Study On Forest Combustibility Of Main Fuel Types In Beijing Mountainous Areas

Based on the forest distribution and natural conditions of the main types of combustibles in Beijing mountainous area,the bumability of the main types of combustibles was analyzed and studied in this paper.Ten districts and counties with high vegetation coverage and related to key forest fire prevention were selected as research objects.Based on dominant tree species,the main types of combustibles in the surrounding mountainous areas of Beijing were classified.Combustibility evaluation index system of combustible material type was constructed by using the method of systematic clustering in SPSS software,taking tree species(plant)composition,stand age,canopy density,slope,slope direction,altitude,combustible material load,combustible material comprehensive attribute value,forest type and combustible continuity index as combustion components.Using the data image processing function of ARCGIS software,the burning grades of different types of combustibles are displayed in the form of images,and the suggestions for forest fire prevention in Beijing area are provided intuitively and pertinently.The results show that:(1)According to the actual situation in Beijing,the main types of combustibles are classified into eight types,namely LB1(coniferous mixed forest dominated by Pinus tabulaeformis),LB2(coniferous mixed forest dominated by Platycladus orientalis),LB3(broad-leaved mixed forest dominated by Robinia pseudoacacia),LB4(broad-leaved mixed forest dominated by oak),LBS(broad-leaved mixed forest dominated by maple,elm and poplar),LB6(plain afforestation land)and LB7(shrub).Weedy grassland,LB8(farmland,nursery and other hard-to-use land).(2)The ranking of combustibility is LB1>LB2>LB7>LB4>LB3>LB5>LB6>LB8 by calculating the combustibility evaluation index system and mathematical methods.(3)Based on the ranking of comprehensive index of combustibility of various types of combustibles,through comparative analysis of the actual situation,five burning grades were classified,namely,low burning(plain afforestation land,farmland,nursery and other difficult-to-use land),medium burning(broad-leaved mixed forest mainly composed of maple,elm and poplar),high burning(broad-leaved mixed forest mainly composed of black locust,broad-leaved mixed forest mainly composed of oak,and broad-leaved mixed forest mainly composed of oak.Mixed forest with leaves,high combustibility(shrubs and weeds)and extremely high combustibility(coniferous mixed forest with Pinus tabulaeformis and coniferous mixed forest with Platycladus orientalis).(4)According to the fire danger zoning map of burning grade,different forest fire prevention measures are put forward according to the burning grade of different types of combustibles.For extremely high burning grade,fire-retardant tree species should be planted to form fire-retardant forest network,and combustible removal work should be carried out,pruning branches and changing the spatial distribution structure of combustibles.For high burning grade,clean-up methods of combustibles and tending methods should be adopted to improve the growth environment of forest classification and optimize forest structure.Grade I,three-dimensional measures should be formulated to clean up dead and combustible materials,increase the accessibility of firefighters and equipment;for the middle burning grade,forest fire prevention measures can be taken to clean up part of the effective surface combustible materials according to the actual situation;for the low burning grade,litter in areas with more human activities should be cleaned up in time to avoid the occurrence of man-made fires.