Effect of burning C3 and C4 plants an the magnetic susceptibility signal in soils

To understand the origin of the ultrafine pedogenic components responsible for the magnetic susceptibility (MS) enhancement remains a major challengin g problem, in linking the magnetic signal with paleoclimatic conditions. He re we examine the influence of natural fires on the MS signal of both plant s and modern soils and in particular the MS difference between C3 and C4 pl ant ashes and their influence possibly on soil magnetic susceptibility. We demonstrate that burning of C3 and C4 plants can enhance MS signal of moder n soils. We show that C4 plants have greater potential to enhance the MS si gnal. The average MS value of C4 plant ashes is (532+/-61) x 10(-8)m(3) kg( -1), much higher than the average MS value of (120 +/-65) x 10(-8)m(3) kg(- 1) of C3 plant ashes. The Fe2O3 concentration in C4 plant is two to four ti mes higher than that in C3 pliant. One burning of the grassland, mainly con sisting of C4 plants, can enhance MS value of the surface soil up to about 30-40%.