Abstract
Silvicultural site preparation methods are used as planned disturbances for counteracting soil and vegetation constraints, as well as facilitating successful tree regeneration and growth. Understanding the possible effects of silvicultural site preparation on the ecosystem and evaluating site preparation as an ecological disturbance can help guide the selection and application of site preparation techniques for forest management goals. This review evaluates silvicultural site preparation techniques that are commonly used in boreal mixedwood ecosystems as agents of ecological disturbance by comparing the effects of each technique on the area disturbed and the degree of biomass modification, and then ordering them along a disturbance severity gradient. With a strong emphasis on the numerical estimation of the spatial footprint of different disturbances, broadcast burning typically has the highest disturbance severity, followed in order by broadcast herbicide use, mixing, plowing, disc trenching, mounding, scalping, and inverting. The evaluation of disturbance severity of various silvicultural site preparation techniques while using the proposed framework is feasible, in which quantitative assessments of area disturbed and biomass modification could be collected and assessed in most managed forests.
Highlights
Silvicultural site preparation techniques are planned anthropogenic disturbances that are designed to aid in the regeneration and establishment of a new stand of trees
We focus on eight types of site preparation treatments—prescribed burning and herbicides, plus six types of mechanical site preparation (MSP), namely mixing, plowing, disc trenching, mounding, scalping, and inverting—that are commonly used today in boreal mixedwood ecosystems [1,4]
Studies indicate that herbicide site preparation results in better crop tree growth when compared to MSP, on mixedwood sites where hardwoods and shrubs compete with planted conifers [49,50]
Summary
Silvicultural site preparation techniques are planned anthropogenic disturbances that are designed to aid in the regeneration and establishment of a new stand of trees. Understanding the possible effects of silvicultural site preparation on the ecosystem and recognizing site preparation as an ecological disturbance can help to select the best option for different forest management goals. An assessment of the disturbance severity of a range of silvicultural site preparation methods can provide insight into the suitability of site preparation options for various land management goals and their underlying ecological impacts. Mixed forests of white spruce (Picea glauca [Moench] Voss) and trembling aspen (Populus tremuloides Michx.) in northwestern Canada are typically clear-cut logged, followed by site preparation to offset the effects of cold wet soils and vigorous competition from species, such as trembling aspen and bluejoint (Calamagrostis canadensis [Michx.] Beauv.), in order to promote establishment of nursery-grown seedlings of the preferred crop tree, white spruce. We (1) review the general effects of the selected site preparation techniques on soil conditions and seedling performance, (2) propose a framework for evaluating site preparation disturbance severity at the cutblock/stand level, (3) analyze site preparation techniques while using our proposed framework with the objective of ordering them along a disturbance severity gradient, and (4) identify research needs and recommend future work
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