A comparison of large-scale spatial vegetation patterns following clearcuts and fires in Ontario’s boreal forests

Abstract

The role of wildfires as the most significant source of disturbance in boreal forests has been equaled by clearcuts during the past five decades. Post-disturbance revegetation patterns are important because they have a direct influence on many ecological processes. However, the knowledge of post-disturbance changes in spatial patterns of forest cover is scarce, especially at large scales. We examined spatial patterns of forest cover in a four decade series of post-fire and post-clearcut landscapes in boreal Canada. A suite of indices was used to quantify spatial patterns of post-disturbance vegetation, based on Landsat TM imagery, and edaphic conditions. Indices were grouped in terms of patch geometry, contagion and composition. We used a general linear model to compare the effects of disturbance type, time since disturbance, edaphic conditions, and their interactions on these indices. Clearcuts produced more heterogeneous landscapes after disturbances in comparison to fires. Time since disturbance also had a significant effect on spatial patterns of vegetation: the older disturbances had more landcover types with higher interspersion. Edaphic conditions also significantly affected spatial patterns of vegetation. Landscapes with complex spatial patterns of edaphic conditions also had complex spatial patterns of vegetation.