Assessing vulnerability to invasion by nonnative plant species at multiple spatial scales

Basic information on where nonnative plant species have successfully invaded is lacking. We assessed the vulnerability of 22 vegetation types (25 sets of four plots in nine study areas) to nonnative plant invasions in the north–central United States. In general, habitats with high native species richness were more heavily invaded than species-poor habitats, low-elevation areas were more invaded than high-elevation areas, and riparian zones were more invaded than nearby upland sites. For the 100 1000-m² plots (across all vegetation types), 50% of the variation in nonnative species richness was explained by longitude, latitude, native plant species richness, soil total percentage nitrogen, and mean maximum July temperature (n = 100 plots; P < 0.001). At the vegetation-type scale (n = 25 sets of four 1000-m² plots/type), 64% of the variation in nonnative species richness was explained by native plant species richness, elevation, and October to June precipitation (P < 0.001). The foliar cover of nonnative species (log) was strongly positively correlated with the nonnative species richness at the plot scale (r = 0.77, P < 0.001) and vegetation-type scale (r = 0.83, P < 0.001). We concluded that, at the vegetation-type and regional scales in the north–central United States, (1) vegetation types rich in native species are often highly vulnerable to invasion by nonnative plant species; (2) where several nonnative species become established, nonnative species cover can substantially increase; (3) the attributes that maintain high native plant species richness (high light, water, nitrogen, and temperatures) also help maintain nonnative plant species richness; and (4) more care must be taken to preserve native species diversity in highly vulnerable habitats.     

RIO GRANDE VALLEY,COLORADO, NEW MEXICO,AND TEXAS1

ABSTRACT: The Rio Grande Valley National Water-Quality Assessment study unit encompasses about 45,700 square miles in Colorado, New Mexico, and Texas upstream from the gaging station Rio Grande at El Paso, Texas, and includes surface-water closed basins east of the Continental Divide in New Mexico, and the San Luis Closed Basin in Colorado. The mean annual precipitation ranges from less than 6 to more than 50 inches; potential evapo-transpiration ranges from less than 35 to more than 80 inches per year. Land use is mainly rangeland, forest land, and cropland. Total irrigated acreage in 1990 was about 914,000 acres and water use was about 3,410,000 acre-feet. Two structural settings are found in the study unit: alluvial basins and bedrock basins. The alluvial basins can have through-flowing surface water or be closed basins. The discussion of streamflow and water quality for the surface-water system is based on four river reaches for the 750 miles of the main stem. The quality of the ground water is affected by both natural process and human activities and by nonpoint and point sources. Nonpoint sources for surface water include agriculture, hydromodification, and mining operations; point sources are mainly discharge from wastewater treatment plants. Nonpoint sources for ground water include agriculture and septic tanks and cesspools; point sources include leaking underground storage tanks, unlined or manure-lined holding ponds used for disposal of dairy wastes, landfills, and mining operations.     

The indicator performance estimate approach to determining acceptable wilderness conditions

Using data from a study conducted in the Cranberry Wilderness Area of West Virginia, United States, this paper describes how a modified importance—performance approach can be used to prioritize wilderness indicators and determine how much change from the pristine is acceptable. The approach uses two key types of information: (1) indicator importance, or visitor opinion as to which wilderness indicators have the greatest influence on their experience, and (2) management performance, or the extent to which actual indicator conditions exceed or are within visitor expectations. Performance was represented by calculating indicator performance estimates (IPEs), as defined by standardized differences between actual conditions and visitor preferences for each indicator. The results for each indicator are then presented graphically on a four-quadrant matrix for objective interpretation. Each quadrant represents a management response: keep up the good work, concentrate here, low priority, or possible overkill. The technique allows managers to more systematically and effectively utilize information routinely collected during the limits of acceptable change wilderness planning process. This paper is submitted with the approval of the Director of the West Virginia Agricultural and Forestry Experiment Station as Scientific Article No. 541. The study was funded in part, through a grant from the USDA Forest Service, Monongahela National Forest.     

Automatic safety belt use in Michigan: A two-year follow-up

The use of automatic safety belts among motorists throughout the state of Michigan was examined as part of a broader direct observation survey to measure compliance with the state's mandatory belt use law. Use of the most common types of automatic belt systems were measured: the nonmotorized detachable three-point lap and shoulder belt system, and the two-belt system with either a motorized shoulder belt and manual lap belt or a nonmotorized shoulder belt and manual lap belt. Belt use rates in vehicles with and without air bags were also compared. A total of 1,367 drivers and front-right passengers were observed with automatic belt systems between June 1 and July 11, 1992. Use of nonmotorized detachable three-point lap and shoulder belt systems was 72.3%. Lap belt use of motorized shoulder and manual lap belt systems was 70.5%. Lap belt use of nonmotorized shoulder and manual lap belt systems was 60.2%. Of all motorized and nonmotorized shoulder belt and manual lap belt systems observed, 94.5% had the shoulder belts connected.     

Using risk assessment to achieve cost-effective property transfers and site closures for former UST sites

Risk assessment has been increasingly applied as a tool in making risk management decisions that affect cleanup of contaminated sites, property transactions, and liability issues. As a site-specific evaluation, risk assessment takes into account the unique characteristics and intended future uses for site property in evaluating chemical concentrations which may remain in place without risk to public health and the environment. The results of a risk assessment can be used to determine reuse options for a property, facilitate site closure, and reduce liabilities (Copeland and Robles, 1994; Copeland et al., 1993a). This article describes the risk assessment process, the role of risk assessment in determining the need for remedial action and identifying site-specific cleanup goals, and the cost effectiveness of applying risk assessment in remedial decisions. Because of the prevalence of former UST sites throughout the United States, this article focuses on risk assessment and remediation of UST sites. However, the process can be applied at sites where other chemicals have been released. Three case studies are presented to illustrate the application of risk assessment in achieving cost-effective site closure at sites containing leaking underground storage tanks.     

Risk management is part of good management

As the use of hazard and risk assessments becomes more commonplace, the need for and importance of an overall risk management system become apparent. Such a system allows companies to prioritize both their efforts to identify and understand risks and their allocation of resources to manage and control risks. In the future, the most effective risk management systems will be integrated into other business processes and management systems, to ensure that their value as well as their costs are recognized and measured by line operations. For example, chemical and petrochemical companies such as BP Exploration, Monsanto, and Union Carbide are improving on well-established risk management systems by increasing their businesses' involvement in and ownership of the process. This article summarizes the key elements of a risk management system and uses the lessons learned by various companies to define best existing and emerging practices.