Pollen evidence for major shifts in forest composition since the mid‐nineteenth‐century in the vicinity of Sudbury,Ontario |
| |
Authors: | Randy W Dirszowsky Sarah A Finkelstein Anthony M Davis |
| |
Institution: | 1. Department of Earth Sciences, Laurentian University;2. Department of Earth Sciences, University of Toronto;3. Department of Geography, University of Toronto |
| |
Abstract: | Numerous anthropogenic stressors have impacted the region surrounding Sudbury, Ontario, leading to pronounced vegetation and landscape change. Few long‐term records exist to understand the nature or timing of this change. We use pollen analysis from radiometrically dated sediments of Clearwater Lake to compare pre‐ and post‐settlement vegetation. Beginning ~1850 CE, the record shows major shifts in forest composition, coincident with settlement and the beginnings of lumbering. These changes are unprecedented for the past ~5000 years, and consist of increases in diversity and abundance of deciduous tree taxa and herbaceous disturbance indicators. While evidence of mining appears as early as 1900 CE, little effect is seen in the pollen record until ~1930 CE, when sedimentation rates increased and acidification of the lake also began. At this time, further increases in palynological disturbance indicators and minimum sediment organic matter levels indicate the period of maximum vegetation loss. As a result of reduced emissions since the 1970s, water quality began to improve in Clearwater Lake and there are some decreases in the abundances of shade‐intolerant disturbance indicators in the pollen record. However, the fact that the pollen assemblages do not resemble those prior to 1850 suggests lasting vegetation changes. |
| |
Keywords: | paleoecology palynology Great Lakes St Lawrence mixed forest ecotone human impact restoration palé oé cologie palynologie forê ts mixtes des Grands Lacs et du fleuve Saint‐Laurent é cotone impact humain restauration |
|
|