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Developing animal-habitat models for management of high-elevation forests Huggard, David John
Abstract
I examined ways to develop better models relating animals to habitat features, forest harvest types and edges, using data on spruce grouse (Falcipennis canadensis) and small mammals (masked shrews, Sorex cinereus; montane shrews, Sorex monticolus; and southern redbacked voles, Clethrionomys gapped). The work was part of the multidisciplinary Sicamous Creek Silviculture Systems project in high-elevation Engelmann spruce-subalpine fir forest in southern British Columbia. Spruce grouse in winter selected knolls and areas with dense, small and short trees, dense canopy cover, and exposed rock. Grouse avoided forest within 5- 10 m of cutblock edges. Occurrence of grouse in forests near open wetlands increased with increasing predicted habitat quality, but declined within 10-20m of the opening. Removing 33% of timber volume with openings of 0.1, 1, or 10 ha reduced occurrence of grouse by a similar amount; uniform partial cutting reduced their occurrence by 69%. Habitat relationships were less evident for small mammals collected in pitfall traps. As a preliminary step in model development, I elaborated techniques that partition environmental and spatial variation in abundance to include variation due to habitat types, habitat elements, and shared variation, and also estimated measurement error. Unexplained variation was high, and equalled expected measurement error in half the cases. Relationships with habitat elements were confounded to varying degrees by habitat type differences and spatial patterns. The elaborated technique is useful to characterize variation observed in habitat relationship studies, and to guide further study and interpretations of results. I compared classification and regression trees (CART) and neural networks (NN) to linear additive models. The more complex NN and CART habitat models fit data better than linear additive models, but had equal or poorer predictive abilities with data from independent sites. The fit of a model and its predictive ability were unrelated across 14 data sets and the 3 techniques. However, CART and NN modelling have heuristic benefits, suggesting non-linear and contingent relationships for future study. I summarized effects of harvest types on small mammals using likelihood functions to facilitate applied interpretations and a Bayesian combination with literature estimates. Sorex cinereus and immature red-backed voles declined in clearcuts by 26 - 57%, while uniform partial cutting had smaller negative or positive effects. Sorex monticolus increased slightly in both harvest types. Edge response varied for the 3 small mammal species. The shrews showed weak positive associations with shrub, herb, or forest floor cover. Red-backed voles showed stronger positive, interacting relationships with canopy, shrub cover and coarse woody debris. Management implications are presented for maintaining spruce grouse and small mammal habitats.
Item Metadata
Title |
Developing animal-habitat models for management of high-elevation forests
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2000
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Description |
I examined ways to develop better models relating animals to habitat features, forest harvest
types and edges, using data on spruce grouse (Falcipennis canadensis) and small mammals
(masked shrews, Sorex cinereus; montane shrews, Sorex monticolus; and southern redbacked
voles, Clethrionomys gapped). The work was part of the multidisciplinary Sicamous
Creek Silviculture Systems project in high-elevation Engelmann spruce-subalpine fir forest in
southern British Columbia. Spruce grouse in winter selected knolls and areas with dense,
small and short trees, dense canopy cover, and exposed rock. Grouse avoided forest within 5-
10 m of cutblock edges. Occurrence of grouse in forests near open wetlands increased with
increasing predicted habitat quality, but declined within 10-20m of the opening. Removing
33% of timber volume with openings of 0.1, 1, or 10 ha reduced occurrence of grouse by a
similar amount; uniform partial cutting reduced their occurrence by 69%. Habitat relationships
were less evident for small mammals collected in pitfall traps. As a preliminary step in model
development, I elaborated techniques that partition environmental and spatial variation in
abundance to include variation due to habitat types, habitat elements, and shared variation,
and also estimated measurement error. Unexplained variation was high, and equalled
expected measurement error in half the cases. Relationships with habitat elements were
confounded to varying degrees by habitat type differences and spatial patterns. The
elaborated technique is useful to characterize variation observed in habitat relationship
studies, and to guide further study and interpretations of results. I compared classification and
regression trees (CART) and neural networks (NN) to linear additive models. The more
complex NN and CART habitat models fit data better than linear additive models, but had
equal or poorer predictive abilities with data from independent sites. The fit of a model and its
predictive ability were unrelated across 14 data sets and the 3 techniques. However, CART
and NN modelling have heuristic benefits, suggesting non-linear and contingent relationships
for future study. I summarized effects of harvest types on small mammals using likelihood
functions to facilitate applied interpretations and a Bayesian combination with literature
estimates. Sorex cinereus and immature red-backed voles declined in clearcuts by 26 - 57%,
while uniform partial cutting had smaller negative or positive effects. Sorex monticolus
increased slightly in both harvest types. Edge response varied for the 3 small mammal
species. The shrews showed weak positive associations with shrub, herb, or forest floor
cover. Red-backed voles showed stronger positive, interacting relationships with canopy,
shrub cover and coarse woody debris. Management implications are presented for
maintaining spruce grouse and small mammal habitats.
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Extent |
8748069 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-07-14
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0089621
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2000-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.