黄土高原天然次生林木质残体的基础特征

Characteristics of woody debris in a natural secondary forest on Loess Plateau,China

以黄土高原黄龙山林区典型的天然次生林为研究对象，研究油松针阔混交林木质残体的基础特征．结果表明：研究区木质残体的总储量为10．73t·hm^-2，其中粗木质残体的储量为10．31t·hm^2，占总储量的96．09％；细木质残体的储量为0．42t·hm^-2，占总储量的3．91％；在粗木质残体中，倒木占了绝大部分，其次为枯立木，大枝和树桩贮量很少．采用指数模型来模拟研究区主要树种木质残体的分解密度，曲线拟合度很高．拟合结果表明木质残体密度随着腐烂等级的增加而呈下降趋势：木质残体的径级主要集中在20～30cm与30～40cm^2个径级，二者在株数与储量分布中占绝对优势．存在状态主要为中级腐烂状态，干扰与竞争是木质残体产生的主要因素．研究区天然次生油松针阔混交林木质残体的基础特征反映了该林区森林群落演替后期木质残体的结构特征．

Woody debris( WD) plays an indispensable role in ecosystem nutrient cycling and forest development. We studied the characteristics of WD in natural secondary Pinus tabulaeformis mixed stands in Huanglong Mountain,Loess Plateau. Results showed that:( 1) the gross reserve of WD of natural mixed forest was 10. 73 t·hm- 2,with 10. 31 t·hm- 2( 96. 09%) from coarse woody debris and 0. 42 t·hm- 2( 13. 91%) from fine woody debris. And coarse woody debris was mainly attributed to fallen trees;( 2)Exponential models indicated that decomposition density of WD was inversely proportional to decaying level;( 3) Woods at diameter of 20- 30 cm and 30- 40 cm were the main source of WD reserve in terms of quantity and proportion. To summerize,overall evaluation of WD in natural secondary forest provides insight into structural characteristics of wood in late succession stage of mixed forest development.