Ongoing Research


	Alpine Treeline Dynamics and Climatic Change High-elevation forest ecotones are arguably bellwethers of climatic change, and most projections of future species distributions assume that climate is the predominant factor affecting species range limits. However evidence from treeline environments suggests that a range of positive and negative biological and climatic interactions both facilitate and inhibit the migration of trees in response to recent climatic change. We are working to assess the role of biotic and abiotic factors in restricting or enhancing the migration of trees beyond their historical limits, and the extent to which climatic factors mediate these interactions. Theses: Rob Brown
	Sensitivity of Sugar Maple to Climatic Change Sugar maple (Acer saccharum) is one of the most economically and ecologically important species in northern hardwood forests. It is also an iconic species for Canada. Climatic change is projected to shift its distribution substantially northward, but this migration will undoubtedly interact with other factors to determine the capacity of sugar maple to occupy climatically suitable habitat. We are working to determine the role of site factors, such as soil properties, stand density and composition, and moisture availability, in mediating the climatic sensitivity of sugar maple. Theses: Kerry Schutten, Laura Benakoun
	Coarse Woody Debris Cycling in Subboreal Forests Coarse woody debris (CWD) plays an essential role in riparian systems, influencing stream hydrology, geomorphology, and ecology. Yet surprisingly little is known about the long-term dynamics of woody debris cycling in Southern Ontario, or how land-use changes may have affected woody debris dynamics. We are undertaking research to quantify to quantify the structure, composition, and residence time of CWD in sub-boreal drainage networks. As part of these efforts we are seeking to identify the important sources of CWD (e.g., wind, fire, flood, and beavers), and to determine the degree to which land management practices have changed these sources. Our ultimate goals are to assess the importance of CWD to long-term carbon storage in sub-boreal Canada, and to provide ecological benchmarks to guide the restoration of drainage basins that have been impaired by historical management practices. Theses: Robert Oliver
	Climate of Southwestern Ontario Over the Last Millennium The ancient cedars of the Niagara Escarpment contain information on the climate of Southern Ontario's industrial heartland that may span more than a thousand years. We are building on the work done by the Cliff Ecology Research Group to extend these chronologies in order to develop a millennium length chronology of climatic variability. This record will provide an essential context for understanding climatic change, the regional effects of El Niño and the North Atlantic Oscillation, and the historic range of variability in the persistence and severity of drought. Map of our study sites in Google Earth. Theses: Graham Clark
	Fire Ecology of Mixed Severity Fire Regimes Fire regimes have typically been characterized as either high-severity, low-frequency (such as in the boreal forest) or low-severity, high-frequency (such as in ponderosa pine forests). At the "pyrotone" between these extremes fire behaviour and effects are complex, exhibiting features of both extremes, but resulting in landscape patterns that are more diverse than either. We are developing models to reconstruct fire history in these environments, as well as assessing interactions with other disturbance agents (e.g., western spruce budworm), and the effects of land use history, fire exclusion, and climatic change. Map of our study sites in Google Earth. Theses: Eric DaSilva, Vesta Mather, Theresa Dinh
Subfossil Wood
	Ecology of Garry oak savannas Garry oak (Quercus garryana) savannas are among the most endangered ecosystems in Canada. Less than 5 percent of their historical range remains undeveloped, and they support over 100 species at risk. The processes that maintain temperate savannas are poorly understood, and many are threatened by exotic species and conifer encroachment. Over the past five years we have undertaken a number of studies on Garry oak savannas to determine the historical frequency of fire and its ecological effects , the rates and patterns of conifer encroachment, the effects of climatic variability on establishment and growth rates, and the effects of introduced species on the soil moisture budget. Insights from these studies are being used to guide management and restoration of Garry oak savannas in Canada and the United States. Map of our study sites in Google Earth. Theses: Shyanne Smith, Jenny Franks, Tom Maertens, Lesley Davy
	CO₂, Forests & Climatic Change Predicting future rates of carbon sequestration and forest distributions depends critically on knowing how trees will respond to elevated atmospheric CO₂. However most available evidence is based on short-term studies of seedlings growing in artificial environments. We are using the global tree-ring record to assess how mature trees have responded to atmospheric CO₂ change over the past century. Our preliminary results suggest that CO₂ fertilization and increasing water use efficiency are more complicated than is suggested by growth chamber studies, or most in situ studies undertaken to date. Theses: Vanessa Stretch
	The Pacific Decadal Oscillation The Pacific Decadal Oscillation (PDO) is a long-lived El Niño-like pattern of Pacific climate variability that has important impacts on ecosystems and water resources throughout the Pacific Northwest. While Ze'ev is no longer actively researching the temporal variability of the PDO, its influence on ecosystem processes is an important part of our work. See the publications page If you would like reprints of our PDO papers, or email Ze'ev if you would like the time series of our PDO reconstructions.