Monitoring The Response Of Winter Wheat Phenology To The Climate Changing And The Effect On Its Yield Using Remote Sensing

Surface-covered vegetation,as a very sensitive indicator of climate change,can affect climate by influencing the exchange of material and energy between vegetation and atmosphere.At the same time,climatic factors also strongly affect the phenology of vegetation.Phenology of vegetation has the potential to broadly impact terrestrial ecosystems and human societies,for example,altering global carton,water,and nitrogen cycles,communication between species and crop production.It is of great significance to study vegetation phenology,and the study of crop phenology can objectively understand the response of crops to climate change,and provide scientific basis for the production and scientific management of crops.The rapid development of remote sensing technology reduces the temporal and spatial limitation of traditional phenological observation and provides a new technical means for monitoring vegetation phenology in a large scale.The Huang-Huai-hai area in China is a semi-arid and sub-humid area,and it is an important food production base in China.It's yield of winter wheat is the highest in China.Studying the phenology of winter wheat in this area helps to understand the response and feedback mechanism of crops to climate change.Based on the 10d synthesized SPOT VEGETATION NDVI data production,the article extracts the phenological period(green period,heading stage and maturity stage)of winter wheat in 2000-2014 years by using double Gaussian model simulating fitting and proportional threshold method,analyzes the temporal and spatial characteristics of winter wheat phenology in Huang-Huai-hai area in the past 15 years.The article also discusses the relationship between phenological changes of winter wheat and climate change(temperature and precipitation)in Huang-Huai-hai area based on the meteorological data of the Huang-Huai-hai area in 2000-2014.The relationship between phenological changes and yield of winter wheat in Huang-Huai-hai area is also analyzed based on winter wheat yield statistic data and GPP data.The main conclusions in this study could be drawn as follows:(1)Spatial and temporal variation of winter wheat NDVIThe spatial distribution of the mean ndvi of winter wheat in the Huang-Huai-hai area in 2000-2014 was obviously zonal,which showed a decreasing trend of spatial variation from south to north.The NDVI in the southeastern part of Henan province is large,and the NDVI in the eastern part of Hebei province is smaller.The variation of ndvi of winter wheat in eastern part of Henan province is larger,while the variation of ndvi of winter wheat in northern Hebei and eastern part of Shandong province is smaller.The time variation characteristics of winter wheat Ndvi in Huang-Huai-hai area in 2000-2014 showed a significant increase trend,and the range of changes was spatial difference.Among them,the ndvi of winter wheat in Henan and Shandong provinces generally increased,and most areas increased by 0.009,while the increase amplitude in Hebei province was relatively small,and in most areas the increase was within 0.006.(2)Spatial and temporal variations of phenology of winter wheatThe spatial distribution of mean phenological period of winter wheat in the Huang-Huai-hai area in 2000-2014 showed obvious regional difference.The general trend of winter wheat green period was gradually delayed from southwest to northeast.The heading stage mainly showed the trend of gradual delay from south to north.However,the overall difference in the maturity period is not very large,showing a slight trend from south to north.During the past 15 years,interannual fluctuations of winter wheat heading was stable,and 98%of winter wheat heading period standard deviation was less than 18d.The interannual fluctuations of the green and mature stages were smaller,with 72%and 74%of winter wheat standard difference less than 18d.The green period of 90%winter wheat in Huang-Huai-hai area in 2000-2014 showed an advance trend,and only 10%was delayed.89%of winter wheat heading stage showed an advance trend and 11%of winter wheat heading stage was delayed.94%of winter wheat mature stage showed an advance trend,and only 6%of winter wheat mature stage was delayed.(3)Correlation between phenology of winter wheat and temperature and precipitationCorrelation of winter wheat green period and annual mean temperature in Huang-Huai-hai area in 2000-2014 showed differences.About 48%Winter wheat green period was negatively correlated with the annual mean temperature,and 39%winter wheat green period was negatively correlated with the average temperature in the pre growing season(December to February).Heading stage was both negatively correlated with the annual mean temperature and the average temperature in the pre growing season(February-April),and the former is 73%negative correlation and the latter is about 75%negative correlation.67%Winter wheat maturity stage and annual mean temperature showed negative correlation,80%winter wheat maturity stage and he average temperature in pre growing season(March-May)were negatively correlated.The effect of annual cumulative precipitation on winter wheat green period in Huang-Huai-hai area in 2000-2014 is inconsistent.The green period of 57%winter wheat is negatively correlated with the annual cumulative precipitation and 65%for the cumulative precipitation in the pre growing season is 65%.The heading stage of 36%winter wheat has negative correlation with annual cumulative precipitation and 63%for pre growing season.The response of winter wheat maturity stage to annual cumulative precipitation and cumulative precipitation in pre growing season is different.About 44%of the former were negatively correlated,while 82%of the latter were negatively correlated.(4)Relationship between phenology and yield of winter wheatAccording to the Statistical data of winter wheat,it is found that Compared with the green period,the yield of winter wheat in 2000-2014 has higher correlation with heading stage and mature stage:the correlation coefficient between heading stage and yield of winter wheat was-0.611,p=0.009,and the correlation coefficient between maturity and yield of winter wheat was-0.640,p=0.006.According to the GPP data of winter wheat,it is found that the yield of winter wheat has a strong negative correlation with the heading stage and mature stage,and the correlation is significant.