Eastern Mineral and Environmental Resources Science Center
Studies of soil quality and ecosystem health employ a wide variety of approaches designed to monitor ecosystem functioning impacted from an array of natural and anthropogenic disturbances. Definitions of soil health, though varied, typically involve the soil's role in mediating nutrient, water and energy cycles in support of associated flora and fauna. Given the essential role of microbes in these ecosystem cycles, their limited mobility and inherent sensitivity, they tend to comprise the backbone of soil health indices. Multiple measures of microbial dynamics provide a means of minimizing the inherent spatial and temporal variability associated with individual chemical and biological measures. Along with key abiotic parameters that directly impact microbial activity (e.g. pH, texture, and moisture), suites of analyses can be developed to examine disturbances and recovery in a variety of ecosystems. In addition, measures of plant community responses can provide a more complete picture of the impact that a particular disturbance may have on an ecosystem. Recent discussions in the literature regarding plants as bioindicators of trace metal interactions highlight the lack of consensus of what constitutes soil health and how it should be measured, but show the utility of incorporating vegetation into measures of soil quality. Vegetation is especially important considering the potential for phytoremediation, impact on the hydrologic cycle, and nutritional value to fauna. Studies of soil health apply to a wide range of disturbances and ecologic settings; the focus of this study is on metal-microbe-vegetation interactions in mineralized terrestrial ecosystems, and the potential impact on ecosystem functioning (e.g. microbial activity), and plant community biomass and composition.
The primary goal of this research is to develop measures of ecosystem health/functioning based on metal-microbe-plant interactions in mineralized areas. A reconnaissance study (Phase 1) within 4 Western U.S. mining districts of contrasting mineralogy and/or climate will be carried out in order to identify a suitable area (i.e. an area where mineralized sites differ in above and/or below-ground biotic response compared with a nearby non-mineralized area) for more comprehensive study and also test some of the techniques used to measure soil health. Phase 1 sites will include the following:
Phase 1 field and lab measures will focus on ecosystem health variables (aboveground plant biomass, plant community composition, soil enzyme activity, soil microbial diversity), and variables that may impact the above measures, including plant metal content, soil pH, total soil C/N/S, and degree of mineralization (bioavailable vs. total soil metals).
A study design utilizing the Ivanhoe mining district of northern Nevada has been chosen as an example of how Phase 2 would be implemented. If this site shows inconclusive results from the Phase 1 study (i.e. no difference in ecological response between mineralized and nonmineralized sites), the design will be modified as necessary to capture more appropriate landscapegeologicecologic features and implemented at one of the other Phase 1 sites.
The objectives of this work remain the same for this year as previous years, but in addition we will continue to work in Lassen National Park on altered areas there and evaluate seasonality (spring vs. summer vs. fall), and climate to the sample design. During the Blecker seminar at the Spokane office it was suggested that the concept of 'ecoregions', i.e., the division of the U.S. into parcels of land characterized by common climate and landscape, might be used to extend this research into mineralized terrane with varying climates. Preliminary plans are to use results from the project on Hydrothermal Geology of the Cascades as a guide in selecting the next field areas for study. The chief of the Cascades project has made helpful suggestions for sites which would compare/contrast with the Subtask 2009 work. Another research objective for this year will be to experiment with using regional, GIS-based data for calculating the index. We recognize that a moving our studies from the scale of a mining district to the scale of an ecoregion will be necessary if the Ecosystem Health Index is to be used as a tool for a regional Mineral Environmental Assessment.
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