توزيع نيتروژن آلي محلول در اكوسيستم هاي جنگلي

چكيده انگليسي :

Distribution of Soluble Organic Nitrogen in Forest Ecosystems Nasim Tartar Nasim82825@gmail com March 1 2011 College of agriculture Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Farshid Nourbakhsh farshid@cc iut ac ir Abstract Land use change can influence the content and balance of nutrients in soil The mineralization and immobilization of N by microorganisms are central processes in terrestrial N cycling Both inorganic and organic N are involved in these processes Inorganic N NH4 and NO3 has been analyzed more frequently while structurally complex organic N molecules represent the largest soil N pool 95 Soluble organic N can be as mobile as nitrate and can be considered as a considerable source of in situ production of inorganic N in higher soil depths Moreover recent evidences have shown that some organic molecules like amino acids can be directly taken up by plant roots This study examined the effect of land use change on soil soluble organic N SON inorganic N and amino acids pools in three forest ecosystems Sites were selected to represent the variable climatic conditions of main forest regions of Iran Soil samples were collected from a humid region in western Guilan Gisum forest in mountainous regions of Mazandaran Roudbarak forest and semi arid regions of Chaharmahal va Bakhtiari Delvara forest The soil samples were taken from three depths in Roudbarak and Gisum forests 0 20 20 40 and 40 60 cm and one depth in Delvara forest 0 15 cm All measurements were performed in three replications Changes in SON IN and soil amino acids pools during a 22 weeks of incubation at 25 C and 50 water holding capacity were monitored The experiment was a factorial combination of factors in a completely randomized design CRD with 2 factors land use and 1depths or tree species and depths Average concentrations of inorganic N ranged from 28 to 180 mg kg N 21 to 178 mg kg 1 N and 30 to 181 mg kg 1 N at Roudbarak forest Gisum forest and Delvara forest respectively Average SON concentrations ranged from 23 to 380 mg kg 1 N 21 to 444 mg kg 1 N and 21 to 441 mg kg 1 N at Roudbarak forest Gisum forest and 1Delvara forest respectively Average soil amino acids concentrations ranged from 0 090 to 2 7 mmol kg 0 043 to 4 7 mmol kg 1 and 0 017 to 1 3 mmol kg 1 at Roudbarak forest Gisum forest and Delvara forest respectively Ratio of SON to inorganic N was 2 43 and 3 61 in 0 20 and 20 40 cm at Roudbarak forest respectively 1 94 and 4 58 in 0 20 and 20 40 cm at Gisum forest respectively The ratio was 2 37 in 0 15 cm at Delvara forest The results of discriminant analysis showed that the first depth 0 20 cm consisted a distinctive community and other depths 20 40 and 40 60 cm were combined The concentrations of SON inorganic N and soil amino acids were decreased with depths Distinctive differences were observed between surface and subsurface depths Land use change from native forest to deforested situation resulted in reduction of SON and amino acids concentrations Besides deforestation decreased the concentration of inorganic N at Delvara forest and increased inorganic N concentrations at Roudbarak forest The amounts of inorganic N pools in soils under maple trees were more than soils under pine trees Also concentrations of SON and soil amino acids in soils under maple trees were less than soils under pine trees Correlation studies among measured parameters were also performed The inorganic N were positively correlated with amino acid concentrations r 0 43 p 0 05 to r 0 65 p 0 001 A negative correlation was consistently observed between SON and inorganic N r 0 46 p 0 001 Overall we conclude that SON constitutes an important soil N pool in forest ecosystems of Iran and land use change and type of tree species can influence the relative importance of SON inorganic N and soil amino acids pools It can also be concluded that the effects of land use change and tree species is widely reflected in surface soil Dynamic of S

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توزيع نيتروژن آلي محلول در اكوسيستم هاي جنگلي

نيتروژن معدني , آمينو اسيدها , آناليزهاي تفكيك جوامع