اثرات بنه (pistacia atlantica desf) بر برخی ویژگی های بیولوژیک خاک توده های جنگلی ایران-تورانی (مطالعه موردی: منطقه فرک تفرش)

خاک به‌عنوان یکی از ارکان اکوسیستم نقش عمده‌ای در ایجاد تغییر و تنوع گونه‌های جنگلی ایفا می‌کند و در مقابل تیپ گیاهی نیز نقش قابل توجهی در تغییر و تحول ویژگی‏های فیزیکی، شیمیایی و زیستی خاک‌ها دارد. علاوه بر این‌ها، جوامع میکروبی خاک نقش بسیار مهمی در تجزیه و پایدارسازی مواد آلی در خاک و همچنین معدنی کردن عناصر غذایی آن داشته و به واسطه تنوع زیاد، خدمات بسیار مهمی در خاک ارائه می‌کنند. لذا ارزیابی درست و دقیق آنها با تکیه بر شاخص‌های کارآمد و قابل اعتماد می‌تواند اطلاعات مفیدی ارائه دهد. در این پژوهش، شاخص‌های تنفس میکروبی پایه، تنفس میکروبی برانگیخته، پتانسیل نیتریفیکاسیون، کربن زیست‌توده میکروبی و کسر متابولیک تحت تاثیر بنه ارزیابی شد. بدین منظور 15 نمونه از خاک زیر تاج و 15 نمونه از بیرون تاج که تحت حضور گیاه نبودند برداشت شده هر سه تکرار با هم ترکیب و به یک تکرار تبدیل شد، درنهایت پنج تکرار برای زیر تاج بنه و پنج تکرار به‌عنوان شاهد به‌دست آمد. نتایج بیانگر آن بود که اثر تیمار بر صفت‌ تنفس پایه، درصد رس، درصد سیلت و درصد شن معنی‌دار نشد. اثر تیمار بر صفت تنفس برانگیخته، کربن زیست‌توده میکروبی و پتانسیل نیتریفیکاسیون در سطح احتمال 1 درصد و کسر متابولیک در سطح احتمال 5 درصد معنی‌دار شد. همچنین مقدار میانگین تنفس برانگیخته، پتانسیل نیتریفیکاسیون و کسرمتابولیک در نمونه خاک زیر درخت بنه بالاتر از بیرون درخت بود. بیشتر ویژگی‌های زیستی در خاک تحت تاثیر بنه قرار گرفته و تغییرات معنی‌داری را نسبت به شاهد نشان دادند که این امر نشان‌دهنده اثر گذاشن بر حلقه‌های حیات در خاک خواهد بود.

effects of pistacia atlantica desf on some soil properties(case study: farak tafaresh region)

background and objectives: soil, as a fundamental component of the ecosystem, plays a crucial role in influencing and diversifying forest species. conversely, vegetation type also significantly modifies the physical, chemical, and biological characteristics of soils. additionally, soil microbial communities are essential for the decomposition and stabilization of organic matter, as well as the mineralization of nutrients. due to their high diversity, these communities provide critical ecosystem services within the soil. therefore, a proper and precise evaluation of these communities based on efficient and reliable indicators can yield valuable information.understanding soil characteristics forms a fundamental basis for forest management, impacting various ecological and forestry options. soil represents a vital natural resource for any nation and is non-renewable on a human timescale. given that forest degradation often begins with soil degradation, this research aims to measure the biological characteristics of the studied forest stands. it also enables long-term monitoring of the physical and chemical changes in the soils of these forest areas.materials and methods: in this research, the indicators of basic microbial respiration, stimulated microbial respiration, nitrification potential, microbial biomass carbon, and metabolic fraction were evaluated in relation to tree stems. to assess soil quality indicators, the biological characteristics of the soil were investigated. soil sampling was conducted for each selected tree trunk from a depth of 0-15 cm, located under the tree crown (specifically, in the area between the trunk and the outer edge of the crown) in the east direction of the tree. fifteen soil samples were randomly collected from the depth of 0 to 15 cm within each sample plot for the existing and dominant tree species (ranging from one to three species). these three soil samples from each plot were thoroughly mixed and combined into one composite sample. in total, five composite soil samples were prepared for each species by pooling the individual samples. additionally, fifteen soil samples were randomly collected from the depth of 0 to 15 cm within each sample plot, outside the crown and in areas without cover. these samples were also mixed well and combined into one composite sample for the plot, resulting in five soil samples for each sample plot. two treatments were tested: one under the tree canopy and the other in pasture-covered areas outside the canopy. in total, 30 soil samples were collected: 15 from beneath the canopy and 15 from outside the canopy in pasture-covered areas. in each treatment, three samples were combined to form one sample. five samples from each treatment were sent to the laboratory, and the coordinates of each sample were recorded to prepare a sampling map. immediately after sampling, part of the soil samples was stored in plastic bags, while the other part was kept at 4°c and transported to the laboratory for further analysis. the biological characteristics measured included microbial biomass carbon, basic respiration, stimulated respiration, and nitrification potential. ultimately, five replicates were obtained for the sub-canopy samples and five replicates for the control samples.. results: overall, the results indicated that most biological characteristics of the soil were significantly influenced by the tree canopy, showing notable changes compared to the control samples. this suggests that the canopy has a substantial impact on soil life cycles. however, the patterns observed in stimulated respiration, nitrification potential, and metabolic deficit under the canopy did not align with changes in microbial biomass carbon. the increased levels of stimulated respiration, nitrification potential, and metabolic fraction beneath the canopy suggest that these indices may be valuable indicators for assessing soil quality in the region. conversely, the observed reduction in microbial biomass carbon under the canopy compared to the control soil (outside the tree canopy) may be attributed to changes in substrate type or differences in microbial population diversity between the soils beneath and outside the canopy.the findings of this research highlight the importance of considering soil biological characteristics in evaluating soil quality, improving soil fertility, and managing plant nutrition. additionally, access to soil biological parameters, as a knowledge-based approach, provides experts and practitioners with valuable information for decision-making aimed at enhancing soil fertility and managing the nutrition of pistacia trees. conclusion: he results indicated that the treatment had no significant effect on basic respiration, clay content, silt content, or sand content. however, the treatment did significantly impact stimulated respiration, microbial biomass carbon, and nitrification potential at the 1% significance level, while the metabolic fraction showed significance at the 5% level. additionally, the mean values for stimulated respiration, nitrification potential, and metabolic deficit were higher in the soil samples collected under the pistacia tree compared to those outside the tree canopy. most biological characteristics in the soil were influenced by the tree canopy, exhibiting significant changes compared to the control samples. this suggests that the treatment positively affects the soil biological cycles.