Effect of environmental gradients on the quantity and quality of fallen logs in Tsuga longibracteata forest in Tianbaoyan National Nature Reserve, Fujian province, China

Abstract

We investigated the quantity and quality of fallen logs in different Tsuga longibracteata forest communities in the Tianbaoyan National Nature Reserve. We used redundancy analysis to determine the spatial distribution of fallen logs in the different forest communities and to analyze the relationships among stand structure, topographic factors and human disturbance. The volume, covered area, mean log length and number of fallen logs differed significantly among forest types (P 0.05). The log volume and covered area in different forest types showed the following trend: T. longibracteata pure forest elevation > slope position > bole height > tree height > slope aspect > density > basal area > slope gradient. The relative contribution of environmental variables on the total variance was topography (76%) > disturbance (42%) > stand structure (35%). Topography and disturbance combined explained 83% of the variance. Fallen logs quantity and quality were negatively related to elevation and slope position, and positively associated to human disturbance. The log volume decreased from northern to southern slopes. Environmental factors had the highest impact on class I (slightly decayed), and lowest impact on class V (highly decayed).