Showing papers in "Restoration Ecology in 1997"

Ecological Theory and Community Restoration Ecology

Abstract: Community ecological theory may play an important role in the development of a science of restoration ecology. Not only will the practice of restoration benefit from an increased focus on theory, but basic research in community ecology will also benefit. We pose several major thematic questions that are relevant to restoration from the perspective of community ecological theory and, for each, identify specific areas that are in critical need of further research to advance the science of restoration ecology. We ask, what are appropriate restoration endpoints from a community ecology perspective? The problem of measuring restoration at the community level, particularly given the high amount of variability inherent in most natural communities, is not easy, and may require a focus on restoration of community function (e.g., trophic structure) rather than a focus on the restoration of particular species. We ask, what are the benefits and limitations of using species composition or biodiversity measures as endpoints in restoration ecology? Since reestablishing all native species may rarely be possible, research is needed on the relationship between species richness and community stability of restored sites and on functional redundancy among species in regional colonist “pools.” Efforts targeted at restoring system function must take into account the role of individual species, particularly if some species play a disproportionate role in processing material or are strong interactors. We ask, is restoration of habitat a sufficient approach to reestablish species and function? Many untested assumptions concerning the relationship between physical habitat structure and restoration ecology are being made in practical restoration efforts. We need rigorous testing of these assumptions, particularly to determine how generally they apply to different taxa and habitats. We ask, to what extent can empirical and theoretical work on community succession and dispersal contribute to restoration ecology? We distinguish systems in which succession theory may be broadly applicable from those in which it is probably not. If community development is highly predictable, it may be feasible to manipulate natural succession processes to accelerate restoration. We close by stressing that the science of restoration ecology is so intertwined with basic ecological theory that practical restoration efforts should rely heavily on what is known from theoretical and empirical research on how communities develop and are structured over time.

Approximating Nature's Variation: Selecting and Using Reference Information in Restoration Ecology

Abstract: Restoration ecologists use reference information to define restoration goals, determine the restoration potential of sites, and evaluate the success of restoration efforts. Basic to the selection and use of reference information is the need to understand temporal and spatial variation in nature. This is a challenging task: variation is likely to be scale dependent; ecosystems vary in complex ways at several spatial and temporal scales; and there is an important interaction between spatial and temporal variation. The two most common forms of reference information are historical data from the site to be restored and contemporary data from reference sites (sites chosen as good analogs of the site to be restored). Among the problems of historical data are unmeasured factors that confound the interpretation of historical changes observed. Among the problems of individual reference sites is the difficulty of finding or proving a close match in all relevant ecological dimensions. Approximating and understanding ecological variation will require multiple sources of information. Restoration, by its inherently experimental nature, can further the understanding of the distribution, causes, and functions of nature's variation.

Restoration Biology: A Population Biology Perspective

Abstract: A major goal of population biologists involved in restoration work is to restore populations to a level that will allow them to persist over the long term within a dynamic landscape and include the ability to undergo adaptive evolutionary change. We discuss five research areas of particular importance to restoration biology that offer potentially unique opportunities to couple basic research with the practical needs of restorationists. The five research areas are: (1) the influence of numbers of individuals and genetic variation in the initial population on population colonization, establishment, growth, and evolutionary potential; (2) the role of local adaptation and life history traits in the success of restored populations; (3) the influence of the spatial arrangement of landscape elements on metapopulation dynamics and population processes such as migration; (4) the effects of genetic drift, gene flow, and selection on population persistence within an often accelerated, successional time frame; and (5) the influence of interspecific interactions on population dynamics and community development. We also provide a sample of practical problems faced by practitioners, each of which encompasses one or more of the research areas discussed, and that may be solved by addressing fundamental research questions.

Stabilization and Erosion Control Value of Oyster Cultch for Intertidal Marsh

Abstract: Oyster cultch was added to the lower intertidal fringe of three created Spartina alterniflora marshes to examine its value in protecting the marsh from erosion Twelve 5-m-wide plots were established at each site, with six randomly selected plots unaltered (non-cultched) and cultch added to the remaining (cultched) plots Within each cultched plot, cultch was placed along the low tide fringe of the marsh during July 1992, in a band 15 m wide by 025 m deep Marsh-edge vegetation stability and sediment erosion were measured for each plot from September 1992 to April 1994 Significant differences (p < 005) in marsh-edge vegetation change were detected at the only south-facing site after a major southwester storm Significantly different rates of sediment erosion and accretion also were observed at this same site Areas upland of the marsh edge in the cultched areas showed an average accretion of 63 cm, while noncultched treatment areas showed an average loss of 32 cm A second site, with a northern orientation, also experienced differential sediment accretion and erosion between treatment type, caused instead by boat wakes that were magnified by the abutment of a dredge effluent pipe across the entire front fringe of the site During this period we observed significant differences in sediment accumulation, with the areas upland of the marsh edge in the cultched treatment having an average accretion of 29 cm and the noncultched an average loss of 13 cm

Exotic grass competition in suppressing native shrubland re-establishment

Abstract: Disturbance of coastal sage scrub in southern California has led to extensive displacement of native shrubs by exotic annual grasses. The initial conversion from shrubland to exotic grassland is typically associated with disturbance caused by intense grazing, high fire frequency, or mechanical vegetation removal. While native shrubs have been shown to recolonize annual grasslands under some conditions, other annual grasslands are persistent and show no evidence of shrub recolonization. This study examined the mechanisms by which annual grasses may exclude native shrubs and persist after release from disturbance. Grass density was manipulated in experimental plots to achieve a series of prescribed densities. Artemisia californica, a dominant native shrub, was seeded or planted into the plots and responses to the grass density treatments were measured over two growing seasons. A. californica germination, first season growth, and survival were all negatively related to the density of neighboring annual grasses. The most probable mechanism underlying the reduction of first season growth and survival was depletion of soil water by the grasses. The effects of the grasses on A. californica were no longer significant in the second season. The results of this study indicate that Mediterranean annual grasses reduce recruitment and can persist by inhibiting post-disturbance establishment of A. californica from seed. Although succession alone may not return disturbed annual grasslands to their former shrubland composition, the results suggest that restoration can be achieved by using container plantings or grass removal followed by seeding.

Smoke Enhanced Seed Germination for Mine Rehabilitation in the Southwest of Western Australia

Abstract: Cool smoke treatments were applied to unmined Eucalyptus marginata (jarrah) forest soils, rehabilitated bauxite mine soils, and broadcast seed to determine if enhancement in germination could be effected with a view toward maximizng the establishment of species in bauxite mines in Western Australia. Forest sites showed a 48-fold increase in total germinants from the soil seed bank when treated with aerosol smoke. Newly returned bauxite mine soils showed a greater than threefold increase in total germinants after the same treatment. There were also significant increases in the number of species germinating in response to the aerosol smoke treatment in both the forest and the mined soils. Similarly, application of smoked water to the soil seed bank in previously mined sites elicited a significant positive germination response, increasing total germinants and species numbers by 56 and 33%, respectively. Treatment of mixed seed lots with aerosol smoke before broadcast resulted in highly significant improvement in germination when compared to untreated seed. Both total number of germinants, and number of species emerging from mined sites were positively influenced (85% and 34% increases, respectively). Ten target species were used to determine the relative effectiveness of different methods of smoke treatment on the germination of broadcast seed. Nine of the species involved displayed a promotive effect with at least two of the treatments. Generally, however, aerosol smoking of seed before broadcast proved to be the more effective approach. As a result of these findings, all broadcast seed for use in Alcoa's bauxite mined areas in the southwest of Western Australia is now routinely smoke treated before application.

Linking Restoration and Landscape Ecology

Abstract: Landscape ecology focuses on questions typically addressed over broad spatial scales. A landscape approach embraces spatial heterogeneity, consisting of a number of ecosystems and/or landscape structures of different types, as a central theme. Such studies may aid restoration efforts in a variety of ways, including (1) provision of better guidance for selecting reference sites and establishing project goals and (2) suggestions for appropriate spatial configurations of restored elements to facilitate recruitment of flora/ fauna. Likewise, restoration efforts may assist landscape-level studies, given that restored habitats, possessing various patch arrangements or being established among landscapes of varying diversity and conditions of human alteration, can provide extraordinary opportunities for experimentation over a large spatial scale. Restoration studies can facilitate the rate of information gathering for expected changes in natural landscapes for which introduction of landscape elements may be relatively slow. Moreover, data collected from restoration studies can assist in validation of dynamic models of current interest in landscape ecology. We suggest that restoration and landscape ecology have an unexplored mutualistic relationship that could enhance research and application of both disciplines.

Quantitatively Evaluating Restoration Experiments: Research Design, Statistical Analysis, and Data Management Considerations

Abstract: Conceptual and logistical challenges associated with the design and analysis of ecological restoration experiments are often viewed as being insurmountable, thereby limiting the potential value of restoration experiments as tests of ecological theory. Such research constraints are, however, not unique within the environmental sciences. Numerous natural and anthropogenic disturbances represent unplanned, uncontrollable events that cannot be replicated or studied using traditional experimental approaches and statistical analyses. A broad mix of appropriate research approaches (e.g., long-term studies, large-scale comparative studies, space-for-time substitution, modeling, and focused experimentation) and analytical tools (e.g., observational, spatial, and temporal statistics) are available and required to advance restoration ecology as a scientific discipline. In this article, research design and analytical options are described and assessed in relation to their applicability to restoration ecology. Significant research benefits may be derived from explicitly defining conceptual models and presuppositions, developing multiple working hypotheses, and developing and archiving high-quality data and metadata. Flexibility in research approaches and statistical analyses, high-quality databases, and new sampling approaches that support research at broader spatial and temporal scales are critical for enhancing ecological understanding and supporting further development of restoration ecology as a scientific discipline.

Restoration Ecology and the Ecosystem Perspective

Abstract: The ecosystem perspective provides a framework within which most other aspects of the ecology of restoration can be incorporated. By considering the ecosystem functions of a restoration project, the restorationist is forced to consider the placement of the project in the landscape—its boundaries, its connections or lack thereof to adjoining ecosystems, and its receipts and losses of materials and energy from its physical surroundings. These characteristics may set limits on the kind(s) of biotic communities that can be created on the site. The ecosystem perspective also gives restorationists conceptual tools for structuring and evaluating restorations. These include the mass balance approach to nutrient, pollutant, and energy budgets; subsidy/stress effects of inputs; food web architecture; feedback among ecosystem components; efficiency of nutrient transfers, primary productivity and decomposition as system-determining rates; and disturbance regimes. However, there are many uncertainties concerning these concepts, their relation to each other, and their relationships to population- and community‐level phenomena. The nature of restoration projects provides a unique opportunity for research on these problems; the large spatial scale of restorations and the freedom to manipulate species, soil, water, and even the landscape could allow ecosystem-level experiments to be conducted that could not be performed otherwise.

Planning and Implementing a Reintroduction of Wolves to Yellowstone National Park and Central Idaho

Abstract: The Northern Rocky Mountain Wolf Recovery plan proposed reintroduction of Canis lupus (gray wolf) to Yellowstone National Park and central Idaho as part of a wolf restoration plan for the northern Rocky Mountains of the United States. Strong opposition from some factions within the region forestalled the action for two decades. An environmental impact statement, conducted in 1992–1994 with extensive public input, culminated in a proposal to reintroduce wolves designated as “non-essential—experimental” under Section 10 (j) of the federal Endangered Species Act. This approach, approved by the Secretary of the Interior in 1994, provided for wolf restoration while allowing management flexibility to deal with concerns of the local public. A reintroduction plan was developed in the summer and fall of 1994. Acquiring, holding, transporting, and releasing suitable wolves for reintroduction presented a myriad of technical and logistical challenges that required effective planning and coordination by all participants. In January 1995, 29 wolves were captured in Alberta and transported to Yellowstone National Park (14) and central Idaho (15). Idaho wolves were freed immediately upon arrival; Yellowstone wolves (three family groups) were held in acclimation pens in the park until late March. Most Idaho wolves traveled extensively within the area intended for them, averaging 82 km net distance away from release sites after 5 months (range = 30–220 km), and three male-female pairs formed by July. After 5 months in the wild, at least 13 of 15 Idaho-released wolves were alive within the intended area, as were 13 of 14 Yellowstone wolves; one wolf was known to have been illegally killed in each area. No livestock were killed. Wolves released into Yellowstone Park continued to live as packs, stayed closer to their release sites (x = 22 km at end of June), and settled into home ranges; two packs produced a total of nine pups. The progress of the reintroduction program in its first year far exceeded expectations. Reintroductions of about 15 wolves to each area for 2–4 more years are scheduled, but the project may be shortened because of early successes. Future reintroduction planners can expect sociocultural issues to pervade the effort, but they can be optimistic that, from a biological standpoint, reintroduction of wolves has strong potential as a restoration technique.

Riparian Restoration in the Western United States: Overview and Perspective

Abstract: This historical and conceptual overview of riparian ecosystem restoration discusses how riparian ecosystems have been defined, describes the hydrologic, geomorphic, and biotic processes that create and maintain riparian ecosystems of the western USA, identifies the main types of anthropogenic disturbances occurring in these ecosystems, and provides an overview of restoration methods for each disturbance type We suggest that riparian ecosystems consist of two zones: Zone I occupies the active floodplain and is frequently inundated and Zone I1 extends from the active floodplain to the valley wall Successful restoration depends on understanding the physical and biological processes that influence natural riparian ecosystems and the types of disturbance that have degraded riparian areas Thus we recommend adopting a process-based approach for riparian restoration Disturbances to riparian ecosystems in the western USA result from streamflow modifications by dams, reservoirs, and diversions; stream channelization; direct modification of the riparian ecosystem; and watershed disturbances Four topics should be addressed to advance

Woodland restoration in the western Australian wheatbelt : A conceptual framework using a state and transition model

Abstract: Woodlands dominated by Eucalyptus spp. in temperate southeastern and southwestern Australia have been extensively cleared for agriculture and are often badly degraded by livestock grazing. This has resulted in the loss of biodiversity and widespread land degradation. The continuing decline of these woodlands has become a concern for the conservation of biodiversity, and there is a growing interest among farmers, land managers, and researchers in developing techniques for restoring them. Currently few scientific guidelines exist for undertaking woodland restoration programs. We use a state and transition model to develop hypotheses on restoration strategies for salmon gum (Eucalyptus salmonophloia) woodlands. We consider that this approach provides a suitable framework for organizing knowledge and identifying areas where further information is needed, and hence provides a useful starting point for a restoration program. The model has the potential to provide a tool for land managers with which they can assess the action and effort needed to undertake woodland restoration in agricultural landscapes.

The Scale of Successional Models and Restoration Objectives

Abstract: Successional models are used to predict how restoration projects will achieve their goals. These models have been developed on different spatial and temporal scales and consequently emphasize different types of dynamics. This paper focuses on the restoration goal of self-sustainability, but only in the context of a long-term goal. Because of the temporal scale of this goal, we must consider the impact of processes arising outside of the restoration site as of greater importance than restoration itself. Because ecological systems are open, restoration sites will be subjected to many external influential processes. Depending on the landscape context, the impact of these processes may not be noticeable, or, at the other extreme, they may prevent the achievement of restoration objectives. A second issue is to emphasize the nature of processes in the long term, that they are a complex of characteristics such as magnitude, frequency, and extent. Ecological systems are only adapted to a range of values in each of these characteristics. Restoration often combines goals that are of different scales. Models appropriate to these goals need consideration.

Reforestation of bottomland hardwoods and the issue of woody species diversity

Abstract: Bottomland hardwood forests in the southcentral United States have been cleared extensively for agriculture, and many of the remaining forests are fragmented and degraded. During the last decade, however, approximately 75,000 ha of land-mainly agricultural fields-have been replanted or contracted for replanting, with many more acres likely to be reforested in the near future. The approach used in most reforestation projects to date has been to plant one to three overstory tree species, usually Quercus spp. (oaks), and to rely on natural dispersal for the establishment of other woody species. I critique this practice by two means. First, a brief literature review demonstrates that moderately high woody species diversity occurs in natural bottomland hardwood forests in the region. This review, which relates diversity to site characteristics, serves as a basis for comparison with stands established by means of current reforestation practices. Second, I reevaluate data on the invasion of woody species from an earlier study of 10 reforestation projects in Mississippi, with the goal of assessing the likelihood that stands with high woody species diversity will develop. I show that natural invasion cannot always be counted on to produce a diverse stand, particularly on sites more than about 60 m from an existing forest edge. I then make several recommendations for altering current reforestation practices in order to establish stands with greater woody species diversity, a more natural appearance, and a more positive environmental impact at scales larger than individual sites.

The Role of GIS in Selecting Sites for Riparian Restoration Based on Hydrology and Land Use

Abstract: Successful long-term wetland restoration efforts require consideration of hydrology and surrounding land use during the site selection process. This article describes an approach to initial site selection in the San Luis Rey River watershed in southern California that uses watershed-level information on basin topography and land cover to rank the potential suitability of all sites within a watershed for either preservation or restoration. This approach requires the use of a geographic information system (GIS) to map relative wetness and land cover within a watershed. Relative potential wetness values were derived from U.S. Geological Survey (USGS) 30-m digital elevation models by calculating the flow that would potentially accumulate at all 30-m x 30-m pixels within the watershed. Land cover was derived from a Landsat scene covering the 1500 km 2 study area. We ranked sites (contiguous groups of pixels > 1 ha with similar land cover) in terms of their potential for restoration or preservation based on their wetness values (low, medium, and high), size, and proximity to existing riparian vegetation. Sites with medium or high wetness values and extant vegetation were identified as potential preservation sites. Agricultural or barren sites with medium to high wetness were identified as potential restoration sites. Approximately 5500 ha (3.67% of the total watershed) were prioritized for preservation or restoration.

Effectiveness of Road Ripping in Restoring Infiltration Capacity of Forest Roads

Abstract: Many forest roads are being closed as a step in watershed restoration. Ripping roads with subsoilers or rock rippers is a common practice to increase the infiltration capacity of roads before closure. When considering the effectiveness of ripping for reducing runoff and erosion and the potential reduction in slope stability by saturating road fills, it is important to know how ripping changes the infiltration capacity of forest roads. Hydrographs from simulated rainfall on 1 × 1 m plots were analyzed to find the saturated hydraulic conductivity, an indicator of infiltration capacity. I examined saturated hydraulic conductivity for three treatments on two different soils. One road was built in a soil derived from the metamorphic belt series geology of northern Idaho, a soil noted for its high rock fragment content. The second road was built in a sandy soil derived from decomposed granitics of the Idaho batholith. On each soil, five plots were installed on a road before ripping, and nine plots were installed on the same road segment following ripping, four covered with a heavy straw mulch and five without. Three half-hour rainfall events with intensities near 90 mm/hr were simulated on each plot. Results show that ripping increases hydraulic conductivities enough to reduce risk of runoff but does not restore the natural hydraulic conductivity of a forested slope. The unripped road surfaces had hydraulic conductivities in the range of 0–4 mm/hr, whereas ripped roads were in the range of 20–40 mm/hr after the second event. Surface sealing and tilled soil subsidence processes are important in reducing the hydraulic conductivity of the soils with repeated wetting. Subsidence appears to be important on the granitic soil, whereas surface sealing was more important on the belt series soil.

Soil Ripping and Herbicides Enhance Tree and Shrub Restoration on Stripmines

Abstract: I evaluated responses by 16 native woody species to differential soil compaction and density of ground cover. The trees and shrubs studied represent sites in southern Illinois that commonly have restrictions to root growth from soil or drainage conditions. The study site was a restored surface coal mine in southern Illinois with a rooting medium compacted by grading and a dense ground cover of pasture species. Soil compaction was alleviated in half the study area before tree planting by mechanically ripping the soil to a depth of 1.2 m. Roots of half the trees and shrubs were dipped in a Terra® slurry before planting, and the ground cover around all planting spots was afterwards sprayed with herbicide. In year 2 after planting the ground cover in half of the unripped and half of the ripped area was further controlled by repeated application of herbicides. Ripping significantly increased height growth of all trees combined and all species individually in each year of the study. Second-year control of ground cover increased height growth of all trees combined and of seven species individually. Some species were damaged by herbicides. Terra® had little evident effect on species performance. Animal damage reduced early survival and growth, especially of Acer (maple) and Cornus (dogwood) species, and later growth of Quercus rubra (red oak). Removal of ground cover with herbicides tended to increase deer browse. Soil ripping, herbicide application, and choosing tree species unattractive to deer can be recommended to increase success in planting trees for forest restoration.

Terrestrial Invertebrate Community Structure as an Indicator of the Success of a Tropical Rainforest Restoration Project

Abstract: Rainforest restoration is a relatively new endeavor, and few attempts have been made to assess the success of such restoration efforts in terms of the reestablishment of an ecosystem. Small plantings of rainforest tree species have been carried out adjacent to mature rainforest at Lake Barrine National Park in North Queensland, Australia, since 1988. The aim of this project was to assess the leaf litter invertebrate fauna of these plantings as indicators of the success of the restoration process. Plots planted in 1988, 1989, and 1990, as well as adjacent mature rainforest, were sampled in the wet and dry seasons of 1994. Invertebrates were extracted from leaf litter samples with Berlese Funnels and sorted to order. Diversity, the abundance of different size classes and orders of invertebrates, and the abundance of different functional groups were examined. In most respects the 1988 plot was found to differ little from the mature rainforest plots, whereas the 1990 plot lacked small and predatory invertebrates, especially in the dry season. The 1989 plot was intermediate in invertebrate abundance and diversity. The use of partially deciduous trees in the 1989 and 1990 plots, resulting in lower canopy cover at the driest time of the year, may have contributed significantly to the differences found between the early and later plantings. It is recommended that trees that provide good canopy cover year-round be used as dominant species in plantings to facilitate the development of a leaf litter ecosystem that can be sustained throughout the year.

Response of understory species to gap formation and soil disturbance in Lonicera maackii thickets.

Abstract: We studied the utility of gap formation and soil disturbance as methods to enhance establishment of plant species in the understory of a northern Kentucky forest where Lonicera maackii (Amur honeysuckle) produced dense thickets. In May 1994, gaps (5 m diameter) were cut in the shrub thicket. In adjacent areas, the shrub canopy remained intact. Subplots were established where soil was either turned with a spade to a depth of 15 cm or not disturbed. We monitored plant establishment for three growing seasons (1994, 1995, and 1996). Shrub removal increased light availability to about 10% of full sun. Gap formation had a significant (p 0.05). After three growing seasons, the most important species were L. maackii, Alliaria petiolata, Parthenocissus quinquefolia, Vitis vulpina, and Acer negundo. Of these species, only V. vulpina showed significantly (p < 0.05) higher densities in gaps. Other less important species such as Phytolacca americana, Campsis radicans, and Eupatorium rugosum occurred almost exclusively in gaps. Of the 44 taxa observed in this study, most were generalist species that also occur in early successional habitats. Long-term dominance of the understory by L. maackii has likely modified system attributes with corresponding effects on community development. Shrub removal provides a window of establishment for various plant species, but successful restoration may require further management species availability and to control new invaders.

Restoring native perennial grasses to rural roadsides in the Sacramento Valley of California : Establishment and evaluation

Abstract: Along rural roadsides of the Sacramento Valley of California, we seeded native and non-native perennial grasses to gauge their potential value in roadside vegetation management programs. In trial I (polycultures), three seeded complexes and a control (resident vegetation only) were tested. Each seeded plant complex included a different mix of perennial grasses seeded into each of several roadside topographic zones. The seeded levels of plant complex were: native perennial grasses 1 (8 species); native perennial grasses 2 (13 species); and non-native perennial grasses (3 species). In trial II, plots were seeded to monocultural plots of 15 accessions of native Californian and three cultivars of non-native perennial grasses. Plots in both trials were seeded during January 1992 and evaluated for three successive years. In trial I polycultures during 1993, canopy cover by seeded species was not significantly different among the three seeded complexes. The three seeded complexes showed statistically equivalent reduction of canopy cover by resident plant species. Biomass of seeded perennial grasses was greater for non-native perennial grasses than for native perennial grasses 1 or native perennial grasses 2. Total biomass (seeded plus resident species) was greatest for non-native perennial grasses. In trial II monocultures during 1993, the non-native Thinopyrum intermedium ssp. trichophorum (pubescent wheatgrass) attained the greatest height, followed by the native species Nassella (Stipa) cernua (nodding needlegrass), Nassella (Stipa) pulchra (purple needlegrass), and Elymus trachycaulus var. majus (slender wheatgrass). By contrast, the non-native Festuca ovina (sheep fescue) and the native Poa secunda ssp. secunda (pine bluegrass) were particularly short. N. cernua, N. pulchra, E. trachycaulus, and T. intermedium ssp. trichophorum showed particularly great canopy cover, whereas particularly low values of canopy cover were obtained for F. ovina and P. secunda ssp. secunda. A highly significant inverse linear relationship was obtained by regression analysis when canopy cover for seeded perennial grasses was used to predict canopy cover for resident plant species (p < 0.0001, r 2 = 0.297, slope = -0.336, intercept = 39.442). In 1994, the following native perennial grasses showed substantial canopy cover in trial II monocultures and appear promising for use in Sacramento Valley rights-of-way: Bromus carinatus (California brome), Elymus glaucus (blue wildrye), E. trachycaulus, all accessions of Hordeum brachyantherum ssp. brachyantherum (meadow barley), a prostrate accession of Hordeum brachyantherum ssp. californicum (California barley), N. cernua, and N. pulchra. In addition, the non-native T. intermedium ssp. trichophorum performed well. By contrast, virtual failure of stands was observed for the non-native F. ovina and the following native species: Elymus multisetus (squirreltail), two accessions of Festuca idahoensis (Idaho fescue), Festuca rubra (creeping red fescue), and P. secunda ssp. secunda.

The flora and invertebrate fauna of abandoned limestone quarries in Derbyshire, United Kingdom

Abstract: Abandoned limestone quarries are hostile environments for plant and invertebrate colonization and establishment. The length of time taken for successful establishment by natural processes may be unacceptable for reclamation purposes; several techniques are used to reduce the time scales involved. A new technique, restoration blasting, aims to replicate natural daleside landforms by selective blasting of modern production quarry faces. We compare the flora and invertebrate fauna of restoration-blasted sites, hydro-seeded with daleside species, with naturally regenerating disused quarries and a natural daleside. Restoration-blasted sites were found to have less plant cover, more bare ground, fewer orders of invertebrates, and generally fewer animals within each order than the other two types of site. The disused quarries tended to have intermediate characteristics between the restoration-blasted sites and the natural daleside. The age of the site may be important in determining the plants and invertebrates occurring there. This may be related to the time available for establishment or a greater degree of settlement or stability within the biotic and abiotic components of the site. Although most of the results indicate that time since establishment may be important, some variations occur. In particular, the development of vegetation cover in areas grazed by rabbits is problematic. These results are important in the assessment of successful reclamation because the invertebrate fauna may contribute greatly to the overall system. Both plant and animal communities appear to be establishing well on the sites reclaimed by restoration blasting. Further monitoring will identify the speed at which such environments achieve the desired aim of replicating daleside communities and the communities best able to be sustained following this technique.

Setting Riparian/Aquatic Restoration Objectives within a Watershed Context

Abstract: Declines in native plant and animal communities have prompted new interest in the restoration of aquatic and riparian ecosystems. Past restoration activities typically have been site specific, with little thought to processes operating at larger scales. A watershed analysis process developed in the Pacific Northwest identifies four operating scales useful in developing restoration priorities: region, basin, watershed, and specific site. Watershed analysis provides a template for restoration practitioners to use in prioritizing restoration activities. The template identifies seven key steps necessary to understand and develop restoration priorities: (1) characterization, (2) identification of key issues and questions, (3) documentation of current conditions, (4) description of reference conditions, (5) identification of objectives, (6) summary of conditions and determination of causes, and (7) recommendations. When a similar process was used in the Uinta Mountains, Utah, and in the Siuslaw National Forest, Oregon, specialists were able to identify key habitat conditions and habitat forming processes and then to establish restoration priorities and implement the appropriate activities. Watershed analysis provides a valuable set of tools for identifying restoration activities and is currently being used throughout the Pacific Northwest to develop management strategies and restoration priorities. Although the analysis requires significant time, money, and personnel, experience suggests that watershed analysis provides valuable direction for managing aquatic and riparian resources.

Restoration of woody plants to capped landfills: Root dynamics in an engineered soil

Abstract: Closed or abandoned landfills represent significant land areas, often in or near urban centers, that are potential sites for ecological restoration of native woodlands. But current guidelines in many jurisdictions do not allow for the installation of trees or shrubs above landfill clay caps, although these plants have many environmental, functional, and aesthetic advantages, including a rapid start to community succession. Typical closure procedures for capped landfills include only a grass cover to control moisture infiltration and impede soil erosion. The main concern that limits the application of a woody cover to a closed landfill is that roots may penetrate and weaken the clay cap. As part of a comprehensive experimental program on woodland restoration, we installed 22 tree and shrub species on Staten Island, New York (the Fresh Kills Sanitary Landfill). We found no evidence that roots of the transplanted woody plants penetrate caps used on these landfills. Root growth requirements and dynamics stop penetration of these materials. Anoxic and acidic conditions were found in the sandy subsoil above the cap, as indicated by corrosion patterns on steel test rods. Also, the intensity of mycorrhizal infection on the experimental plants was high in the surface soil and decreased progressively with increasing soil depth. The potential vertical rooting depth during this time period was greater than that occurring over the clay cap. This was shown from data collected on a nearby control site, where seven of the species were installed on an engineered soil lacking a clay barrier layer, and roots of all seven species penetrated deeper than on the landfill. The engineered landfill soils are poor growth media for roots, and below ground constraints that limit restoration on these sites must be addressed.

Identifying Sites for Riparian Wetland Restoration: Application of a Model to the Upper Arkansas River Basin

Abstract: We present a conceptual model for identifying restoration sites for riparian wetlands and discuss its application to reaches within the Upper Arkansas River basin in Colorado. The model utilizes a Geographic Information System (GIS) to analyze a variety of spatial data useful in characterizing geomorphology, hydrology, and vegetation of riparian wetland sites. The model focuses on three basic properties of riparian wetland sites: relative soil moisture, disturbance regime, and vegetative characteristics. A relative wetness index is used to define nominal soil moisture classes within the watershed. These classes generally coincide with uplands (low), channel margins (moderate), and channels or open water (high). Vegetative conditions are characterized using color infrared aerial photographs. Land cover types are grouped into five major land cover classes: riparian, moist herbaceous, bare ground, upland, and open water. Disturbance regime is characterized by a reach-based index of specific power (ω). Preliminary results indicate that reaches within the Upper Arkansas River basin can be classified as high energy (ω ≥ 8 W/m 2 ) or low energy (ω ≤ 3W/m 2 ), using discharge estimates that reflect the 10-year flood event. Field surveys of channel and flood-plain conditions plain conditions show that high-energy reaches (ω ≥ 8 W/m 2 ) are characterized by sites where the channel occupies a large proportion of the valley bottom. By contrast, low-energy reaches (ω ≤ 3 W/m 2 ) are characterized by meandering channels with wide alluvial valleys. Restoration potential is evaluated as a combination of nominal scores from wetness, land cover, and disturbance indices. Application of these methods to field sites within the Upper Arkansas River basin identifies a wide range of riparian wetland sites for preservation or restoration. Potential sites within identified reaches are prioritized using size and proximity criteria.

Constructed Crevasses and Land Gain in the Mississippi River Delta

Abstract: Extensive land loss, which is mostly wetland loss, has taken place during this century in the Mississippi River delta and other river deltas. Our purpose was to evaluate the effectiveness of constructing “artificial” crevasses, or cuts in the natural levee, made by the U.S. Fish and Wildlife Service in the Delta National Wildlife Refuge (DNWR) to slow or reverse this type of land loss. Land growth of the crevasses was determined from aerial photographs and was related to crevasse-site characteristics. The newly constructed crevasses create emergent wetlands after 2 years of subaqueous growth at about 4.7 ha/year and an average cost of $21,377 per crevasse. The present total cost per hectare declines with age as new land builds, and it will equal $48 per hectare if all the open water in the receiving ponds fills in. At these rates, the net land loss rates in the DNWR measured from 1958 to 1978 would be compensated for by the building of 63 crevasses, 24 of which are already in place.

Native Colonizing Species and Degraded Land Restoration in La Gran Sabana, Venezuela

Abstract: We evaluated the ecological and reproductive characteristics of plant species occurring in severely disturbed areas that were revegetated with exotic grasses. We identified those species with the best combination of attributes that increase their probability of success in degraded lands. Fifteen degraded areas were studied in two different bioclimatic regions, a high premontane humid bioclimate and a low premontane humid bioclimate. The frequency of native colonizing species and the presence of arbuscular mycorrhizal colonization in their roots were evaluated. The sexual and breeding system, pollination mode, fruit set, and dispersal syndrome of ten of the most frequent colonizing species were also studied. The floristic survey of the colonizing species revealed a similarity to the reported flora of the treeless savannas that are dominant in the region. Bioclimatic conditions prevailing in the degraded lands seem to be an important factor for the presence of colonizing species and for species richness. All colonizing species studied were mycorrhizal, and for this reason the restoration program in these degraded areas should take mycorrhizae into account, reintroducing them or manipulating the soils to increase the mycorrhizal inoculum. We suggest Scleria cyperina and Trachypogon plumosus to start or promote the natural succession in the degraded areas from La Gran Sabana. Because their frequency is high and their reproductive system is less dependent on biotic factors, these species stand out in the studied areas.

Role of Legumes in Release of Successionally Arrested Grasslands in the Central Hills of Sri Lanka

Abstract: Most of the world's forest has been cleared, cultivated, and then often abandoned. In many instances these areas have changed to successionally arrested grasslands, shrublands, or fernlands maintained by frequent fires and high herbivore populations. Many studies have shown that various herbaceous, nitrogen-fixing legumes can protect soil surfaces, retain soil moisture, improve soil fertility, and retard ground fires. Our objective was to ascertain if some of these species can potentially inhibit herbivory and satisfactorily establish in these arrested grassland areas to serve as sites for reforestation. We evaluated the potential for four species of nitrogen-fixing legumes (Calapogonium mucunoides, Centrosema pubescens, Desmodium ovalifolium, and Pueraria phaseoloides) to establish on exposed soil within successionally arrested grasslands of Panicum maximum and Cymbopogon nardus in the central hills of Sri Lanka. Four different sites within rectangular grassland areas were cleared of graminoids and sown with seed of each legume. Half of each clearing was protected from browsing rabbits and porcupines, and half was not protected. After 6 months, certain plots were destructively sampled to determine dry biomass gain for each species and treatment. Analyses of variance were performed to test for differences among sites, treatments, and species. All three factors revealed differences, indicating that species must be matched to site. On sites with high amounts of herbivory, D. ovalifolium had the greatest dry biomass gain after 6 months of growth, possibly because of its relatively low nitrogen and moisture content. Where herbivory was absent, P. phaseoloides and C. muconoides had the greatest dry biomass gain. Dry biomass gain of all four legume ground covers was low on sites with lowest pH and nutrient concentrations. Under conditions of low relative fertility and low pH, establishment of the tested legumes failed. Though soil moisture availability was not measured, we speculate that these low fertility sites were also prone to drought. Findings support the site-specific establishment of legume species for purposes of reforestation and watershed protection in central Sri Lanka. This work is applicable to other regions particularly dominated by successionally arrested grasslands with similar circumstances in other parts of south and southeast Asia.

Two-Stage System for Prioritizing Riparian Restoration at the Stream Reach and Community Scales

Abstract: This paper describes a two-stage system for prioritizing stream reaches and riparian communities along a given river for protection or restoration. The system uses associations between geomorphology and riparian vegetation at stream reach and community scales as a basis for defining reference conditions. First-stage reach classification involves collecting and analyzing data from topographic maps and aerial photographs. These data, along with judgment-based criteria for ranking reaches relative to reference conditions, are used to classify stream reaches as suitable for protection, recommended for mitigation or restoration within existing site-specific regulatory procedures, or requiring further analysis to evaluate community-scale restoration needs. Second-stage field sampling is conducted on the reaches needing further analysis to determine the riparian communities present, the associations between communities and floodplain landforms, and reference community conditions. This stage requires collection of field data on geomorphic conditions, plant species composition, and plant community structure. Cluster analysis or a comparable technique is used to classify plant communities associated with floodplain landforms and identify reference conditions for each landform. Community structure and species composition are compared to reference conditions to define restoration possibilities at the community scale. The combined results from stream reach and community-scale analysis provide a strategy for protecting and restoring riparian resources for a whole river. Implementation requires further site-specific information on hydrology, geomorphology, and other factors.