Abstract:The effects of 5 topographic factors on the spatial patterns of gap characteristics and 3 types of gap makers (GM) were investigated in mixed evergreen and deciduous montane forest at Mt. Dalaoling in the Three Gorges area. The mountain topography plays a significant role in the intensity, frequency, as well as spatial and temporal pattern of gaps and different types of GM. Gap disturbance intensifies with increasing altitude and slope, turning of slope position from ridge to valley bottom, and changing of slope shape from convex to concave. No apparent effect of exposure gradient was detected. Gap characteristics were shown to respond to gradients of a number of topographic factors: extended gap area, gap height, GM frequency and richness and average diameter at breast height (DBH) were all sensitive to the effects of topography. Maximum and average DBH of GM as well as extended gap area were significantly positively correlated with altitude and slope position. The number of GM decreased as the slope exposure turned from N to S, as slope increased, and as slope shape turned from convex to concave. A similar trend was found for species richness of gap makers along the gradient of slope and shape. The height of gaps and the forest in general decrease with increasing elevation and slope as well with decreasing slope position. The contribution of topography-induced variation is largest for the spatial variation of gap height and the average DBH of gap makers (75.9% and 67.0% respectively). The dominant topographic factors associated with the spatial pattern of the trunk snapping are elevation and slope position. Local slope position and shape control the distribution of standing death, while the key topographic factor determining the likelihood of uprooting treefall is slope.