Effects of pimento (Pistacia atlantica Desf) on some soil biological characteristics of Iran-Turanian forest masses (Case study: Farak Tafaresh region)

Soil, as one of the elements of the ecosystem, plays a major role in changing and diversifying forest species, and on the other hand, the type of vegetation also plays a significant role in changing and transforming the physical, chemical and biological characteristics of soils. In addition to these, soil microbial communities play a very important role in the decomposition and stabilization of organic matter in the soil, as well as in the mineralization of its nutrients, and due to their great diversity, they provide very important services in the soil. Therefore, their correct and accurate evaluation based on efficient and reliable indicators can provide useful information. In this research, the indices of basic microbial respiration, stimulated microbial respiration, nitrification potential, microbial biomass carbon and metabolic fraction were evaluated under the influence of stem. In order to obtain the soil quality indicators, the biological characteristics of the soil were investigated. Soil sampling was taken for each selected trunk tree from a depth of 0-15 cm under the tree crown (in the distance between the trunk and the end edge of the crown) in the east direction of the tree. 15 soil samples were randomly taken from the depth of 0 to 15 cm in each sample plot for this existing and dominant tree species (one to three species) and all three soil samples in each sample plot were well mixed and made into one composite sample for each sample plot. Species were transformed (five soil samples for each species). Also, 15 soil samples were randomly taken from the depth of 0 to 15 cm inside each sample plot, outside the crown and in the place outside the cover, and all three soil samples were mixed well and made into one composite sample for the sample plot. transformed (5 soil samples for each sample plot). In this research, two treatments were used, one under the canopy and the other outside the canopy with pasture cover. A total of 30 soil samples were collected, 15 samples under the canopy and 15 outside the canopy with pasture vegetation, in each treatment three samples were combined and converted into one sample. In fact, for each treatment, 5 samples were sent to the laboratory, and the coordinates of each sample were recorded in order to prepare a sampling map. Immediately after sampling, a part of the soil samples was kept in plastic bags and the other part was kept in cold conditions (4°C) and transferred to the laboratory for further analysis.

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. The results showed that the effect of treatment on basic respiration, clay percentage, silt percentage and sand percentage was not significant. The effect of treatment on stimulated respiration, microbial biomass carbon and nitrification potential was significant at 1% probability level and metabolic fraction at 5% probability level. Also, the average value of stimulated respiration, nitrification potential and metabolic deficit in the soil sample under the baneh tree was higher than outside the tree. Most of the biological characteristics in the soil were affected by the stem and showed significant changes compared to the control, which will indicate the effect of the application on the life rings in the soil. In general, the results indicated that most of the biological characteristics in the soil were affected by the log and showed significant changes compared to the control, which would indicate the effect of the application on the life cycles in the soil. The trend of changes in stimulated respiration and the potential of nitrification and metabolic deficit under the canopy was not consistent with the trend of changes in microbial biomass carbon. Due to the increase in the characteristics of stimulated respiration and the potential of nitrification and metabolic fraction under the crown of the corm cover in the region, these indices can be useful for evaluating the soil quality of the region. While the reduction of microbial biomass carbon under the canopy compared to the control soil (outside the tree canopy), could be due to the change in the type of substrate or the difference in the diversity of the microbial population in the soil under the canopy or outside it. The results of this research show that in evaluating soil quality, improving soil fertility and managing plant nutrition, the role of soil biological characteristics cannot be ignored. On the other hand, having the biological parameters of the soil, as a knowledge-based approach with accessibility and flexibility, more information can be provided to experts and users for decision-making to improve soil fertility and manage root tree nutrition.