تاثیر کاربری اراضی بر برخی شاخص‌های میکروبی خاک در منطقه لاسجرد، استان سمنان

پژوهش حاضر به‌منظور بررسی نقش کاربری‌های مختلف اراضی بر برخی شاخص‌های میکروبی خاک در لاسجرد سمنان در دو عمق صفر تا cm10 و 10 تا cm30 انجام شد. بعد از تعیین اراضی مختلف به عنوان تیمارهای تحقیق، نمونه برداری از خاک صورت گرفت؛ به این صورت که یک پروفیل در مرکز و چهار پروفیل بصورت متقاطع در اطراف با در نظر گرفتن اثر حاشیه ای، حفر شد. داده های مربوط به ویژگی های میکروبی خاک با بهره‌گیری از آزمون فاکتوریل در قالب طرح کاملا تصادفی با 5 تکرار و آزمون دانکن تجزیه و تحلیل شد. در عمق اول، تنفس پایه خاک، تنفس برانگیخته، c زیست‌توده میکروبی، n زیست‌توده میکروبی، ضریب میکروبی و ضریب متابولیک تحت تاثیر کاربری‌های مختلف قرار گرفته‌اند. بیشترین میزان تنفس پایه خاک در اراضی رها شده معادل 0.424mgco2g^-1dm24h^-1 و کمترین میزان در کشت .triticum aestivum l و برابر mgco2g^- 1dm24h^-1 0.006 اندازه‌گیری شد. همچنین در عمق دوم، تنفس پایه خاک، ضریب میکروبی و ضریب متابولیک از انواع کاربری ها متاثر شدند، بطوری که بیشترین میزان ضریب متابولیک در اراضی رها شده برابر 0.068mgco2-cg-1mbcday^-1 و کمترین آن در اراضی کشت .medicago sativa l برابر 0.013mgco2-cg^-1mbcday^-1 مشاهده شد. بطور کلی شاخص های میکروبی خاک به تغییرات کاربری اراضی حساس هستند و اولین عمق مورد بررسی، بیشترین تاثیر را از این شاخص ها داشته است. تغییر اراضی مرتعی به کاربری کشاورزی، با شکستن خاکدانه های خاک، سرعت تجزیه مواد آلی را افزایش می‌دهد و ذخیره‌سازی عناصر غذایی، جمعیت، ترکیب و فعالیت میکروبی خاک را به‌عنوان شاخص کیفیت، سلامت و حاصلخیزی خاک کاهش می‌دهد.

influence of different land uses on some soil microbial indices (case study: lasjerd, semnan province, iran)

introduction widespread lands in arid, semi-arid, or dry sub-humid areas of the world have been influenced by the consequences of the land degradation resulting from natural factors and human activities like agriculture, changes in the land use. a large part of iran is located in arid and semi-arid regions. the degradation of soil can be greatly impacted by agricultural activities, incorrect management, and improper land management. the most suitable solution to reduce the negative effects of land use change on the desert is to choose the best type of land management with the least degradation. the fragile nature of these ecosystems and the large area of arid and semi-arid areas of the country require proper and accurate management. soil is an important and valuable terrestrial source of oc storage, which plays a significant role in the global c cycle by storing about 1500 billion tons of c. the total c in microbial biomass is 1.4% of the total soc. demonstrating the significant contribution of this sector to the global c cycle. land use change can be one of the most important factors of land degradation that affects the quality and quantity of soil organic c, and soil characteristics. the present study was done to investigate the role of different land uses including rangeland as control, abandoned land, triticum aestivum l. cultivation, hordeum vulgare l. cultivated lands and medicago sativa l. cultivation, on some soil microbial indices such as basal soil respiration, substrate induced respiration, microbial biomass carbon, microbial biomass nitrogen, microbial quotient, metabolic coefficient and carbon access index, in lasjerd , semnan province in two depths of 0 to 10 cm and 10 to 30 cm . material and methods the initial step was to select various treatments that included rangeland as control treatment, abandoned land, triticum aestivum cultivation, hordeum vulgare cultivated lands and medicago sativa cultivation. in the second step, soil sampling was performed at two depths of 0-10 and 10- 30 cm in five replications. in this regard, one soil profile in the center and four other profiles were dug in the form of a cross, considering the marginal effect. the samples needed for soil biological tests were carried and stored in the refrigerator containing dry ice and biological tests were performed later. the considered factors were measured by valid scientific guidelines and methods. data related to soil microbial properties were analyzed by a factorial test in the form of a completely random design with five repetitions. all statistical computing was done using spss 19 software and the mean comparison tests were performed by duncan test . results and discussion the results of the present study indicated that there is significant impact of the treatments on the properties studied at the two depths, at the first soil layer equals to the depth of 0 to 10 cm, basal soil respiration, substrate induced respiration, microbial biomass carbon, microbial biomass nitrogen, microbial quotient, and metabolic coefficient have been affected by different land uses, as the highest level of basal soil respiration in the abandoned land equals to 0.424 mgco2g-1dm24h-1 and the lowest in triticum aestivum cultivation 0.006 mgco2g-1dm24h-1, as well as the second depth- 10 to 30 cm- basal soil respiration, microbial quotient, metabolic coefficient are affected by different types of land uses. the highest amount of metabolic coefficient was observed in abandoned lands as 0.068 mgco2-cg-1mbcday-1 and the lowest was found in medicago sativa cultivation lands equals to 0.013 mgco2-cg-1mbcday-1. soil microbial indices are sensitive to land use changes. the first top 10 cm of the soil studied, has been most affected by these indices. due to the failure of soil pedons, the change in land use from rangeland to agricultural lands increases the speed of litter decomposition and decreases the