ارزيابي پيامدهاي كوتاه مدت آتش سوزي بر برخي ويژگي هاي فيزيكي و شيشمايي خاك مراتع در منطقه فريدن

چكيده انگليسي :

Abstract Fire burning has been widely used for cleaning of agricultural fields and rangelands in Iran However intensive use of this management practice would result in destruction of soil structure and decline of soil organic matter and nutrients Firing might decrease water infiltration into the soil and enhance surface runoff There is little documentation about the effect of firing on soil properties in Iran s rangelands This study was conducted to investigate the short term effects of firing on selected soil physical chemical and hydraulic properties and water repellency at three rangeland locations in Friedan Isfahan province Controlled firing was imposed in autumn when the grazing finished after the hot season of summer and before initiation of rainfalls First soil sampling and measurement were done immediately after burn to explore the effect of firing on selected soil physical chemical and bilological properties Second soil samling was done in the same locations in the following spring when the soil became workable passing the cold frost and wet season of winter Second sampling would explore the short term residual effect of burning Soil samples were collected from the 0 5 cm layer in both times with three replicates for some physical and hydraulic properties soil water characteristic curve bulk density and real density and with foyr replicates for the rest The soil sampling was peformed in a systematic way from both burn and unburned contol sites Water infiltration into the soil was measured using a tension infiltrometer with three replicates and water repellency was characterized usig water droplet penetration time WDPT The results showed that pH and electrical conductivity values of the burn soils were significantly greater than those in the corresponding unburned soils for both times Firing also increased soil nutrients in both sampling times Burning non significantly increased the soil organic matter content which was measured immediately after fire This finding is related to the ash incorporation into the soil However soil organic matter significantly declined in the burn sites in the second sampling time due to translocation of ash and semi burn residues during the wet season Soil mechanically dispersible clay of the burn sites significantly decreased in the first sampling time due to organic matter input into the soils Whereas spontaneously and mechanically dispersible clays significantly increased in the second sampling time due to organic matter decline and soil erosion Increasing effect of firing on base microbial transpiration rate due to ash input was not significant in the first and second sampling times However induced microbial transpiration rate was significantly increased in the burn sites at first sampling time The increase was not significant in the second sampling time Firing induced soil water repellency immediately after burning due to production of hydrophobic materials However hydrophobic materials were washed out from the soil surface during the wet season and all soils became hydrophilic Water infiltration was reduced due to burning at both measurement times In the second time spring water infiltration was lower than first time which is attributable to soil erosion and crust formation during the wet season Soil water retention was also affected by burning significantly The negative effect of burning on soil water retention was much obvious at low matric suctions at the wet end Keywords Fire Rangeland Soil hydraulic properties Soil water repellency Water infiltration Dispersible clay

خسروي، الهه

ارزيابي پيامدهاي كوتاه مدت آتش سوزي بر برخي ويژگي هاي فيزيكي و شيشمايي خاك مراتع در منطقه فريدن

ويژگي هاي هيدروليكي خاك , آب گريزي خاك , نفوذ آب , رس قابل پراكنش