Paul L. Ringold

A calcium‐based invasion risk assessment for zebra and quagga mussels (Dreissena spp)

We used calcium concentration data from over 3000 stream and river sites across the contiguous United States to classify ecoregions relative to their risk for Dreissena species invasion. We defined risk based on calcium concentrations as: very low ( 28 mg L−1). Ecoregions comprising 9.4% and 11.3% of land area were classified as very low risk and low risk, respectively. These areas included New England, most of the southeast, and western portions of the Pacific Northwest. High-risk ecoregions comprised 58.9% of land area. Ecoregions with highly variable calcium concentrations comprised 19.8% of land area; none could be classified as moderate risk. The majority of Dreissena occurrences (excluding the Great Lakes) were located in high-risk ecoregions, and most exceptions occurred in highly variable ecoregions. In low-risk ecoregions, mussels occurred in large rivers flowing from high-calcium regions. Our map provides guidance for the allo...

Adaptive Monitoring Design for Ecosystem Management

Adaptive management of ecosystems (e.g., Holling 1978, Walters 1986, Everett et al. 1994, Grumbine 1994, Yaffee 1994, Gunderson et al. 1995, Frentz et al. 1995, Montgomery et al. 1995) structures a system in which monitoring iteratively improves the knowledge base and helps refine management plans. This adaptive approach acknowledges that action is necessary or appropriate with imperfect knowledge (Raiffa 1968, Walters 1986, Everett et al. 1994, USDA/FS and DOI/BLM 1994b) and that initial actions can be refined as more information becomes available. Imperfect knowledge is the case in ecosystem management particularly when the plan includes the management of complex ecological patterns and processes over large areas and long periods of time. In such cases, we suggest that an adaptive approach should apply not only to the management of the ecosystem, but also to the design of the monitoring program.

What data should we collect? A framework for identifying indicators of ecosystem contributions to human well-being

The lack of a clear framework identifying data to link ecosystems to analyses of human well-being has been highlighted in numerous studies. To address this issue, we applied a recently developed economic theory termed “final” ecosystem goods and services – the biophysical features and qualities that people perceive as being directly related to their well-being. The six-step process presented here enabled us to identify metrics associated with streams that can be used in the analysis of human well-being; we illustrate these steps with data from a regional stream survey. Continued refinement and application of this framework will require ongoing collaboration between natural and social scientists. Framework application could result in more useful and relevant data, leading to more informed decisions in the management of ecosystems.

Twelve invasive plant taxa in US western riparian ecosystems

Abstract Assessments of stream ecosystems often include an evaluation of riparian condition; a key stressor in riparian ecosystems is the presence of invasive plants. We analyzed the distribution of 12 invasive taxa (common burdock [Arctium minus], giant reed [Arundo donax], cheatgrass [Bromus tectorum], musk thistle [Carduus nutans], Canada thistle [Cirsium arvense], teasel [Dipsacus fullonum], Russian olive [Elaeagnus angustifolia], leafy spurge [Euphorbia esula], English ivy [Hedera helix], reed canarygrass [Phalaris arundinacea], Himalayan blackberry [Rubus armeniacus], and saltcedar [Tamarix spp.]) to characterize a portion of that stressor. Observations from 961 probability survey reaches and 355 additional reaches distributed across 12 western US states provided a statistically defensible foundation for trend monitoring, risk assessments, or economic evaluation of these 12 taxa over a large area. We estimate that ≥1 of these taxa are present in riparian areas on 47 ± 3.6% of the perennial stream length in the western US. One or more of these taxa were present in >⅓ of the reaches identified as least-disturbed (reaches that define reference condition and are used to quantify instream biotic integrity). Association between target invasive presence and instream biotic integrity varied, particularly as a function of ecoregion. Relationships were often statistically significant in the Mountain climatic region, sometimes significant in the Xeric climatic region, and never significant in the Plains climatic region. Regional variations in associations and confounding relationships between multiple factors suggest that multiple variables should be examined to explain or predict the presence of invasive species or their associations. Our survey illustrates strengths and limitations of collecting information on a limited number of invasive plants in riparian vegetation as part of general probability surveys of aquatic ecosystems. Our survey of only 12 somewhat arbitrarily selected invasive plants provided much information for a limited cost. We recommend including similar efforts in future surveys.

Patterns of tree dominance in coniferous riparian forests

This research quantified patterns of riparian tree dominance in western Oregon, USA and then compared the observed patterns with the expected patterns defined from the literature. Research was conducted at 110 riparian sites located on private and public lands. The field sites were selected by probability surveys that were post-stratified by stream order and riparian forest type. An importance value index (IVI), which was the summation of tree relative density, relative frequency, and relative basal area, was used to define tree dominance. The IVI patterns of 19 riparian tree species with respect to ecoregion, geomorphic landform, stream order, and management practice were evaluated. In addition, the riparian trees were assigned to growth habit, life history strategy, and wetland indicator guilds depending on their taxonomy, response to flood disturbance, and wetland ecology, respectively. Douglas-fir, alder, western hemlock, and bigleaf maple were the trees with the highest IVI scores in western Oregon. The general IVI pattern of tree importance on the geomorphic landforms was hardwoods dominating the floodplain, hardwood and coniferous trees co-dominating the terrace, and conifers dominating the transition slope. However, there was considerable variability in the mix of the tree species because of differences in ecoregion, stream order, and management practice. The ecological importance of the dominant species was illustrated by their influence in determining the IVI patterns of the different guilds. For example, Douglas-fir, alder, and western hemlock were one, two, and three in their IVI rankings in western Oregon. The avoider, invader, and resister guilds were also ranked one, two, and three in importance because Douglas-fir, alder, and western hemlock were respectively classified in these groups. Such information is meaningful to developing conservation policy and plans to maintain or restore properly functioning riparian forests for aquatic and terrestrial biota, and to characterize reference condition and biological indicators for long-term ecological monitoring.

EVALUATION OF METRIC PRECISION FOR A RIPARIAN FOREST SURVEY

This article evaluates the performance of a protocol to monitor riparian forests in western Oregon, United States based on thequality of the data obtained from a field survey. Precision isthe criteria used to determine the quality of 19 field and 6 derived metrics. The derived metrics were calculated from thefield data. The survey consisted of 110 riparian sites on publicand private lands that were sampled during the summers of 1996 and 1997. In order to calculate metric precision, some of the field plots were re-measured. Metric precision was defined in terms of the coefficient of variability (CV) and standard deviation and then compared with a pre-defined data quality objective (DQO). A metric was considered precise if the CV met or exceeded the DQO. The geomorphology metrics were not precisewhile the forest stand inventory metrics and forest cover metrics, with some exceptions, were precise. The precision formany of the field and derived metrics compared favorably withthe level of precision for similar metrics reported in the literature. Recommendations are made to improve the precision for some metrics and they include changing the way precision is calculated, re-defining the field protocol, or improving field training.

A national critical loads framework for atmospheric deposition effects assessment: II. Defining assessment end points, indicators, and functional subregions

The United States Environmental Protection Agency, with support from the US Department of Energy and the National Oceanographic and Atmospheric Administration, has been evaluating the feasibility of an effects-based (critical loads) approach to atmospheric pollutant regulation and abatement. The rationale used to develop three of the six steps in a flexible assessment framework (Strickland and others, 1992) is presented along with a discussion of a variety of implementation approaches and their ramifications. The rationale proposes that it is necessary to provide an explicit statement of the condition of the resource that is considered valuable (assessment end point) because: (1) individual ecosystem components may be more or less sensitive to deposition, (2) it is necessary to select indicators of ecosystem condition that can be objectively measured and that reflect changes in the quality of the assessment end point, and (3) acceptable status (i.e., value of indicator and quality of assessment end point at critical load) must be defined. The rationale also stresses the importance of defining the assessment regions and subregions to improve the analysis and understanding of the indicator response to deposition. Subregional definition can be based on a variety of criteria, including informed judgment or quantitative procedures. It also depends on the geographic scale at which exposure and effects models are accurate and on data availability, resolution, and quality.

Ecosystem Services Indicators: Improving the Linkage between Biophysical and Economic Analyses

For ecosystem services analysis, a key to collaboration between natural and social scientists is the identification and measurement of linking indicators: biophysical indicators that facilitate social evaluation, including monetary valuation of ecological changes. As ecosystem service analysts and practitioners better recognize the various ways in which people benefit from ecosystems, natural scientists will be called on to develop, use, and report on metrics and indicators that link to those diverse benefits. The paper develops principles to guide the identification of linking indicators, compares their features with those of more commonly collected ecological measures, and reviews empirical evidence pertinent to their identification, definition, and performance, primarily from the point of view of conducting monetary valuation of ecological outcomes.

A national critical loads framework for atmospheric deposition effects assessment: I. Method summary

The United States Environmental Protection Agency (EPA), with the assistance of the US Department of Energy (DOE) and the National Oceanographic and Atmospheric Administration (NOAA) is examining the utility of a critical loads approach for evaluating atmospheric pollutant effects on sensitive ecosystems. A critical load has been defined as, “a quantitative estimate of an exposure to one or more pollutants below which significant harmful effects on specified sensitive elements of the environment do not occur according to present knowledge.” Working in cooperation with the United Nations Economic Community for Europe’s (UN-ECE) Long Range Transboundary Air Pollution (LRTAP) Convention, the EPA has developed a flexible, six-step approach for setting critical loads for a range of ecosystem types. The framework is based on regional population characteristics of the ecosystem(s) of concern. The six steps of the approach are: (1) selection of ecosystem components, indicators, and characterization of the resource; (2) definition of functional subregions; (3) characterization of deposition within each of the subregions; (4) definition of an assessment end point; (5) selection and application of models; and (6) mapping projected ecosystem responses. The approach allows for variable ecosystem characteristics and data availability. Specific recognition of data and model uncertainties is an integral part of the process, and the use of multiple models to obtain ranges of critical loads estimates for each ecosystem component in a region is encouraged. Through this intercomparison process uncertainties in critical loads projections can be estimated.

Emission reductions and ecological response: Management models for acid rain control

Abstract Presented in this paper is a series of optimization analyses for acid rain control in eastern North America. The analyses involve models that minimize cost or emissions removed subject to environmental quality restrictions at selected sensitive receptor locations. Site-specific critical loads are the measures of environmental quality, where critical loads are roughly interpreted as levels of areal pollutant deposition beyond which deleterious ecological effects are thought to occur. Our approach is demonstrated with an application that includes critical loads estimated for 768 lakes in the Adirondacks. As well, a stratified random subsample of 122 sites is modeled to assess the effects of sampling intensity on the control scenarios that are identified through the optimization procedures. Two different models for estimating site-specific critical loads are used and their effects on control strategies are assessed. From a somewhat broader perspective, this work is a demonstration of the feasibility and usefulness of large-scale integrated assessment and the role that operations research methods can play in that process.