ارزیابی شناسه‌های زیستی کیفیت خاک‌های لسی زیر پوسته‌های زیستی گلسنگی شمال استان گلستان

نوع مقاله: کاربردی

نویسندگان

1 دانشجوی دکتری گروه علوم خاک دانشگاه علوم کشاورزی و منابع طبیعی گرگان ، ایران

2 استاد گروه علوم خاک دانشگاه علوم کشاورزی و منابع طبیعی گرگان ، ایران

3 استادیار سازمان پزوهش‌های علمی و صنعتی، تهران، ایران

4 استادیار گروه علوم خاک دانشگاه علوم کشاورزی و منابع طبیعی گرگان ، گرگان، ایران

5 استاد موسسه جغرافیا دانشگاه کلن، آلمان

10.22055/agen.2019.26696.1445

چکیده

پوسته­های زیستی خاک گروه گسترده­ای از سیانوباکتری­ها، جلبک­های سبز، گلسنگ­ها، خزه­ها و جانداران دیگر هستند، که در سرزمین­های خشک و نیمه خشک کارکرد ویژه ای در چرخه جهانی کربن و افزایش کربن آلی خاک دارند. کربن آلی خاک که آمیخته­ای ازبخش های گوناگون است، یکی از شناسه­های مهم برای بررسی کیفیت خاک می­باشد. پوسته­های زیستی و فیزیکی خاک، پوشش اصلی سطح لس­های شمال استان گلستان در شیب­های رو به جنوب و قله شیب می­باشند. از اینرو بررسی باهدف شناخت کارکرد پوسته­های زیستی گلسنگی بر کربن آلی و بخش­های فراهم کربن خاک انجام شد. پس از انجام بررسی میدانی دو گونه از پوسته­های زیستی گلسنگی غالب گردآوری و پس از شناسایی در آزمایشگاه، نمونه‌برداری از خاک زیر آن­ها و پوسته­های فیزیکی از عمق 0-2 و 2-5 سانتی­متری انجام شد. کربن و بخش­های گوناگون کربن آلی  فراهم نمونه­های خاک اندازه‌گیری شدند. یافته­ها نشان داد که پوسته­های زیستی گلسنگی مایه افزایش کربن آلی و بخش‌های کربن فراهم خاک در برابر پوسته فیزیکی شده­اند. خاک­های زیر پوشش گونه  Diploschistes diacapsis دارای اندازه­های بیشتر کربن و بخش­های فراهم کربن آلی خاک در برابر گونه Fulgensia fulgens و پوسته فیزیکی  بودنند. کربن آلی همبستگی بالایی با کربن بیومس میکروبی، کربوهیدرات و کربن عصاره­گیری شده با آب داغ داشت. بنابراین می­توان از این سه شناسه برای ارزیابی کیفیت خاک در این سرزمین بهره­گیری کرد. بودن پوسته­های زیستی گلسنگی مایه افزایش کربن آلی خاک می­شود و در نتیجه سطح افزایش کیفیت و پایداری خاک­های لسی منطقه می­شود.

کلیدواژه‌ها


عنوان مقاله [English]

Evaluating biological attributes of soil quality in loessial soils under lichen biological soil crusts in northern Golestan province

نویسندگان [English]

  • M. Soleimanzadeh 1
  • F. Khormali 2
  • M. Sohrabi 3
  • R. Ghorbani Nasrabadi 4
  • M. Kehl 5
1 Ph.D Student, Gorgan University of Agricultural Sciences and Natural Resources, Iran
2 Professor, Gorgan University of Agricultural Sciences and Natural Resources, Iran
3 Assistant Professor, Iranian Research Organization for Science and Technology, Iran
4 Assistant Professor, Gorgan University of Agricultural Sciences and Natural Resources, Iran
5 Professor, Institute of Geography, Cologne University, Germany
چکیده [English]

Introduction Biological soil crusts are a widespread community of cyanobacteria, green alga, lichens, mosses, and other organisms. These crusts play important roles in arid and semi-arid ecosystems, such as carbon and nitrogen fixation, soil protection against water and wind erosion, and water retention. In arid and semi-arid regions, the biological soil crusts also possess a key role in the global carbon cycle due to the carbon fixation (photosynthesis) and its release (respiration) into the atmosphere. These organisms increase the organic carbon content of the soil in arid and semi-arid regions by performing photosynthesis. Soil organic carbon is a mixture of various components and one of the important characteristics for soil quality evaluation. Biological attributes of soil quality include many soil components and processes related to the organic material cycle, such as total organic carbon and nitrogen, microbial biomass, carbon and nitrogen mineralization, labile fractions of elements, the activity of enzymes, and animals and plants in soil. These biological attributes respond rapidly to natural and human-derived changes, and therefore they are used as indices for quality of soils. Biological soil crusts are the main cover of the loess soil surface in the northern parts of Golestan Province. The region that was selected to be studied in the province was Maraveh Tappeh. This region has arid and semi-arid climate and is attributed to low vegetation, especially on the slopes to the south. In these slopes, biological and physical crusts are dominant. Therefore, a study was conducted to investigate the effect of lichen biological soil crusts on organic carbon and different fractions of labile carbon.
Materials and Methods After extensive field studies, two species of lichen biological soil crusts were collected and transferred to the laboratory for identification. The results elucidated that the studied species were Diploschistes Diacapsis (Ach.) Lumbsch, and Fulgensia Fulgens (Sw.) Elenk, based on taxonomical identification. Soil sampling was done from 0-2 and 2-5cm depths under lichen biological and physical crusts. Soil samples were transferred to the laboratory, and then the organic carbon, carbohydrate, permanganate oxidizable carbon, microbial biomass carbon, cold-water extractable organic carbon, and hot-water extractable organic carbon were measured by standard methods.
Results and Discussion Results show that lichen biological soil crusts led to the increase in soil organic carbon and different fractions of labile organic carbon related to the physical crust. As a result, the highest values for these traits were observed in soils affected by lichen biological soil crusts. Soil covered by the Diploschistes Diacapsis species had the highest amount of soil organic carbon and different fractions of labile organic carbon in comparison to the Fulgensia Fulgens species in 0-2cm depth, which had a significant difference at 5% probability level. the physical crusts had the least amount of soil organic carbon and different fractions of labile organic carbon related to the lichen biological soil crusts, which was caused by the loss of topsoil and the lack of biological coverage. There was a positive correlation between the measured traits. There was a high correlation between hot water-extractable carbon and carbohydrate. There were high correlation coefficients between organic carbon with microbial biomass carbon, hot water-extractable carbon, and carbohydrate. In general, there was a high correlation coefficient between hot water-extractable carbon with organic carbon and other labile fractions of organic carbon except for cold water-extractable carbon, whereas there was low correlation coefficient between hot water-extractable carbon with organic carbon and other labile fractions of organic carbon.
Conclusion According to the results attained from the following study, the presence of biological soil crusts on loessial soils led to the increase in organic carbon, carbohydrate, permanganate oxidizable carbon, microbial biomass carbon, cold-water extractable organic carbon, and hot-water extractable organic carbon. Diploschistes Diacapsis Species have the highest impact on organic carbon and different fractions of labile organic carbon. The High correlations show that the best attributes to evaluate the quality of soil organic carbon in the studied area are microbial biomass carbon, carbohydrate, and hot water-extractable carbon and these may be used as a good indicator to evaluate soil quality. The studied area falls within the arid and semi-arid climate, and given the erosion-prone nature of loess deposits, improper management may lead to severe problems, such as erosion and dust production. Hence, protecting lichen biological loess crusts against human activity and livestock grazing may result in lower water and wind erosion, and increase soil quality in this region.

کلیدواژه‌ها [English]

  • Organic and labile carbon
  • Physical crusts
  • Soil quality indicators
  • Terricolous lichens