ارزيابي اكوسيستم هاي جنگلي به كمك مطالعات آنزيمي خاك با استفاده از درخت ملج به عنوان شاخص زيستي

Evaluation of forest ecosystems by means of soil enzyme studies with usage of Ulmus glabra as an bioindicator

Ulmus glabra is one of the most important species of the industrial forests of northern forests of Iran. It is distributed from Gorgan (at the northeast) to Arasbaran (at the northwest). Due to development of Dutch elm disease in their habitats, countless numbers of this species have died and its presence in the forest ecosystems is in danger of being eliminated. There have been so many studies and efforts to save this valuable species all over the world. One of the efforts has been focusing on the evaluating both sound and diseased individuals in order to study natural balance ecosystem on sound physiological trees. nowadays one of the methods that are used to assess the ecosystem is to study the soil microorganism enzyme. Based on decreasing living conditions from top to bottom of the soil and also increasing living limits biological potential (constraints) towards the deep soil, the frequency of micro and macro organisms will decrease. Therefore the soil enzyme activities that are themselves related to these activities have a descending gradient from top to lower levels of soil. If the natural process for any reason will be abrupt may lead to an unbalanced ecosystem, which at the end will result to migrate to the living organisms to the lower levels. This will cause the change of the gradient shape and will follow a fluctuation. In this research, following the theorem and emphasis on phosphomonoesterase enzyme study, the soil of four forest habitats were studied which were located at Gorgan, Noshahr, Asalem and Arasbaran. Sampling was done on during Spring of 2004. The soil samples were analyzed and phosphomonoesterase activities were measured. The goal was to study the effects of natural balance on both sound and diseased elm individuals in normal and abnormal ecosystems. The results were analyzed by GLM (General Linear Model) method and were compared by Tukey test. The results show that all of the sound elms are on the balance ecosystems (except one) and the diseased ones are on balanced. In addition the comparison of enzyme activity in each horizon in both groups shows that decrease of organisms activities in unbalanced elm ecosystem is quiet significant. In fact it can be stated that to save this valuable species it is not enough to only follow and find the resistant phenotypes and genotypes elms to Dutch elm disease. In other words, the interactions of different biological factors and balanced ecosystems have the main effects on saving sound elms, which may result to control the disease. This means that we have to induct a sound and powerful management for these forests.