Impacts Of Fuel Management On Forest Combustibility In Daxing’anling

Fires often destroy the ecology environgment and cause the loss of lives property.Fuel managemen is an important way to prevent wildfires and reduce fire risk,which includes fuel treatment,prescribe burning,and firebreaks.To evaluate the effects of fuel management measures is the basis for effective fuel management.This paper studied the impacts of prescribed burning,firebreaks,and fuel treatments with different intensities on burn probability and fire behavior in Daxing’anling.We used Fuel Characteristic Classification System(FCCS)to analyze the effects of fuel treatments with different intensities on potential fire behavior for each forest combining with the field investgation.The Burn-P3 model was used to simulate the burn probability(BP)and fire behavior under various scenarios.The paper clarified the influence of the prescribed burning on the landscape combustibility by comparing and analyzing the changes of burn probability,fire intensity,and spread speed before and after the prescribed burning.We evaluated the effects of firebreaks density,width,and spatial distribution pattern on combustibility and fire behavior by simulating the burn probabilities under different firebreak scenarios.The optimal firebreak design was determined according to the objectives of forest and fire management.The paper revealed the relationship between the burn probability and fuel treatments.The results provides scientific basis for the fuel management and guideline for local fire agency to carry out fuel management activities.The main conclusions are as follows:(1)Prescribe burning reduced the fuel loading of grass and breached their continuity in spatial.The burn probability and pontential fire behavior reduced significantly after prescribed burning.The areas with high and very high classes of BP reduced 18.2%and 1.9%,respectively.(2)The average BP of the study area decreased significantly with increased firebreak density(range from 2.1 to 4.5 m/hm~2).Expansion of firebreak width can effectively reduce BP,FI,and ROS in adjacent areas,and the changes showed significantly within 2000 m from firebreaks.An optimal firebreak design was determined,which is 4.1 m/ha in density,30 m wide in grasslands and 60 m wide in forests,and the optimized BP-based spatial distribution pattern.The optimal firebreak design may reduce BP by 25.2%in comparison to that under current scenario and with further reductions in high-and very-high-BP areas.(3)The larch natural forest has the maximum fire behavior indices among the all forest types under the same fire environment,while the birch forest would not occur crown fire.The potential fire behavior indices for each forest types would decrease significantly with the increasing intensity of fuel treatment under normal and drought weather scenarios.The surface fire spread rate will be less than 1 m/min,and flame length less than 1 m after mid-intensity treatments in each forest type,which can be suppressed directly.The occurrence index and spread speed index of crown fire for coniferous and broad-leaved mixed forest,larch forest,and pine forest(Pinus sylvestris)wold decrease by 19.6-41.8%and 6.4-45.6%under drought scenario,respectively.