Article

Tree mortality following partial harvests is determined by skidding proximity

Faculty of Forestry, University of Toronto, 33 Willcocks St., Toronto, Ontario M5S3B3, Canada.
Ecological Applications (Impact Factor: 4.09). 11/2008; 18(7):1652-63. DOI: 10.1890/07-1697.1
Source: PubMed

ABSTRACT

Recently developed structural retention harvesting strategies aim to improve habitat and ecological services provided by managed forest stands by better emulating natural disturbances. The potential for elevated mortality of residual trees following such harvests remains a critical concern for forest managers, and may present a barrier to more widespread implementation of the approach. We used a harvest chronosequence combined with dendrochronological techniques and an individual-based neighborhood analysis to examine the rate and time course of residual-tree mortality in the first decade following operational partial "structural retention" harvests in the boreal forest of Ontario, Canada. In the first year after harvest, residual-tree mortality peaked at 12.6 times the preharvest rate. Subsequently, mortality declined rapidly and approached preharvest levels within 10 years. Proximity to skid trails was the most important predictor both of windthrow and standing death, which contributed roughly equally to total postharvest mortality. Local exposure further increased windthrow risk, while crowding enhanced the risk of standing mortality. Ten years after harvest, an average of 10.5% of residual trees had died as a result of elevated postharvest mortality. Predicted cumulative elevated mortality in the first decade after harvest ranged from 2.4% to 37% of residual trees across the observed gradient of skid trail proximity, indicating that postharvest mortality will remain at or below acceptable rates only if skidding impacts are minimized. These results represent an important step toward understanding how elevated mortality may influence stand dynamics and habitat supply following moderate-severity disturbances such as partial harvests, insect outbreaks, and windstorms.

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    • " seed dispersal , pollination and facilitation ( Ballantyne and Pickering , submitted for publication ) . The current study provided a ' snapshot ' of impacts , with no data on the amount of use and age of trails . Consequently , some confounding temporal information that could have contrib - uted to the observed differences may have been missed ( Thorpe et al . , 2008 ) . These types of limitations are common to non - experimental studies in recreation ecology where important sour - ces of variance cannot be removed . It is unlikely however , that landscape level trail creation using an experimental approach would be ethically or physically feasible ."
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