Study on effect of cutting method exploitation on survival and generation of Tragacanth producing plants.

Tragacanth is one of the most important by-products in Isfahan range lands. It takes From Astragalus gossypinus, A. keyserlingii, A. parrowianus and A. sofficus. This study was carried out in tow regions, Yahya-Abad and Ghale Mosakhan since 2000 to 2006 for finding out the effects of exploitation on survival and regeneration of mentioned species. Experimental plant of this study was randomized complete block design in factorial format with 3 replications. Treatments were including: number of cuts on plant (2 and 3 cuts) and number of exploitation (2, 4 ,6 times and 0). Each plot had 30 plants which had not exploitated before. Gum production mortality, 1000 seeds weight and plant coverage were measured and analyzed in each plot. According to the results: exploitation limited the coverage of plants. Number of cuts (2 and 3 cuts) on all 4 species didn&rsquot have any significant effects on Gum production. The highest amount of Gum production on A. gossypinus was 72.25 grams per plants in 6 times exploitation which didn&rsquot have any significant difference with 4 times one. The highest plant mortality was in 6 times exploitations for 4 spacing.The highest amount of Gum production on A. keyserlingii, was 156.9 grams in 6 times exploitations which didn&rsquot have any significant difference with 4 times one. The highest amount of Gum production on A. parrowianus averagely was 179.8 grams in 6 times exploitations which had a significant difference with 4 times one. The highest amount of Gum production on A. sofficus averagely was 120.3 gram in 6 times exploitations which didn&rsquot have any significant difference with 4 times one. Exploitation affected on 1000 seeds weight in A. gossypinus and A. sofficus and decreased them and caused them to an incomplete seed production on plants. In 2005 the highest amount of Gum production on A keyserlingii averagely was 129.74 grams in 6 times exploitation and interaction of 6 times exploitation with 2 cuts, The highest gum production in A. keyserlingii averagely was 121.56 grams in 6 times exploitations which didn&rsquot have any significant difference with 4 times one. . The highest amount of Gum production on A. parrowianus averagely was 127.22 grams in 4 times exploitation. The highest amount of Gum production on A. sofficus averagely was 107.55 grams in 2cuts and interaction of 2 times exploitation with 2 cuts which didn&rsquot have any significant difference with 4 and 6 times exploitation with 2 cuts and 4 times exploitation with 3 cuts. Finally according to the plants mortality percentage in 4 species, 4 times exploitation with 2 cuts can be recommended.