Pollen and charcoal analyses were used to reconstruct the Holocene vegetation and fire history of Pender Island (48°46’59” N, 123°18’11” W), located in the southern Gulf Islands on the south coast of British Columbia. A 9.03 m sediment core was retrieved from Roe Lake, a small, deep lake on Pender Island. Four AMS radiocarbon ages, the stratigraphic position of the Mazama tephra and a series of 210Pb ages were used to produce an age-depth model that estimated the base of the sediment core to be 9880 ± 126 calendar years before present (cal yr BP).
The vegetation history from Roe Lake is similar to other paleoecological studies from the region. The early Holocene (10,000-7500 cal yr BP) was characterized by mixed woodlands with abundant Pseudotsuga menziesii and a diverse understory that included abundant Salix shrubs and Pteridium aquilinum ferns in these open canopy communities. An open Quercus garryana-dominated community with Acer macrophyllum and Arbutus menziesii in the canopy and xeric associations in the understory occurred from 7500-5500 cal yr BP. By 3500 cal yr BP, modern mixed Pseudotsuga menziesii forests with an increasingly closed canopy were established on Pender Island.
Charcoal analyses of the uppermost sediments revealed low charcoal accumulation in the Roe Lake sediment core over the last 1300 years with a mean fire return interval of 100 years for the period before modern fire suppression, suggesting that fire was not a major control on plant community composition on Pender Island on this timescale. Fires were more frequent (i.e., every 47 years on average) during the Medieval Climate Anomaly with warm, dry conditions facilitating a higher fire frequency. Few fires (i.e., every 141 years on average) occurred between 1200-1850 AD, coinciding with the Little Ice Age. As climate was cooler and wetter during the Little Ice Age, fires during this time may reflect intentional burning by First Nations.
In general, changes in vegetation and fire dynamics on Pender Island correlate well with changes in climate throughout the Holocene period, suggesting that climate change was likely the principal mechanism driving plant community composition and changes in the fire regime. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/4219 |
| Date | 30 August 2012 |
| Creators | Lucas, Jennifer D. |
| Contributors | Lacourse, Terri |
| Source Sets | University of Victoria |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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