Document: HOL-3-41-8

The influence of substrate on long-term ecosystem development and its paleoecological record.

EWING, H.A.*

University of Minnesota, St. Paul, MN 55108, USA ¹

Abstract:
Ecosystem ecologists have characterized the flux of water and nutrients between terrestrial and aquatic ecosystems, but they have few records longer than three decades. Analysis of sediment chemistry and pollen from two lakes in the upper Midwest reveals a history of terrestrial ecosystem changes and evidence for long-term differences in the flux from catchments. The geochemical record from a lake on sandy outwash provides evidence for soil development, showing base cation leaching, acidification, and podzolization in the catchment soils. In contrast, a site 10 km away on till has a strongly developed soil, but a record only of gradual soil acidification; nearly all weathering products have remained in the soil rather than moving to the lake. This difference in the retention of water and soil weathering products, the "leakiness" of the terrestrial system, has had a strong influence on the development of soil and vegetation at the two sites. The "leaky" site on outwash has had relatively less soil development and has had incomplete forest cover for much of its history. The less "leaky" site on till has a strongly developed soil and fire-intolerant, mesic vegetation with a history of more complete forest cover for the last 10,500 years. At both sites, late Holocene changes in vegetation correspond to increases in weathering within the catchments, but the degree of change in soil and vegetation is not directly related. While paleoecological reconstruction of both soil and vegetation can provide a history of ecosystem development, the physical properties of the site strongly influence both the response of a site to climatic change and the record of that response preserved in lake sediments.

Keywords: substrate, soil development, vegetation, ecosystem development, paleoecology, linkages between terrestrial and aquatic ecosystems

This abstract is being presented at: 2:45 PM in session:
Oral Session #32: Paleoecology.