在全球气候变暖和冻土退化背景下,大兴安岭非连续冻土区森林火灾风险不断加剧。探究采伐对地表可燃物燃烧性的影响机制,可为大兴安岭非连续冻土区森林可持续经营提供科学依据。以辽东桤木林为研究对象,设置对照(未采伐,CK)、轻度择伐(15%强度,LC)、重度择伐(45%强度,HC)、皆伐(100%强度,CC)4个采伐强度处理,通过烘干法、点燃法、氧弹法及线性回归分析地表可燃物(灌木、草本、枯落物、腐殖质)的含水率、燃点、热值特征及其相互作用关系,探讨不同采伐强度处理对地表可燃物理化性质及耦合作用的影响机制。结果表明:1)地表可燃物的含水率和燃点随采伐强度增加呈下降趋势,地表可燃物热值随采伐强度的增加呈上升趋势;2)轻度择伐对辽东桤木林地表可燃物的含水率、燃点和热值影响均不显著,而重度择伐和皆伐则显著降低地表可燃物的含水率和燃点(P<0.05),且提高热值,从而增加了引发森林火灾的可能性;3)4种采伐强度处理下,地表可燃物的燃点整体上与热值无显著相关性,与含水率呈极显著正相关(P<0.01);地表可燃物的热值与含水率无显著相关性。不同采伐强度处理对大兴安岭非连续冻土区地表可燃物燃烧性的影响存在差异,轻度择伐在保障森林资源合理利用的同时,最大限度地降低了森林火灾的隐患,是该区域森林可持续经营的最优选择。

Amidst global warming and permafrost degradation,forest fire risk in the discontinuous permafrost region of the Greater Khingan Mountains has significantly increased.Fcosing on Alnus hirsuta forest,this study elucidatethe mechanism of different cutting intensities on the combustibility of surface fuels,providing a scientific basis for the sustainable management of forests in this region.Four harvesting intensity treatments were established:control(CK,unharvested),light selective cutting(LC,15%),heavy selective cutting(HC,45%),and clear-cutting(CC,100%).The water content,ignition point,and calorific value of surface fuels(shrubs,herbs,litter,and humus)were measured using the drying method,ignition method,oxygen bomb calorimeter.Linear regression analysis was employed to analyze the physicochemical properties of surface fuels and their interaction mechanisms.The results showed:1)Both the moisture content and ignition point of surface fuels exhibited a decreasingtrend with the escalating harvesting intensity,while the calorific value of displayed an upward trajectory.2)LC exerted no significant effect on the moisture content,ignition point,and calorific value of surface fuels in Alnus hirsuta forests.In contrast,HC and CC significantly reduced the moisture content and ignition point(P<0.05)while elevating the calorific value,thereby exacerbating the potential for forest fires.3)Under the four cutting intensity treatments,overall there was no significant correlation between the ignition point and calorific value of surface fuels,but exhibited a highly significant positive correlation between the ignition point and moisture content(P<0.01).No significant correlation was found between the calorific value of surface fuels and moisture content.In conclusion,the impacts on surface fuel combustibility vary across harvesting intensities in the discontinuous permafrost region of the Greater Khingan Mountains.LC is the optimal choice for sustainable forest management in this region as it ensures the rational utilization of forest resources while minimizing fire hazards.