Regional moose (Alces alces) responses to forestry cutblocks are driven by landscape-scale patterns of vegetation composition and regrowth
Introduction
Among landscape disturbances, forestry cutblocks (defined areas where trees were harvested) are widespread globally and are estimated to account for ~26% of the total global loss in forests over the last 15 years (Curtis et al., 2018). Although lawfully harvested forests are often managed to ensure vegetation regrowth, changes in forest-successional stage can affect the behaviour and space-use of many species, with cascading effects on populations and communities. Amphibians experienced higher dispersal and lower survival rates in regenerating pine plantations in the southeastern USA (Haggerty et al., 2019). Stark differences were also observed in the composition of bird species as a function of time since cut in Missouri, USA (George et al., 2019) and northern Alberta, Canada (Leston et al., 2018). In Brazil, regenerating tropical forests demonstrated a shift in small mammal communities from generalists to specialists as forests aged post-logging (Pinotti et al., 2015).
These studies suggest that the effects of forestry on wildlife vary greatly and change as forest succession ensues, but differences in the progression of vegetation regrowth among similarly aged cutblocks contributes additional variability. In Sweden, differences in slope among re-growing cutblocks predicted the occurrence of bilberry (Vaccinum myrtillus), which in turn drove the selection of cutblocks by grizzly bears (Ursus arctos) (Domevščik, 2018). In Canada, differences in vegetation regrowth affected the use of regenerating cutblocks by grizzly bears (Kearney et al., 2019) and American marten (Martes americana) (Potvin et al., 2000). Gaining a better understanding of the complexities underlying wildlife responses to cutblocks is paramount for managers to strategically plan in order to limit negative and maximize positive effects of forestry activities on individual populations and their interconnected communities.
Among species linked to forestry cutblocks, moose (Alces alces) are thought to benefit from the creation of early successional vegetation via logging (Fisher and Wilkinson, 2005). Past studies on moose demonstrated greater use of younger cutblocks in comparison to other forest patches (Heikkilä and Härkönen, 1993, Bjørneraas et al., 2011) and logging has been associated with increases in moose abundance (Forbes and Théberge, 1993). Other studies, however, suggest a decline in moose abundance and a more complex relationship between moose and logging. In Québec, Canada, for example, logging reduced moose abundance by nearly 50% in resource-poor, black spruce (Picea mariana) forests (Potvin and Courtois, 2004). More recent research in Québec—examining the potential for logging to exacerbate apparent competition between moose and woodland caribou (Rangifer tarandus caribou)—demonstrated a decrease in the strength of selection by moose for cutblocks along a 400-km latitudinal gradient as a function of lower amounts of deciduous shrub regrowth at higher latitudes (Gagné et al., 2016).
Our objective was to examine differences in spatial responses by moose to cutblocks as a function of year since cut, while also considering vegetation composition and regrowth, to better inform forestry planning in order to maintain stable moose populations. Because forests are often managed at the landscape scale, we compared moose spatial responses to cutblocks between two regions in British Columbia (BC), Canada that differed in vegetation composition and regrowth. In BC, moose populations are declining in abundance across the majority of the province (Kuzyk et al., 2018a), following mountain pine beetle (Dendroctonus ponderosae) outbreaks and extensive salvage logging. The decline, however, is not consistent as populations in several regions are stable or increasing and the magnitude of the decline varies across regions with similar amounts of disturbance (Kuzyk et al., 2018a). We hypothesized that (i) moose avoid younger cutblocks, but (ii) select for regenerating cutblocks that likely contain more structure, thus providing greater browse and lateral cover, which provides concealment from predators. We also hypothesized that (iii) selection for regenerating cutblocks is greater in areas demonstrating more vegetation regrowth (i.e., structure) and (iv) as a function of an individual’s reproductive status (calf presence or absence), potentially resulting from the avoidance of more open areas with higher predation risk for calves. Our mechanistic approach allowed us to estimate thresholds for moose in response to forest succession and provided a greater understanding for why moose often demonstrate variable responses to forestry cutblocks across studies.
Section snippets
Study areas, animal capture, and monitoring
Our study areas, Prince George South (PGS) and Bonaparte (BP), spanned 9942 km2 and 6009 km2, respectively and were located on the interior plateau of BC (Fig. 1). The interior plateau is characterized by a humid continental climate with dry, warm summers and moderately dry, cold winters. Lodgepole pine (Pinus contorta var. latifolia) was the dominant tree species, while other common coniferous tree species included spruce (Picea engelmannii × glauca), subalpine fir (Abies lasiocarpa), and
Study area differences
Prince George South had a larger proportion of broadleaf-, lodgepole pine-, and spruce-dominant stands and a smaller proportion of Douglas fir-dominant stands in comparison to BP (Table 1). The proportions of fir-dominant, open, shrub, and wet vegetation classes were similar between study areas (Table 1). A greater proportion of BP burned within the last 40 years in comparison to PGS as a result of one large fire in 2017 (Elephant Hill Fire, ~1896 km2 total area burned both within and outside
Moose responses to vegetation composition and regrowth
Not all cutblocks are the same, nor should all cutblocks be considered high quality habitat for moose. Previous research demonstrated that moose responses to forestry cutblocks vary dependent upon successional stage (Bjørneraas et al., 2011). Our research suggests that succession can vary across seemingly similar regions in relation to vegetation composition and regrowth (i.e., structure), which are likely related to landscape productivity (Beets et al., 2019) and directly influence the
Conclusion
Dissimilar moose responses to forestry cutblocks across regions are a reflection of the underlying complexity exhibited by cutblocks of differing ages with disparate patterns of vegetation composition and regrowth. This study highlights this complexity and provides a better understanding for why not all cutblocks are equivalent with regards to habitat quality for moose. Moose demonstrated more positive spatial responses to cutblocks in a study area with higher proportions of lodgepole pine and
CRediT authorship contribution statement
Matthew A. Mumma: Conceptualization, Investigation, Formal analysis, Data curation, Writing - original draft, Writing - review & editing, Visualization, Supervision. Michael P. Gillingham: Conceptualization, Writing - review & editing, Supervision, Funding acquisition. Shelley Marshall: Investigation, Resources, Data curation, Writing - review & editing, Supervision. Christopher Procter: Investigation, Resources, Data curation, Writing - review & editing, Supervision. Alexandre R. Bevington:
Declaration of Competing Interest
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: SM, CP, ARB, and MS are employed by the Province of British Columbia.
Acknowledgments
We would like to thank the Habitat Conservation Trust Foundation and Fulbright Canada for funding our analyses. We also thank British Columbia’s Ministry of Forestry, Natural Resource Operations, and Rural Development, along with Gerry Kuzyk, Francis Iredale, Doug Jury, Helen Schwantje, Mike Klaczek, Morgan Anderson, Adrian Batho, Doug Heard, and Glen Watts for financial, field and logistical support. We thank Doug Beattie for his insightful review of the manuscript. We also appreciate the
Data accessibility
Data is under the ownership and control of British Columbia’s Ministry of Forestry, Natural Resource Operations, and Rural Development.
Funding
This work has been funded by the Habitat Conservation Trust Foundation, Fulbright Canada, and through British Columbia’s Ministry of Forests, Lands, Natural Resource Operations, and Rural Development.
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