Postglacial evolution and spatial differentiation of seasonal temperate rainforest in western Canada

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Abstract

Surface samples from Vancouver Island, Canada, were used to assess the relationship between discrete seasonal temperate rainforest (STR) plant communities and their corresponding pollen signatures. Pollen from ten sediment cores was further used to evaluate the postglacial development of these communities. Principal components analysis (PCA) of the surface data revealed the distinctiveness of the modern pollen rain, with samples from the Coastal Douglas Fir (CDF) zone, the dry Coastal Western Hemlock (CWH) zone, the wet CWH subzones and the Mountain Hemlock (MH) zone clustering distinctly. PCA of the fossil data revealed early-seral open canopy, wet rainforest, subalpine rainforest and Lateglacial plant associations and showed that the STR has changed markedly through time. Pinus woodlands with low palynological richness prevailed in the early Lateglacial period, only to be supplanted by mixed conifer forest with increased pollen richness. In the early Holocene, STR vegetation differentiated spatially as early-seral open canopy forests expanded, though a non-analogue Picea-dominated forest persisted on the moist outer coast. Generally high pollen richness is attributed to the expansion of dryland habitat coupled with the development of a fire-maintained vegetation mosaic. In the mid- and late-Holocene intervals, open canopy communities persisted in eastern areas, eventually developing into modern CDF and dry CWH forest. In contrast, moist and oceanic CWH rainforest developed on central and western Vancouver Island, whereas subalpine forest established at high elevation. Pollen richness declined in the mid Holocene concomitant with increased precipitation and a general reduction in the incidence of fire, though this trend was offset somewhat in the late Holocene by paludification.

Detaljer

Författare
Externa organisationer
  • External Organization - Unknown
Forskningsområden

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Geologi

Nyckelord

Originalspråkengelska
Sidor (från-till)715-727
TidskriftThe Holocene
Volym18
Utgivningsnummer5
StatusPublished - 2008
PublikationskategoriForskning
Peer review utfördJa
Externt publiceradJa

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