Forms, amounts and distribution of carbon, nitrogen, phosphorus and sulfur in a boreal aspen forest soil

Abstract

The forms, amounts and distribution of carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) were assessed in soil profiles under trembling aspen (Populus tremuloides Michx.) stands in the southern boreal forest of Saskatchewan, Canada. The total mass of organic C storage in the LFH horizon and mineral soil to a depth of 1 m ranged from 95 352 to 103 430 kg ha-1, with an average of 99 220 kg ha-1. Organic C and N in the LFH horizon accounted for the greatest proportion of the total storage (47.3% of C and 34.2% of N), followed by the B horizon (22.4% of C and 32.7% of N), the A horizon (17.3% of C and 18.3%, of N) and the C horizon (13.0% of C and 14.8% of N). Unlike C and N, more than 96% of the total P was found in the mineral soil and only 3.5% in the LFH horizon. Much of the P stored in the mineral horizons is contained in non-labile primary minerals forms. The greatest proportion (36.5%) of organic S was found in the C horizon, with 26.6% in the LFH horizon. The contribution of the LFH horizon to total organic C and N stored in boreal forest soils should not be neglected in global nutrient cycling models.