Short-term effects of a prescribed burn on songbirds and vegetation in mountain big sagebrush

I measured songbird abundance and vegetation cover in and around a 420-ha prescribed burn in a mountain big sagebrush community located at 2133 m elevation. Data were collected during the 3rd growing season after the fire. Brewer's Sparrow and Sage Thrasher occurred in lower abundance on sites that were largely or completely burned relative to sites that were outside the fire perimeter or within unburned islands of shrubs. The number of Brewer's Sparrow detections was linearly related to remaining sagebrush cover. In contrast, Horned Lark occurred at higher abundances on sites where shrub cover had been removed in the prescribed burn. Cover of perennial grasses and cover of 4 of the 5 most common forbs was greater on burned sites than on unburned sites.     

Controls on radial growth of mountain big sagebrush and implications for climate change

Mountain big sagebrush ( Artemisia tridentata Nutt. ssp. vaseyana ) covers large areas in arid regions of western North America. Climate-change models predict a decrease in the range of sagebrush, but few studies have examined details of predicted changes on sagebrush growth and the potential impacts of these changes on the community. We analyzed effects of temperature, precipitation, and snow depth on sagebrush annual ring width for 1969 to 2007 in the Gunnison Basin of Colorado. Temperature at all times of year except winter had negative correlations with ring widths; summer temperature had the strongest negative relationship. Ring widths correlated positively with precipitation in various seasons except summer; winter precipitation had the strongest relationship with growth. Maximum snow depth also correlated positively and strongly with ring width. Multiple regressions showed that summer temperature and either winter precipitation or maximum snow depth, which recharges deeper soil horizons, are both important in controlling growth. Overall, water stress and perhaps especially maximum snow depth appear to limit growth of this species. With predicted increases in temperature and probable reduced snow depth, sagebrush growth rates are likely to decrease. If so, sagebrush populations and cover may decline, which may have substantial effects on community composition and carbon balance.     

New approaches for sampling and modeling native and exotic plant species richness

We demonstrate new multi-phase, multi-scale approaches for sampling and modeling native and exotic plant species to predict the spread of invasive species and aid in control efforts. Our test site is a 54,000-ha portion of Rocky Mountain National Park, Colorado, USA. This work is based on previous research wherein we developed vegetation sampling techniques to identify hot spots of diversity, important rare habitats, and locations of invasive plant species. Here we demonstrate statistical modeling tools to rapidly assess current patterns of native and exotic plant species to determine which habitats are most vulnerable to invasion by exotic species. We use stepwise multiple regression and modified residual kriging to estimate numbers of native species and exotic species, as well as probability of observing an exotic species in 30 × 30-m cells. Final models accounted for 62% of the variability observed in number of native species, 51% of the variability observed in number of exotic species, and 47% of the variability associated with observing an exotic species. Important independent variables used in developing the models include geographical location, elevation, slope, aspect, and Landsat TM bands 1-7. These models can direct resource managers to areas in need of further inventory, monitoring, and exotic species control efforts.     

Using sampling and inverse distance weighted modeling for mapping invasive plants

Accurate time- and cost-efficient mapping is central to successful rangeland invasive plant management. In this study sampling together with Inverse Distance Weighted (IDW) interpolation modeling was tested as a mapping alternative to expensive full-coverage delineation survey mapping methods. Our objective was to examine accuracies of presence/absence maps generated from 18 sampling strategies (3 sampling methods × 6 sample densities) using IDW. Invasive plant field survey maps with known accuracies were used to generate samples and to test interpolation results at 2 sites. Site 1 was approximately 6.0 km 2 , dominated by Russian knapweed ( Acroptilon repens L.). Site 2, an upland area of approximately 13.5 km 2 , was dominated by spotted knapweed ( Centaurea maculosa Lam). Sampling method × sample density combinations were gathered from field survey infestation maps using repeated computer-based sampling methods. IDW modeling was applied to each of the sample data sets. Accuracies of the IDW interpolation results were calculated by re-referencing field survey maps. We determined that sampling at density of 0.25% (about 1 point per ha) using a systematic sampling method was the preferred sampling strategy for both sites. This combination of sampling density and method yielded 85% accurate presence/absence maps. We conclude that sampling combined with IDW interpolation modeling can generate accurate invasive plant maps and is a potential alternative to current delineation survey methods.     

Considerations for Wood River sculpin conservation: historical occurrence and sampling efficiency

Records of Wood River sculpin ( Cottus leiopomus ) from 1893 to 2003 were examined and new data were gathered in 2004 and 2006 to estimate the species’ historical range and to search for evidence of changes in its occurrence. Detections of Wood River sculpin were reported in 49 subwatersheds, primarily in the Idaho Batholith ecoregion. The remainder of the Wood River basin was classified as either potential historic range or unknown. Mark-recapture sampling was conducted to estimate the efficiency of electrofishing as a method to detect this sculpin. Sampling efficiency was calculated for 1 upstream pass and 1, 2, and 3 bidirectional passes. A mean sampling efficiency of 45.9% (range 15.4%–63.0%) was achieved using 3 bidirectional passes, block nets, and 0.942 minutes of electrofishing per m2 of stream surface. Efficiency declined an average of 38% between electrofishing passes. The rates and reduced efficiencies observed between passes suggest that multiple passes and visits are needed to reliably estimate sculpin presence or absence. Se examinaros registros observacionales de los charrascos espinosos Wood River ( Cottus leiopomus ) de 1893 a 2003 y nuevos datos fueron reunidos en 2004 y 2006 para estimar su extensión histórica y buscar evidencia de cambios en su presencia. Se ha reportado la detección de charrascos espinosos Wood River en 49 subcuencas, principalmente en la ecorregión del Batolito de Idaho. El resto de la cuenca del Wood River fue clasificado, ya sea como posible distribución histórica o como desconocida. Se llevó a cabo un muestreo de marcaje y recaptura para estimar la eficiencia de la electropesca como método para detectar el charrasco espinoso. Se calculó la eficiencia del muestreo para un pase río arriba y 1, 2 y 3 pases bidireccionales. Se alcanzó una eficiencia promedio del muestreo de 45.9% (del 15.4 al 63.0%) usando 3 pases bidireccionales, redes de bloqueo y la aplicación de corriente eléctrica por 0.942 minutos por metro cuadrado de superficie del arroyo. La eficiencia disminuyó 38% en promedio entre pases de electropesca. Las tasas y la reducción de eficiencia observadas entre pases sugieren que múltiples pases y visitas son requeridos para estimar con precisión la presencia o ausencia del charrasco espinoso.     

Improved geographic sampling provides further evidence for the separation of Glossiphonia complanata and Glossiphonia elegans (Annelida: Clitellata: Glossiphoniidae)

Historically, there has been much confusion surrounding the identity and separation of European and North American species of Glossiphonia (Annelida: Clitellata: Glossiphoniidae). Using cytochrome c oxidase subunit I (COI) sequences from newly collected specimens of Glossiphonia complanata and Glossiphonia elegans from a broad geographic range covering southern Canada, parts of the US, Slovenia and Croatia, we confirm that G. complanata is likely confined to Europe. The species is phylogenetically distinct from G. elegans, which seems to exclusively inhabit North America. Parsimony and maximum likelihood of the COI locus show the European samples placing as the sister group to an unidentified species of Glossiphonia from Russia, while the North American samples are the sister group to all other Glossiphonia species. We also investigate the consistency of number of crop cecae for separating these species and contrary to previous reports, this character shows no differences between our specimens of the two species. Additionally, the trees show evidence of subdivisions within both G. complanata and G. elegans, with some sequences separated by high ‘intraspecific’ distances. Forces might be shaping population structure and/or potential incipient speciation within these species, emphasizing the need for future research into the biogeography and population genetics of Glossiphonia.