Application of T-square sampling method in Zagross forests (Case Study: Kermanshah province)

T-square sampling method is one of the distance sampling methods for estimating the plant density and canopy cover. For plant density measurements, three formulas, of Diggle and Byth have been used. In this study, applicability of these formulas regarding to accuracy of estimate for density and canopy cover of Zagross Oak (Quercus brantii) forests in research and educational Forest of Qasr-e Shirin (Kermanshah province) were examined. At first, 50 hectares of the forest area was selected and the inventory of the population was carried out. Then, 50 systematic random sampling points for T-square sampling method in this area were measured and recorded. The results show that none of the formulas could provide an acceptable estimate based on 10% accepted accuracy; even though, the Byth formula has more accuracy level for density and crown coverage for this kind of forests