ارزیابی ویژگی‌های خاک زیر تاج پوشش درختان بنه (.pistacia atlantica desf) و بادام کوهی (prunus orientalis (mill.) koehne) (مطالعه موردی: تنگ خشک، سمیرم)

حفظ پایداری اکوسیستم‌های جنگلی به‌ویژه در مناطق خشک و نیمه‌خشک با پوشش غیرانبوه بستگی به حفظ کیفیت خاک دارد. بنابراین آگاهی از ویژگی‌های خاک‌های این مناطق می‌تواند در مدیریت آن‌ها نقش تاثیرگذاری داشته باشد. هدف از این پژوهش بررسی برخی ویژگی‌های فیزیکی، شیمیایی و زیستی خاک تحت پوشش بنه (.pistacia atlantica desf) و بادام کوهی (ارژن) (prunus orientalis (mill.) koehne) ذخیره‌گاه جنگلی تنگ خشک در شهرستان سمیرم بود. نمونه‌‌برداری از خاک رویین (0 تا 15 سانتی‌متر) زیر تاج پوشش گونه‌های بنه و بادام کوهی و بیرون از تاج (نمونه شاهد) به‌صورت تصادفی انجام شد. برخی ویژگی‌های شیمیایی (رسانایی الکتریکی، ph، نیتروژن کل، کربن آلی کل، پتاسیم، فسفر، آهن، روی، مس و منگنز قابل دسترس، کلسیم و منیزیم محلول، کربنات کلسیم معادل)، فیزیکی (چگالی ظاهری، بافت خاک، درصد رطوبت جرمی) و زیستی (تنفس پایه، تنفس برانگیخته، کربن زیست‌توده میکربی، پتانسیل نیتریفیکاسیون) خاک‌ها اندازه‌گیری شد. مقادیر رسانایی الکتریکی، کربن آلی و پتاسیم قابل دسترس در خاک زیر تاج پوشش درختان بنه و بادام کوهی به‌طور معنی‌داری بیش‌تر از خاک شاهد بود. عکس این روند برای عناصر فسفر، آهن و مس قابل دسترس مشاهده شد. میزان ph خاک تفاوت معنی‌داری بین زیر تاج پوشش با نمونه شاهد نداشت. میانگین درصد نیتروژن کل در خاک زیر تاج پوشش حداقل 1/46 برابر خاک شاهد به‌دست آمد. وجود تاج پوشش سبب کاهش معنی‌دار چگالی ظاهری خاک نسبت به خاک شاهد شد. مقادیر تنفس پایه و برانگیخته خاک در زیر تاج پوشش در مقایسه با بیرون تاج به‌طور معنی‌داری بیش‌تر بود، درحالی‌که بررسی مقادیر کربن زیست‌توده میکربی و پتانسیل نیتریفیکاسیون حاکی از افزایش معنی‌دار این ویژگی‌ها در خاک شاهد نسبت به زیر تاج پوشش بود. با توجه به نتایج پژوهش حاضر می‌توان بیان نمود که نوع گیاه و تاج پوشش آن، می‌توانند آثار متفاوتی بر ویژگی‌های خاک داشته باشند.

evaluation of soil properties under the canopy of wild pistachio (pistacia atlantica desf.) and wild almond (prunus orientalis (mill.) koehne) (case study: tang khoshk, semirom)

abstractstability of forest ecosystems, especially in arid and semi-arid areas with non-dense cover, depends on the soil quality maintenance. therefore, knowledge of the soil properties of these areas can play an effective role in their management. the purpose of this study was to investigate some physical, chemical and biological properties of the soil under wild pistachio (pistacia atlantica desf.) and wild almond (prunus orientalis (mill.) koehne) canopy in tang khoshk forest reserve of semirom. surface soil samples (0 to 15 cm) were randomly collected from the sites under the canopy of p. atlantica and p. orientalis species and outside the canopy (control sample). some chemical properties including electrical conductivity, ph, total nitrogen, organic carbon, available phosphorus, potassium, iron, zinc, copper and manganese, soluble calcium and magnesium and calcium carbonate equivalent, physical properties including bulk density, soil texture and gravimetric water content, and biological properties of basal respiration, induced respiration, microbial biomass carbon and nitrification potential of soils were measured. the electrical conductivity, organic carbon and potassium in the soil under the canopy of p. atlantica and p. orientalis species were significantly higher than those in the control soil. the reverse trend was observed for the available phosphorus, iron and copper. the mean total nitrogen in the soil under the canopy was at least 1.46 times higher than that of the control soil. soil bulk density decreased significantly at the presence of canopy compared to the control soil. the basal and induced respirations of the soil under the canopy were significantly higher than in the canopy outside, while the microbial biomass carbon and nitrification potential were significantly greater in the control soil compared to the sites under the canopy. according to the results of current research, the type of plant and its canopy can have different effects on soil properties.background and objective: soil is one of the important components in the forest ecosystem, which, along with other ecological factors, determines the distribution pattern of vegetation. on the other hand, trees and their canopy provide various amounts of organic matter with different chemical compositions, therefore can affect the soil properties (2). semi-dense or thin forests of arid and semi-arid regions make up about 86% of the country’s forest area. the effect of canopy on soil properties in arid and semi-arid ecosystems is quite evident (1). this study compared some physical, chemical and biological properties of the soils under the wild pistachio (pistacia atlantica desf.) and wild almond (prunus orientalis (mill.) koehne) canopy in the tang khoshk forest reserve, semirom.methods: the research was carried out in tang khoshk forest reserve, located 41 km south of semirom city. the main tree and shrub cover of tang khoshk are wild pistachio (pistacia atlantica desf.) and wild almond (prunus orientalis (mill.) koehne), respectively. a square plot of one hectare was selected in the region, which was a good representative of the area with a suitable cover of p. atlantica and p. orientalis. fifteen soil samples were randomly collected from the layer of 0 to 15 cm under the canopy of each plant. then, all three soil samples were well mixed with each other and a composite sample was obtained. similarly, soil samples were collected from the outside of canopy, as control. some chemical, physical and biological properties of the soils were measured. the data was statistically analyzed in the form of a completely random design using sas software.results: the mean total nitrogen contents in the soils under the canopy of p. orientalis and p. atlantica, and control were in the order 0.40 > 0.38 > 0.26%, respectively. the organic carbon contents in the soils under the canopy of p. atlantica and p. orientalis were 3.40 and 3.62%, respectively, while it was 2.33% in the control soil. different plant tissues including aerial parts, dead leaves and tree roots are added to the soil as the main source of organic matter. the secretions of the roots into the soil are also another factor that increase the soil organic matter (3). soil bulk density in the samples collected under the canopy was significantly lower than the control. in other words, the soil porosity under the canopy is higher compared to the control. the highest amount of basal respiration was observed in the soil under the p. orientalis canopy, which was significantly higher than others. a similar trend was observed for the induced respiration. the maximum amount of microbial biomass carbon was obtained in the control soil, which was significantly higher than in the soil under the canopy. the results of nitrification potential also had a trend similar to that of microbial biomass carbon.conclusions: the canopy of p. atlantica and p. orientalis improved the soil physical and chemical properties. it seems that basal and induced respirations under the canopy can be useful to evaluate the soil quality in the region. while the microbial biomass carbon and nitrification potential decrease under the canopy compared to the control soil, could be due to the change in the type of substrate, and these properties are probably not suitable indicators for characterizing the soil quality.references:1. anonymous (a). 2020. forest, range and watershed organization, isfahan province.2. bazgir, m., menati, t., rostaminya, m., mahdavi, a., 2020. soil microbial biomass and activity of oak forest in three different regions in ilam province. journal of soil biology 8(2): 155–164. (in persian with english abstract)3. rostamizad, p., hosseini, v., mohammadi samani, k., 2018. the effects of persian turpentine (pistacia atlantica desf) single-trees crown on the amount of nutrients in the forest soil (sarvabad region in kurdistan province). journal of water and soil science 22(2): 383–393. (in persian with english abstract)