Vertical trends of oxalate concentration in two soils under Abies 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 ab undant 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 pr esent up to two metres depth, but accumulates preferentially in the upper h orizons. We determined also the bulk density of the fine earth, and organic carbon and available phosphorus. In one of the two soils, the oxalate conc entration along the profile was regressed negatively with depth and bulk de nsity, and positively with organic C and available P.