Article: If we build habitat, will they come? Woody debris structures and conservation of forest mammals

Bunnell, F. L., and I. Houde. 2010. Down wood and biodiversity—implications to forest practices. Environmental Reviews. 18:397–421.                                http://www.nrcresearchpress.com/doi/full/10.1139/A10-019#.UUE2UKVEF8E

Craig, V. J. 2002. Population and habitat use characteristics of forest-dwelling small mammals in relation to downed wood. Graduate thesis UBC.                                                       https://circle.ubc.ca/handle/2429/12974

Craig, V. J., W. Klenner, M. C. Feller, and T. P. Sullivan. 2006. Relationships between deer mice and downed wood in managed forests of British Columbia. Canadian Journal of Forest Research. 36:2189–2203.                                                                                     http://www.nrcresearchpress.com/doi/abs/10.1139/x06-118#.UUE2a6VEF8E

Sullivan, T.P. Sullivan, D.S., Lindgren, M.F. Ransome, D.B. 2012. If we build habitat, will they come? Woody debris structures and conservation of forest mammals. Journal of Mammalogy. 93(6): 1456-1468.                                                                                    http://www.bioone.org.ezproxy.tru.ca/doi/full/10.1644/11-MAMM-A-250.1  

                                               

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Clear-cutting a forest is a drastic alteration of habitat for forest mammals in BC because where there were once trees, there are no longer. After logging, there is usually a lot of coarse woody debris (CWD) leftover scattered over the ground (Bunnell and Houde 2010). As we have talked about in seminar discussions before, the CWD is sometimes burned to reduce future fire hazard, and is sometimes left scattered over the ground. A group of scientists from UBC had an interesting new idea to make use of the CWD by gathering it in massive rows or piles as possible new habitat opportunities for forest mammals in clear cuts. The piles and rows of CWD were intended to create opportunities for dens, or a place to hide in open clearings (Sullivan 2012). This blog takes a brief look at the 2012 article which investigates the effect of this new idea. An interesting point to note when considering this study is the importance of scale; the world looks very different depending on whether you are a mouse, or a coyote.

The experimental treatments were piles of CWD, long rows of CWD, scattered CWD, and uncut forest. The study took place in BC at three locations; Summerland (with large amounts of CWD making big piles), Vernon, and Salmon arm (both with less available CWD leading to smaller piles). The method involved live trapping of small mammals in the treatment areas, as well as snow tracking analysis for larger mammals (Sullivan 2012).

The results were highly variable depending on species. Generalists like deer mice were always able to remain in higher numbers no matter what the treatment, which didn’t add any new insight. However something interesting happened regarding a closed canopy specialist, the red backed vole which often disappears after clear-cuts. The especially large CWD rows in Summerland allowed the vole to persist in clear-cut habitat. It was also found that there was a general trend summarized by the following statement. The more, and the bigger the piles and rows of CWD, the greater the species abundance, species richness, and species diversity for small forest floor mammals. No major exciting insights were revealed by the large mammal track analysis (Sullivan 2012).

Other studies have been conducted on the effect of CWD presence or absence, and micro-scale organization, but none which yielded unambiguous results, and none of the scale executed here (Craig 2002, Craig 2006). This was a massive study which broke new ground. It was demonstrated that CWD organized into piles or rows have clear conservation implications for the fate of native forest-floor small-mammal communities after clear cutting.

To apply this method in real world application, this study suggests that piles/ rows need to be large (at least 2m tall and 5m wide), and constructed promptly after logging to prevent immediate loss of species in the area. The piles/ rows will help conserve small mammals by providing habitat in the form of den location opportunities, and safe corridors connecting mature forest (Sullivan 2012).