Presettlement forest in southern Ontario: Ecosystems measured through a cultural prism

Abstract

To better manage southern Ontario's natural forests, the former and present status of old growth must be understood. We hypothesize that old-growth pine (Pinus spp.), although dominant elsewhere, was less common in southern Ontario than popular history suggests: we are obliged to evaluate historical information that has been filtered both by the original compilers and through our own biases. Beginning around 600 AD, the predominant beech (Fagus americana) forest was partially replaced by maple (primarily Acer saccharum), oaks (Quercus spp.) and eastern white pine (P. strobus). This pine increase either followed abandonment of pre-Columbian agriculture or, more plausibly, accompanied climate cooling. Eighteenth and 19th century European settlers encountered abundant large trees, which they hewed for square pine timber, milled timber, and tanbark. Other stands were cut and burned for agricultural clearance, with a potash by-product. Until recently, Ontario research emphasized the old-growth pine stands of central and northern Ontario to the relative exclusion of other kinds of old forest because very few southern Ontario old-growth stands remained to study. Ontario forest resource inventory data (FRI) show stands of over 150 years totalling only 1475 ha in 1978, concentrated on the Oak Ridges Moraine, the St. Lawrence Valley and the Awenda Peninsula. Red (P. resinosa) and eastern white pine stands constituted only 5.3% of the 1978 forested area, with virtually none of over 150 years, whereas eastern hemlock (Tsuga canadensis) stands constituted 12.8%. The difficulty in finding modern old growth necessitates historical reconstruction using physical, written and graphical resources, including early survey records and trade statistics. In a case study of 1822 survey data from Darling Township (Lanark Co.) and 1960 FRI, vegetation was classified using TWINSPAN and mapped using ARC/INFO Thiessen polygons. In 1822, dominant hemlock occupied half the township but it has since been eliminated as a dominant. Conversely, there were no pine-dominated forests in 1822, but these had increased to 16% of the area by 1960. A second case used similar methods, with 1855 data for St. Edmunds and Lindsay townships (Bruce Co.) and 1981 FRI. Although logging halved the area and reduced the stature of pines in the large pinery, the elimination of dominant hemlock (originally 41% by area) is more significant. Fragmentary square timber trade data suggest that at least half the large pines in Bruce County were in St. Edmunds, so pine must have been spectacularly concentrated in a few areas. The third case, a map constructed from Gourlay's 1817–1819 survey, also demonstrates that pine-dominated areas were in the minority in southern Ontario, concentrated on sandy soils around Lakes Ontario and Erie. However, big hemlocks, beeches, maples and oaks were much more common overall. Management responses to this information should include designation of older southern Ontario forest stands (especially those never cleared since settlement) for maturation into an old-growth state, and the systematic restoration of eastern hemlock and beech stands for conservation purposes in southern Ontario. Key words: old-growth forest, Canada, Ontario, historical ecology, forest history