老爷岭典型林分内地表不同层可燃物含水率动态变化及湿度码预测模型适用性

森林地表不同层可燃物含水率对林火的垂直蔓延和地下火的发生具有重要影响。加拿大火险等级系统是目前使用最广泛的火险等级系统,其中3个湿度码模块分别代表不同层可燃物湿度。研究地表不同层可燃物含水率动态变化,使用湿度码预测不同层可燃物含水率,并对其适用性进行分析,对可燃物含水率预测及火险预报研究有重要意义。以黑龙江省老爷岭生态定位站的蒙古栎-红松针阔混交林和白桦林内凋落物、半腐殖质、腐殖质为研究对象,在春季防火期以日为步长,连续监测3层可燃物含水率动态变化,计算得到3个湿度码:细小可燃物湿度码(FFMC)、腐殖质湿度码(DMC)、干旱码(DC),并进行可燃物含水率预测适用性分析。结果表明:蒙古栎-红松针阔混交林、白桦林内凋落物含水率动态变化与FFMC、DMC呈显著相关;半腐殖质与3个湿度码都呈显著相关;腐殖质仅与DC呈极显著相关。使用湿度码进行凋落物含水率预测时,使用非降雨数据预测效果优于使用全部数据,使用降雨数据预测效果最差;对于半腐殖质,使用湿度码进行预测时,是否区分降雨对预测精度没有显著影响;对于腐殖质,使用降雨数据无法建立与湿度码之间的线性关系。湿度码法预测可燃物含水率精度略低于气象要素回归法,但在含水率较低时,湿度码预测效果更符合实际火险需要。以后研究中,应从湿度码尺度模型、机理对湿度码进行修正。提高地表不同层含水率预测精度,对可燃物含水率研究和火险预报具有重要意义。

Dynamic Change and Prediction Model with Moisture Code of Moisture Content of Fuel in Different Surface Layerin the Typical Forest Stand of Laoyeling Mountain

The moisture content of fuel in different layers of forest surface has an important impact on the vertical spread of forest fire and the possibility of underground fire.The Canadian Forest Fire Danger Rating System is the most widely used in the world,in which three moisture code represent the moisture content of fuel materials in different layers.We analyzed the dynamic change of moisture content of fuel in different layer of forest surface,and predicted the applicability of moisture code for the moisture content,which is great significance for fuel moisture content and fire risk prediction.The litter,semi-humus and humus of Mongolian oak-red pine mixed forest and birch forest in Laoyeling Ecological location were taken as the research objects.During the spring fire prevention period,the dynamic changes of the moisture content of the fuel in three layers were continuously with daily steps.Three moisture code:FFMC,DMC and DC were used to analyze the applicability of moisture content prediction.The dynamic change of litter in Mongolian oak-red pine mixed forest and broadleaves forest was significantly related to FFMC and DMC,the semi-humus was significantly related to all three moisture code,and the humus was only significantly related to the DC.When using moisture code to predict litter moisture content,the non-rainfall data was better than all the data.The prediction effect of rainfall data was the worst.For semi-humus,when the moisture code is used for prediction,the difference of rainfall has no significant effect on the prediction accuracy.For humus,the linear relationship between rainfall data and moisture cond cannot be established.The accuracy of moisture content prediction by moisture code is slightly lower than that by meteorological factor regression method.In the future research,but when the moisture content is low,the prediction effect of moisture code is more in line with the actual fire risk needs.In the future research,the moisture code should be modified from the scale model and mechanism of the moisture code to improve the prediction accuracy of moisture content in different surface layers,which is of great significance to the research of moisture content of fuels and fire risk prediction.