The series for UBC's Celebrate Research Week continues today with an entry from Dr. Brian Klinkenberg today's photograph by him via Flickr) and graduate student Claire Wooten. Lindsay writes the introduction:
Dr. Brian Klinkenberg is a professor in the UBC Department of Geography where his research focuses on advanced spatial analysis with respect to physical, health and social sciences (and the intersection of these disciplines). Dr. Klinkenberg is also the editor and project coordinator of E-Flora BC / E-Fauna BC.
Dr. Klinkenberg writes: Understanding the spatial aspects of plant dynamics is a critical part of landscape ecology today. Recently in my lab our focus on spatial analysis has led us to explore the decline of yellow-cedar in BC (see gallery link at bottom of page). Exploring the spatial occurrences on these species in the landscape has led to key insights into distributions and biogeographic changes.
Claire Wooten (graduate student) and Dr. Klinkenberg co-wrote the following about yellow-cedar die-off:
For over two decades, the phenomenon of yellow-cedar decline has perplexed researchers. Yellow-cedar (Chamaecyparis nootkatensis) (D. Don) Spach), which ranges from southern Oregon to Prince William Sound, Alaska, was known to be declining on over 200,000 ha of undisturbed forest in southeast Alaska (Snyder et al. 2008). During an aerial survey in 2004, numerous large areas of dead and dying yellow-cedar were found in coastal locations in B.C., and the nature of the dieback was found to be consistent with the phenomenon in southeast Alaska (Hennon et al. 2005).
Research into the decline of this long-lived species began in the early 1980s and a sequence of symptoms was identified. The initial symptom was determined to be fine root death, followed by death of small-diameter roots (Hennon et al. 2006) (PDF). As the roots start to die, the trees develop thin off-colour crowns and necrotic lesions spread from larger roots up the bole (Hennon et al. 2006). The natural resistance of yellow cedar heartwood to decay allows dead trees to remain standing for 80 to 100 years after death. By examining the standing snags it was possible to establish that the decline of yellow-cedars began in about 1880-1900 (Hennon & Shaw, 1997).
Investigations initially focused on finding a biotic cause of the decline, but one by one the suspected agents were ruled out (Hennon et al. 1990). Attention then shifted to abiotic factors potentially associated with the decline--an association with wet, poorly drained soils was found. However the relationship with soil drainage is inconsistent, with limited decline occurring on wet sites at higher elevations (Hennon et al. 2006). Air and soil temperature were determined to be stronger risk factors than poorly drained soils (D'Amore & Hennon, 2006).
These clues led researchers to propose a new, complex hypothesis to explain yellow-cedar decline. According to Hennon et al. (2006), saturated soils create open, exposed canopies which experience soil warming early in the spring. This warming triggers the yellow-cedars to lose their cold tolerance, making them more susceptible to freezing injury. Snow appears to protect yellow-cedar against this freezing injury by preventing soil warming. However, the end of the Little Ice Age, which coincided with the onset of decline, has led to a reduction in snowpack at lower elevations (Hennon et al. 2006). This shift in climate may represent the environmental trigger responsible for the decline and suggests that the dieback may expand if warming trends continue (Hennon et al. 2006).
Our research questions are being addressed through a combination of remote sensing and GIS techniques. Spatial patterns of biophysical factors (e.g. elevation, slope, aspect) are being used in our assessment of the relations between the distribution of decline and the environmental predictors.
The high value of yellow-cedar wood and the desire to conserve species diversity means that a management strategy incorporating the influence of a warming climate is required. Ultimately, this research may provide insight into the devastating effects that climate change can have on a forest ecosystem.
Dr. Klinkenberg also adds an additional note regarding the name of this species:
There has been much debate over the taxonomic status of yellow-cedar following the discovery of a closely related tree species in northern Vietnam, Xanthocyparis vietnamensis Farjon & Hiep. Whether yellow-cedar is transferred to this newly established genus as Xanthocyparis nootkatensis or the older Callitropsis nootkatensis (D.Don) Örest name is adopted, will be determined at the next International Botanical Congress in 2011 (Mill & Farjon, 2006).
D'Amore, D. and Hennon, P.E. 2006. Evaluation of soil saturation, soil chemistry, and early spring soil and air temperatures as risk factors in yellow-cedar decline. Global Change Biology. 12: 524-545
Hennon, P.E., D'Amore, D., Wittwer, D., Johnson, A., Schaberg, P., Hawley, G., Beier, C., Sink, S. and Juday, G. 2006. Climate warming, reduced snow, and freezing injury could explain the demise of yellow-cedar in southeast Alaska, USA. World Resource Review. 18(2): 427-450.
Hennon, P.E., D'Amore, D., Zeglen, S. and Grainger, M. 2005. Yellow-cedar decline in the North Coast Forest District of British Columbia. Res. Note RN-549. Portland, OR: U.S. Dep. Agric., Pacific Northwest Research Station. pp.20.
Hennon, P.E. and Shaw, C.G. III. 1997. The enigma of yellow-cedar decline - What is killing these long-lived, defensive trees? Journal of Forestry. 95(12): 4-10.
Mill, R. R. And Farjon, A. 2006. Proposal to conserve the name Xanthocyparis against Callitropsis Oerst. (Cupressaceeae). Taxon. 55(1): 229-231.
Snyder, C., Schultz, M.E. and Lundquist, J. (Compilers) 2008. Forest health conditions in Alaska - 2007: a forest health protection report. Gen. Tech. Rep. R10-PR-18. Anchorage, AL: U.S. Dep. Agric., Forest Service, Alaska Region.