All seminars are held Thursday afternoons in 108 Clark Hall at 4:00 PM. Reception at 3:30 PM in foyer in front of Clark 108.

September 4
Jim Fourqurean, Florida International University
TBA

September 11
Amber Soja, University of Virginia
Fire in Siberia: A Signal of Climate-Induced Change?

September 18
Lee MacDonald, Colorado State
Effects of Forest Fires on Runoff and Erosion in the Colorado Front Range: Causal Processes, Recovery, and Rehabilitation

September 25
Grace Brush, Johns Hopkins University
Climate, Land Use, and Chesapeake Bay Food Webs: The Paleoecological Record

October 2
Laura Wasylenki, Virginia Tech
Deciphering Controls on Non-Uniform Partitioning of Trace Elements into Calcite: A Critical Step Toward Accurate Calcite Paleothermometry

October 9
Eric Davidson, Woods Hole Research Center
Losses of Nutrients to Streams and to the Atmosphere From Forests and Cattle Pastures of the Lower Amazon Basin

ABSTRACT
The soils of the Amazon Basin are diverse, and this variation in soil properties affects the degree to which nutrients are lost from terrestrial ecosystem to the atmosphere and to aquatic ecosystems following deforestation. In general, nitrogen (N) is abundant relative to other plant nutrients in the mature forests, but the productivity of pastures, agricultural fields, and secondary forests are often at least partly limited by N availability. Total soil N stocks may remain large following deforestation, depending on soil texture, depth, and organic matter content, but the actively cycling N pool is usually severely diminished due to ecosystem losses during site clearing and burning. Most of the phosphorus (P) in highly weathered soils is bound in forms that are poorly available to plants, so that P is at least partly limiting in both mature and secondary forests and in pastures and agricultural fields. However, although P availability is low in most Amazonian soils, the severity of this limitation varies significantly spatially, which may help explain why pasture management has been more successful in some regions than in others and why P leaching is detectable following deforestation in some regions. The pH-dependent cation exchange capacity of most highly weathered Amazonian soils, which is derived from organic matter and secondary clay minerals, is usually effective in retaining cations from the original forest biomass following deforestation and burning. Gradual export of cations to streams and reacidification of the soil occurs on decadal time scales. A better understanding is needed of the kinetics of releases of N, P, Ca, Mg, and K from soil pools in order to explain the edaphic component of observed variation in the effects of land use change on agricultural productivity, secondary forest succession, and inputs to aquatic ecosystems.

October 16
Art Schwarzschild, University of Virginia
Clonal Integration, Resource Allocation and Whole Plant Productivity of the Seagrass Syringodium Filiforme in the Florida Keys, Florida

October 23
Eric Small, University of Colorado
Coupled Water and Carbon Cycling in Semiarid Ecosystems

October 30
Howard Epstein, University of Virginia
Vegetation Dynamics in Arctic Tundra Ecosystems

November 6
Richard Anthes, UCAR
GPS Radioocculation Sounding of the Earth's Atmosphere--The Most Accurate Global Thermometer

November 13
Robert Naiman, University of Washington
The Ecology of Interfaces: New Perspectives From Pacific Coastal Riparian Systems

ABSTRACT
Riparian zones, intimately located at the terrestrial and aquatic interface, are suspected to possess important ecological characteristics, which include controls on the routing of materials, energy, and information as well as influences on habitat and biodiversity. My presentation will focus on riparian systems associated with rivers along the Pacific Coast of North America where I, and my colleagues and students, have been conducting research for nearly 15 years. This will be a broad-based presentation of what is known about the presumably important ecological characteristics associated with riparian systems, especially with respect to system-scale heterogeneity, biodiversity, tree production, interactions between large woody debris and plant succession, and the ecological consequences of marine-derived nutrients for riparian soil and plant communities. The presentation will conclude with a brief discussion of how a riparian perspective is being used to improve basin-scale management in the Pacific Northwest as well as in other countries.

November 20
William Ruddiman, University of Virginia
Farming, Plagues and Pre-Industrial Climate Change

November 27
Thanksgiving

December 4
Jeff Chanat, University of Virginia
Modeling the Hydrochemistry of Forested Catchments: Application and Limitations of Catchment-Scale Observations

Environmental Sciences Department 291 McCormick Rd Charlottesville, Virginia (434) 924-7761