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Permanent link (DOI): https://doi.org/10.7939/R34X3J

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Patterns and causes of variation in understory plant diversity and composition in mature boreal mixedwood forest stands of western Canada Open Access

Descriptions

Other title
Subject/Keyword
Boreal mixedwood forest; vegetation patches; understory communities; habitat heterogeneity; plant composition, plant diversity
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Chavez Varela, Virginia
Supervisor and department
Macdonald, S. Ellen (Renewable Resources)
Examining committee member and department
Comeau, Philip G. (Renewable Resources)
Vellend, Mark (Botany & Zoology & Biodiversity Research Centre, University of British Columbia)
Cahill, James F. (Biological Sciences)
He, Fangliang (Renewable Resources)
Department
Department of Renewable Resources
Specialization

Date accepted
2010-09-30T15:52:49Z
Graduation date
2010-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Boreal mixedwood forest stands are comprised of a mixture of small canopy patches of varying dominance by conifer (mostly white spruce (Picea glauca (Moench) Voss)) and broadleaf (mostly trembling aspen (Populus tremuloides Michx.) trees. The purpose of this work was to extend our understanding of the patterns and causes of variation in understory vascular plant communities in unmanaged, mature boreal mixedwood forests. First, I assessed variation in understory community composition in relation to canopy patch type (conifer, mixed conifer-broadleaf, broadleaf, gaps) within mixedwood stands. The mosaic of canopy patches leads to different micro-habitat conditions for understory species, allowing for communities that include both early and late successional species and contributing to greater understory diversity. This study suggests that the mosaic of small canopy patches within mixed forest stands resembles a microcosm of the boreal mixedwood landscape, across which understory community composition varies with canopy composition at the stand scale. Second, I investigated the hierarchical organization of understory diversity in relation to the heterogeneous mosaic of canopy patch types through additive partitioning of diversity. The largest proportion of species richness was due to turnover among patches within patch type while individual patches had higher evenness. The mosaic of canopy patch types within mixedwood forests likely plays a crucial role in maintaining the hierarchical levels at which understory diversity is maximized. Third, I examined interactions among understory plant species by investigating the effect of shrub removal on biomass, composition and diversity of herbs using a 3-yr removal study in a natural understory community. There is asymmetric competition for light between erect shrub and herb species but herb response to erect shrub removal was species-specific. Plant interactions play an important role in structuring boreal understory communities. Finally, I explored the relative influence of space, environmental variables, and their joint effects, on understory composition and richness. The environmental variation caused by small canopy patches and biotic processes, such as species interactions, converge at the fine scale to create a spatially patchy structure in understory communities in boreal mixedwood forests. Modifications in the natural mixture of small canopy patches could disrupt the spatial and environmental structures that shape understory composition and diversity patterns.
Language
English
DOI
doi:10.7939/R34X3J
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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2014-04-29T19:17:20.739+00:00
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File format: pdf (Portable Document Format)
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File size: 1352739
Last modified: 2015:10:12 15:28:36-06:00
Filename: Chavez Varela_Virginia_Fall 2010.pdf
Original checksum: 031968c5dd5ddacc6258a95873b56cd0
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File title: Study II: Spatial relationships and associations between Canopy and Understory Species Composition and Diversity
File author: Virginia Chavez
Page count: 176
File language: en-CA
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