Bulkley Valley Research Centre - Science in the Public Interest

Testing Ecological Resilience Theory in Pine-lichen Ecosystems of West Central British Columbia

Project Reference Number: 2009-06

Project Status: Complete

Led by: Sybille Haeussler, PhD, UNBC, Smithers

Alana Clason, NSERC Industrial Scholarship; Beth Henderson, Bulkley Valley Research Centre

Funder: NSERC; University of Alberta; Private Donation; Ministry of Forests (In-Kind Support)

Clump Of Whitebark Pine Seedlings In Lichen, Photo by Harry Williams Aug 2006

The response of ecosystems to changes in environmental conditions is typically non-linear (Scheffer et al. 2001; Schneider 2004). Instead of shifting incrementally, ecosystems often display threshold-type behaviour whereby significant events serve as tipping points, precipitating a sudden switch from one state to another. A massive event such as the mountain pine beetle (MPB) outbreak that recently spread through BC provides an unparalleled opportunity to investigate such tipping point behaviour in forest ecosystems.

In 2007, scientists from the Bulkley Valley Research Centre, UBC Forest Sciences Dept & MoFR undertook a 1 yr study (BC Forest Science Program Project M08-1568) to demonstrate tipping point behaviour in whitebark pine-lichen ecosystems south of Smithers. We hypothesized that cumulative effects of MPB, white pine blister rust, fire exclusion & climate change would cause Pine-Lichen ecosystems to shift towards mesic Subalpine Fir-Hemlock-Moss ecosystems with a net loss of ecosystem diversity (homogenization) across the subalpine landscape. Our study was prompted by Bulkley Valley Research Centre project 2007-22 which showed short-term increases in Ericaceous shrubs or mosses & declines in lichen abundance after MPB.

The results were decidedly equivocal: 3 study sites showed evidence of a shift towards mesophytic vegetation over 25-30 yr, whereas 2 sites had increases in lichens & associated oligotrophic species. The net result was no significant change in ecosystem condition across 5 study sites & no statistically significant evidence of lower ecosystem diversity.

We now believe that a threshold exists whereby Pine-Lichen ecosystems below the threshold shift into the mesic Fir-Hemlock-Moss stability domain, whereas ecosystems above the threshold retain (even amplify) their distinct soil & vegetation features after MPB outbreaks through positive plant-soil feedback processes. Rather than becoming homogeneous, the ESSF landscape should thus retain nodes of highly resilient Pine-Lichen woodlands within a matrix of Fir-Hemlock-Moss forest. We refer to our revised hypothesis as the ‘Wal-Mart’ hypothesis because an analogous situation arises when highly competitive chain stores move into a retail landscape: local businesses that are not sufficiently distinctive go under, whereas specialty stores often demonstrate high resilience & enhanced competitiveness by increasing their distinctiveness from the superstore.

Graduate Student Alana Clason who holds an NSERC Industrial Scholarship jointly at the Bulkley Valley Research Centre and the University of Alberta is testing the Wal-Mart hypothesis by remeasuring vegetation and soils at existing 25-30 yr old ESSFmc/02-03, & ESSFmk/02-03 Biogeclimatic Ecosystem Classification plots within the study area. The increased sample size should confirm whether or not there has been a net homogenization & identify threshold conditions (soil, landform, past disturbance, stand structure) that create resilient Pine-Lichen ecosystems. Her results will guide forest management activities seeking to enhance the ecological resilience of the future forest.


Scheffer et al. 2001. Nature 413:591-596
Schneider, S.H. 2004. Global Env. Chg. 14:245-258

To see all the work that the Bulkley Valley Research Centre has undertaken with respect to whitebark pine, please view our Whitebark Pine website at http://bvcentre.ca/whitebark.

Related Reports

Publication Date Report Title Authors
2014 Forest response to cumulative disturbance and stress: Two decades of change in whitebark pine ecosystems of west-central British Columbia Alana Clason, Ellen Macdonald, Sybille Haeussler
February 2011 Amending SARA List of Species at Risk to Include Whitebark Pine (Pinus albicaulis) Sybille Haeussler, Alana Clason, Joanne Vinnedge
2010 Exploring Whitebark Pine at its Northwest Limit Sybille Haeussler
2010 Ecosystem Change at Whitebark Pine’s Northern Limit Alana Clason, Ellen Macdonald, Sybille Haeussler
October 2009 Effects of Cumulative Disturbance on Endangered Whitebark Pine-Lichen Woodland Ecosystems of West Central BC - Extension Note #8 Sybille Haeussler
October 2009 Do Whitebark Pine-Lichen Ecosystems of West Central British Columbia Display Tipping Point Behaviour in Response to Cumulative Stress? Sybille Haeussler; Alex Woods; Ken White; Elizabeth Campbell; Allen Banner; Phil LePage
2009 Forest change under stress and disturbance Alana Clason
2008 Ecological resilience of Whitebark pine - Cladina lichen ecosystems at the northwest limit of the species' range Sybille Haeussler, Leanne Helkenberg, Anita Norman, Suzanne Simard and Alex Woods
2008 Threatened Whitebark Ecosystems at their Northern Limits in BC Sybille Haeussler