Plant taphonomy of late Holocene deposits in Trinity (Clair Engle) Lake, northern California

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Abstract
Six drainage basins at the margins of Trinity Lake were analyzed to determine the relations of source vegetation (largely coniferous forest) to plant debris in deltaic deposits that represent high-energy depositional environments. Thirty-one samples containing an estimated 1,043,000 identifiable plant fragments were subjected to a multivariate statistical (correspondence) analysis; in the resulting ordination, samples from the more mesic side of the lake clustered separately from samples from the drier side of the lake. The distribution of a species in the source vegetation is generally paralleled by the distribution of the same species in the samples, and all major forest trees are present in the samples. However, relative abundances in the source vegetation have no direct relation to relative abundances in the samples. Plants growing far away from depositional sites are poorly represented, even if these plants produce organs suited to long-distance transport; this occurs by dilution by material derived from plants in proximity to depositional sites and suggests that megafossil assemblages that contain putative mixtures of high-altitude “temperate” and low-altitude “thermophilic” taxa represent true biotic associations. The information gained from the Trinity analysis is compared to information gained from analysis of plant debris in low-energy depositional environments; each environment contains different kinds of information that is significant in paleoecological reconstructions of regional vegetation. Whereas high-energy environments contain the best taxonomic representation of source vegetation, low-energy environments retain information on spatial distributions of taxa within source vegetation. High-energy environments typically also contain the best representation of different organs of a given taxon.