Comparison of Species Diversity of Natural and Man-made Gaps at Different Physiographic Conditions in Siahkal Forests of Gilan Province

<p</pThis study was conducted to compare regeneration density and biodiversity indices in the natural and man-made gaps in the Tutaki forests of Siahkal in Gilan province. Data were collected from 60 gaps (including 30 natural and 30 man-made gaps). The results of species composition indicated that three tree species including Diospyros lotus L., Carpinus betulus L. and Alnus glutinosa L. in both gaps. In the shrub floor, for both gaps and all kinds of species, the  average number in hectares of man-made gaps (with the exception of  Ilex) was  higher than that of natural gaps. Ilex & Crataegus pentagyna indicated the significant difference at 95% level between 2 gaps. Also, the regeneration density for all species at the natural gaps was more than man-made gaps and the average number in hectares for Diospyros lotus, Alnus glutinosa and Acer sp indicated the significant difference at the 95% level between the 2 gaps. So the regeneration of Fagus orientalis Lipsky was observed only in the natural gaps. The results of biodiversity indices  also revealed that in natural gaps, the average of diversity, evenness and richness had the highest value, whereas in shrub, the average of these indices had the highest value.