Kern Ewing

Tolerance of four wetland plant species to flooding and sediment deposition

Abstract A greenhouse assessment of the physiological responses of four common Pacific Northwest wetland plant species ( Carex rostrata and Carex stipata (sedges) and the flood-tolerant trees Alnus rubra (red alder) and Fraxinus latifolia (Oregon ash)) to flooding and sediment deposition was conducted. Experiments simulated two ecosystem perturbations which occur when watersheds are urbanized: (1) alteration of hydroperiod and (2) deposition of sediment along channels and in wetlands. Sedges were subjected to alternating flooding and drying cycles and to sediment deposition with different flooding levels. The trees were subjected to static flooding, cycled flooding and drying, and sediment deposition. C. rostrata and C. stipata were resilient to cycles of flooding and drying, but sediment deposits resulted in decreased biomass which was diminished further by high water levels. Static flooding to or above the soil surface killed saplings of A. rubra and F. latifolia in less than a week. A. rubra saplings exhibited decreased photosynthesis and growth when subjected to cycles of flooding and drying, more so if the soil were completely saturated during flooding cycles. F. latifolia saplings showed no significant response to cycles of flooding and drying. Sediment addition to the soil surface resulted in an immediate drop in photosynthesis for A. rubra . These experiments showed that sediment negatively impacted the sedges and trees, and that flooding differentially affected the trees, with A. rubra being more sensitive than the other three species.

The Role of Botanic Gardens in the Science and Practice of Ecological Restoration

Many of the skills and resources associated with botanic gardens and arboreta, including plant taxonomy, horticulture, and seed bank management, are fundamental to ecological restoration efforts, yet few of the worlds botanic gardens are involved in the science or practice of restoration. Thus, we examined the potential role of botanic gardens in these emerging fields. We believe a reorientation of certain existing institutional strengths, such as plant-based research and knowledge transfer, would enable many more botanic gardens worldwide to provide effective science-based support to restoration efforts. We recommend botanic gardens widen research to include ecosystems as well as species, increase involvement in practical restoration projects and training practitioners, and serve as information hubs for data archiving and exchange.

A field comparison of indicators of sublethal stress in the salt-marsh grassSpartina patens

There is a need for research into bioindicators of stress in threatened plant communities such as coastal wetlands. Land subsidence, diversion of sediment, and salt-water intrusion produce stresses associated with waterlogging, elevated salinity, and nutrient depletion. Temporal and spatial environmental variation (soil redox potential, interstitial water salinity, pH, ammonium and phosphorus, and cation and trace metal concentrations) was analyzed near Lake de Cade, Louisiana, in a brackish marsh which is a mosaic of healthy plant communities interspersed with areas where wetland loss is occurring. Environmental variation was related to indicators of stress inSpartina patens, which included variables derived from the adenine nucleotide levels in plants, leaf spectral reflectance, leaf proline concentrations, and shoot elongation. In a comparison of burned and unburned sites, streamside and inland marsh, and along a salinity gradient, among-site differences were found in spectral reflectance and adenine-nucleotide-related indicators. Although it was difficult to relate a single causal environmental variable to the response of a specific indicator, spectral reflectance in the visible light range responded to salinity or to elements borne in seawater, and adenine-nucleotide indices were sensitive to nutrient availability. The ability of indicators to detect plant responses changed during the growing season, suggesting that they were responding to the changing importance of different environmental factors. In addition, some reflectance indicator responses occurred along salinity gradients when salinity differences were less than those that were found to have ecologically meaningful effects in greenhouse experiments. A multivariate numerical approach was used to relate environmental variation with indicator responses. We concluded that factors which in combination cause the degradation and loss of Louisiana wetlands produce environmental conditions that are only subtly different from those in vigorously growing marsh communities.

Limitations to vegetation establishment and growth in biofiltration swales

Abstract Limitations to vegetation establishment and abundance in biofiltration swales (also called biofilters or bioswales), vegetated storm-water facilities intended to improve runoff water quality, was studied through field monitoring and greenhouse experimentation. The various environmental factors influencing vegetation and organic litter abundance was investigated in eight bioswales in western Washington state, including three that were retrofitted. A nested 4×4 factorial greenhouse experiment tested the response of four turfgrass species commonly seeded in bioswales to three inundation regimes plus a control. In the greenhouse experiment and in the field, persistent inundation significantly suppressed germination and growth. Field monitoring further revealed that heavy shade overwhelms all other environmental factors. Where light is adequate, vegetation and organic litter biomass is strongly and inversely related to the proportion of time bioswales are inundated above 2.5-cm depth during the driest time of year (summer). For most bioswales, flow velocity and hydraulic loading during storm events appear too large to permit sedimentation of silt and clay particles, even with dense vegetation and abundant organic litter. Thus, herbaceous vegetation abundance may not provide a good indication of bioswale treatment performance, and actual storm-water treatment may be much poorer than is generally anticipated from previous studies.

A comparison of indicators of sub-lethal untrient stress in the salt marsh grass, Spartina patens

Abstract Wetland plant communities in coastal Louisiana are degrading, resulting in the loss of live emergent vegetation and subsequent succession to open water. Nutrient deprivation caused by compartmentalization of marsh parcels and impaired water exchange is one of the potential sources of sub-lethal stress on plants. Greenhouse experiments were conducted on Spartina patens (Ait.) Muhl. to compare the usefulness of several indicators for the detection of nutrient stress. Responses were measured at the end of 7, 14 and 35 days, with experiments timed to end simultaneously. Leaf expansion rate, aboveground biomass, leaf spectral reflectance, adenine nucleotide levels and CO 2 exchange rate all detected significant differences among treatments (0, 25, 50 and 100% Hoaglands solution). All but aboveground biomass were able to detect some treatment differences as early as 7 days after initiation of treatments; aboveground biomass detected differences after 14 days. Adenine nucleotide levels showed the best ability to discriminate among the 0, 25, 50 and 100% Hoaglands treatments, while all other indicators were able to detect differences only between the 0% treatment and the higher levels of nutrient application.

South Texas Tamaulipan Thornscrub Restoration Experiment Measures Growth of Planted Woody Vegetation

11 Habitat management and habitat restoration in the American West have had different meanings and managers have employed different methodologies based on their interpretations of those meanings for a specific site or project (Bradshaw 1987, Allen 1988, Roundy 1995). The practice of installing plants to replicate native shrub communities is of fairly recent origin in this region. In south Texas, habitat restoration began in the late 1950s on the Longoria Unit of the Las Palomas Wildlife Management area, which is overseen by the Texas Parks and Wildlife Department. At that time, live plants were transplanted onto the site from other locations where they were naturally occurring (Vora 1992). The primary emphasis of this original restoration was for white-wing dove (Zenaida asiatica) habitat. The improvement of hunting has been a continuing rationale for the acquisition of tracts of intact, wooded areas. In the decades since then, both land managers and the public have gained an understanding of the richness of the flora and fauna of the Tamaulipan thornscrub ecosystem—a unique North American ecosystem that, in south Texas and northern Mexico, has been degraded by farming, grazing, and other range management practices in combination with flood control efforts (Ewing 2000). They have also embraced the idea of restoring arid and semi-arid environments (Aronson and others 1993). Studies continue into the restoration and management of habitat for both game animals (Fulbright and others 1991) and to increase non-game bird diversity (Brush and Cantu 1998), both of which will benefit ecotourism.

Long-Term Effects of Initial Site Treatment on Fescue in a Novel Prairie Ecosystem (Washington)

Although there are a number of invasive species on the preserve, the major task of Phase I of the restoration of Bat Fork Bog has been removing reed canary grass and halting its spread into as yet uninfested areas. This perennial species forms a dense root mat that appears to exclude nearly all other species of vegetation and grows to heights exceeding 2.5 m. For reed canary grass control, glyphosate (Accord) was applied to uncut flowering stems at a rate of 395 L/ha (53.8% a.i.) between June 30 and July 21, 2010, resulting in near complete treatment of the wet meadow. We used a small boom sprayer mounted on an all-terrain vehicle to broadcast the herbicide in the monoculture. In transition zones adjacent to the swamp-forest-bog complex, and around islands of native vegetation, we cut the grass culms, allowed the grass to regrow to about 50 cm, and then sprayed the new growth using backpack and handheld sprayers (Figure 2). This allowed a more precise application of the herbicide, where required to protect native vegetation. Small infestations of reed canary grass that had penetrated the interior of the forested area were either removed by hand or sprayed with a handheld sprayer. With preliminary treatment completed, we will closely monitor the site for resprouts, seedling emergence, or surviving patches. The results so far have been very promising with a near complete kill of the grass in those areas sprayed (Figure 2). The initial stages of restoration are expected to take 12–18 months; by then, reed canary grass should be significantly reduced. The removal of much of the grass has allowed us to more carefully study and understand the hydrology of the preserve and, equally importantly, the intent of the original owner to drain the land. Baugh and Evans (2011) report on Phase II, the strategies for restoring the topography of the site and its hydrology. Within three years, we hope to provide a complete report on the removal of invasive vegetation, the restoration of hydrology, and the beginnings of revegetation of areas reclaimed from reed canary grass.

Preliminary observations of using smoke-water to increase low-elevation Beargrass Xerophyllum tenax germination

Through a greenhouse experiment, we found that smoke-water can be an effective restoration tool in germinating bear-grass (Xerophyllum tenax (Pursh) Nutt. [Liliaceae]) seeds. We studied the effects of smoke-water on germination rates of beargrass seeds collected from low-elevation dry forests of the southeastern Olympic Peninsula of Washington State and from a wetland of the western Peninsula. Seeds received a treatment of either smoke-water or tap water (the control), which was followed by a cold stratification treatment for 0, 8, 10, 12, 14, or 16 wk. The highest success of beargrass seed germination resulted from seeds collected from the wetland habitat being exposed to smoke-water prior to undergoing 14 wk of cold stratification. This study supports the use of smoke technology in restoration when the reintroduction of burning is not feasible.

Techniques to Promote Germination of Seed from Puget Sound Prairies

procedures. T he vast majority of prairies in the lowlands around Puget Sound in Washington State have been lost to development, fire suppression (which has led to encroachment of woody plants), and other anthropogenic disturbances. Those fragments of prairie that do remain are highly vulnerable to additional fragmentation and invasion by exotic plants. In an attempt to reverse these trends, a number of conservation groups have recently begun intensive restoration efforts on remnant prairies in the Puget Sound lowlands (see map). A primary objective of this work is to expand and upgrade existing remnants of prairies, which requires large-scale planting projects. This, however, involves working with some 150 species, including many whose germination requirements are not well understood. It was the need for better techniques for germinating seeds of these species, whether for production of nursery stock or when seeding directly in the field that prompted this study.

The Role of Botanic Gardens in the Science and Practice of Ecological Restoration: Role of Botanic Gardens in Restoration

Many of the skills and resources associated with botanic gardens and arboreta, including plant taxonomy, horticulture, and seed bank management, are fundamental to ecological restoration efforts, yet few of the worlds botanic gardens are involved in the science or practice of restoration. Thus, we examined the potential role of botanic gardens in these emerging fields. We believe a reorientation of certain existing institutional strengths, such as plant-based research and knowledge transfer, would enable many more botanic gardens worldwide to provide effective science-based support to restoration efforts. We recommend botanic gardens widen research to include ecosystems as well as species, increase involvement in practical restoration projects and training practitioners, and serve as information hubs for data archiving and exchange.