PARENT SESSION
Oral Session # 50: Forest Ecology III: Modeling; Nutrient Cycling.
Presiding: L Comas
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 100.

Modelling the soil carbon and nitrogen cycles in three eastern Canadian forest types.

Larocque, Guy¹, Boutin, Robert¹, Paré, David¹, Robitaille, Gilles¹, Lacerte, Valérie¹, ¹ Natural Resources Canada, Ste-Foy, Quebec, Canada

ABSTRACT- A process-based model was developed to simulate the soil carbon and nitrogen cycles in sugar maple (Acer saccharum Marsh.), balsam fir (Abies balsamea (L.) Mill.) and black spruce (Picea mariana (Mill.) B.S.P.) forest types in eastern Canada. The development and calibration of the model are part of the ECOLEAP project that involved the establishment of field stations and laboratory incubation microcosms for collecting data on the carbon and nitrogen pools and fluxes in the litter, organic and mineral layers of the soil in these forest ecosystems. Litter samples were also incubated on several sites along a climatic gradient to monitor site-specific litter decomposition rates for a complete annual cycle. Soil temperature was monitored on a daily basis. The model simulates the carbon and nitrogen transfers among the different pools, as well as the amount of CO₂ respired. For the organic and mineral layers, the carbon was partitioned into active, slow and passive pools. An Arrhenius-type function was used to model the effect of temperature on mineralization rates. The simulations conducted over a period of 50 years indicated that the different carbon pools will decrease significantly with a gradual 3°C increase in temperature, while the amount of CO₂ respired will increase. However, the results also indicated that the decrease in carbon pools may be offset by an increase in litter production.

Key words: carbon, modelling, soil, nitrogen