Richard K. Olson

Cloud droplet deposition in subalpine balsam fir forests : hydrological and chemical inputs

Subalpine forests of the northern Appalachians are subject to significant deposition of water and chemicals via cloud droplet impaction. This deposition has been estimated by a method linking micrometeorological measures of turbulent transfer, a detailed representation of canopy structure, and experimentally derived capture efficiencies. Water inputs from clouds are about 46 percent, and chemical inputs range from 150 to 430 percent of the bulk precipitation.

Protein-binding phenolics and the inhibition of nitrification in subalpine balsam fir soils

Abstract Nitrification in a highly active Al horizon of a balsam fir forest floor soil can be greatly inhibited by an aqueous methanol extract of the forest floor. This extract was fractionated in an attempt to identify the compounds responsible for the inhibition. Condensed tannins, smaller molecular weight phenolics, and their distribution on particulate matter in the extract were the most important inhibiting components of the extract. When all phenolic material was removed from the extract, the remaining solution stimulated nitrification.

Nitrification in subalpine balsam fir soils: Tests for inhibitory factors

Previous work has shown that nitrification is negligible in floors of subalpine balsam fir forests but proceeds vigorously in the Al horizon beneath the forest floor. This paper describes a series of experiments designed to determine the causes for lack of NO−3 production in the forest floor. These experiments showed that denitrification was not important and that autotrophic nitrifiers were present. Increases in pH, essential nutrients and inoculum did not enhance nitrification, indicating that an inhibitor rather than a limiting factor was involved. Analysis of forest floor and Al showed that aluminum was present at concentrations greater than those found to inhibit nitrification in culture. Since the Al was actively nitrifying, it seemed unlikely that aluminum was responsible for nitrification inhibition in the forest floor. Finally, a methanol extract of polyphenols from the forest floor was added to the Al significantly reducing nitrification. These experiments suggest that the higher phenolic concentrations are responsible for inhibition of nitrification in the forest floor.

Effects of canopy components on throughfall chemistry: An experimental analysis

SummaryFive canopy components of subalpine balsam fir forests (branches with young needles, branches with old needles, non-foliated twigs, lichen-covered twigs, and boles) were treated with simulated rain to test the influence of these components on throughfall and stemflow chemistry. Effects on the fluxes of potassium, sodium, hydrogen, sulfate, nitrate and ammonium ions by the canopy components were tested in relation to rain application rate, duration of rain, and time since the last rain. Interactions between ionic behavior and components were complex. In general, the ionic behavior ranged from high levels of net efflux to mixed influx-efflux to high levels of influx in the order: sulfate, potassium, sodium, nitrate, hydrogen, ammonium. In cases in which application rates produced significantly different results, net flux rates increased with application rate. Branch components mostly ranged from low flux rates (either influx or efflux) to high rates according to the order: young needles

The Response of western forests to air pollution

This volume presents a summary of research conducted between 1986 and 1990 by the Western Conifers Research Co-Operative on the effects of acid rain and associated pollutants on the forests of the Western United States. The book opens with background chapters on topics including physiography, climate, soil sensitivity to acid rain, and methods of air pollution assessment in forests. The second section of the book presents five regional studies of forest growth and condition in the coniferous forests of the American West. The book concludes with a chapter of summary, projections and recommendations. All studies analyze the impact of air pollution on plant growth and include research conducted at scales ranging from small (open-tip chambers) to large (regional growth trends), and at biological levels of organization ranging from seedlings to stands.

Topographic control of vegetation in a mountain big sagebrush steppe

Mountain big sagebrush steppes in Wyoming have strong spatial patterning associated with topography. We describe the spatial variability of vegetation in a sagebrush steppe, and test the relationship between topography and vegetation using canonical correlation. Results of the analysis suggest that the main control over vegetation distribution in this system is wind exposure. Exposed sites are characterized by cushion plant communities and Artemisia nova, and less exposed sites by the taller sagebrush species Artemisia tridentata ssp. vaseyana. Topographic depressions and leeward slopes are characterized by aspen stands and nivation hollows. Measurements of soil microclimate suggest that a major influence of topographic position on vegetation is snow redistribution and its effect on soil moisture and temperature.

Human Impact of the Managua Earthquake Transitional societies are peculiarly vulnerable to natural disasters

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Under the blade : the conversion of agricultural landscapes

* Foreword Marian Buckner * Introduction * Farmland Loss in America * A Landscape Perspective on Farmland Conversion * The Law of the Land * The Economics of Farmland Conversion * Preserving Community Agriculture in a Global Economy * Ethics and Aesthetics in the Loss of Farmland * A National Policy for Farmland Preservation * Case Studies

Evaluating the role of created and natural wetlands in controlling nonpoint source pollution

Abstract Nonpoint source (NPS) pollution control and wetlands protection are two overlapping scientific and policy issues of the US Environmental Protection Agency. Created, restored, and natural wetlands can contribute significantly to watershed water quality but at the same time must be protected from degradation by NPS pollution. Effective use of wetlands in NPS control requires an integrated landscape approach including consideration of social, economic, and government policy issues as well as scientific knowledge.

Factors controlling throughfall chemistry in a balsam fir canopy: A modeling approach

This paper presents a model of water flux and throughfall concentrations of K+ and NH4+ in a subalpine balsam fir forest. The model is based on a multi-layer submodel of hydrologic flow. Cloud water deposition and evaporation are incorporated as separate submodels. Chemical exchange is parameterized with diffusion resistances and internal foliar concentrations determined from leaching experiments on isolated canopy components. The model is tested against within-storm throughfall measurements and found to agree reasonably well in most instances. Some specific departures from observed data are noted, of which some can be explained. Differences between observed and modeled concentrations of K+ early in the storm events suggest that pre-storm conditions, which were not modeled, are important in controlling the chemical exchange.Responses of throughfall chemistry to changes in rain rate, rain concentration, and stand surface area index (SAI) were investigated by simulation with the model. Increasing rain rates increased leaching of K+ and uptake of NH4+. Increasing concentrations of K+ in rain decreased slightly the amount of K+ leached, but increasing concentration of NH4+ in rain increased NH4+ uptake proportionately. Increasing canopy SAI increased the leaching of K+ and the uptake of NH4+, with the pattern of the increase dependent on rain rate.