Forest overstorey and age as habitat? Detecting the indirect and direct effects of predators in defining habitat in a harvested boreal landscape

• Published in: Forest ecology and management Vol. 326; pp. 101 - 108
• Main Authors: Boan, Julee J., Malcolm, Jay R., McLaren, Brian E.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.08.2014; Elsevier
• Subjects: Alces alces; Animal and plant ecology; Animal productions; Animal, plant and microbial ecology; Apparent competition; Biological and medical sciences; Canis lupus; Caribous; Forest harvesting; Forestry; Forests; Fundamental and applied biological sciences. Psychology; Habitats; Moose; Niche modeling; Rangifer tarandus caribou; Regression; Roads; Structural equation model; Synecology; Terrestrial animal productions; Terrestrial ecosystems; Vertebrates; Winter habitat; Wolves; Woodland caribou; Woodlands; Canada, Ontario; Forest harvesting; Niche modeling; Winter habitat; Woodland caribou; Apparent competition; Structural equation model; Competition; Forests; Boreal zone; Herbivorous; Ruminant animal; Overstorey; Modeling; Habitat; Vegetation structure; Ungulata; Age; Direct effect; Structural equation modeling; Harvesting; Forest ecology; Vertebrata; Mammalia; Forestry; Cervidae; Artiodactyla; Predator; Detection
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2014.03.052

•We model caribou use based on timber harvesting, roads, predators and apparent competitors.•Increases in roads and wolves result in a decrease in caribou use at the broad scale (>10,000ha).•Increases in moose and moose browse result in a decrease in caribou use at the fine scale (<1000ha).•The relationship between logging roads and moose browse and decreases in caribou use are indirect.•Forest overstorey and age, alone, are not strong predictors of caribou use. Given the importance of wildlife habitat protection in meeting land use management objectives, criteria for “habitat” identification are surprisingly amorphous. For example, while much current habitat modeling has tended to avoid the term “niche modeling”, niche assumptions are implicit – meaning the presence of predators and competitors is essential to whether or not a species uses, or will use, an area. In this paper, we examine environmental variables associated with woodland caribou (Rangifer tarandus caribou) presence in the boreal forests of northwestern Ontario, Canada. Based on winter aerial surveys conducted in 2010–2013, we used logistic regression to identify important habitat characteristics (and/or their surrogates) and structural equation modeling (SEM) to explore causal and indirect caribou habitat relationships, at broad and fine scales. The best-fit regression model (>10,000ha) to explain caribou presence, at the broad scale, included the presence of moose (Alces alces), wolves (Canis lupus), logging roads and primary roads, and all top models included wolves. In contrast, at the fine scale (<1000ha), older, conifer forest was included in all of the top models of caribou presence. Using SEM, at broad scales, we found significant effects of increases in logging road density resulting in a direct increase in wolf presence, and indirectly in a decrease in caribou presence. However, at fine scales, we found significant direct positive effects between moose browse and moose presence, with indirect negative effects on caribou presence. We provide evidence that, at broad scales, habitat identification that includes logging roads and wolves provides a better measure of suitability of an area for caribou occupation than does forest cover alone. We suggest modeling of present or future habitat for woodland caribou will only be marginally effective if additional covariates of predation risk are not inclusive to the quantification of habitat supply.