Growth Release of Trees Following Fine-scale Canopy Disturbances In Old-growth Forests of Coastal British Columbia, Canada
Department of Geography, University of British Columbia, Vancouver
Growth release of trees following canopy disturbances is of interest to ecological scientists and forest managers. Using dendroecological techniques, I examined growth release of canopy and subcanopy trees following the formation of natural, fine-scale canopy gaps in old-growth, western redcedar-western hemlock forests of coastal British Columbia. I aimed to quantify detailed information on release of the three shade-tolerant tree species that constitute these stands: western redcedar (Thuja plicata), western hemlock (Tsuga heterophylla), and Pacific silver fir (Abies amabilis).
As a first step, I calibrated the radial-growth averaging method to account for regional-scale variability and capture a more complete range of growth releases that may occur following the formation of fine-scale gaps in the study stands. A 25% threshold, 5-year moving average, and 10-year window emerged as appropriate parameters for detecting releases using radial-growth averaging. Basal area increment was also the most appropriate growth index for detecting releases. Establishing these empirically-based criteria was important for quantifying the magnitude and duration of releases.
Tree diameter and growth prior to release were the most important predictors of the magnitude and duration of releases, but species and distance from gap center were also important. Western hemlock and Pacific silver fir were often growing slowly both in the canopy and subcanopy, giving them tremendous potential to release. For these species, releases were generally intensive and persistent. In contrast, western redcedar were often growing quickly both in the canopy and subcanopy, giving them less potential to release. Compared to western hemlock and Pacific silver fir, western redcedar releases were less intensive and persistent. Patterns related to distance from the gap center emerged for trees growing along the north-south axis of gaps. Regardless of species, increasing distance from the gap center resulted in decreasing magnitude and duration of releases. However, patterns for duration were complex, as the distance effect was greater for trees north of the gap center.
Information on growth release of trees is useful for reconstructing the history of past canopy disturbances, elucidating mechanisms of tree species coexistence, and assessing and predicting stand changes due to forest management in coastal British Columbia.
Daniels, L.D. and A.B. Stan. 2007. Part 4. Dendroecology of gaps Pp. 42-51 in Canopy gaps in the Bamfield Huu-ay-aht Community Forest: baseline information for variable retention silviculture. Report to the BC Forest Science Program, Forest Investment Account, Victoria, BC. October 2007.
Daniels, L.D. J. Passmore, A.B. Stan, K. Golinski, and T.A. Jones. 2007. Part 7. Regional comparisons of species composition and gap attributes. Pp. 69-83 in Canopy gaps in the Bamfield Huu-ay-aht Community Forest: baseline information for variable retention silviculture. Report to the BC Forest Science Program, Forest Investment Account, Victoria, BC. October 2007.
Daniels, L.D. and A.B. Stan. 2004. Canopy gaps in the submontane forest of coastal BC: a baseline for variable retention silviculture. 2003-4 Technical Report. Submitted to Forestry Innovation and Investment, Forest Research Program, Vancouver, British Columbia. April 2004. 29p.
CONFERENCE PRESENTATIONS AND POSTERS
Radial-growth release following the creation of canopy gaps in coastal British Columbia, Canada. Presented by A. Stan, Co-Author: L.D. Daniels. Presentation at the Annual Meeting of the Association of American Geographers, Chicago, IL, March 2006.
Dendroclimatic analysis of Douglas-fir in the Cariboo region of British Columbia. Presented by A. Stan, Co-Authors: L.D. Daniels and J. Dobrý. 6th International Conference on Dendrochronology, Quebec City, QC, August 2002.
CONFERENCE FIELD TRIPS
Temperate Rainforest Dynamics in Coastal British Columbia. Co-Presenters: L.D. Daniels, A.B. Stan and J. Passmore. Field Trip at the First American Dendrochronology Conference, Vancouver, BC, June 2008.
Temperate Rainforests – Sea and Sky. Co-Presenters: L.D. Daniels, K.P. Lertzman, A.B. Stan, S.P.J. McCloskey and J. Passmore. Field Trip at the North American Forest Ecology Workshop, Vancouver, BC, June 2007.
Dr. Amanda Stan is now a post-doctoral researcher in the Tree-Ring Laboratory at the University of British Columbia, studying the dynamics of yellow-cedar forests.
For further information, contact Dr. Lori Daniels, Department of Geography,University of British Columbia, firstname.lastname@example.org