CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Beaudoin, A. B.; and Reasoner, M.A.
Date : 1995
Title : An investigation of pollen focussing and differential pollen deposition in Lake O'Hara, Yoho National Park, British Columbia
Publication : Abstracts of the 28th Annual Meeting of the American Association of Stratigraphic Palynologists, Ottawa 1995
Issue :
Page(s) : A1- A2.
Abstract
We have examined pollen spectra from three discrete intervals, dated by tephras and radiocarbon, in a lake wide series of nineteen cores from Lake O'Hara, a comparatively large (34.4 ha, 43 m deep) lake situated in the upper subalpine ecozone, Yoho National Park. The three sample sets, which represent three different pollen zones identified in a single core (LOH25), provide pollen assemblages at about 2350, 6800, and 10,100 yr BP. We used these spectra to investigate two aspects of pollen accumulation in the lake sediments: 1. whether pollen taxa have been differentially deposited in different parts of the lake basin, and 2. whether the entire assemblage has accumulated more in deeper parts of the basin (an effect that has been called "pollen focussing"). The present surrounding vegetation is coniferous forest. This is reflected in the pollen spectra, which are dominated throughout by the major arboreal taxa, especially Pinus (>50%) and, to a lesser extent, Picea and Abies (generally < 20% each, with greatest values in the upper sample set). Percentages of the ten major taxa in the assemblages show remarkable basin wide consistency within each sample set, suggesting that in this case a single core provides a representative Late Quaternary pollen record. Multivariate statistical analyses (discriminant function analysis and analysis of variance) on pollen percentage, concentration, and PAR data confirm that sample sets are distinctly different and supports zonation of the pollen record from a single core. Minor components of the assemblages (<1% of the pollen sum), mainly NAP, show great variability within and between sample sets and are therefore unreliable for interpretation of vegetation history. Lack of evidence for differential pollen deposition confirms that qualitative inferences based on major components of the pollen sum are probably trustworthy regardless of core location within the lake basin. We did not find evidence for greater pollen accumulation at deeper water sites, implying that pollen focussing has not been a major process in this lake. The morphology of the lake (steep sides, relatively flat floor) may exert considerable control over this process. Sedimentation rates are variable across the basin at each level, suggesting that pollen concentration and particularly PAR data are not dependable for interpretation of vegetation history from a single core, without much greater chronologic control. Additional details may be found in Beaudoin and Reasoner, 1992, Review of Palaeobotany and Palynology 75:103 131.
Bibliography of Canadian Geomorphology