evaluation of k-tree distance and fixed-sized plot sampling in zagros forests of western iran

three k-tree distance and fixed-sized plot designs were used for estimating tree density in sparse oak forests. these forests cover the main part of the zagros mountain area in western iran. they are non-timber-oriented forest but important for protection purposes. the main objective was to investigate the statistical performance of k-tree distance and fixed-sized plot designs in the estimation of tree density. in addition, the cost (time required) of data collection using both k-tree distance and fixed-sized plot designs was estimated. monte-carlo sampling simulation was used in order to compare the different strategies. the bias of the k-tree distance designs estimators decreased with increasing the value of k. the moore’s estimator produced the smallest bias, followed by kleinn and vilcko andthen prodan. in terms of cost-efficiency, moore’s estimator was the best and prodan’s estimator was superior to kleinn and vilcko’s estimator. cost-efficiency of k-tree distance design is related to three factors: sample size, the value of k, and spatial distribution of trees in a forest stand. moore’s estimator had the best statistical performance in terms of bias, in all four-study sites. thus, it can be concluded that moore’s estimator can have a better performance in forests with different tree distribution.