The Regeneration Structure and Biodiversity of Trees and Shrub Species in Understory of Pure and Mixed Oak Plantations

The regeneration structure and biodiversity of trees and shrub species in the understory of pure and mixed oak plantations were investigated at Chamestan Forest and Rangeland research station. Planted species included oak (as the main species) and maple and nettle trees (as associated species). These species were planted in 1995 on the basis of a split plot design with two mixtures (oak-maple and oak-nettle tree) and four mixing rates (including oak rate: 40 %، 50 %، 60 % and 70 %). All the seedlings and saplings of woody plants were divided into two height classes including 15-200 cm and more than 200 cm. In the biodiversity study، the Berger-Parker dominance index، Fisher alpha diversity index، Margalef richness index and Equitability J evenness index were used. The results showed that the abundance and diversity of regenerated species in the understory of mixed plantations of oak-nettle tree was greater than in a pure stand of oak and a mixed oak-maple stand. Crown cover and litter layer depth showed a negative significant effect on their abundance and richness. The presence of primary forest species in the understories of mixed plantationa showed the usage of these plantations in the development of succession in natural forests.