Selecting the most appropriate distance method for estimating the density of Astragalus gossypinus Fisch. in rangelands of Kurdistan province

Assessing vegetation characteristics (e.g. cover and density) is an essential part of quantitative ecology and is also required for vegetation management. This research was carried out to select the most appropriate distance method for estimating density of Astragalus gossypinus in rangelands of Kurdistan. Four range sites including Khoroseh in Sanandaj, Baharestan and Zarrineh in Divandarah and Varmakan in Kamyaran were selected. In each range site, four places with size of 5000 m2 (100 × 50 m) were selected and all Astragalus gossypinus plant individuals were counted. The average number of plants in the 4 places was used as reference or control for other methods. Systematic random sampling was used to establish 100 meters transects in each place. Sample size was determined by statistical method and using data from the first 30 observations. Closest Individual, Nearest Neighbor, Random Pairs, Quarter-Point Center and Third Closet Individual techniques were used to measure A. gossypinus density. The density of A. gossypinus was calculated using Ecological Methodology software. The obtained results from each method compared with reference method and relative density difference between each method with the reference was calculated. Although measurement time did not vary between the methods, their accuracy and precision were significantly different. Random Pair and Quarter-Point Center methods were identified as the most appropriate approaches for measuring A. gossypinus density.