تاثير توالي طبيعي تجزيه لاشبرگ جنگل هاي بلوط زاگرس بر برخي ويژگي هاي بيولوژيك خاك و لاشبرگ

چكيده انگليسي :

85 Successional changes in soil and litter microbial properties during decomposition of oak litter Raheleh Khaleghi khaleghi38@gmail com Juane 12 2016 Department of Soil Science Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor F Nourbakhsh farshid@cc iut ac irAbstractEcological succession is a process that changes biological species community over time As succession occurs mostof ecosystem characteristics is presumed to be changed It can also be expected that incorporation of plant residuesinto soil underlies ecological succession Incorporation of plant residues in to soil especially in arid and semi aridregions is one of the major principles of ecosystem sustainability In forest ecosystem litter is the main part of plantresidues and litter decomposition has an important role in food cycle and nutrient balance that maintains soil fertilityand provides nutrient for plant growth Litter have different initial composition and hence nutrient release pattern Successional changes in the grassland ecosystems has been extensively investigated however little information isavailable regarding the litter successional evolution toward climax condition The objectives of the study were toidentify the biological and biochemical indices of oak Quercus brantii Lindle litter during successional changesand to characterize the association of litter properties to decomposition kinetics in soil Deforestation effects ondecomposition kinetics of litters with various age was also investigated For this purpose plant samples includingoak leaves L0 litter with low decomposition L1 litter with medium decomposition L2 and litter with highdecomposition L3 from Oak forest of Dalvara located in Chaharmahal province were collected Soils 0 15 cm under natural and undisturbed oak forest soil and the adjacent cultivated area were sampled To address the questionthat how succession influence the litter properties inorganic nitrogen soluble organic nitrogen microbial biomassnitrogen urease L asparaginase and L glutaminase activities were measured in the plant material In secondexperiment the plant material were separately incorporated to forest and cultivated soils with a rate of 10 g C kg 1soil and incubated under optimum condition Evolved carbon dioxide were determined periodically during theincubation The cumulative amounts of CO2 C Cm were calculated and plotted versus time to calculate potentiallymineralizable carbon C0 decomposition rate constant K and initial potential rate KC0 Results indicatedadvancing the degree of biodegradation in the plant material diminish the storage of organic C and other measuredproperties so that a positive and significant correlation was consistently found between organic carbon and inorganicnitrogen r 0 98 soluble organic nitrogen r 0 73 microbial biomass nitrogen r 0 91 urease r 0 75 L asparaginase r 0 97 and L glutaminase r 0 84 As litters became more decomposed adecreasing trend was observed for the above mentioned indices L0 L1 L2 L3 The results of the secondexperiment showed that effects of plant residues on carbon mineralization microbial biomass nitrogen and metabolicquotient was significant The organic C content of the plant materials were significantly associated with Cm r 0 96 C0 r 0 97 KC0 r 0 93 and soil microbial biomass nitrogen r 0 83 whereas the metabolicquotient qCO2 showed to be negatively related to the carbon content of the plant material r 0 71 Advancingthe decomposition stage in litters resulted in a decreasing trend in the C content and hence all positively relatedindices Contrarily an increasing trend was observed in qCO2 In conclusion succession in the litter ecosystemresulted in decreasing of C storage and implemented C and or energy availability stress to the heterotrophic microbialbiomass which are mostly responsible for plant material biodegradation This was obviously indexed by increasingqCO2 values This finding was observed consistently in both natural fo

خالقي، راحله

تاثير توالي طبيعي تجزيه لاشبرگ جنگل هاي بلوط زاگرس بر برخي ويژگي هاي بيولوژيك خاك و لاشبرگ

كليماكس , نيتروزن توده زنده ميكروبي , كسر متابوليك , پتانسيل معدني شدن كربن