Research On Forest Fuel Loadings And Potential Surface Fire Behavior Of Major Forest Types In Southern Daxing’an Mountains

Selecting8major forest types in Southern Daxing’an Mountains as the research objects,based on site factors(altitude,slope percent,slope aspect) and stand factors(canopy cover,density,mean total height,mean DBH),the typical forests were selected.Surface fuel loading including shrub, herbage, lh fuel,1Oh fuel,100h fuel were measured by harvesting method and canopy fuel loading(space density of fuel) were determined by standard branch estimating method.Through correlation relationship anlysis on site and stand factors affecting forest fuel distribution.Based on Rothermel forest fire spread model,potential fire behavior of target forests can be calculated by means of Behaveplus forest fire predicting system which combined with parameters such as slope percent,wind speed,fuel type and fuel loading in Southern Daxing’an region.The results may provide a theoretical reference for the precaution and extermination work against forest fire,the main research results as follows:(1) For surface fuel distribution,herbage loading mainly had correlation with slope percent,canopy cover,density and DBH;shrub loading had correlation with slope aspect and density,1h fuel loading had correlation with canopy cover and DBH,10h fuel loading had correlation with canopy cover and mean total height,100h fuel loading had correlation with density and mean total height. Surface fuel loading in each forest type which were Ledum palustre-Larix gmelinii forest>Corylus heterophylla-Betula platyphylla forest>Rhododendron dauricum-Larix gmelinii forest>Herbages-Larix gmelinii forest>Betula platyphylla-Larix gmelinii forest>Betula platyphylla-Populus davidiana forest>Herbages-Betula platyphylla forest>Quercus mongolica forest in order.(2) For vertical fuel distribution,fuel loading among0-1.5m had correlation with DBH,among1.5-4m had correlation with density and slope percent,among4-8m had correlation with mean total height,higher than8m had correlation with mean total height and canopy cover. Vertical fuel loading in each forest which were Herbages-Larix gmelinii forest>Betula platyphylla-Larix gmelinii forest> Ledum palustre-Larix gmelinii forest>Rhododendron dauricum-Larix gmelinii forest>Betula platyphylla-Populus davidiana forest>Herbages-Betula platyphylla forest>Quercus mongolica forest>Corylus heterophylla-Betula platyphylla forest in order.(3) The research of potential surface forest fire behavior of major forest type in Southern Daxing’an Mountains show that in addition to Betula platyphylla-Populus davidiana forest,the spread rates of fire and flame length increased with acceleration of the average flame speed.The spread rates of fire were affected by forest fuel humidty,which were extreme low humidty> low humidty>middle humidty>high humidty in order.Within0-9m/s average wind speed of flame,the heat per fire area keep constant. It was affected by forest fuel humidty,the order of which are extreme low humidty> low humidty>middle humidty>high humidty. The fire intensity aceelerated with increment of the average flame speed as well.(4) The ratio of transition to crown fire of major forest types in in Southern Daxing’an Mountains which were Ledum palustre-Larix gmelinii forest>Betula platyphylla-Larix gmelinii forest>Rhododendron dauricum-Larix gmelinii forest>Herbages-Larix gmelinii forest>Betula platyphylla-Populus davidiana forest>Herbages-Betula platyphylla forest>Corylus heterophylla-Betula platyphylla forest>Quercus mongolica forest in order.Ledum palustre-Larix gmelinii forest,Betula platyphylla-Larix gmelinii forest,Rhododendron dauricum-Larix gmelinii forest,Herbages-Larix gmelinii fforest,Betula platyphylla-Populus davidiana forest,Herbages-Betula platyphylla forest were not only inclined to occur floor fire,but the floor fire could be easily transformed into crown fire while Corylus heterophylla-Betula platyphylla forest and Quercus mongolica forest were likely to occur floor fire but not crown fire.