Vertical trends of oxalate concentration in two soils underAbies alba from Tuscany (Italy)

Low-molecular-weight organic acids (LMWOA's) play an important role in soil genesis and plant physiology. Oxalic acid is one of the more common and abundant LMWOA's in forest soils, where it accumulates especially as salts of Ca. In two soils under silver fir (Abies alba Mill.) from Tuscany, Italy, we measured the oxalate concentration of the entire profile. Oxalate was present up to two metres depth, but accumulates preferentially in the upper horizons. We determined also the bulk density of the fine earth, and organic carbon and available phosphorus. In one of the two soils, the oxalate concentration along the profile was regressed negatively with depth and bulk density, and positively with organic C and available P.