Ecosystem Patterns and Processes

Pilot study

In a one-year pilot study, researchers from the Bulkley Valley Research Centre and the University of British Columbia, led by Dr. Sybille Haeussler, returned in 2007 to four whitebark pine ecosystems south of Houston, BC that had been carefully described (trees, understory vegetation and soils) during Biogeoclimatic Ecosystem Classification (BEC) fieldwork between 1978 and 1985. Our objective was to determine how the whitebark pine ecosystems had changed as a result of 2 mountain pine beetle (MPB) outbreaks in the late 1980s and the mid-2000s as well as other on-going stresses.


Berglund Lake moderately-dry ecosystem: 1978


Spot the differences: 2007


The pilot study revealed an >80% decline in whitebark pine basal area over 2-3 decades. In the forest understory ericaceous shrubs (huckleberries, false azalea) increased, while reindeer lichens (Cladina, Cladonia, Stereocaulon spp.) declined on some, but not all, sites. It appeared that that dry whitebark pine ecosystems on rocky or gravelly soils might be more resilient to the cumulative changes than moderately dry ecosystems on loamy soils.  

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Research Report

Extension Note


MSc study by Alana Clason:

To follow up on the pilot study, the Research Centre recruited graduate student Alana Clason to undertake MSc research under the supervision of Dr. Ellen Macdonald at the University of Alberta (2009-2010). Fourteen BEC forest plots from 1978-1988 were revisited to examine the overstory and understory dynamics of whitebark pine ecosystems in northwest BC affected by mountain pine beetle (2 outbreaks), ongoing death from blister rust, and successional changes due to a general lack of wildfires.  

Two distinct ecosystem types (‘dry’ and ‘moderately-dry’) were tracked to assess their response and vulnerability to these multiple stressors and disturbances. Vegetation changes over time were compared to a reference non-whitebark pine ecosystem. Over the previous 21-29 years, the overstories in the dry ecosystems became progressively more similar to those of the reference ecosystems, while the moderately-dry ecosystems acquired more mountain hemlock. Understories did not change significantly in either type of ecosystem.


Changes in whitebark pine overstories from the 1980s to 2000s. Pa = whitebark pine, Hm = mountain hemlock, Bl = subalpine fir.

Spatial analysis of vegetation patterns indicated that physical site factors such as soil appear to determine patterns on rocky dry sites, while biotic interactions between canopy and understory plants may drive patterns on gravelly dry sites. Rocky dry sites likely require the least intensive restoration, followed by gravelly dry, and then moderately-dry sites.

Research publication (Clason et al. 2015)

More details and publications