PARENT SESSION
Oral Session #30: Landscape Ecology: Dynamics and patterns. Presiding: A. Hansen.
Tuesday, August 7, 2001. 1:00 PM to 5:00 PM. Madison Ballroom D.

Modeling spatially explicit transition of boreal forest cover in the absence of disturbances.

Yemshanov, Dennis ¹, Perera, Ajith¹, ¹

ABSTRACT- We developed a spatially explicit model of large-scale, post-fire forest cover change for the North-American boreal biome. We used a semi-Markovian approach, with discrete states corresponding to dominant tree species. Species persistence in the canopy and their replacement rates formed the constraints of the time-dependent Markov chain. Probabilities of discrete state transition were stratified spatially by geoclimate, soil moisture, and edaphic gradients. Information collected from published literature was used to parameterize the model. Canopy composition, age, time since last disturbance, geoclimate, soil moisture and nutrient status were used as input data. Model output included forest cover, time since last disturbance, and canopy age at 10-year time steps, and 1-ha resolution. As a case study, we simulated post-fire forest cover transitions in a 3.7 million ha region in northern boreal Ontario, Canada. We initialized the model with a large-scale fire disturbance using a spatial fire regime model. The replacement of early successional forest cover by late successional forest cover produced by the model was compatible with existing theories of boreal forest succession. Geoclimate and soil moisture variability substantially influenced the rate of replacements. The model predicted transitions among late successional species, indicating that the distribution of late successional forest cover is not stable in space and time. We propose these results as a null hypothesis of forest cover change in the absence of disturbances or fire suppression in boreal landscapes.

KEY WORDS: boreal forest, landscape model, forest cover change, post-fire transition