Trace metal accumulation and loss

Atmospheric lead deposition has decreased significantly in the last two decades. However, there are large quantities of lead bound in the organic horizon of forest soils. Earlier work identified that this lead was slowly moving downwards, and could possibly enter streams and aquifers in 50-100 years. In the summer of 2001, we resampled forested sites sampled in 1980 and 1990 to gain an understanding of lead losses and indirectly calculate lead leaching rates. In collaboration with Stefan Sturup and Jim Kaste, we sampled a 1 X 1 m plot that was sprayed with an enriched Pb-207 lead carbonate in 1983. Preliminary analyses have allowed a direct determination of lead migration in soil during the intervening 18 years. Migration rates appear to be similar to estimates by other methods. Early indications are that atmospheric lead will remain in soils for the immediate future.

Analysis of personal energy use

With increasing frequency, individuals deliberately choose specific actions which they hope will lessen environmental impact. Given the complexity of modern society, it is not always easy to know how to minimize environmental harm without sacrificing one's standard of living. Recycling of solid waste materials is a personal choice made by many people in the U.S.A. guided by the belief that recycling is not only good for the environment but that it constitutes a major contribution to improving environmental quality. By using energy usage as a proxy for overall environmental impact, we show that the overall impact reduction achieved through recycling varies for different materials. It is small but significant for some materials, such as aluminum, and minimal for other materials, such as plastic, when compared to other choices individuals make such as the type of vehicle they drive or the amount they drive. While the recycling of certain materials, such as aluminum, does result in measurable energy savings, the net benefit of recycling is orders of magnitude smaller than the gains that can be achieved from switching to more fuel-efficient vehicles. Despite this fact, environmental policy and public perception in the United States have focused on recycling rather than fuel efficiency and fuel economy.

Sustainability of the Northern Forest

The Northern Forest is among the largest areas of relatively intact and undeveloped forest in the eastern United States. Increasing changes in landownership, wood extraction, nutrient cycling, air pollution and other human-caused impacts raise concern about long-term ecological and economic health of the forest. The division of the Northern Forest among several distinct groups of landowners makes the forest potentially vulnerable to large-scale fragmentation and development. We examined and characterized the current status of and potential threats to various aspects of the Northern Forest including land-use patterns, extent of forested area, species diversity, biological threats such as introduced species, pests and pathogens and air and water quality. Our findings reveal that total area of the Northern Forest and the sum total of tree growth minus tree removals is approximately stable, although there are variations within the region. Tree species diversity in recent decades is approximately equal. A number of viable woodland bird species show significant decreases both in the long-term and short-term while others are increasing in abundance. The water quality of most lakes, streams, and rivers, while generally improving, is still hampered by high levels of mercury, PCBs, and other contaminants in fish tissue. Land development and habitat fragmentation have remained a minor threat to the health of the Northern Forest in comparison to more highly disturbed forests (e.g., tropical forests). Continuation of this pattern will depend largely on whether or not trends in land purchases persist and if development--and resulting fragmentation--of the Northern Forest becomes economically viable.

Water relations and micrometeorology

Simulation models of trees can provide useful information about physiological processes such as water relations. In the past decade, we have used the winter water relations model, WINWAT, for spruce and fir species growing in the middle of their ranges. Here we use it to model the winter water relations of three conifer species--eastern hemlock (Tsuga canadensis (L.) Carr.), eastern white pine (Pinus strobus L.) and red pine (P. resinosa Ait.)--growing at their upper elevational limits on Mt. Ascutney, Vermont, USA, in the winters of 1997 and 1999. Modeled relative water contents remained above 60% in the two youngest foliar age classes of all three species during both winters, indicating that desiccation stress in winter is not responsible for setting the upper elevational limits of these species at this site under present climatic conditions. WINWAT indicated that water relations in these mid-elevational species are sensitive to low relative humidity levels, which increase transpiration rates, and low temperatures, which inhibit recharge, but much less sensitive to summer climate than subalpine conifers in Colorado. Because desiccation damage could be induced by different levels of these climatic factors, they These climatic factors should be incorporated into models that predict the response of these conifers to climate change. Forthcoming in Tree Phys.

Major Element Cycling

Still under construction

Last modified: 9 July2008
©2008 Andrew J. Friedland