PARENT SESSION
Contributed Oral Session 32: Soil Nutrient Dynamics and Acid Deposition
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 521 A, Level 5, Palais des congrès de Montréal
The effects of above- and below-ground inputs on soil characteristics: a reciprocal transfer study.
Hannam, Kirsten*,1, Quideau, Sylvie1, 1 University of Alberta, Edmonton, AB, Canada
ABSTRACT- Inputs from above-ground litter have a strong influence on soil nutrient cycling processes, such as N mineralization and respiration. However, the effect of fine root inputs on these processes is less clear. The boreal mixedwood forest is characterized by a mosaic of stand types, ranging from stands dominated by deciduous species whose soils typically exhibit high nutrient availability and microbial activity, to stands dominated by coniferous species whose soils typically exhibit lower nutrient availability and microbial activity. A reciprocal transfer study, using forest floor placed in open-topped mesh bags that allowed or excluded fine root in-growth, was established in three deciduous and three coniferous stands in the boreal mixedwood forest of northern Alberta. After one year of incubation in the field, the forest floor materials contained in the mesh bags were collected and analyzed. The origin of the forest floor most strongly controlled soluble organic C and N concentrations, microbial biomass C and N concentrations, and microbial respiration rates. However, nitrate concentrations were most dependent on the stand type in which the forest floor was incubated, indicating a strong control of aboveground litter inputs. Forest floor pH declined in the presence of fine root in-growth, and forest floor incubated in spruce stands had higher microbial biomass C and N when fine root in-growth was excluded, indicating a strong control of fine root inputs. These results clearly indicate that inputs from fine roots and from aboveground litter have different effects on nutrient cycling processes in the forest floors of these stands.
Key words: fine roots, forest floor, litter inputs, boreal mixedwood forest