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Ecological restoration in a changing world: case studies from Californiaorganized by Jeffrey Corbin (University of California, Berkeley) and Michael Vasey (San Francisco State University)ECOLOGICAL RESTORATION IN CALIFORNIA: CHALLENGES AND PROSPECTS Michael Vasey and Karen Holl, Environmental Studies, University of California, Santa Cruz, CA, USA, mvasey@sfsu.edu Given the extraordinarily rich biological diversity in California and the dramatic loss and modification of many of its habitats, species populations, and ecosystems, there has emerged a concerted effort to restore and recover large areas of the state’s public and private lands. Under these circumstances, ecological restoration may well represent the best strategy to conserve numerous at-risk species and maintain vital ecosystem services. We briefly summarize some of the areas in which ecological restoration is most active in California to illustrate the scope of this effort. We then identify some of the key challenges, both practical and theoretical, that are likely to affect the success of this restoration undertaking. These challenges include integrating considerations of global change factors into local restoration design and implementation. Finally, we assess the prospects for ecological restoration in California to contribute to the conservation of its biological diversity and make suggestions for how the ultimate success of this effort may be enhanced. ATMOSPHERIC NITROGEN DEPOSITION AND CALIFORNIA BIODIVERSITY: IMPLICATIONS OF CHEMICAL CLIMATE CHANGE FOR CONSERVATION AND RESTORATION STUART WEISS, Creekside Center for Earth Observations, Menlo Park, CA, USA, stubweiss@netscape.net Atmospheric nitrogen (N) deposition—smog acting as slow-release nitrogen fertilizer on terrestrial and aquatic ecosystems—is a profound and unprecedented change in “chemical climate.” The effects of N deposition on ecosystem function and biodiversity are not generally well known among the conservation community. In the San Francisco Bay area, conservation of serpentine grasslands and the threatened Bay checkerspot butterfly illustrate diverse scientific, policy, and stewardship challenges posed by N deposition. Fertilization allows N loving non-native annual grasses to invade nutrient-poor soils and crowd out native wildflowers and forbs that support the butterfly. Regulatory actions to mitigate increased N deposition from power plants, roads, and urban developments have led to the conservation of hundreds of acres of serpentine in Santa Clara County through fee acquisition, easements, and management endowments. Key stewardship strategies to maintain habitat for the butterfly and many rare plants include managed cattle grazing, mowing, prescribed fire, and reintroduction of the butterfly to restored habitat. A state-wide analysis indicates that many other listed species and sensitive ecosystems across California are at risk. The realities of N deposition—our new chemical climate—will require reassessment of conservation, stewardship, and restoration methods and goals in many ecosystems. THE HITS KEEP COMING: CONTINUING PLANT INVASIONS IN CALIFORNIA GRASSLANDS JEFFREY CORBIN, Joel Abraham, and Carla D’Antonio, Department of Integrative Biology, University of California, Berkeley, CA, USA, (JC, JA), Department of Ecology, Evolution and Behavior, University of California, Santa Barbara, CA, USA (CD), corbin@berkeley.edu The vast majority of the approximately 10 million ha of grasslands in California are dominated by non-native annual grasses and forbs. By no means, however, has the prominence of one group of invaders precluded the successful spread of other non-native species. In some cases, earlier invasions appear to have facilitated subsequent establishment and spread of later invaders. For example, a comparison of the germination and growth of Foeniculum vulgare (fennel) seedlings in plots dominated by native perennial bunchgrasses versus plots dominated by exotic annual grasses suggests that the formerly-dominant native species are better able to resist the establishment and spread of fennel than the now-dominant exotic annuals species. Many recent invaders also have more dramatic impacts on ecosystem processes, and offer more complex restoration challenges, than the first wave of invading species that rose to dominance in the late 1800s. Recently spreading exotic perennial grasses, for example, are strongly competitive against both native perennial and exotic annual grasses and are very difficult to eradicate once established. Most alarming is evidence that traditional management techniques may not be effective in controlling these exotic perennial grasses. New species introductions will continue to present unforeseen challenges to the management and restoration of natural ecosystems. PROJECTING THE FATE OF NATIVE BUNCHGRASSES IN NORTHERN CALIFORNIA’S CHANGING CLIMATE KENWYN SUTTLE and Meredith Thomsen, Department of Earth and Planetary Sciences, University of California, Berkeley, CA, USA (KS), Department of Integrative Biology, University of California, Berkeley, CA, USA (MT), kbsuttle@socrates.berkeley.edu Healthy populations of native bunchgrasses persist in northwestern California despite their near-wholesale replacement by exotic annuals throughout much the rest of the state. This is thought in part to be climatically mediated, stemming from the longer winter rainy seasons and shorter summer droughts that characterize the region. Changes in the seasonality and intensity of annual precipitation could thus critically influence both persistence of remaining populations and restoration efforts where these plants are rare or absent. We established a long-term experimental manipulation of rainfall in a northern California grassland in 2000 to examine the consequences of projected changes in rainfall for three native bunchgrasses, Elymus glaucus, Elymus multisetus, and Danthonia californica. Over five years, we examined effects of intensified versus extended seasonal precipitation on seedling establishment, survival of young tussocks, and reproductive output by mature tussocks of all three species. Responses were not consistent across species despite similar life histories, with Elymus glaucus and Danthonia californica responding favorably in all variables measured to an extension of the rainy season relative to intensification of winter rains and control conditions, and Elymus multisetus exhibiting no differences across treatments. Only through consideration of community-level interactions can we interpret life stage-specific responses of each species. CHANGING ISSUES FOR THE RESTORATION OF TIDAL MARSH ECOSYSTEMS IN THE CONTEXT OF PREDICTED CLIMATE CHANGE JOHN CALLAWAY, V. Thomas Parker, Michael Vasey, and Lisa Schile, Department of Biology, University of San Francisco, CA, USA (JC), Department of Biology, San Francisco State University, CA, USA (VTP, MV, LS), callaway@usfca.edu The principal historic goal of tidal marsh restoration has been the maintenance and expansion of community structure, food web dynamics, and ecosystem function. However, tidal marshes are extremely vulnerable to changes in sea level and salinity, both of which will be affected by climate change. Restoration sites may be particularly vulnerable given unpredictable sediment inputs and newly established vegetation. Within the San Francisco Bay region, climate models predict more rapid sea-level rise and increasing encroachment of salinity from the San Francisco Bay to the freshwater Delta region. Based on monitoring data from San Francisco Bay marshes, we predict that salinity will have a more immediate impact on tidal marsh vegetation. Dominant species show salinity preferences, and it is likely that relatively small salinity changes could lead to shifts in dominant species, species diversity and abundance, and non-linear changes in primary productivity. Over longer time periods, many tidal marshes are unlikely to keep pace with increased rates of sea-level rise, and marshes with high rates of subsidence will be particularly vulnerable. Therefore, it is critical that knowledge of potential impacts from current climate change models be incorporated into restoration strategies of tidal marsh ecosystems. ECOLOGICAL RESTORATION IN AN ERA OF RAPID GLOBAL CHANGES: POTENTIAL PITFALLS AND REDEFINITION OF GOALS NATHAN STEPHENSON, USGS Western Ecological Research Center, Sequoia–Kings Canyon Field Station, Three Rivers, CA, USA, nstephenson@usgs.gov U.S. National Park Service (NPS) policies direct natural resource managers, when possible, to restore and maintain naturally-functioning ecosystems. When this is not possible, managers are to “maintain the closest approximation of the natural condition.” Using supporting examples from California’s Sierra Nevada and elsewhere, I examine whether these policies are sensible, or even possible, in an era of rapid global changes. Natural conditions are already impossible to maintain in some ecosystems, and are likely to soon become impossible in others. Thus, managers are increasingly forced to try to maintain the closest approximation of natural conditions. Yet such efforts might result in ecosystems that are inherently unstable to novel environmental conditions, potentially leading to catastrophic loss of some of the very resources that we are trying to protect. I therefore suggest that NPS and similar conservation agencies need to reexamine their missions. A realistic new mission might focus on maintaining native biodiversity, even if community structure and composition are no longer natural. The means toward achieving this end would probably emphasize enhancing or maintaining ecosystem resistance (ability to resist stress) and resilience (ability to recover from stress). Regardless, “natural” is rapidly losing its utility as a sensible, meaningful, or possible benchmark for restoration. CONSERVING ENDANGERED PLANT SPECIES USING FIRE AND FIRE SURROGATES IN AN INVADED, FIRE-ADAPTED COMMUNITY AT THE WILDLAND-URBAN INTERFACE JODI MCGRAW, Boulder, CA, USA, jodimcgraw@sbcglobal.net Fire exclusion in systems adapted to recurring fire can reduce native biodiversity and threaten persistence of disturbance-dependent plant species, many of which are poor competitors and require disturbance to maintain refugia from competition. However, restoration of fire regimes can be difficult in habitat located near human development. Habitat management can be further complicated by the presence of exotic plants, as many are also facilitated by disturbance. I examined the direct and indirect effects (via exotic plant species) of fire and a fire surrogate on the demographic performance of two federally endangered plants, Chorizanthe pungens var. hartwegiana and Erysimum teretifolium, which are endemic to the Santa Cruz Sandhills, a unique edaphic community adapted to fire in central coastal California. I found that both fire and its surrogate enhanced native plant cover and population growth of both endangered plants directly by removing accumulated litter that inhibits establishment and survivorship. In addition, fire disproportionately reduced exotic plant cover and, in doing so, indirectly facilitated endangered plant performance as well as the cover and richness of the native plant assemblage. Results have been integrated within management plans designed to maintain persisting populations of these endangered species and plant biodiversity in the endemic system. URBAN STREAM RESTORATION AS AN OUTDOOR CLASSROOM: JOINING COLLEGE AND HIGH SCHOOL STUDENTS FOR CONSERVATION ALISON PURCELL, ESPM, University of California, Berkeley, CA, USA, alisonp@nature.berkeley.edu Despite the tremendous challenges involved in urban creek restorations, there are also great educational opportunities in conservation for local residents. An urban creek restoration project along Strawberry Creek (Berkeley, California) began with the goal of removing invasive nonnative vegetation and restoring native plant diversity. Through the involvement of high school and college students, the project has also served to demonstrate the value of conservation to the public. University of California, Berkeley undergraduate students conducted baseline vegetation surveys of species richness and cover in order to assess initial species composition. Students also developed habitat restoration plans that included the removal of invasive plant species, the selection of native species for revegetation, and a long-term monitoring approach. Berkeley High School students, under the guidance of University of California, Berkeley graduate student mentors, assisted with the removal of exotic species from an 800 square m area of riparian habitat, and restored native diversity by planting over 1000 individual plants. Subsequent vegetation surveys found a drastic reduction in exotic species and an increase in native diversity. Despite the various challenges of coordinating such diverse groups, this project succeeded in bringing together many branches of the community to educate citizens about conservation and restoration. | |||||||||||||||||
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