Holocene ecosystem dynamics of a central Vancouver Island wetland: development, vegetation change, and carbon accumulation




Beer, Kyle

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A multi-proxy paleoecological study that included pollen, microfossil, carbon (C), and nitrogen (N) analyses was conducted at a central Vancouver Island wetland near Courtenay British Columbia to reconstruct the site’s history, C and N accumulation rates, and surrounding vegetation over the last 14,000 years. The paleoecological record shows that the lake that occupies the southeast corner of the wetland today was much larger during the late glacial period. Peat accumulation began through terrestrialization of the site, leading to vegetation and edaphic conditions characteristic of a bog or fen with variable water table depth inferred from testate amoebae and other microfossil remains. C accumulated with maximum and time-weighted mean accumulation rates of 81 and 19 g C/m2/cal yr, respectively. The highest C accumulation occurred during the accumulation of herbaceous peat in the early Holocene, which, given the similarity to other Northern Hemisphere peatlands, suggests a strong climate forcing of C accumulation. N accumulated with a time-weighted mean of 0.55 g N/m2/cal yr. Forest community composition was also affected by the changing climate. Pinus contorta dominated open forests near the site between at least 13,900 and 11,200 cal yr BP. Picea and Abies increased during Younger Dryas cooling (12,900-11,700 cal yr BP). Pseudotsuga menziesii was the most abundant tree species in the area during the early Holocene (11,200-7500 cal yr BP). Around 7000 cal yr BP there was a shift to Tsuga heterophylla dominated forest, which continues to the present. This multi-proxy 14,000-year record provides evidence of the importance of climate and local factors in bog development, C and N accumulation, and vegetation history since the last glaciation.



Peat, Carbon, Nitrogen, Vancouver Island, British Columbia, Holocene, Pollen, Accumulation