Cherry birch (Betula lenta) COSEWIC assessment and status report: chapter 8

Biology

The following information is based on the author’s field observations in Ontario, plus three sites in western New York, as well as a variety of references as noted.

Life cycle and reproduction

This species is a long-lived woody perennial attaining an age of 200 years or more. Fruiting began before the age of 16 years on the trees of the University of Guelph Arboretum living gene bank.

The species is monoecious with male and female flowers borne on separate catkins but on the same tree. Catkins develop the year before flowering, which occurs early in the spring before the leaves expand. Pollen is dispersed by wind. Hybrids with yellow birch can be artificially produced but are not known in nature (Sharik & Burton, 1971).

Seeds develop through the summer and are released in late fall to winter. Seeds germinate without stratification, but require light (Ontario Ministry of Natural Resources [OMNR], 2000; Kock, 1998). Seedling establishment was observed in western New York in openings in the forest canopy on areas of fine gravel but not in the duff covered part of the forest floor. Some of the trees had stilt roots indicating an origin on a decayed stump or nurse log. Saplings were also observed in this site. The species is dependent on sexual reproduction; clonal growth is not known beyond re-sprouting from cut stumps.

Herbivory

Birches are browsed by large herbivores and sometimes subject to defoliating insects but these were not observed as threats in any of the populations observed.

Physiology

In southern Ontario, soils are generally alkaline due to the presence of limestone bedrock. In the New York populations the soils were likely more neutral to acidic on the basis of the associated species (e.g., Vaccinium spp., Quercus prinus). In cultivation, the species does well on lime-rich soils; it appears that soil pH is not a limiting factor.

Dispersal/migration

Seeds have small wings and are dispersed by wind; dispersal distances can be enhanced by blowing over snow and ice during winter release. The historical sighting of another tree in the same 15-16 Mile Creek valley was likely the result of dispersal from this one stand.

Interspecific interactions

This species is not dependent on animal vectors for pollination or seed dispersal. No negative interspecific interactions were observed.

Adaptability

Cherry birch can establish in small openings in the forest. Two saplings and a small tree were observed in the ravine below the main population at 15 Mile Creek.

This species can be grown readily from seed. The University of Guelph Arboretum has offspring from each mature individual of the northerly15 Mile Creek sub-population. In addition, the Region of Niagara Tree Advisory Committee purchased trees from Little Otter Tree Farm for planting throughout St. Catharines; the seeds came from the lakeshore trees that no longer exist. The trees acquired by the land owners at the northerly 15 Mile Creek and the lakeshore sites were from Niagara College, but also originally grown by Little Otter Tree Farm. Four of these were planted at the 15 Mile Creek site a few years ago where mature trees were recently lost to storm damage (May 2004 and before); two trees were planted at the lakeshore property and one survives.

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