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Composition and structure of spider assemblages in layers of the mixedwood boreal forest after variable retention harvest Open Access


Other title
Vertical Stratification
Variable Retention
Spider Assembalges
Boreal Mixedwood Forest
Forest Management
Type of item
Degree grantor
University of Alberta
Author or creator
Pinzon, Jaime
Supervisor and department
Spence, John R. (Renewable Resources)
Langor, David W. (Renewable Resources-Canadian Forest Service)
Examining committee member and department
Proctor, Heather (Biological Sciences)
Hamann, Andreas (Renewable Resources)
Macdonald, Ellen (Renewable Resources)
Wise, David (Biological Sciences, University of Chicago)
Sperling, Felix (Biological Sciences)
Department of Renewable Resources

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Natural disturbances are important drivers of ecosystem change in the boreal forest and new approaches to sustainable forest management draw on natural disturbance patterns as a template for harvesting. The main premise for such approach is that species have evolved and adapted to stand-replacing natural disturbances and thus are more likely to be maintained on landscapes managed so as to preserve spatial patterns of natural disturbance. I used spiders – one of the most important, diverse and ubiquitous groups of terrestrial predatory invertebrates – as a model for assessing the impacts of variable retention harvesting practices on biodiversity in the mixedwood boreal forest. Spiders were collected from the Ecosystem Management Emulating Natural Disturbance (EMEND) project landbase over a period of five years (five to nine years post-disturbance) from different harvest treatments and forest habitats. Results from this study show that changes in composition of spider assemblages clearly followed the variable retention disturbance gradient (clear-cut to uncut treatments) and these changes were linked to habitat and forest structure. In general, low tree retention (i.e., 10-20% which is the range currently applied by the forestry industry) showed some ability to mitigate adverse effects of clear-cutting; yet, higher retention levels are needed to maintain forest specialist species, especially in late successional seres (e.g., conifer dominated). A “life-boating” effect of aggregated retention was also evident, and it was more effective when applied in combination with dispersed retention. The application of different harvesting practices alone is unlikely to entirely emulate some of the effects and processes caused by major disturbances on the landscape. Thus, keeping in mind that fire is an important and vital component in the boreal forest, this type of disturbance cannot be excluded from management if the goal is to preserve a natural range of biodiversity. In conclusion, to sustain rich and diverse spider assemblages, management of the boreal mixedwood should aim towards maintaining landscape heterogeneity. Consequently, no single harvesting practice is effective to emulate natural post-disturbance patterns and to adapt harvesting to effectively imitate the processes of a disturbance driven system, a combination of prescriptions is recommended.
License granted by Jaime Pinzon ( on 2011-08-22T21:18:01Z (GMT): 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 the above terms. The author reserves all other publication and other rights in association with the copyright in the thesis, and except as herein 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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