Big bams (Populus balsamifera) coming down

Shellie English wrote:

I observed that the Balsam Poplar (commonly known as big bams in our area), a deciduous tree common in the Montney Valley, have become weaker such that they are subject to unusual amounts of blow-down during a somewhat gentle winter of snow and wind. This blow-down includes both uprooting and breakage. This species typically give way to successional conifers or other deciduous species. It appears, however, that there is an unusual abundance that are in poor health or are down. Balsam Poplars prefer higher moisture and I am curious which aspects of environmental change might be causing this. Potential factors include shifts in rainfall and moisture regimes and temperature shifts.

Tom Okey, LEO BC coordinator, wrote:

The mean temperature in Fort St. John has increased by about 20℃ since 1976, and is projected to increase another 9℃ by 2080, as shown on the Climate Atlas of Canada. This atlas shows changes and projections for numerous metrics of change for any location in Canada. In the case of this observation, examination of these variables would be useful, but additional experts on this species should be consulted to shed more light on this observation.

The surface air temperature anomaly for February 2019 relative to the February average for the period 1981-2010 showed an extremely cold anomaly over Western Canada in February. It is possible that these unusually cold temperatures damaged and weakened these trees. Trees make loud popping sounds at extremely cold temperatures (T. Okey, personal observation, January 1983, Dead Creek Flow, Cranberry Lake, New York) representing sap freezing and damage to supporting structures. These popping sounds have been discussed by others recently (Dorn 2000, Levine, 2004), and they are known to Indigenous communities as the "Moon of the Cold-Exploding Trees" (Howard 1994, Morris 2001, Kirpatrick 2006, Sherow 2007; see ).

Gu et al (2008) found that mild winters, or winter periods of unusually warm weather followed immediately by periods of unusual cold weather can cause particular vulnerability and damage to trees. It would be worth examining the daily or weekly temperature data for Fort St. John through the winder of 2018-2019 to explore the possibility of unusual temperature variability, and wind and precipitation, which may have caused this anomalous blow down.

References

Dorn, Jonathan (May 2000). "Pop Goes the Forest". Backpacker Magazine. Active Interest Media, Inc. 28 (186, number 4): 72. ISSN 0277-867X

Gu, L., Hanson, P.J., Post, W.M., Kaiser, D.P., Yang, B., Nemani, R., Pallardy, S.G. and Meyers, T., 2008. The 2007 eastern US spring freeze: increased cold damage in a warming world?. BioScience, 58(3), pp.253-262.

Kirkpatrick, Sidney (2006). The revenge of Thomas Eakins. Henry McBride series in modernism and modernity. Yale University Press. p. 337. ISBN 0-300-10855-9. ISBN 9780300108552.

Levin, Judith (2004). Life at a High Altitude. Life in extreme environments. The Rosen Publishing Group. p. 10. ISBN 0-8239-3987-1. ISBN 9780823939879.

Howard, Joseph Kinsey (1994). Strange empire: a narrative of the Northwest. Borealis Books. Minnesota Historical Society Press. p. 43. ISBN 0-87351-298-7. ISBN 9780873512985.

Morris, Edmund (2001). The rise of Theodore Roosevelt. Modern Library Paperbacks Series. Modern Library. p. 365. ISBN 0-375-75678-7. ISBN 9780375756788.

Sherow, James Earl (2007). The grasslands of the United States: an environmental history. Nature and human societies. ABC-CLIO. p. 105. ISBN 1-85109-720-1. ISBN 9781851097203.

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