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Principles of Paleoecological Reconstruction Can not observe past ecosystems directly • The biotic and abiotic aspects are inferred – from fossils and sedimentary context in which the fossils were found. • Limited to study of organisms whose fossils are preserved. Uniformitarianism • Present is the key to the past Key assumptions of Uniformitarianism • Assume know environmental parameters controlling present-day distribution of plants and animals – (e.g. Temperature, precipitation, growing season, food resources, etc.) • Present day plant/animal distributions are in equilibrium with controlling processes and former distributions were also in equilibrium. Uniformitarianism (continued) • Former plant/animal distributions have analogues in the modern flora/fauna. • Ecological affinities of plants/animals have not changed through time. Uniformitarianism (continued) • The fossil assemblage is representative of the death assemblage, and has not been biased by differential destruction or by contamination with older/younger material. • Taphonomy (origin) of the fossils can be established. Uniformitarianism (continued) • Fossils can be identified to a sufficiently low taxonomic level to enable uniformitarian principles to be applied. Plant Macrofossils E.S.E.M of Scirpus cf. americanus from Browns Island, S.F. Bay Macrofossils • Describes any potentially identifiable fossil preserved in sediments – Seen by naked eye – binocular 'scope – mm to m • Includes plants and animal remains Plant Macrofossils • Any part of plant – Typically fruits and seeds – But include: stamens, leaves, megaspores, buds, cuticle fragments, and rarely flowers. Birks, 1980 Blytt-Sernander Scheme Lowe and Walker, 1984 Advantages of Plant Macrofossils • Frequently determinable to species level – Precise ecological inferences • e.g. “Pine pollen Problem” • Diversity of species each with different requirements Osgood Swamp Adams, 1967 Edlund, nd Advantages of Plant Macrofossils (continued) • Local origin – Peats • Local community – Lake sediments • Aquatic and lake margin Advantages of Plant Macrofossils (continued) • Identifiable remains of plants that produce• little pollen – e.g Dryas octopetala • fragile pollen – e.g. Najas flexilis • No distinctive microfossils – e.g. mosses and charophyte algae Disadvantages • Unsuitable for reconstructing regional vegetation – Not effectively mixed over a large area • Produced in small quantities • Difficult to assess influx Picea Jackson et al., 1997 Jackson et al., 1997 Packrat Middens Joshua Tree, CA “Avidly acquisitive and prodigiously excretory” Cole, 1983 Oak Chaparral Maurice J. Kaurmann Ponderosa forest John Crossley
