CGRG Bibliography of Canadian Geomorphology
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Author : Finkelstein, S.A.; and Dirszowsky, R.W.
Date : 2007.
Title : Late Holocene vegetation responses to climatic change and human impact in the southern boreal forest of central Ontario, Canada.
Publication : CANQUA Ottawa 2007. Canadian Quaternary Association Conference, June 4-8, 2007. Carleton University, Ottawa, Ontario, Canada.
Issue :
Page(s) :
Abstract
Numerous anthropogenic stressors have impacted the region surrounding Sudbury, Ontario over the past ~115 years, including metal contamination, atmospheric pollution and acid rain, fire suppression, clear-cut logging and urbanization. These impacts are super-imposed over long-term climatic change. Ecological response in the region has included a change in forest composition, with decreases in previously dominant boreal conifers (Picea glauca, P. mariana, Pinus banksiana), and increases in shade-intolerant deciduous trees, especially Betula papyrifera. Because of differences in albedo, flammability and ecosystem function between these species, the recent changes are likely to have significant impacts on forest dynamics, wildlife, microclimate, and biogeochemical cycling. The increase in the deciduous make-up of the forests of central Ontario has been ascribed to all of the above stressors; however, few long-term data are available to directly understand the cause, or the relationship between natural and anthropogenic factors. Paleoenvironmental records provide evidence of ecological change over the long term (rate, character, magnitude) and allow comparisons between recent response and natural background variation. We present here a late Holocene pollen record from Clearwater Lake (46.4°N, 81.1°W), a small (76 ha) oligotrophic lake within the City of Greater Sudbury that has been monitored in terms of water quality and aquatic ecology for ~20 yrs. 210Pb activity was used to assess sedimentation rates and develop a context for pollen analysis and assessment of regional vegetation change. The pollen data indicate that the readily observed increase in deciduous trees is not limited to Betula, but also includes increases in Acer, Fraxinus and Tilia. Among the conifers, the decrease in Pinus-types is most significant. Declining sediment organic matter content (as determined by loss-on-ignition) in recent sediments coincides temporally with increases in the pollen of deciduous species, Ambrosia and other disturbance indicators, suggesting a role for land clearance. Along with an overall increase in diversity of local pollen types, these recent changes in the composition of local forests are in strong contrast to the relatively consistent vegetation and pollen rain during the pre-historic late Holocene.
Bibliography of Canadian Geomorphology