Response Of Grass Yield In Hulunbeir Grassland To Snow Cover In Winter Based On RS And GIS

In arid and semi-arid regions,water from melting ice and snow is an important supplementary source of water for plant growth.Snow has important potential impacts on greening,growth and final yield of grassland vegetation.Studying the correlation between snow cover and grassland yield,and analyzing the effect of snow characteristics on grass production in different regions,is of great significance to guiding grazing and reducing losses caused by spring drought.In this study,the Hulunbeir grassland was used as the research area.Based on the MODIS snow product MOD10A1,the spatio-temporal differences of snow cover and snow days between2000 and 2014 were extracted and analyzed.The temporal and spatial evolution of grassland grass production was analyzed based on NDVI data and light energy utilization model.The analysis was performed on the basis of simulation analysis.Based on the analysis,principal components analysis,grey relational degree model and coordination degree were used to study the image features of snow cover on grassland yield.The main conclusions are as follows:(1)The annual snow cover rate(YSCF)in the Hulun Buir grassland is between 20-40%,the snow cover rate is the highest(44.61%)in February,and the annual snow cover days(YSCD)is more than 30 days.The number of snow days in the counties(cities)differed significantly.Among them,the Ewenki Autonomous Banner had the highest average snow cover days(56.69 days),while the Manzhouli City had the least average snow days(33.36 days).The monthly snow cover rate(MSCF)changes in the number of days of snow cover are first increased and then decreased,but the two peaks appear in different years and have a four-year change cycle.(2)The grass production in the Hulun Buir grassland in 2000-2014 showed an overall increase trend in tortuous changes.There was an equation expressed as Y=0.05x~3-1.10x~2+7.47x+110.39between the grass production(Y)and the year(x)(R~2=0.59).Large differences in grass production were shown in county level.Overall,the total grass production in Xinbalhuyouqi and Xinbalhuzuoqi were relatively high,but the grass productions per unit area were relatively lower.On the contrary and the total productions in Hailar and Manzhouli were relatively lower,while grass yields per unit area were relatively high.This was caused by geographical conditions such as geographical location,vegetation condition and hydrothermal conditions of each county.The spatial distribution characteristics of the annual average grass yield are less east and west,and the overall longitude and zonality.The grass production changes expressed mainly as increasing trend,and the increase range was 20-40 g/m~2,and the rate of change of grass production was positive in most areas of the study area.(3)Snow cover fraction,snowfall,snow cove days,snow cover index,extreme snow cover,variance,and variability for snow cover fraction of the seven snow feature parameters were correlated to remove high correlation snow coverage fraction,snow cover days and extreme snow coverage.The grey relational degree between the remaining independent variables and the grass production is ranked from highest to lowest as snow cover index>snowfall>snow cover fraction variability>snow cover fraction standard deviation and the grey correlation between the snow cover index and grass production is the highest.The analysis of coordination of snow cover and grass production over the years also found that the coordination degree of snow cover and grass production had a good overall coordination degree.Among them were Xinbaerhuzuoqi,Manzhouli City,Ewenki Autonomous county and Chenbaerhuqi are in better coordination.