The Study Of Spatio-temporal Pattern And Influencing Factors Of Fires In Hulunbuir Grassland

Grassland is the most important component of terrestrial ecosystem,assuming a very powerful function in many fields such as production,ecology and life,and playing an important supporting role in maintaining the security of national ecosystem and promoting sustainable economic and social development in pastoral areas.Under the background of global climate change,human activities have intensified the warming and drying of climate and the occurrence of extreme climate events,and increased the possibility of grassland fires.Grassland fire has the characteristics of sudden and destructive,which seriously threatens the safety of terrestrial ecosystem and people’s life and property.The grassland fire is serious in China,and Hulunbuir City is the major fire risk area affected by it.Hulunbuir Grassland,as one of the four major grasslands in the world,is located at the border of China,Mongolia and Russia,and has special geographical significance.Therefore,it is important to explore the spatial and temporal patterns and influencing factors of its grassland fires to clarify the key areas and time periods for grassland fire prevention and control,improve the comprehensive prevention and control capability of grassland fires in China,and strengthen the prevention and control of border fires.In this study,global wildfire monitoring product data Fire＿CCI51 and China wildfire Atlas data(WFAC)were used as the main data sources,and GIS spatial analysis technology was applied to extract the fire area and number in the Hulunbuir Grassland during 2001-2020 to explore its spatial and temporal distribution characteristics;and methods such as Kriging spatial interpolation and Pearson correlation test were used to comprehensively analyze the influencing factors of grassland fires(natural elements such as meteorological elements and combustible material conditions and human elements such as roads and settlement conditions).Meanwhile,it is supplemented with the attribute analysis of historical statistics of grassland fires in Hulunbuir to explore the main driving factors of grassland fires.In view of the particularity of the geographical location of Hulunbuir Grassland,this paper made a special extraction and analysis of the border fire,comprehensively studied the characteristics of the transit fire by comparing the overfire areas inside and outside the border and the overfire areas in China,Mongolia and Russia,and analyzed the differences of the transit fire by combining the different prevention and control policies of the three countries to provide feasible suggestions for the prevention and control of border fires.The main conclusions are as follows:(1)The temporal distribution of the Hulunbuir grassland fire is as follows: On the annual scale,the fire showed a downward trend and fluctuated periodically every four years on average,with large inter-annual differences and strong randomness.Among them,2014 the worst year for grassland fires,and its burned area and number reached the highest value,while 2018 was the least.On the monthly scale,the fires in Hulunbuir grassland showed a showed a bimodal distribution,concentrated in spring and autumn,among which,April,May,September and October were the four months most affected by fires.They accounted for 27%(20%),20%(10%),29%(38%)and 13%(15%)of the total area(number of fires),respectively,and 89%(83%)of the total area(number of fires)of the year.(2)The Hulunbuir grassland fire had obvious spatial aggregation,with the highest frequency of fire in the eastern meadow steppe,forest steppe belt and the China-Russia border in the northeast,followed by the China-Mongolia border in the west,and the lowest frequency in the typical steppe area in the central and western regions,showing a spatial pattern of more fires in the east and less in the west,and more in the north and less in the south.(3)Human activity is the main cause of prairie fires.The statistics of recent 35 years show that the percentage of human-caused grassland fires is as high as 87%.However,among the many factors that affect prairie fires,the driving force of grassland fire occurrence was presented as meteorological factors > human factors > combustible conditions,and the driving force of grassland fire spread was presented as combustible conditions > meteorological factors >human factors.It can be seen that climate image factors are strongly driving the occurrence of grassland fire.Temperature and wind speed are significantly positively correlated with grassland fire,while precipitation and relative humidity are negatively correlated with them.The combustibles condition has a strong driving effect on the spread of grassland fire,and the combustibles load is positively correlated with it.There is little correlation between human factors such as road and settlement density and grassland fire,and grassland fire usually occurs within a certain distance.The results show that the influence of human activities on grassland fire is complex and dual.(4)The time distribution of the transit fires was bounded by 2010.In the first 10 years,the area of transit fire is small and the fluctuation is weak,while in the second 10 years,the area of transit fire is large and the fluctuation is obvious.The spatial distribution shows that the area of the fire in transit between China and Mongolia is higher than that in China and Russia,and the area of the fire on the Russian side is higher than that on the Mongolian side.This is closely related to the natural geographical environment of the border area and the different grassland management and grassland fire prevention and control policies of the three countries.