Late Quaternary Dynamics of Pollen Influx at Mineral
south of the Puget Lobe of the Fraser Glaciation, tundra was a characteristic vegetation until 16,300 years ago. Invasion of Pinus contorta began 17,500 years B.P., and boreal climax conifers (Abies, Pieea and Tsuga mertensiana), 16,300, but was tem-porarily interrupted by the Vashon advance (14,500...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.524.2210 http://nisquallydeltarestoration.org/pdf/Tsukada_Sugita. 1982. pollen core.pdf |
| Summary: | south of the Puget Lobe of the Fraser Glaciation, tundra was a characteristic vegetation until 16,300 years ago. Invasion of Pinus contorta began 17,500 years B.P., and boreal climax conifers (Abies, Pieea and Tsuga mertensiana), 16,300, but was tem-porarily interrupted by the Vashon advance (14,500-14,000 yr B.P.). Pseudotsuga menziesii began to grow in population 10,750 years ago, and woodland was established within a time span of 1,000 years. Modern lowland coniferous forests began to form 7,000 years ago. Logistic analysis of pollen abundance changes show that the intrinsic growth rate, r (yr-1), of pioneer species (e.g. 0.024-0.026 in Pteridiu~ aquilinum) is higher than that of climax species (e.g. 0.003 in Thuja plicata). P. menziesii, a subclimax species, shows an intermediate r value (0.013) between these two ecologically different axa. The absolute r value of P. contorta (-0.011) is only slightly lower than that of P. menziesii, although their replacement began almost simultaneously. Thus competition between these species was intense before the inflection point of Pinus curve 10,100 years ago. At this time, forest gaps became abundantly available for Pseudotsuga, asindicated by a peak of the diagnostic factor (the reciprocal of the pollen influx). |
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