Dynamics of carbon, nitrogen, phosphorus and sulfur in a boreal aspen forest soil
Huang, W. 1996. Ph.D. Dissertation. Dept. Soil Science, University of Saskatchewan, Saskatoon, SK
Abstract
The objectiveof this research was to document the forms, amounts and cycling patters of Carbon (C), nitrogen (N), phosphorus (P) and sulfer (S) in soil profiles under trembling aspen (Populus tremuloides Michx.) stands located in Prince Albert national Park, Saskatchewan, Canada. A novel technique, involving in situ burial of ion exchange membranes was used to follow changes in supply rates of nutrient in the field and laboratory.
Organic C and N in the forest floor accounted for the greatest proportion of the total storage (C 47.3% and N 34.2%), followed by the B horizon (C 22.4% and 32.7%), the A horizon (C 17.3% and 18%) and the C horizon (C 13.0% and N 14.8%). Unlike C and N, more than 96% of the total P was found in the mineral soiland 3.5% in the forest floor. Much of the P stored in the mineral horizoons is contained in non-labile primary mineral forms. The greatest proportion (36.5%) of organic S was found in the C horizon, with 26.6% in the forest floor. The distribution of water soluble organic C within the soil profiles was related to the distribution of organic C.
The patterns in nutrient supply rates and uptake reflect the effect of a combination of factors. Summer is the period of active plant nutrient mineralization and uptake in the forest. in general, most of the N and P uptake takes place in the H horizon, where the plant roots are concentrated. late fall appears to be an important time for nutrient recycling back into available forms, with replenishment of bioavailable forms coinciding with late season litterfall. Hazel leaf litter decomposed at a more rapid rate than aspen leaf litter. Most of the N and P taken up by vegetation was returned through annual leaf litterfall. Rainfall and throughfall inputs of nutrients, though small, likely play an important role as a long term source of plant nutrient to replace that lost from the system by leaching or volatization.
