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 19 th 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 mat...

Avian Assemblages Differ between Old-Growth and Mature White Pine Forests of Ontario, Canada: A Role for Supercanopy Trees?

“…Most of the logged stands were >200 years old, with individual trees being 46 to 61 m in height and 1.2 to 2.1 m in diameter (Frotheringham 1914). This historical logging, plus a policy of eliminating old growth earlier this century, fire suppression, and, in some areas, fungal disease, have together contributed to the loss and fragmentation of eastern old-growth pine forests, and to the resulting landscape pattern of remnant, isolated stands seen today (Suffling et al 2003, Thompson et al 2006). Evidence for significant reductions in red and white pine comes from broad-scale studies (e.g., >180,000 km 2 by Pinto et al 2008; see also Leadbitter et al 2002).…”

Disassociating tree species associations in the eastern United States

“…Because long periods without disturbance by current land use (i.e., tree removals occur more frequently than the lifespan of most tree species) are not present in the landscape, sugar maple and beech were not likely to continue as a dominant association; indeed, current correlation between the two species was not particularly strong and American beech currently is a minor species. Sugar maple has increased whereas beech has declined, probably due to multiple factors including forestry selection against beech and larger gaps that favors sugar maple, poor beech dispersal after harvest, and beech back disease (Cryptococcus fagisuga and Neonectria - Dyer 2001, Suffling et al 2003. Likewise, the oak-chestnut association of the eastern side of eastern broadleaf forests has been disassociated by chestnut blight and subsequent preemptive harvest that removed potentially resistant genotypes.…”

Predicting the potential for old-growth forests by spatial simulation of landscape ageing patterns

“…The n potential ignitions are then placed randomly across the landscape in 1-ha cells; whether a fire "starts" or not depends on the forest cover and age-based fuel type, and the DMC where ignition occurs. A fire will not ignite if DMC is ≤ 20, which represents the equilibrium moisture content in fuel (van Wagner 1987). Once ignited, a fire can spread to the neighbouring cells as simulated by the fire spread sub-module.…”

“…For each simulation year, a calendar year is randomly selected from these databases to provide daily estimates of historical forest fire weather indices and lightning-caused fire counts. The following indices of the Canadian Forest Fire Weather Index (FWI) System are used in the model: duff moisture code (DMC)-a rating of the moisture content of loosely compacted, decomposing organic layers of moderate depth; fine fuel moisture code (FFMC)-a rating of the moisture content of litter and fine cured fuels; and build-up index (BUI) -a rating of the total fuel available to a spreading fire (van Wagner 1987). For a given day of the simulation, the historical database is queried for the number of lightning-caused fires, m, that occurred on that day.…”

“…The first category includes various methods of extracting evidence of past disturbances (e.g., Suffling et al 2003) and extrapolating that information to the future. The second category includes methods of theoretical prediction, based on empirical information (e.g., Johnson and van Wagner 1985), mechanistic processes (e.g., Finney 1999), or a hybrid of both (e.g., Keane et al 1996).…”