توزيع خاكدانه اي آنزيم هاي آلكالين فسفاتاز، اسيد فسفاتاز و آريل سولفاتاز در اكوسيستم هاي مختلف

چكيده انگليسي :

Aggregate Distribution of Alkaline Phosphatase Acid Phosphatase and Arylsulfatase in Various Ecosystems Marzieh Shamsaee m shamsaee@iut ac ir 24 December 2011 College of Agriculture Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Languege FarsiFarshid Nourbakhshfarshid@cc iut ac irAbstractSoil enzyme activities are thought to be central in nutrient cycling in the natural and agroecosystems Hydrolases including phosphatase and arylsulfatase play important roles in mineralization of P and S respectively This study was conducted to investigate aggregate distribution of alkaline and acidphosphatase in natural ecosystems including Gisum forest Delvara forest and Hanna rangeland A wetsieving procedure was used to separate soil aggregate into classes of 2 2 1 1 0 5 0 5 0 25 0 25 0 1 Soil alkaline phosphatase and soil acid phosphatase which are thought to be of different origins microbialand plant root exudates respectively were measured either in bulk soil or in the separated aggregates aswell as soil organic C SOC In spite of their different optimum pH and probable difference in theirorigin they both catalyze the hydrolysis of phosphate esters to inorganic orthophosphates Soilarylsulfatase was also measured as a hydrolase which is responsible to catalyze the hydrolysis of sulfateesters to inorganic sulfate Non aggregate sand particles and also total sand content of all aggregateclasses were determined and therefore the activity of the enzymes were calculated according to the massfractions of each aggregate classes with or without considering sand contents Results indicated that in theGisum forest pine standing has resulted in increasing SOC content Moreover large macroaggregateswere more abundant in the pine compared to the maple standing The activity of acid phosphatase alkaline phosphatase and arylsulfatase were also greater in the pine than that of maple standing The acidphosphatase was consistently greater than that of alkaline phosphatase due to the natural acidity of thesoil either in pine or maple stands The enzyme activities enhanced as the aggregate size increased in bothpine and maple standings In the Delvara oak forest and Hana rangeland the enzyme activiuties showedto be highly sensitive to management practices while alkaline phosphatase acid phosphatase andarylsulfatase decreased significantly as cultivation practiced in the ecosystems The activity of theenzymes was distributed unequally in the aggregate size fractions The greater fractions showed higherenzyme activity Multiplying the mass fraction of each aggregate class to the enzyme activities bringabout the aggregate derived enzyme activity which is affected by both the initial activity of the enzymesand the aggregate mass fraction Exceptionally due to high prevalence of small aggregates in the Hannarangeland aggregate derived enzyme activity was decreased as the aggregate size increased In otherword the greatest fraction of total soil enzyme activity is concentrated in the small macro andmicroaggregates The activity of alkaline phosphatase was predictably greater in both ecosystems ofDelvara oak forest and Hanna rangeland Changing the land use could not influence the predominance ofthe alkaline phosphatase The response of the enzyme activities to the management practices causedunequal distribution of the aggregate derived activity in the two counterparts of the ecosystems Thisclearly indicates that land use change not only influences the total soil enzyme activity but also impactthe distribution of the enzyme molecules in the soil aggregates Our study showed that cultivation wouldenhance the mass fraction of either small macroaggregate or microaggregates and therefore wouldincrease their aggregate derived activity Key WordsAlkaline Phosphatase Acid Phosphatase Management and Land Use Aggregate Aggregate distribution of enzyme

شمسايي، مرضيه

توزيع خاكدانه اي آنزيم هاي آلكالين فسفاتاز، اسيد فسفاتاز و آريل سولفاتاز در اكوسيستم هاي مختلف

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