ارزيابي اثرهاي باقي مانده آتش سوزي بر نفوذ آب، فرسايش پذيري و مقاومت برشي خاك در مراتع شهرستان فريدن

چكيده انگليسي :

Assessing the Residual Effects of Fire on Water inFiltration Soil Erodibility and Shear Strength in Fereydan Rangelands Hamed Shahabinejad Shahabi hamed2@yahoo com January 15 2013 Department of Soil Science Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Dr M R Mosaddeghi E mail Mosaddeghi@cc iut ac irAbstractNowdays firing is considered important among several factors destroying the plant cover in rangelandecosystems Rangelands in Fereydan region Isfahan province are considered critical because of frequentannual and extensive firings The objective of this study done in August and September 2012 after thegrazing season was to explore the residual effect of firing events 2008 to 2012 on soil organic matter texture carbonate water infiltration hydraulic properties water repellency mechanical strength anderodibility in the rangelands of Fereydan region It was also intended to distinguish the critical locations andcondition in terms of fire effects on soil Ten stations per year were selected from the fire events of 2008 to2011 whereas five stations were studied in 2012 because of low number of 2012 fire events In order tostudy the independent effect of firing at each year paired t test was used The residual effect of firing upontime on the measured soil properties was tested using an unequal completely randomized design Moreover factor analysis was employed to evaluate the impact of important soil properties organic matter OM carbonate CaCO3 clay content Clay porosity f saturated hydraulic conductivity Ks water repellency R saturated water content s and scaling parameter of van Genuchten model on soil stability anddegradation in each location in order to recognize the locations which were highly and least affected by fireevents The results showed that fire significantly increased OM in all the years however the effect on soiltexture and particle size distribution was not significant Results of Wooding s analysis using tensioninfiltrometer data indicated that firing in 2010 2011 and 2012 significantly decreased the soil hydraulicconductivity at suctions of 15 and 10 cm however there was no significant difference for other fire events 2008 and 2009 because of soil recovery In all fire events the hydraulic conductivity at suctions of 2 and 5cm and saturated hydraulic conductivity were not significantly different between burn and unburn locations Moreover fires in 2010 2011 and 2012 significantly reduced soil sorptivity at suctions of 10 and 15 cm however the effect was not significant for fire events in 2008 and 2009 Firing non significantly decreasedsoil soptivity at suctions of 2 and 5 cm and macroscopic capillary length c Steady state water flow rate q at all suctions was significantly reduced due to firing in 2010 2011 and 2012 However for the fire events in2008 and 2009 the effect was not significant on the q values at suctions of 5 10 and 15 cm and was onlysignificant at suction of 2 cm The firing did not significantly affect infiltration parameters which werepredicted by DISC software Ks n and s and Dexter s index of soil physical quality SDexter The fire didnot significantly affect R but highest R values were observed immediately after the firing The fire reducedsoil shear strength and penetration resistance this effect was significant for the fire events of 2010 2011 and2012 Firing significantly increased the suspended sediment concentration ratio of sediment mass to runoffvolume The effect was diminished over the time after fire events and the lowest difference was observed intwo years after fire events The suspended sediment concentrationwas significantly increased three years afterfiring due to livestock overgrazing Overall the results indicate that controlled firing of locations on north facing slopes might be beneficial for soil stability against erosion if livestock grazing is prevented and orcontrolled Keywords Firing Saturated hydraulic condictivity Soil water repellenc

شهابي نژاد، حامد

ارزيابي اثرهاي باقي مانده آتش سوزي بر نفوذ آب، فرسايش پذيري و مقاومت برشي خاك در مراتع شهرستان فريدن

هدايت هيدروليكي اشباع , آب گريزي خاك , رسوب معلق , شبيه ساز باران , شاخص پايداري خاك