中文摘要：

四川瓦屋山国家森林公园是我国西部的中亚热带湿性常绿阔叶林的典型代表,具有四川现存的较为完好的扁刺栲（Castanopsis platyacantha）-华木荷（Schima sinensis）群系,该研究利用土钻法探讨了该群系内主要建群种扁刺栲标准木的细根分布及其碳氮特征。结果表明：（1）扁刺栲细根总生物量为173.62 g·m（-2）,其中活根生物量为135.29 g·m（-2）。（2）随着土层深度的增加,扁刺栲细根生物量、根长密度、根系表面积和比根长呈下降趋势,0-30 cm土层所占比例分别为67.23%、69.53%、69.48%和57.20%;根长密度、根系表面积和比根长均随细根直径的增加而显著下降,直径小于1 mm的根系所占比例分别为58.84%、52.59%和51.36%。（3）扁刺栲细根生物量、根长和表面积消弱系数β均随根系直径的增加而增加。（4）根系C含量在第Ⅰ土层中随细根直径的增加而显著增加,在其他土层则无显著差异;直径小于2 mm的根系C含量在第Ⅰ土层中显著低于其他土层,大于2 mm的根系C含量在各土层间的差异不大。（5）根系N含量随根系直径和土层深度的增加而减少,C/N值则与之相反。该研究结果在一定程度上反映了该次生林地下细根的垂直分布及养分特征,为揭示该生态系统地下生态过程及今后在该生态系统研究环境变化对地下生态过程的影响提供了基础数据。

英文摘要：

The Wawushan Mountain National Forest Park in Sichuan Province,where there is relatively intact Castanopsis platyacantha-Schima sinensis formations,is a typical representative of the mid-subtropical moist evergreen broad-leaved forest in West China.Using the soil core method,this study investigated the fine root distribution and characteristics of carbon and nitrogen of sample C.platyacantha which is the main constructive species in this formation.The results were as follows：（1） The total fine root biomass of C.platyacantha was173.62 g · m~（-2） and the total biomass of live fine roots was 135.29 g·m~（-2）.（2） The fine root biomass,root length density,root surface area and specific root length decreased with the increase of soil depth,and their proportions in0- 30 cm layers were 67.23%,69.53%,69.48%and 57.20%,respectively;root length density,root surface area and specific root length decreased significantly with increasing root diameter,and 58.84%,52.59%and 51.36%of them were in the roots that diameter was less than 1 mm,respectively.（3） Root extinction coefficient in biomass,length and surface area of C.platyacantha fine root increased with the rise of the root diameter.（4） In the first soil layer,the roots C content increased significantly with the rising root diameter,but there was no significant difference in other soil layers;the C content of the roots whose diameter was less than 2 mm in the first soil layer was significantly lower than other soil layers,while the differences of roots C content of greater than 2 mm among soil layers was insignificant.（5） The roots N content decreased with the increase of soil depth and root diameter,while the C/N ratio value was opposite.These results reflected the vertical distribution of the secondary forest underground fine root system and nutrient characteristics,which would provided some basic data for revealing the subsurface ecological processes and the effects of environmental change on ecological processes in the underground in the eco