Comparison of inventory methods for woody species biodiversity assessment in Northern Zagros forests (Case study: Blakeh Forests, Baneh)

To assess the diversity of woody species (as a major task to understand the changes in forest ecosystem), collection of appropriate qualitative and quantitative data is of particular importance. This study attempts to introduce the most appropriate sampling method for estimating woody species diversity in the northern Zagros forests. An area of 40 ha in Blakeh forest was selected, in which 40 quadrangular samples of one ha each in a 100 m × 100 m grid were established. In each plot a set of characteristics such as species, tree position, the number of trees and smallest/largest crown diameter were measured. All inventory data were processed in GIS to produce a dispersion map of trees. Different sampling methods (rectangular samples with 20 × 50 m, transect methods with 50 and 100 m length, quadrangular method with 10 × 10 m, 15 × 15 m, 20 × 20 m, 40 × 40 m sample sizes) were implemented in a 100×100m sampling grid. The %E2 ×T criterion was used to compare the results. In addition, quadrangular methods were analyzed using the Shannon-Wiener and Simpson diversity and the Margaleff and Minhinick enrichment indices. The quadrangular method with 40 × 40 m and 20 × 20 m sample size was shown to be the most appropriate method for estimating stem number per ha and percentage of canopy cover.