.In each growth stage,the maize yield in sowing jointing stage was negatively correlated with soil moisture in dryland,and the maize yield in other stages and the whole growth stage was positively correlated with soil moisture;The soil moisture level of dryland in Henan Province was lower than the soil moisture threshold of optimal yield during the growth period of maize,and increasing the soil moisture of dryland was conducive to further yield increase;In the past 20 years,the dryland soil moisture showed an insignificant upward trend during the maize growth period in Henan Province,which promoted the per unit yield of maize,with an impact value of-1.07%～1.90%.The comprehensive impact of climate change on maize yield was negative,with an impact value of10.28%～17.75%,of which the discomfort of temperature was the most obvious. |
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