Brett G. Purdy, S. Ellen Macdonald, Mark R. T. Dale. (2002). The regeneration niche of white spruce following fire in the mixedwood boreal forest. Silva Fennica vol. 36 no. 1 article id 564. https://doi.org/10.14214/sf.564

Keywords: boreal forest; regeneration; natural disturbance; white spruce; mycorrhizae

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Early establishment of white spruce (Picea glauca) in mixedwood boreal forest stands following fire was examined at several times-since-fire (1-, 2-, 4-, 6-, 14-years). Abiotic and biotic conditions in the stands were assessed at two scales, tree plot (5 m x 5 m) and microsite (1 m x 1 m), along with presence, density and height of white spruce seedlings. Germination and survival of seed sown 1- and 4-years post fire were quantified. Survival and growth of nursery-grown seedlings, and mycorrhizal colonization, survival and growth of sterile seedlings, planted 1-year post-fire were assessed. At the tree plot scale, presence of white spruce seedlings 1-year post-fire could be reliably predicted by organic layer depth and distance to and strength of seed source. In contrast, none of the biotic or abiotic factors measured was strongly correlated with occurrence or density of white spruce seedlings 6- and 14- years post-fire. At the microsite scale, seedling recruitment immediately post-fire was limited to a distinct subset of available microsites (greater % cover of downed wood and moss, lower % cover of litter and herbaceous vegetation). Likewise, seedling occurrence in older burns was associated with distinct microsite conditions; although this was more likely an effect of white spruce presence, rather than the cause. Less than 3% of seed sown 1 yr post-fire survived to become 1yr old germinants, survival was 41% over the next three years. Availability of suitable regeneration microsites declines rapidly with time-since-fire; less than 0.3% of seed sown 4 yrs post-fire survived one year. High rates of mycorrhizal colonization were found on white spruce seedlings planted 1-year post-fire, including early and late stage fungal species. Microsite characteristics were only weakly correlated with mycorrhizal fungal communities. We propose that immediate post-fire recruitment of white spruce is a key process in mixedwood boreal succession.

Purdy, Dept. of Renewable Resources, University of Alberta, Edmonton, AB, Canada T6G 2E3 E-mail: bgp@nn.ca
Macdonald, Dept. of Renewable Resources, University of Alberta, Edmonton, AB, Canada T6G 2E3 E-mail: ellen.macdonald@ualberta.ca
Dale, Dale, Dept. of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E9 E-mail: mrtd@nn.ca

Category : Review article

article id 74, category Review article

Philip J. Burton, S. Ellen Macdonald. (2011). The restorative imperative: challenges, objectives and approaches to restoring naturalness in forests. Silva Fennica vol. 45 no. 5 article id 74. https://doi.org/10.14214/sf.74

Keywords: afforestation; disturbance regime; ecological restoration; forest rehabilitation; native species; reclamation

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Many of the world’s forests are not primeval; forest restoration aims to reverse alterations caused by human use. Forest restoration (including reforestation and forest rehabilitation) is widely researched and practiced around the globe. A review of recent literature reveals some common themes concerning forest restoration motivations and methods. In some parts of the world, forest restoration aims mainly to re-establish trees required for timber or fuelwood; such work emphasizes the propagation, establishment and growth of trees, and equates with the traditional discipline of silviculture. Elsewhere, a recent focus on biocentric values adopts the goal of supporting full complements of indigenous trees and other species. Such ecosystem-based restoration approaches consider natural templates and a wide array of attributes and processes, but there remains an emphasis on trees and plant species composition. Efforts to restore natural processes such as nutrient cycling, succession, and natural disturbances seem limited, except for the use of fire, which has seen widespread adoption in some regions. The inherent challenges in restoring “naturalness” include high temporal and spatial heterogeneity in forest conditions and natural disturbances, the long history of human influence on forests in many regions of the world, and uncertainty about future climate and disturbance regimes. Although fixed templates may be inappropriate, we still have a reasonably clear idea of the incremental steps required to make forests more natural. Because most locations can support many alternative configurations of natural vegetation, the restoration of forest naturalness necessarily involves the setting of priorities and strategic directions in the context of human values and objectives, as informed by our best understanding of ecosystem structure and function now and in the future.

Burton, Canadian Forest Service, Natural Resources Canada, 3333 University Way, Prince George, British Columbia, Canada V2N 4Z9 E-mail: Phil.Burton@NRCan-RNCan.gc.ca
Macdonald, Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada E-mail: sem@nn.ca

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