Patricia N. Manley

DISTINGUISHING STRESSORS ACTING ON LAND BIRD COMMUNITIES IN AN URBANIZING ENVIRONMENT

Urbanization has profound influences on ecological communities, but our understanding of causal mechanisms is limited by a lack of attention to its component stressors. Published research suggests that at landscape scales, habitat loss and fragmentation are the major drivers of community change, whereas at local scales, human activity and vegetation management are the primary stressors. Little research has focused on whether urbanization stressors may supplant natural factors as dominant forces structuring communities. We used model selection to determine the relative importance of urban development, human activity, local and landscape vegetation, topography, and geographical location in explaining land bird species richness, abundance, and dominance. We analyzed the entire community and groups of species based on ecological characteristics, using data collected in remnant forests along a gradient of urban development in the Lake Tahoe basin, California and Nevada, USA. Urbanization stressors were consistently among the principal forces structuring the land bird community. Strikingly, disturbance from human activity was the most important factor for richness in many cases, surpassing even habitat loss from development. Landscape-scale factors were consistently more important than local-scale factors for abundance. In demonstrating considerable changes in land bird community structure, our results suggest that ecosystem function in urban areas may be severely compromised. Such changes compel local- and landscape-scale management, focused research, and long-term monitoring to retain biodiversity in urban areas to the extent possible.

Effects of Urban Development on Ant Communities: Implications for Ecosystem Services and Management

Research that connects the effects of urbanization on biodiversity and ecosystem services is lacking. Ants perform multifarious ecological functions that stabilize ecosystems and contribute to a number of ecosystem services. We studied responses of ant communities to urbanization in the Lake Tahoe basin by sampling sites along a gradient of urban land development. We sampled ant communities, measured vegetation characteristics, quantified human activities, and evaluated ant-community responses by grouping ants into service-providing units (SPUs), defined as a group of organisms and their populations that perform specific ecosystem services, to provide an understanding of urbanization impacts on biodiversity and their delivery of ecosystem services. Species richness and abundance peaked at intermediate levels of urban development, as did the richness of 3 types of ant SPUs (aerators, decomposers, and compilers). With increasing land development aerator and decomposer ants significantly declined in abundance, whereas compiler ants significantly increased in abundance. Competing models demonstrated that precipitation was frequently among the strongest influences on ant community structure; however, urban development and human activities also had a strong, negative influence on ants, appearing in most models with DeltaAIC(c) < 2 for species richness and abundance patterns of SPUs and generalists. Response diversity was observed within SPUs, which suggests that the corresponding ecosystem services were maintained until development reached 30-40%. Our data provide evidence that ecosystem functions, such as water infiltration and soil productivity, may be diminished at sites subject to greater levels of urbanization and that conserving ant communities and the ecosystem services they provide could be an important target in land-use planning and conservation efforts.

A FIELD-BASED EVALUATION OF A Presence-Absence PROTOCOL FOR MONITORING ECOREGIONAL-SCALE BIODIVERSITY

Abstract Declines in populations of many species across the United States are prompting the need for monitoring programs that can detect population change effectively for large suites of species. The proliferation of reliable standardized monitoring techniques enhances the potential that we may meet these burgeoning information needs. However, multiple-species monitoring approaches are still a rarity. In an attempt to meet monitoring information needs on National Forest System (NFS) lands, the U.S. Forest Service developed the Multiple Species Inventory and Monitoring (MSIM) protocol, an approach that employs a variety of vertebrate and habitat survey methods to obtain presence–absence data for a broad spectrum of species at a systematic array of sample points throughout ecoregions. A recent evaluation of the MSIM protocol predicted that its implementation across the Sierra Nevada ecoregion would detect a 20% change in proportion of points occupied for 76% of the species with 80% confidence and power. This evaluation was based on a qualitative estimate of probability of detection and basic habitat association information to estimate probability of presence. We conducted a field test to evaluate the ability of a multi-taxonomic, presence–absence monitoring approach to detect and estimate population change at multiple scales and to meet the monitoring needs of land management agencies. Our field data consisted of bird, mammal, amphibian, and reptile surveys conducted at terrestrial and aquatic sites in the Lake Tahoe basin, located in the central Sierra Nevada. We used a maximum likelihood function to quantitatively estimate the probability of detection and sampling adequacy of species and species groups. We compared these observed estimates to the previously derived expected estimates. We detected 185 species by field testing, including 89% of the expected species and several species that were not expected. Observed probabilities of detection were generally lower than we expected. Sampling adequacy was also lower than we expected but still relatively high, with 66% of the Lake Tahoe species and 47% of all Sierra Nevada species adequately sampled. Species with small geographic ranges, narrow habitat specificity, or small population sizes were considered rare, and they were not sampled as adequately as other species groups. Still, 69 of the rarest species, including 12 species with state or federal designation as endangered, threatened, or sensitive, were estimated to be adequately sampled. Our analysis highlighted the ability of a broad-scale, multi-taxonomic presence–absence monitoring approach, such as the MSIM protocol, to detect population change for a large number and wide variety of vertebrate species. The outcome of our test also suggests that many data yields would be garnered at the scale of National Forests and National Parks, such as distribution and occurrence data for most species, including little-known species, population trend data for many species, habitat relationships and habitat condition data, and data on association strengths of indicator species.

Use of Tree Species by Forest Birds during Winter and Summer

We recorded the foraging behavior of bird species during winter and summer in a mixed conifer forest of the western Sierra Nevada. All bird species increased their relative use of incense cedar (Calocedrus decurrens) in winter compared to summer. We noted no obvious difference in the vigor (health) of trees used by birds between seasons. Most species revealed a general trend towards increased use of the bark of incense cedar in winter relative to summer. It appears that birds are able to obtain food from under the loose, flaky bark of incense cedar more easily than from under the more firm, compact bark of other timber species in winter. The overwinter survival of birds may be lowered by reduction in the stocking level of small (<30 cm dbh) incense cedar. J. WILDL. MANAGE. 49(4):1098-1102 Birds are known to alter patterns of habitat use and foraging behavior between seasons (Willson 1970, 1971; Travis 1977; Conner 1980, 1981; Hutto 1981; Lewke 1982). These variations are of importance in land use planning because the manager may have to allow for a different suite of habitat needs on both speciesspecific and season-specific bases. Although vegetation structure (both vertical and horizontal) has been inferred to be important in influencing the species composition and abundance of birds (MacArthur and MacArthur 1961, Karr and Roth 1971, Willson 1974, Roth 1976), bird diversity may also be influenced by the diversity of plant species present, independent of structural considerations (MacArthur and MacArthur 1961, Holmes and Robinson 1981, Robinson and Holmes 1984). Therefore, the task of providing adequate habitat is complicated by many factors. The land manager changes the composition of plant species in an area based on numerous, often competing, factors (e.g., economical, biological, sociological). In the western Sierra Nevada, for example, the composition of the forest i being changed as areas are harvested and replanted (converted) to economically desirable species. Although the response of birds to gross cha es in their habitats has been examined (e.g., see Verner and Boss 1980), the effects of more subtle changes in plant species composition are not well known, especially interseasonally. Our objective in this study was to determine if the use of tree species by birds differed between winter and summer in the western Sierra Neva a. Our intent was to describe general patterns that might deserve increased attention by

Multiple species inventory and monitoring technical guide.

The National Forest Management Act (1976) recognizes the importance of maintaining species and community diversity on National Forest System (NFS) lands as a critical component of our ecological and cultural heritage. Monitoring is required of land management to assess the success of management activities in meeting legal, regulatory, and policy objectives, including sustaining populations of native and desired nonnative species. The Multiple Species Inventory and Monitoring (MSIM) protocol is intended to serve as a consistent and efficient method for obtaining basic presence/absence data and associated habitat condition data for a large number of individual species at sites that represent a probabilistic sample. It is designed to be implemented in association with Forest Inventory and Analysis (FIA) grid points on NFS lands. The MSIM protocol is designed as a base monitoring approach on which regions and forests can build to meet their specific National Forest Land and Resource Management Plan monitoring needs with the greatest possible efficiency (measured as the amount of useful and high-quality information gained per unit cost).

Conservation of Avian Diversity in the Sierra Nevada: Moving beyond a Single-Species Management Focus

Background As a result of past practices, many of the dry coniferous forests of the western United States contain dense, even-aged stands with uncharacteristically high levels of litter and downed woody debris. These changes to the forest have received considerable attention as they elevate concerns regarding the outcome of wildland fire. However, attempts to reduce biomass through fuel reduction (i.e., thinning of trees) are often opposed by public interest groups whose objectives include maintaining habitat for species of concern such as the spotted owl, Strix occidentalis, the northern goshawk, Accipiter gentilis, and the Pacific fisher, Martes pennanti. Whether protection of these upper-trophic level species confers adequate conservation of avian forest diversity is unknown. Methodology and Principal Findings We use a multi-species occurrence model to estimate the habitat associations of 47 avian species detected at 742 sampling locations within an 880-km2 area in the Sierra Nevada. Our approach, which accounts for variations in detectability of species, estimates occurrence probabilities of all species in a community by linking species occurrence models into one hierarchical community model, thus improving inferences on all species, especially those that are rare or observed infrequently. We address how the avian community is influenced by covariates related to canopy cover, tree size and shrub cover while accounting for the impacts of abiotic variables known to affect species distributions. Conclusions and Significance Environmental parameters estimated through our approach emphasize the importance of within and between stand-level heterogeneity in meeting biodiversity objectives and suggests that many avian species would increase under more open canopy habitat conditions than those favored by umbrella species of high conservation concern. Our results suggest that a more integrated approach that emphasizes maintaining a diversity of habitats across environmental gradients and minimizing urbanization may have a greater benefit to ecosystem functioning then a single-species management focus.

The persistence of Black-backed Woodpeckers following delayed salvage logging in the Sierra Nevada

The Black-backed Woodpecker (Picoides arcticus) is a snag-associated species that colonizes and utilizes patches of burned forests typically within 10 years of fire. Previous research has indicated that salvage logging, the removal of dead and dying trees from burned forests, has a negative effect on nesting densities of Black-backed Woodpeckers. One strategy proposed to ameliorate the impacts of dead tree removal on Black-backed Woodpeckers is to retain patches, or islands, of dense snags within the salvage matrix, but this approach remains largely untested. Following the Angora fire of South Lake Tahoe, CA several snag islands were retained within the larger salvage prescription to conserve habitat for Black-backed Woodpeckers and other snag-associated species. In this observational study, we evaluate whether these snag islands were effective at maintaining Black-backed Woodpecker populations following logging operations that covered 45% of the burned area. We systematically searched the postfire landscape for Black-backed Woodpecker nests for two years before and after salvage operations and compared nesting densities between logged and unlogged areas. Similar to other studies, we found that nest densities at the stand scale declined significantly in areas that were salvage logged, but Black-backed Woodpeckers did nest in both snag islands and in other peripheral unlogged areas, indicating that this approach may help balance habitat for wildlife with management needs at the scale of the fire. In this study, the removal of dead trees, which is usually implemented in the first two years following fire, did not occur until the fourth year, which may have also contributed to the persistence of Black-backed Woodpeckers postlogging.