|Title||Interception and modification of acidic precipitation by bigtooth aspen forest canopies in northern lower Michigan|
|Year of Publication||1983|
|Academic Department||School of Natural Resources and Environment|
|Degree||Master of Science|
|Number of Pages||207 pp.|
|University||University of Michigan|
|City||Ann Arbor, MI|
The effects of acidic precipitation on the productivity of forest soils is an important ecological and public concern. The evidence that acid rain does indeed have a deleterious effect on forests is not yet conclusive. Current research indicates that some ares of the US previously thought to be highly sensitive to degradation may not be as susceptible as first hypothesized. The sensitivity of aquatic systems to acidic precipitation is primarily a function of the capacity of the soil to adsorb hydrogen ions, which is related to the chemical characteristics of the soil and the underlying bedrock. Indices of sensitivity for aquatic systems have been developed from information based on various combinations of the following components: bedrock geology, mineral weathering, cation/anion exchange and acid neutralizing capacity. Research concerning the effect of acidic precipitation on forest soils and, therefore, forest productivity, focuses on the evaluation of the cycling of nutrients and water in a watershed or ecosystem. The quantification of the important nutrient budgets of an ecosystem is necessary to evaluate the impacts of ecological disturbances such as acid rain. This thesis represents only a partial synthesis of the data collected during the three-year study. The focus of the thesis is primarily concerned with the measurements of gross precipitation and throughfall. The thesis is divided into three additional chapters. The second is an explanation of the steps in the development of a model to predict measures of throughfall from gross precipitation. The third chapter concentrates on the applicability of four predictive models for determining throughfall in the aspen forest of northern lower Michigan. The fourth chapter quantifies the precipitation chemistry over two growing seasons (1980 and 1981) and modification of the precipitation by the bigtooth aspen canopy in northern lower Michigan. The raw data values which serve as the basis of this thesis will be presented as an appendix. This study is based on research conducted as part of a three-year grant funded by the McIntire-Stennis program concerning the effects of acidic precipitation on the productivity of forest soils. This project was designed by James R. Boyle to complement prior research on the same plots in northern lower Michigan by Boyle, Paul W. Adams, and Curtis J. Richardson. The research has three objectives: (1) to assess chemical concentrations of gross precipitation, throughfall, soil leachate, and snowmelt; (2) to integrate with that an earlier assessment of chemical concentrations in precipitation throughout Michigan (Richardson and Merva 1976), or estimates of soil weathering rates (Adams and Boyle 1979, Adams and Boyle 1982), biomass nutrient concentrations (Adams 1982), and of an evaluation of the effects of clearcutting on these sites (Richardson and Lund 1975); (3) to evaluate the determine possible effects of acidic precipitation on forest productivity, particularly within the context of intensive management of bigtooth aspen (Populus grandidentata Michx.) stands in Michigan.