بررسی تأثیر پوسته های زیستی بر برخی از خصوصیات زیستی خاک (مطالعه موردی، مراتع قره قیر استان گلستان)

نوع مقاله : مقالات پژوهشی

نویسندگان

1 دانشگاه تهران

2 سازمان پژوهش های علمی و صنعتی ایران

چکیده

پوسته های زیستی خاک، اجتماعی تنگاتنگ بین ذرات خاک و موجودات زنده ای از قبیل سیانوباکتری، جلبک، قارچ، گلسنگ ها و خزه ها در نسبت های مختلف هستند که بر روی سطح خاک یا در داخل چند میلی متر فوقانی آن مستقر می گردند. این پوسته ها فرایندهای ابتدائی اکوسیستم از جمله تثبیت کربن و نیتروژن اتمسفری، و وضعیت آبی را تحت تاثیر قرار می دهند. این پژوهش به منظور بررسی تاثیر پوسته های زیستی بر برخی از خصوصیات زیستی خاک در مراتع قره قیر استان گلستان انجام شد. بدین منظور خصوصیاتی چون جمعیت میکروبی خاک، تنفس میکروبی، کربن و نیتروژن زیتوده میکروبی و دیگر خصوصیات موثر بر آنها از قبیل کربن آلی، نیتروژن کل، قابلیت هدایت الکتریکی، درصد رطوبت قابل دسترس، در دو عمق 5-0 و 15-5 سانتی متری دو تیمار پوسته دار و بدون پوسته در چهار ناحیه، اندازه گیری شدند. سپس داده ها در قالب طرح آشیانه ای مورد تجزیه و تحلیل و میانگین داده ها با آزمون دانکن مورد مقایسه قرار گرفتند. نتایج به دست آمده نشان دادند که جمعیت میکروبی، تنفس، کربن و نیتروژن زیتوده میکروبی و همچنین کربن آلی، نیتروژن کل و رطوبت قابل دسترس خاک در هر دو عمق مذکور به ویژه عمق سطحی در تیمار پوسته دار نسبت به تیمار بدون پوسته به طور معنی داری بیشتر است اما قابلیت هدایت الکتریکی در تیمار پوسته دار نسبت به بدون پوسته در هر دو عمق به طور معنی داری کمتر است. در کل می توان نتیجه گرفت که پوسته های زیستی موجب بهبود وضعیت خاک و فراهم نمودن زیستگاهی مناسب برای ریزجانداران هتروتروف خاک و افزایش فعالیت آنها می شوند.

کلیدواژه‌ها


عنوان مقاله [English]

Investigating the Effect of Biological Crusts on Some Biological Properties of Soil (Case Study: Qare Qir Rangelands of Golestan Province)

نویسندگان [English]

  • J. Kakeh 1
  • M. Gorji 1
  • A. A. Pourbabaei 1
  • A. Tavili 1
  • M. Sohrabi 2
1 University of Tehran
2 Iranian Research Organization for Science and Technology (IROST)
چکیده [English]

Introduction: Physical and biological soil crusts are the principal types of soil crusts. Physical and biological soil crusts are distributed in arid, semi-arid and sub-humid regions which constitute over 40% of the earth terrestrial surface. Biological soil crusts (BSCs) result from an intimate association between soil particles and cyanobacteria, algae, fungi, lichens and mosses in different proportions which live on the surface, or in the immediately uppermost millimeters of soil. Some of the functions that BSCs influences include: water absorption and retention, nutrient retention, Carbon and nitrogen fixation, biological activate and hydrologic Status. BSCs are important from the ecological view point and their effects on the environment, especially in rangeland, and desert ecosystems and this caused which researchers have a special attention to this component of the ecosystems more than before.
Materials and Methods: This study carried out in the Qara Qir rangelands of Golestan province, northeast of Iran (37º15′ - 37º23′ N &54º33′ -54º39′ E), to investigate the effects of BSCs on some of soil biological properties. Four sites including with and without BSCs cover were selected. Soil biological properties such as microbial populations, soil respiration, microbial biomass carbon and nitrogen, as well as, other effective properties such asorganic carbon percent, total nitrogen, electrical conductivity, and available water content were measured in depths of 0-5 and 5-15 cm of soil with four replications. The gathered data were analyzed by nested plot, and the mean values were compared by Duncan test.
Results and Discussion: The results showed that organic carbon and water content were higher at the surface under BSCs, followed by 5-15 cm soils under BSCs. Both soil depths of uncrusted soils showed substantially lower organic carbon and water content than the BSC-covered soils. Total nitrogen was far higher in BSC-encrusted surface soils than uncrusted surface soils or BSC sub-surface soils. All Electrical conductivities were lower in surface soils covered with BSCs than sub-surface soils. The values for non-BSC covered soils were far higher than values for soils covered with BSCs. The values of soil biological properties such as microbial populations, soil respiration, microbial biomass carbon and nitrogen were higher at the surface under BSCs, followed by 5-15 cm soils under BSCs. The values for non-BSC covered soils were far lower than values for soils covered with BSCs at 0-5 cm depth but these properties in the uncrusted soils did not differ with BSCs covered surface at 5-15 cm depth. The amount of organic carbon was higher in BSC-covered surface soils at both measured depths, likely due to the ability of BSCs to fix atmospheric carbon. This leads to enhanced BSCs biomass and thus organic carbon especially in the soil surface layer (0-5 cm). An extensive cover of even a thin layer of photosynthetically active organisms can be an important basis for carbon input into the soil. BSCs also produce and secrete extracellular polysaccharides into surrounding soils, increasing the soil carbon and nitrogen pool. In general, there is a positive correlation between C and N fixation by BSCs. Also distribution of soil microbial population is positively correlated with the distribution of organic carbon and nitrogen. Microbial population is reduced following increase at depth, which is proportional to reduce of the concentration of nutrient and suitable conditions such as water content for growing them. Therefore proportionate to Microbial population, the properties such as soil respiration and microbial biomass carbon and nitrogen were reduced following increase at depth, because it did not provide the conditions for living organisms. These conditions were more inappropriate for non-BSC covered soils due to lower water content, organic carbon, total nitrogen and much higher electrical conductivity at both depths especially at 5-15 cm depth.
Conclusion: Biological soil crusts can play a key role in the biological properties of soil. Our data showed that organic carbon percent, total nitrogen, and available water content and biological properties such as microbial populations, soil respiration and microbial biomass carbon and nitrogen were increased significantly in two mentioned depths especially in 0-5 cm depth on sites covered with BSCs, relative to without BSCs. Electrical Conductivity had a reverse trend. In general, it can be concluded that BSCs improve soil conditions and provide suitable habitats for heterotrophic microorganisms and increase soil microbial activity. As the presence of BSCs generally increased the positive qualities of the soil, it is suggested that they can be used as a qualitative indicator of soil quality in rangelands.

کلیدواژه‌ها [English]

  • Biological soil crusts
  • Microbial biomass carbon
  • Microbial Biomass Nitrogen
  • Microbial population
  • Soil respiration
1- Alexander M. 1982. Most probable number method for microbial populations. In: Page AL., Miller RH., Keeney DR. (Eds.), Methods of Soil Analysis Part2. Amer. Soc. for Agron, Madison USA: 815–820.
2- Anderson E., and John P. 1982. Soil respiration. Methods of Soil Analysis Part2. Amer. Soc. for Agron, Madison USA: 831–870.
3- Anderson T.H. 2003. Microbial eco-physiological indicators to asses soil quality. Agriculture, Ecosystems & Environment 98:285-93.
4- Belnap J., Kaltenecker J.H., Rosentreter R., Williams J., Leonard S., and Eldridge D. 2001. Biological soil crusts: ecology and management. pp 110. United States Department of the Interior Bureau of Land Management,National Science and Technology Center.
5- Belnap J. 2003. Comparative Structur of Physical and Biological soil crusts. In Biological Soil Crusts: Structure, Function, and Management, ed. J Belnap, O Lange:177-91: Springer-Verlag:Berlin. Number of 177-91 pp.
6- Belnap J. 2003. Microbes and Microfauna Associated with Biological Soil Crusts. In Biological Soil Crusts: Structure, Function, and Management, ed. J Belnap, O Lange:167-74: Springer-Verlag:Berlin. Number of 167-74 pp.
7- Belnap J. 2006. The potential roles of biological soil crusts in dryland hydrologic cycles. Hydrological Processes 20:3159-78.
8- Bremner J., and Mulvaney C. 1982. Nitrogen-total. In Methods of soil analysis. Part 2. Chemical and microbiological properties: 595-624: American Society of Agronomy-Soil Science Society of America. Number of 595-624 pp.
9- Büdel B. 2005. Microorganisms of Biological Crusts on Soil Surfaces: In Microorganisms in Soils: Roles in Genesis and Functions, ed. A Varma, F Buscot, 3:307-23: Springer Berlin Heidelberg. Number of 307-23 pp.
10- Castillo-Monroy A., Maestre F., Rey A., Soliveres S., and Garcia-Palacios P. 2011. Biological Soil Crust Microsites Are the Main Contributor to Soil Respiration in a Semiarid Ecosystem. Ecosystems 14:835-47.
11- Dane J.H., and Hopmans J.W. 1986. Water retention and storage: Pressure plate extractor. In Methods of soil analysis. Part 1. Physical and mineralogical properties, including statistics of measurement and sampling.: American Society of Agronomy-Soil Science Society of America.
12- Evans R., and Lange O. 2003. Biological soil crusts and ecosystem nitrogen and carbon dynamics. In Biological soil crusts: structure, function, and management, pp. 263-79.
13- Froughifar H., Jafarzadah AA., Torabi Gelsefidi H., and Aliasgharzadah N. 2010. Effect of Different Landforms on Spatial Variability and Frequency Distribution of Soil Biological Properties in Tabriz Plain. Water and soil science. Volume 21, Issue 4, Winter 2011, Page 35-52 (in Persian with English abstract).
14- Horwath W.R., and Paul E.A. 1984. Microbial biomass. In: Buxton DR(Ed). Methods of Soil Analysis, Part 2: Microbiological and Biochemical Properties. Soil Sci Soc Am. No. 5. Pp. 753-773.
15-Maestre F.T., Bowker M.A., Canton Y., Castillo-Monroy A.P., and Cortina J. 2011. Ecology and functional roles of biological soil crusts in semi-arid ecosystems of Spain. J Arid Environ 75:1282-91.
16- Miralles I., Trasar-Cepeda C., Leiros M.C., and Gil-Sotres F. 2012. Labile carbon in biological soil crusts in the Tabernas desert, SE Spain. Soil Biology and Biochemistry, 5:1-8.
17- Nelson B.W., and Sommers L.E. 1986. Total carbon, organic carbon and organic matter. In: Page AL, Miller RH and Keeney DR (Eds). Methods of Soil Analysis. Part 2. Soil Sci Soc of Am, Madison WI. Pp: 539 - 577.
18- Qi Y.C., Dong Y.S., Jin Z., Peng Q., Xiao S.S., and He Y.T. 2010. Spatial heterogeneity of soil nutrients and respiration in the desertified grasslands of Inner Mongolia, China. Pedosphere 20:655-65.
19- Rhoades J. 1982. Soluble salts. In Methods of soil analysis. Part 2. Chemical and microbiological properties, pp. 167-79: American Society of Agronomy-Soil Science Society of America.
20- Rossi F., Potrafka R.M., Pichel F.G., and De Philippis R. 2012. The role of the exopolysaccharides in enhancing hydraulic conductivity of biological soil crusts. Soil Biology and Biochemistry 46:33-40.
21- Safari sinegani A.L. 2003. Soil Biology and Biochemistry.
22- Su Y., WU L., and Zhang Y. 2012. Characteristics of carbon flux in two biologically crusted soils in the Gurbantunggut Desert, Northwestern China. Catena 96:41-8.
23- Su Y.g., Zhao X., Li A.x., Li X.r., and Huang G. 2011. Nitrogen fixation in biological soil crusts from the Tengger desert, northern China. European Journal of Soil Biology 47:182-7.
24- Tavili A. 2005. Study of some moss and lichen species effects on range soil and plants properties, case study: Qara Qir ranges, Golestan province, Iran. Natural Resources Faculty, University of Tehran, Ph.D thesis (in Persian with English abstract).
25- Thomas A.D., Hoon S.R., and Dougill A.J. 2011. Soil respiration at five sites along the Kalahari Transect: Effects of temperature, precipitation pulses and biological soil crust cover. Geoderma. 167:284-94.
26- Thomas A.D., Hoon S.R., and Linton P.E. 2008. Carbon dioxide fluxes from cyanobacteria crusted soils in the Kalahari. Applied Soil Ecology 39:254-63.
27- Williams J.D. 1994. Microbiotic Crusts: A Review.
28- Wright A.L., Hons F.M., and Matocha J.r JE. 2005. Tillage impacts on microbial biomass and soil carbon and nitrogen dynamics of corn and cotton rotations. Applied Soil Ecology 29:85-92.
29- Xu Y., Rossi F., Colica G., Deng S., Philippis R., and Chen L. 2012. Use of cyanobacterial polysaccharides to promote shrub performances in desert soils: a potential approach for the restoration of desertified areas. Biology and Fertility of Soils: 1-10.
30- Zaady E., Kuhn U., Wilske B., Sandoval-Soto L., and Kesselmeier J. 2000. Patterns of CO2 exchange in biological soil crusts of successional age. Soil Biology and Biochemistry 32:959-66.