Growth parameters of Pinus nigra J.F. Arnold and Picea abies (L.) H. Karst. plantations and their impact on understory woody plants in above-timberline mountain areas in the north of Iran

Abstract

We investigated the growth parameters of 20-year-old plantations of Pinus nigra J.F. Arnold and Picea abies (Linnaeus) H. Karsten and their impact on understory woody plants and we compared them with a natural stand in above-timberline mountain areas. 30 sample plots (each of 400 m2 in area) were systematically established on each site. Tree height, DBH, collar diameter, crown diameter and crown length of all trees were measured in each sample plot. The results of the diameter growth analysis of both species covered by this study showed higher numerical values in P. nigra than in P. abies. On the contrary, what was observed for data concerning height growth, showed higher numerical values in P. abies than in P. nigra. These conclusions showed that P. nigra has a lower slenderness ratio than the other species and is therefore more resistant to the adverse weather. Considering the effects on biodiversity, the planting of P. nigra showed a significant increase in density and species richness of woody plants while it decreased the diversity and evenness compared to the natural stands and plantations of P. abies.

Keywords

• ecotone
• slenderness ratio
• tree species importance value
• woody species diversity