Effects of oil sands disturbances on shrub and tree structure along forest edges in Alberta's boreal forest

Abstract

Deforestation causes forest fragmentation and associated edge effects. The boreal forest of Alberta, Canada has undergone substantial fragmentation via the creation of seismic lines, roads, and wellpads for resource exploration and extraction, but their associated edge effects have not been fully assessed, particularly for the latter two footprint types. We examined how these disturbances influence forest composition and structure along anthropogenic forest edges in the oil sands region of northeastern Alberta. We then used generalized linear models to test distance to edge responses in tree and shrub density given treatment (disturbance) type and forest canopy composition. Our results indicate the presence of edge effects, even along narrow seismic lines. Tree and shrub density and tree basal area were greater at the forest edge, being two times greater at 1 m from the forest edge relative to intermediate interior forest distances (∼30 m). Variations in tree basal area, tree density, and shrub and sapling density were best explained by interactions between disturbance type, distance from the forest edge, and % conifer composition. This study demonstrates that anthropogenic disturbances from energy exploration in the boreal forests cause changes in tree and shrub density (structure), and this effect is most pronounced in deciduous-dominated forests.