Canadian Forest Service Publications

The generation of USDA-equivalent extreme minimum temperature models and a comparison with Canada's plant hardiness zones. 2006. McKenney, D.W.; Hutchinson, M.F.; Papadopol, P.; Campbell, K.L.; Lawrence, K.M. Canadian Journal of Plant Science 86: 511 - 523.

Year: 2006

Issued by: Great Lakes Forestry Centre

Catalog ID: 28684

Language: English

Availability: PDF (request by e-mail)

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Hardiness zones are widely used in North America to support the trade of plants and recommendations on local use of perennial plant species. In Canada, two zonation approaches are in use, a made-in-Canada model that integrates seven climate variables and the United States Department of Agriculture's (USDA) extreme minimum temperature map/model. In this paper we develop and present several extreme minimum temperature models for the 1961-1990 and 1971-2000 climate normal periods and annual models for the winter seasons of 1961 through 2000. These models are similar in nature to the USDA plant hardiness model/map. We compare these models with a recent update of the Canadian plant hardiness zones developed with the same mathematical interpolation techniques (thin plate smoothing splines). Individual Canadian zones typically span five to nine USDA-equivalent sub-zones in total, although most of the area (>75%) of each zone generally spans 3-4 USDA sub-zones. We note that there is no simple transformation of one zonation approach to the other, but values for both systems can now be obtained for any location in Canada using an internet mapping tool. Over the period of 1961-2000 extreme minimum temperature has been trending upward in most provinces. These trends may be affecting plants in some locations, but a lack of survival and/or hardiness data is a significant impediment to assessing this. Variation in extreme minimum temperature over the 1961 to 2000 period was greatest in western North America, particularly interior British Columbia.