Assessing Differences in Competitive Effects Among Tree Species in Central British Columbia, Canada

<i>Research Highlights:</i> We investigated the competitive interactions among three tree species (interior Douglas-fir (<i>Pseudotsuga menziesii</i> var. <i>glauca</i> (Beissn.) Franco), interior spruce (<i>Picea glauca</i> [Moench] Voss &#215; &l...

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Main Authors: Stella Britwum Acquah, Peter L. Marshall
Format: Article
Language:English
Published: MDPI AG 2020-02-01
Series:Forests
Subjects:
Online Access:https://www.mdpi.com/1999-4907/11/2/167
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spelling doaj-3104d9cca61840bbbd5d802566c207582020-11-25T01:45:51ZengMDPI AGForests1999-49072020-02-0111216710.3390/f11020167f11020167Assessing Differences in Competitive Effects Among Tree Species in Central British Columbia, CanadaStella Britwum Acquah0Peter L. Marshall1Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, CanadaFaculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada<i>Research Highlights:</i> We investigated the competitive interactions among three tree species (interior Douglas-fir (<i>Pseudotsuga menziesii</i> var. <i>glauca</i> (Beissn.) Franco), interior spruce (<i>Picea glauca</i> [Moench] Voss &#215; <i>Picea engelmannii</i> Engelm.), and lodgepole pine (<i>Pinus contorta</i> Dougl. Ex Loud. var. <i>latifolia</i> Englem.)) in multi-aged stands in central British Columbia, Canada. <i>Background and Objectives:</i> Understanding competitive interactions among tree species in mixed-species stands is fundamental to supporting silvicultural decision-making in such stands. Using the periodic annual basal area increment for single trees as our dependent variable, we investigated whether neighboring trees competed with subject trees independently of species identity. We also examined the differences in single-tree basal area growth among the three conifer species over time under different levels of competition. <i>Materials and Methods:</i> We developed several spatially explicit, single-tree basal area growth models for interior Douglas-fir, interior spruce, and lodgepole pine using data from 16 plots in two blocks of a long-term study (five measurements over a 21-year period) on the response to pre-commercial thinning. We compared these equations to assess whether intraspecific or interspecific competition predominated. We also examined the differences in basal area growth among the three conifer species over time under different levels of competition. <i>Results:</i> We found asymmetrical relationships between the conifer trees and their neighbors for all species, indicating that the main driver limiting growth in these stands is aboveground competition for light. There was evidence of higher intraspecific competition for small (&lt;10.0 cm DBH) interior Douglas-fir in one block. However, there was no general pattern among larger subject trees with respect to the identity of neighborhood competitive effects and the equivalence of neighbors. We observed a higher level of basal area growth over time for interior Douglas-fir than for lodgepole pine and interior spruce, irrespective of the competition intensity and, not surprisingly, the growth rate declined with increasing competition levels for the three species. <i>Conclusions:</i> Our results provide an understanding of how interior Douglas-fir stands will develop over time and information on species interactions that could help forest managers explore different silvicultural options and their effects on individual tree growth in these complex stands.https://www.mdpi.com/1999-4907/11/2/167competitionmixed-species forestsneighborhood effectsbasal area increment
collection DOAJ
language English
format Article
sources DOAJ
author Stella Britwum Acquah
Peter L. Marshall
spellingShingle Stella Britwum Acquah
Peter L. Marshall
Assessing Differences in Competitive Effects Among Tree Species in Central British Columbia, Canada
Forests
competition
mixed-species forests
neighborhood effects
basal area increment
author_facet Stella Britwum Acquah
Peter L. Marshall
author_sort Stella Britwum Acquah
title Assessing Differences in Competitive Effects Among Tree Species in Central British Columbia, Canada
title_short Assessing Differences in Competitive Effects Among Tree Species in Central British Columbia, Canada
title_full Assessing Differences in Competitive Effects Among Tree Species in Central British Columbia, Canada
title_fullStr Assessing Differences in Competitive Effects Among Tree Species in Central British Columbia, Canada
title_full_unstemmed Assessing Differences in Competitive Effects Among Tree Species in Central British Columbia, Canada
title_sort assessing differences in competitive effects among tree species in central british columbia, canada
publisher MDPI AG
series Forests
issn 1999-4907
publishDate 2020-02-01
description <i>Research Highlights:</i> We investigated the competitive interactions among three tree species (interior Douglas-fir (<i>Pseudotsuga menziesii</i> var. <i>glauca</i> (Beissn.) Franco), interior spruce (<i>Picea glauca</i> [Moench] Voss &#215; <i>Picea engelmannii</i> Engelm.), and lodgepole pine (<i>Pinus contorta</i> Dougl. Ex Loud. var. <i>latifolia</i> Englem.)) in multi-aged stands in central British Columbia, Canada. <i>Background and Objectives:</i> Understanding competitive interactions among tree species in mixed-species stands is fundamental to supporting silvicultural decision-making in such stands. Using the periodic annual basal area increment for single trees as our dependent variable, we investigated whether neighboring trees competed with subject trees independently of species identity. We also examined the differences in single-tree basal area growth among the three conifer species over time under different levels of competition. <i>Materials and Methods:</i> We developed several spatially explicit, single-tree basal area growth models for interior Douglas-fir, interior spruce, and lodgepole pine using data from 16 plots in two blocks of a long-term study (five measurements over a 21-year period) on the response to pre-commercial thinning. We compared these equations to assess whether intraspecific or interspecific competition predominated. We also examined the differences in basal area growth among the three conifer species over time under different levels of competition. <i>Results:</i> We found asymmetrical relationships between the conifer trees and their neighbors for all species, indicating that the main driver limiting growth in these stands is aboveground competition for light. There was evidence of higher intraspecific competition for small (&lt;10.0 cm DBH) interior Douglas-fir in one block. However, there was no general pattern among larger subject trees with respect to the identity of neighborhood competitive effects and the equivalence of neighbors. We observed a higher level of basal area growth over time for interior Douglas-fir than for lodgepole pine and interior spruce, irrespective of the competition intensity and, not surprisingly, the growth rate declined with increasing competition levels for the three species. <i>Conclusions:</i> Our results provide an understanding of how interior Douglas-fir stands will develop over time and information on species interactions that could help forest managers explore different silvicultural options and their effects on individual tree growth in these complex stands.
topic competition
mixed-species forests
neighborhood effects
basal area increment
url https://www.mdpi.com/1999-4907/11/2/167
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