Defining the most appropriate transect method for estimation of Basal area: case study in Dalab forests, Ilam Province

Forest management and planning require a proper level of quantitative and qualitative information on forest stands. Such data is usually collected by means of different sampling methods e.g. transect method. This study aims at exploring the most appropriate sampling method for estimating basal area incorporating their on precision and cost in a case study of Dalab forests of Ilam province. To this aim, a representative area encompassing 37.2 hectares of forests was selected and surveyed by a 100% inventory. Three sampling methods (transect based on probability theory, transect with fixed 50 m length and transect with fixed number of 5 trees) were applied. Based on a regular random sampling pattern, 37 samples were selected for each sampling method in a 100 × 100m grid. The results showed significant difference between the measured basal area and those estimated by any of the three sampling methods. The E%2×T criteria was additionally applied for a better evaluation of the applied sampling methods. These cost and precision criteria turned out the transect method with fixed number of 5 trees to be the superior to other tested methods, which can be further suggested for estimation of basal area of trees in Dalab Forests of Ilam province.