James O. Luken

Assessment and management of plant invasions

SECTION I. Human Perceptions.- 1. Defining Indigenous Species: An Introduction.- Defining Native Species.- Mechanisms for Change in Species Distributions.- Humans as a Component of the Natural.- Consequences of Choosing a Definition.- Conclusions.- 2. Defining Weeds of Natural Areas.- Definitions of Weed.- Definition and Examples of Natural-Area Weeds.- Adaptive Management of Natural-Area Weeds.- Conclusions.- 3. Potential Valuable Ecological Functions of Nonindigenous Plants.- Assessing Potential Ecological Values of Nonindigenous Plants.- Case Histories and Examples: Anecdotal, Hypothetical, and Otherwise.- Future Ecological Values of Nonindigenous Plants in a Changing Global Environment.- Conclusions.- SECTION II. Assessment of Ecological Interactions.- 4. Documenting Natural and Human-Caused Plant Invasions Using Paleoecological Methods.- Nature of the Paleoecological Record.- Paleoecological Assessments of Human-Related Plant Invasions.- Long-Term Records of Plant Invasions and Environmental Change.- Interactions Between Environmental Change and Human Disturbance.- Conclusions.- 5. Community Response to Plant Invasion.- Potential Mechanisms of Community Effects.- Possible Instances of Effects on Community Composition and Structure.- Invasion by Indigenous Species and the Paleoecological Record.- Generalizations.- Conclusions.- 6. Impacts of Invasive Plants on Community and Ecosystem Properties.- Primary Productivity.- Soil Nutrients.- Soil Water and Salinity.- Disturbance Regimes.- Community Dynamics.- Case Studies.- Conclusions.- 7. Animal-Mediated Dispersal and Disturbance: Driving Forces Behind Alien Plant Naturalization.- Naturalization.- Conclusions.- 8. Outlook for Plant Invasions: Interactions with Other Agents of Global Change.- Primary Agents of Global Change.- Interactions Among Factors.- Conclusion.- 9. Experimental Design for Plant Removal and Restoration.- Scientific Methods.- Principles of Design.- Experimental Design.- Applications: Managing Study Plots and Data.- Conclusions.- 10. Response of a Forest Understory Community to Experimental Removal of an Invasive Nonindigenous Plant (Alliaria petiolata, Brassicaceae).- Biology of the Study Species.- Methods.- Results.- Discussion.- Conclusions.- Appendix 10.1. Species list.- SECTION III. Direct Management.- 11. Management of Plant Invasions: Implicating Ecological Succession.- Succession: The Rise and Fall of Populations.- Plant Invasion: A Successional Interpretation.- The Decision to Manage.- The Response to Management.- A Paradigm for Management.- Conclusions.- 12. Methods for Management of Nonindigenous Aquatic P] ants.- Why Manage Nonindigenous Aquatic Plants?.- Management Techniques.- Developing an Integrated Management Plan.- Conclusions.- 13. Biological Control of Weeds in the United States and Canada.- Comparison of Control Methods.- Community-Level Effects of Invasion and Response to Biological Control.- Research Protocol.- Regulations and Safeguards.- Control of Major Weeds in the United States and Canada.- Future Directions of Biological Control.- Conclusions.- 14. Prioritizing Invasive Plants and Planning for Management.- Why Prioritize Invasive Plants?.- How to Prioritize.- Steps in the Decision-Making Process.- Decision-Making Tools.- A Generalized Nonindigenous Plant Ranking System.- Conclusions.- Appendix 14.1. A system for ranking nonindigenous plants.- SECTION IV. Regulation and Advocacy.- 15. Prevention of Invasive Plant Introductions on National and Local Levels.- Modes of Species Entry.- Current Laws.- Developing Predictive Methods.- Monitoring for New Invasions.- Preventing Invasions on the Local Scale.- Conclusions.- 16. Exotic Pest Plant Councils: Cooperating to Assess and Control Invasive Nonindigenous Plant Species.- Measuring the Impact of Invasions.- Overall Significance of Invasions.- The Need for Coordination.- Role of Exotic Pest Plant Councils.- Conclusions.- 17. Team Arundo: Interagency Cooperation to Control Giant Cane (Arundo donax).- Historical Setting.- Plant Biology.- The Problem.- The Solution? Team Arundo.- The Future.- Conclusions.- 18. A Multiagency Containment Program for Miconia (Miconia calvescens), an Invasive Tree in Hawaiian Rain Forests.- Distribution and Ecology of Miconia.- Agencies and Citizen Groups Involved in Miconia Control in Hawaii.- Strategies and Tactics.- Prospects for Success.- Appendix: Selected Plant Species Interfering with Resource Management Goals in North American Natural Areas.- References.

Response of Woody Plant Communities in Power-Line Corridors to Frequent Anthropogenic Disturbance.

Ecological theory predicts that diversity should decline as disturbance frequency increases beyond an intermediate level. However, few data exist on the responses of deciduous forests to high-frequency disturbance. We compared regenerating woody plant communities in northern Kentucky power-line corridors to adjacent second-growth forests to determine if high-frequency disturbance (5-6 yr mechanical or manual cutting cycle) modifies forest development. Black locust (Robinia pseudoacacia) and white ash (Fraxinus americana) dominated corridor communities. Still, many species present in adjacent forests persisted in corridors, with the result that 15 of 20 corridor samples were classified by TWINSPAN close to samples taken from adjacent forests. Of the most important tree species found in the study sites, sugar maple (Acer saccharum) was least favored by high-frequency cutting. In general, high-frequency cutting did not totally inhibit regeneration of a single species, diversity showed a small but nonsignificant increase, and several early-successional, shade-intolerant species established anew. When forests are repeatedly cut before stems reach the stem exclusion stage, individualistic patterns of sprouting and carbon allocation will likely determine dominance. White ash and black locust will assume greater importance in fragmented forests as disturbance frequencies increase.

Fine root production of astringent phenolics

SummaryChemical quality of fine roots (<1 mm diameter) was determined over a gradient of species composition in the Mixed Mesophytic Forest Region. Ash-free nitrogen, calcium, and phosphorus concentrations of roots declined by 49, 41, and 72%, respectively, over a gradient of increasing soil acidity (pH 5.3 to 4.7). Lignin concentration was unrelated to either the vegetation gradient or any of the soil changes it encompassed; however, astringent phenolics increased by 275% over the same gradient. Trends in the chemical constituency of fine roots suggest that the production of phenolics in below-ground plant parts is increased on nutrient-poor sites. This response is best related to changes in species composition, especially increasing importancy of Quercus spp.

Assessment of frequent cutting as a plant-community management technique in power-line corridors.

Repeated cutting of vegetation at or near ground level in power-line corridors is a common practice for inhibiting tree growth and regeneration. However, few data exist on long-term community responses. In this study, we sampled 20 northern Kentucky power-line corridors and compared their seedling and sapling communities to the edges and interiors of adjacent undisturbed forests. Mean seedling and sapling density in corridors was roughly twice that of adjacent undisturbed forest interiors, suggesting that repeated cutting is not a viable method of inhibiting tree regeneration. Corridor communities were dominated byRobinia pseudoacacia (black locust) andFraxinus americana (white ash), but ordinations indicated strong similaritties among communities in corridors and adjacent forests. Many of the tree species found in adjacent forests, with the exception of a few shade-tolerant species, had highest seedling and sapling densities in corridors. Stump or root sprouting by many species appears to regenerate forests quickly after cutting. However, disturbed soil and detritus accumulations caused by management crews and their equipment may also create a large variety of microsites for seedling establishment. Because repeated cutting selects for dominance by species with highest sprout growth rates, it should not be used as the sole management technique. It may instead be used to alter the vigor, stature, and stored reserves of trees so that herbicides or other methods of tree control can be used more efficiently.

Forest edges associated with power-line corridors and implications for corridor siting

Abstract In addition to the effects of power-lines on the visual perceptions of urban landscapes, planners and designers need to consider ecological factors and long-term maintenance costs when siting new corridors in forested areas. A survey of 20 corridors in the forests of northern Kentucky revealed higher mean density and basal area of tree seedlings and saplings in forest edges adjacent to power-line corridors. Some edges also showed distinct community shifts entailing increased importance of shade intolerant tree species. In forests already fragmented by development activities, the presence of a single power-line corridor may render forest patches unsuitable for plant and animal species requiring large forest interior habitats. To avoid this, corridors can be sited in non-forested areas, along existing corridors, along the edges of existing forest patches, or in forest patches that at present lack viable interiors. Applying these recommendations to new corridor projects will stop further forest fragmentation and minimize long-term line maintenance costs, but may also degrade visual perceptions of urban landscapes. Where visual perception is a common facet of land use, corridors may be camouflaged or hidden in forests to reduce visual impact.

PLANT COMMUNITIES ASSOCIATED WITH DIFFERENT SHORELINE ELEMENTS AT CAVE RUN LAKE, KENTUCKY

The purpose of this research was to determine if slope and exposure are important determinants of plant communities emerging on reservoir shorelines. We sampled 30 sites on the previously inundated shoreline of Cave Run Lake, a U.S. Army Corps of Engineers flood-control reservoir in east-central Kentucky, USA. These sites were categorized as either flats, riparian forests, exposed banks, or sheltered banks Two-way indicator species analysis (TWINSPAN) and detrended correspondence analysis were used with presence/absence data to group sites of similar community composition. These were 167 species of plants identified in the study plots, of which 29% were annuals, 2% were biennials, 69% were perennials, 11% were non-indigenous, and 63% met the criterion for inclusion in community analysis. A distinct assemblage of plant species was associated with all riparian forests, with six of eight flats, and with five of twelve exposed banks. Six sheltered banks were not obviously associated with a single community type. The TWINSPAN group including riparian forests had the highest percentage of wetland species; the TWINSPAN group including most flats had the highest species richness; the TWINSPAN group comprised entirely of exposed banks had low species richness and low representation of wetland species. Our results suggest that plant communities of high conservation value can emerge on relatively flat sites under a human-controlled flooding regimen as long as the soil remains intact. However, steep exposed banks are susceptible to soil loss, and the resulting rock substrates support a depauperate flora of low conservation value.

Conservation in the Context of Non-Indigenous Species

There is currently worldwide concern regarding the invasion of natural areas by non-indigenous species. Several recently published books have addressed this issue in terms of ecological interactions (Mooney and Drake 1986), resource management problems (McKnight 1993), and regulatory impact (OTA 1993). Furthermore, specific regions of the United States have been analyzed relative to invasion pressure and the threat that non-indigenous species pose to biological communities [e.g., the Pacific Northwest (Mack 1986), California (Rejmdnek and Randall 1994), and Hawaii (Stone et al. 1992)]. Relatively little effort has been devoted to understanding biological invasions of natural areas in the midwestern United States.

Target and nontarget discrimination of herbicides applied to vegetation in a power-line corridor

We tested two cutting regimens (cut/spray and cut/delay spray) and four radiarc-applied herbicides (Garlon + Tordon, Accord, Accord + Escort, and Krenite) in an Ohio power-line corridor to determine which management combination best eliminated target species (i.e., trees) and preserved nontarget species (i.e., low shrubs, vines, perennial herbs, and grasses).When spraying was delayed after cutting, the herbicide with the least impact on nontarget species (Krenite) also was least efficient at killing target trees. Spraying soon after cutting improved tree-killing efficiency of several herbicides, but it also increased the negative impact on nontarget species. The herbicide with the most consistent tree-killing ability (Accord + Escort) had the most impact on nontarget species.Because none of the herbicide/cutting treatments performed ideally, resource managers must decide the acceptable impact on nontarget species when considering herbicide use. Future success of herbicides as part of an integrated succession management approach requires more selective application methods and formulations so that target effects can be maximized and nontarget effects can be minimized.