Species diversity of herb and shrub layers in gaps of a mixed conifer broad-leaved forest in Taiyue Mountain of Shanxi Province

The gaps of forest gaps were estimated by the "press release" method and from experience.We studied the characteristics of edge effects of gaps in relation to diversity in the herb and shrub layers by accurately measuring the areas of forest gaps.Results show that the diversity index in gaps was higher than that in the closed forest.The edge effect of gaps on species diversity in the herb layer was not obvious.Species diversity in the shrub layer of gaps varied with age of the gap:during their first and last stages diversity was larger than that of canopy gap,but this trend was reversed during its middle stage.Species diversity in the herb and shrub layers was positively related to the size of gaps.The augment of species diversity in the herb layer was accomplished quickly and it was delayed in the shrub layer during its first stage.The species diversity index was negatively related to the age of the gap during the middle to last stages.Gaps are shelters for accidental species.