平地无风条件下蒙古栎阔叶床层的火行为Ⅰ.蔓延速率影响因子与预测模型

以东北林业大学帽儿山实验林场蒙古栎次生林下的蒙古栎凋落叶片为材料，根据研究地区同类可燃物的野外条件，在实验室内构建了不同载量、高度和含水率的可燃物床层，进行100次平地无风条件下的点烧试验.结果表明：平地无风条件下蒙古栎阔叶床层的林火蔓延速率不超过0.5 m·min^-1；可燃物含水率、床层载量和高度对蒙古栎阔叶床层的林火蔓延速率具有显著影响；含水率对林火蔓延速率的影响与可燃物床层高度、载量等无显著关系，而可燃物床层高度对林火蔓延速率的影响与可燃物床层载量有关.可燃物床层压缩比对蒙古栎阔叶床层的林火蔓延速率影响不大.以可燃物含水率、床层载量和高度为预测因子的林火蔓延速率预测模型能解释83%的林火蔓延速率变差，模型的平均绝对误差为0.04 m·min^-1，平均相对误差不超过17%.

Characteristics of soil labile organic carbon in poplar plantations of different ages in coastal area of North Jiangsu

To understand the characteristics of soil labile organic carbon and its correlations with soil physical and chemical properties in the poplar(Populus euramericana cv.San Martino) plantations of different ages in coastal area of North Jiangsu,five poplar plantations of 4-,8-,12-,15-,and 20 years old were selected,with the total organic carbon(TOC),water-soluble organic carbon(WSOC),microbial biomass carbon(MBC),and physical and chemical properties in 0-10,10-25,and 25-40 cm soil layers analyzed.In the five plantations,the contents of soil TOC,WSOC,and MBC all decreased with soil depth,and the soil TOC content had a trend of decreased after an initial increase with increasing plantation age,being the maximum in the 15 years old plantation and the minimum in the 4 years old plantation.Overall,the contents of soil WSOC and MBC had the same variation trend as soil TOC content,and the soil WSOC/TOC and MBC/TOC ratios increased with increasing plantation age.There was a significant correlation between soil WSOC and MBC,and the soil WSOC and MBC were significantly correlated with soil TOC,TN,C/N,pH,and bulk density but not correlated with soil total S and soil moisture.This study indicated that with the increasing age of the poplar plantations in the coastal area of North Jiangsu,soil labile organic carbon content had no definite variation pattern,which affected the plantations acting as a carbon sink to a certain extent.