Event Title

Competitive Effects on Tree Canopies: a Spatially Explicit Analysis of Crown Structure for Three Sub-Boreal Forest Species

Presenter Information

Hilary Thorpe

Event Website

http://www.nafew2009.org/

Start Date

22-6-2009 1:50 PM

End Date

22-6-2009 2:10 PM

Description

Changing forest management goals have led to increased focus on maintaining stand-level complexity. Understanding complex, mixed species stands requires the quantification of competitive interactions among individual trees. A suite of recent studies has explored the influence of neighbourhood competition on factors such as growth and mortality of adult trees and saplings. In this study, we used a neighbourhood approach to quantify the influence of local competition on the structure of individual tree crowns. We measured and mapped the locations and crown dimensions of ~2400 trees in north-central British Columbia, where forests are dominated by interior spruce (Picea glauca x engelmanii), subalpine fir (Abies lasiocarpa), and lodgepole pine (Pinus contorta). Using maximum likelihood methods, we quantified crown structure as a function of tree size, species, and competition levels, estimated by the identity and spatial arrangement of neighboring trees. In the absence of competition, we found the widest tree crowns in pine, followed by spruce and fir. Crown depth showed the opposite pattern, with the deepest crowns found in fir and the shallowest in pine. All species displayed declining crown dimensions with increasing neighborhood competition, but the pattern was most dramatic in pine, where crown dimensions decreased by 75% across the observed range of neighbourhood competition. Our results will be used to parameterize a new, distance-dependent crown model for the stand simulation model SORTIE-ND. This model will improve the accuracy of understory light predictions, and consequent sapling and sub-canopy tree dynamics, across a wide range of stand densities.

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Jun 22nd, 1:50 PM Jun 22nd, 2:10 PM

Competitive Effects on Tree Canopies: a Spatially Explicit Analysis of Crown Structure for Three Sub-Boreal Forest Species

Changing forest management goals have led to increased focus on maintaining stand-level complexity. Understanding complex, mixed species stands requires the quantification of competitive interactions among individual trees. A suite of recent studies has explored the influence of neighbourhood competition on factors such as growth and mortality of adult trees and saplings. In this study, we used a neighbourhood approach to quantify the influence of local competition on the structure of individual tree crowns. We measured and mapped the locations and crown dimensions of ~2400 trees in north-central British Columbia, where forests are dominated by interior spruce (Picea glauca x engelmanii), subalpine fir (Abies lasiocarpa), and lodgepole pine (Pinus contorta). Using maximum likelihood methods, we quantified crown structure as a function of tree size, species, and competition levels, estimated by the identity and spatial arrangement of neighboring trees. In the absence of competition, we found the widest tree crowns in pine, followed by spruce and fir. Crown depth showed the opposite pattern, with the deepest crowns found in fir and the shallowest in pine. All species displayed declining crown dimensions with increasing neighborhood competition, but the pattern was most dramatic in pine, where crown dimensions decreased by 75% across the observed range of neighbourhood competition. Our results will be used to parameterize a new, distance-dependent crown model for the stand simulation model SORTIE-ND. This model will improve the accuracy of understory light predictions, and consequent sapling and sub-canopy tree dynamics, across a wide range of stand densities.

http://digitalcommons.usu.edu/nafecology/sessions/adaptive_ecology/4