Current issue: 54(2)

Under compilation: 54(3)

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Silva Fennica 1926-1997
Acta Forestalia Fennica

Articles by Karen A. Harper

Category: Research article

article id 1267, category Research article
Caroline Mary Adrianne Franklin, Karen A Harper, Liam Kyte Murphy. (2015). Structural dynamics at boreal forest edges created by a spruce budworm outbreak. Silva Fennica vol. 49 no. 3 article id 1267.
Highlights: Insect outbreak edges were 10 m wide with different canopy cover, stem density and tree structural diversity than adjacent ecosystems; Although edge influence on forest structure was weak, forest influence was stronger and extended further, creating an edge zone skewed towards the disturbed area; After thirty years, high-contrast and structurally-diverse transition zones persist on the landscape.
Natural disturbances such as insect outbreaks create boundaries that influence vegetation patterns and ecological processes.  To better understand the effects of natural edge creation on relatively intact forests and adjacent disturbed areas, we investigated forest structure on both sides of 30 year-old forest edges created by a spruce budworm (Choristoneura fumiferana Clemens) outbreak in the boreal forest of Cape Breton Highlands National Park, Canada.  Our objectives were: 1) to determine edge influence (compared to interior forest) and forest influence (compared to disturbed areas) on vegetation structure, and 2) to gain insight into the structural development of the edges.  Canopy cover, tree density, radial growth and deadwood were sampled in 5 m x 20 m plots along 120 m transects across six edges.  Randomization tests were used to estimate the magnitude and distance of edge and forest influence.  Narrow transition zones approximately 10 m wide characterized the spruce budworm-induced edges.  Edge influence did not extend into the forest; however, forest influence on structure was detected up to 40 m from the edge into the disturbed area.  We found evidence of the insect outbreak in the form of reduced radial growth during the disturbance across the entire disturbed area-forest gradient, which indicates that spruce budworm activity may not have ceased directly at the edge.  Tree mortality caused by the insect outbreak resulted in snags, many of which have transformed into logs since the outbreak collapsed.  Spruce budworm outbreak-induced forest edges are narrow but dynamic boundaries separating two distinct vegetation communities in the boreal landscape.
  • Franklin, Department of Renewable Resources, University of Alberta, 751 General Services Building, Edmonton, Alberta, T6G 2H1, Canada ORCID ID:E-mail: (email)
  • Harper, School for Resource and Environmental Studies, Dalhousie University, Suite 5010, 6100 University Ave., Halifax, Nova Scotia, B3H 3J5, Canada ORCID ID:E-mail:
  • Murphy, Department of Environmental Science, Saint Mary’s University, 923 Robie St., Halifax, Nova Scotia, B3H 3C3, Canada ORCID ID:E-mail:
article id 561, category Research article
Karen A. Harper, Yves Bergeron, Sylvie Gauthier, Pierre Drapeau. (2002). Post-fire development of canopy structure and composition in black spruce forests of Abitibi, Québec: a landscape scale study. Silva Fennica vol. 36 no. 1 article id 561.
Fire reconstruction and forest inventory maps provided an opportunity to study changes in stand-level characteristics following fire using a data set comprised of all forest stands of fire origin in an area of over 10 000 km2. We assigned the date of the most recent fire occurrence to over 31 000 forest stands in an ecoforestry database. We categorized stands on different substrates into age classes to investigate differences in canopy composition, cover and height, and incidence of secondary disturbance. Stands with over 75% Picea mariana (Mill.) BSP dominated all age classes on organic sites. On other substrates, there was a change in canopy composition from deciduous stands and stands dominated by Pinus banksiana Lamb. to Picea mariana stands after about 100 yr. This transition was later for xeric sites. After a peak in canopy cover and height at about 100 yr, there was a decrease in the area occupied by stands with dense, tall canopies. Structural development was slower on less productive sites. There was little incidence of spruce budworm outbreaks. Partial disturbance by windthrow coincided with canopy break-up at 100 yr, but appeared to have little effect on overall canopy structure in later stages. Structural diversity was independent of compositional diversity; on organic sites, stands with similar composition had different canopy structure. Diversity of stands with different composition and structure was greatest in the first 150 yr following fire. Maintaining stands in different stages of structural development on the landscape would serve to maintain regional biodiversity.
  • Harper, Université de Québec à Montréal, Groupe de recherche en écologie forestière interuniversitaire, CP 8888, succ. A, Montréal, QC, Canada H3C 3P8 ORCID ID:E-mail: (email)
  • Bergeron, NSERC-UQAT-UQAM, Industrial Chair in sustainable forest management, CP 8888, succ. Centre-Ville, Montréal, QC, Canada H3C 3P8 ORCID ID:E-mail:
  • Gauthier, Canadian Forest Service, Laurentian Forestry Centre, P.O. Box 3800, Sainte-Foy, QC, Canada G1V 4C7 ORCID ID:E-mail:
  • Drapeau, Université de Québec à Montréal, Groupe de recherche en écologie forestière interuniversitaire, CP 8888, succ. A, Montréal, QC, Canada H3C 3P8 ORCID ID:E-mail:

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