Abstract

In the managed boreal forest, harvesting has become a disturbance as important as fire. To assess whether forest recovery following both types of disturbance is similar, we compared post-disturbance revegetation rates of forests in 22 fire events and 14 harvested agglomerations (harvested areas over 5–10 years in the same vicinity) in the western boreal forest of Quebec. Pre-disturbance conditions were first compared in terms of vegetation cover types and surficial deposit types using an ordination technique. Post-disturbance changes over 30 years in land cover types were characterized by vectors of succession in an ordination. Four post-disturbance stages were identified from the 48 land thematic classes in the Landsat images: “S0” stand initiation phase; “S1” early regeneration phase; “S2” stem exclusion phase; and “S3” the coniferous forest. Analyses suggest that fire occurs in both productive and unproductive forests, which is not the case for harvesting. Revegetation rates (i.e., rapidity with which forest cover is re-established) appeared to be more advanced in harvested agglomerations when compared with entire fire events. However, when considering only the productive forest fraction of each fire, the revegetation rates are comparable between the fire events and the harvested agglomerations. The S0 is practically absent from harvested agglomerations, which is not the case in the fire events. The difference in revegetation rates between the two disturbance types could therefore be attributed mostly to the fact that fire also occurs in unproductive forest, a factor that has to be taken into account in such comparisons.

Highlights

  • Natural disturbances such as fire or insect outbreaks play an important role in the dynamics of boreal forests and contribute to their maintenance and renewal [1]

  • (1) we compared the pre-disturbance conditions in terms of vegetation composition and surficial deposit characteristics; (2) we analyzed the post-disturbance recovery after fire or harvesting using succession vectors that describe changes in vegetation composition throughout time; (3) we evaluated the rate of revegetation over the first 30 years following the disturbance by comparing Landsat imagery taken at different times since the disturbance; and (4) we compared the post-disturbance land cover composition of fire events and harvested agglomerations

  • The pre-fire events are situated on the left side of axis 2, while the pre-harvested agglomerations are on the right

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Summary

Introduction

Natural disturbances such as fire or insect outbreaks play an important role in the dynamics of boreal forests and contribute to their maintenance and renewal [1]. Of these natural disturbances, fire remains the most important in terms of the sheer magnitude of the area that is affected [2,3] and this disturbance is responsible for shaping the boreal forest [4,5]. The resilience of the boreal forest and its underlying dynamics may differ considerably between fire and harvesting [10,11]. There is a wide range of arguments that have contrasted the beneficial and detrimental effects of both types of disturbance on forest recovery

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