تغييرات زماني اجزاء فيزيكي ماده آلي خاك پس از رخدادهاي آتش سوزي در منطقه فريدن

چكيده انگليسي :

Temporal Variation of Physical Fractions of Soil Organic Matter Following Fire Events in Fereydan Farzaneh Aslani Farzaneh aslani69@yahoo com December 20 2014 Department of Soil Science Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor M R Mosaddeghi Mosaddeghi@cc iut ac ir AbstractRangelands are precious natural ecological resources and occupy the largest area of terrestrial lands in theworld Rangeland with diverse plant species is a natural ecosystem rich in genetic resources Biologicaldiversity is responsible for the sustainability of rangeland ecosystems against biological andenvironmental variables Firing is considered important among several factors affecting the biologicaldiversity in rangelands Controlled firing is considered as a management strategy to improve therangeland ecosystems However it might be a destroying agent for forests and pastures in arid and semi arid regions The objective of this study was to investigate the residual effects of firing events on soiltexture carbonate content organic matter OM particulate organic matter POM hot water extractablecarbohydrates CbHW structural stability indices MWD GMD and WSA organic carbon OC andtotal nitrogen TN and C N ratio in the physical fractions of aggregates in the rangelands of Fereydanregion Isfahan Province Ten stations per year were selected from the fire events of 2008 to 2011 whereas five stations were studied in 2012 because of low number of 2012 fire events In each location atreatment plot burn and control plot unburn were selected and the soil sampling and measurementswere done in the border between burn and unburn plots in order to minimize the influence of spatialvariability on the results Therefore 45 samples from burn locations and 45 samples from correspondingunburn locations in total 90 locations were collected and brought to the lab The statistical comparisonsbetween fired F and non fired NF locations at each year were examined using paired t test Theresidual effect of firing upon time on the OC and TN of aggregates physical fractions was studied usingfactorial arrangement in an unequal completely randomized design The results showed that fire and timeafter firing significantly increased OM CbHW TN and contribution of all aggregate fractions to total soilorganic carbon The fire significantly increased total POM and occluded POM but the increase in freePOM was not significant On a relative basis the fire decreased the POM i e POM OM ratio and CbHW i e CbHW OMratio indicating the sensitivity of these properties to soil management Soil structuralstability indices MWD GMD and WSA were significantly increased after fire due to greater OM POMand CbHW However time after firing decreased the differences of MWD GMD and WSA between burnand unburn locations Firing significantly decreased the mean percents of primary particles very fineaggregates 0 053 mm but non significantly decreased the water stable micro aggregates 0 053 0 25mm However the water stable macro aggregates 0 25 4 mm were significantly increased after fire The effects of time after firing and aggregates size on OC and TN of aggregates were significant but theireffects on C N ratio were not significant The fire increased the C N ratio but the effect was significant insome years The findings of this study indicated that controlled firing in rangelands of Fereydan region inlocations on north and east facing low slopes with loamy soils might improve soil quality and physicaland chemical properties if livestock grazing is prevented and or controlled Keywords Firing Aggregate Structural stability indices Hot water extractablecarbohydrates Water infiltration Free and occluded particulate organic matter C Nratio

اصلاني، فرزانه

تغييرات زماني اجزاء فيزيكي ماده آلي خاك پس از رخدادهاي آتش سوزي در منطقه فريدن

خاكدانه , شاخص هاي پايداري ساختمان , كربوهيدرات هاي قابل عصاره گيري با آب داغ , ماده آلي ذره اي آزاد و محبوس