Climate change and fire suppression have facilitated expansion of pinyon-juniper woodlands into sagebrush-steppe ecosystems of the Great Basin, USA, resulting in a loss of biological diversity. To assess the effects of using prescribed fire in restoration efforts, ant abundance, species richness, and composition were examined pre- and post-burn along the elevation and tree cover gradients encompassed by a pinyon-juniper woodland in a central Nevada watershed. Ants were sampled using pitfall traps in 6 sites for the elevation study and in 2 sites for the tree cover study, representing paired burn and control sites in a randomized block design. Vegetation and ground cover variables were also sampled to determine how variation in ant populations was correlated with differences in vegetation and ground cover. Ant species richness remained unchanged for all treatments. Tree cover had no significant effect on ant populations. Significantly more ants were trapped after the burn treatment on burn plots. Variation in ant populations was not directly correlated with any of the vegetation or ground cover variables. According to ANOVA and multivariate analyses, elevation had the greatest effect on changes in ant communities, likely due to increased moisture availability. Our results suggest that management for conservation of sagebrush-steppe ecosystems in this and similar watersheds should include a range of elevations to ensure maximum ant species diversity.

We report on growth and demography of Sceloporus mucronatus mucronatus, a lizard subspecies endemic to central Mexico. We characterize the life history of this subspecies, provide quantitative information relevant to conservation, and add to the growing literature on the diversity of life histories in the genus Sceloporus. We calculated body growth rates and fitted them to the Von Bertalanffy, the logistic-by-length, and the logistic-by-weight growth models. The Von Bertalanffy model provided the best fit, and we used it to analyze the growth pattern. Growth rates were similar during the 1st year of life in both sexes, but after that point males grew faster and reached maturity earlier (20 months) than females (31 months). We used a population projection matrix to model population dynamics during 2003–2004 and found a positive population growth rate (λ= 1.769). However, based on the projected stable size-class vector (w), this population does not appear to have reached stability, and it might be currently experiencing considerable interannual fluctuations. Elasticity values showed that the transition from the juvenile stage to the 1st adult stage was the vital rate that contributes the most to population growth rate, followed by fecundity and stasis of the 1st reproductive category. While total elasticities for demographic processes were similar, elasticities per size class showed the relatively high importance of small adults in comparison to juveniles and large adults. The restriction of this endemic subspecies to central Mexico, where human activities and consequent habitat destruction are increasing, demands further quantitative evaluation and monitoring of populations, even though our results indicate a potential for population growth.

Predictive models of aboveground biomass of nonnative Tamarix ramosissima of various sizes were developed using destructive sampling techniques on 50 individuals and four 100-m² plots. Each sample was measured for average height (m) of stems and canopy area (m²) prior to cutting, drying, and weighing. Five competing regression models (P < 0.05) were developed to estimate aboveground biomass of T. ramosissima using average height and/or canopy area measurements and were evaluated using Akaike's Information Criterion corrected for small sample size (AIC_c). Our best model (AIC_c = −148.69, ΔAIC_c = 0) successfully predicted T. ramosissima aboveground biomass (R² = 0.97) and used average height and canopy area as predictors. Our 2nd-best model, using the same predictors, was also successful in predicting aboveground biomass (R² = 0.97, AIC_c = −131.71, ΔAIC_c = 16.98). A 3rd model demonstrated high correlation between only aboveground biomass and canopy area (R² = 0.95), while 2 additional models found high correlations between aboveground biomass and average height measurements only (R² = 0.90 and 0.70, respectively). These models illustrate how simple field measurements, such as height and canopy area, can be used in allometric relationships to accurately predict aboveground biomass of T. ramosissima. Although a correction factor may be necessary for predictions at larger scales, the models presented will prove useful for many research and management initiatives.

The diatom flora of selected sites in the Animas River Watershed, San Juan County, Colorado, was studied. Eighty diatom taxa were identified from 10 sites: 8 sites on the Animas River and 1 site each on the Cement and Cascade tributaries. The sample diatom abundance was dominated by Achnanthidium minutissimum, Encyonema silesiacum, Aulacoseira distans, Hannaea arcus, and Diatoma mesodon. The presence of teratologic specimens of Fragilaria and Achnanthidium in the samples indicated the possibility of metals contamination. Diatom diversity was low and Lange-Bertalot pollution index scores indicated little organic pollution evidenced from diatom composition. There was evidence that diatom composition at the sites was differentially affected by pH and possibly by the concentrations of Zn alone or in combination with Cd, Cu, and Fe.

Seed moisture has been shown to influence the rates of seed cache removal by rodents. Although the precise mechanism is not known, this knowledge might prove useful in field applications. We examined whether moistened bait would increase trap success in desert rodent populations. We placed traps 15 m apart in grids within a 500-ha study area and randomly baited traps with either dry or moistened seeds. We found that traps baited with moistened seeds had 34.9% higher success than traps baited with dry seeds (n = 190, χ² = 5.389, df = 1, P = 0.020). Our results suggest that application of water to dry seed bait can lead to increased trap success for desert rodents.

We compared the maximum scotopic visual sensitivity of 4 species of trout from twilight (mesotopic) to fully dark-adapted vision. Scotopic vision is the minimum number of photons to which a fully dark-adapted animal will show a behavioral response. A comparison of visual sensitivity under controlled laboratory conditions showed that brown trout (Salmo trutta) and brook trout (Salvelinus fontinalis) had maximum scotopic thresholds (1.1 × 10⁻⁴ μmol · m⁻²s⁻¹, ∼0.005 lux) 2 times lower than rainbow trout (Oncorhyncus mykiss) and Snake River cutthroat trout (Oncorhynchus clarki bouvieri), which did not differ from each other (2.1 × 10⁻⁴ μmol · m⁻²s⁻¹, ∼0.01 lux). A literature review tended to corroborate these results in that brown trout and brook trout were reported to be more active during the night and at twilight than cutthroat trout and rainbow trout. We also measured light intensity within open versus shaded reaches during the day, dusk, and night in 3 Rocky Mountain streams. The scotopic sensitivity of brown trout and brook trout was sufficient to allow foraging during all twilight periods and under average nighttime light intensities in open and shaded reaches, whereas the scotopic sensitivity of rainbow trout and cutthroat trout may restrict their foraging to relatively bright nocturnal conditions (twilight or a moonlit night). Native cutthroat trout restoration efforts may have greater success in open versus shaded stream reaches in the Rocky Mountains and elsewhere.

We estimated bobcat (Lynx rufus) density for 3 different locations in northern California using active infrared-triggered cameras. Using differences in pelage pattern as well as other physical characteristics, we identified individual bobcats from photographs, and used mark-recapture techniques to estimate population density. Camera density affected the precision of population estimates. The same population was estimated using camera densities of 0.5, 1, 2, 4, 6, and 8 cameras · km⁻². Higher camera densities resulted in more captures and recaptures of bobcats and, consequently, in more precise density estimates. Similarly, the number of photo-captures and recaptures increased with increasing study duration. Increasing the area sampled resulted in the capture of more individuals but did not increase the percentage of recaptures. While some locations captured multiple bobcat photographs (e.g., 15 at 1 station), these photos tended to be recaptures of the same individual. There were no more than 2 individuals photo-captured at any 1 camera location. Bobcat density varied among habitat types as predicted. We estimated density as 0.27 bobcats · km⁻² (s = 0.16) overall in an area in the northern Sacramento River Valley and as 0.35 bobcats · km⁻² (s = 0.56) in a steep and rocky canyon within the area. At a 3rd site in the Coast Range, the estimate was 0.39 bobcats · km⁻² (s = 1.44). Bobcats were more diurnal where human activity was less common. In addition, photo-capture was significantly higher along roads and trails without an attractant than it was off-trail with an attractant.

Western juniper (Juniperus occidentalis spp. occidentalis Hook.) expansion in the northern Great Basin has reduced shrubsteppe productivity and diversity. Chainsaw cutting of western juniper woodlands is commonly applied to remove tree interference and restore sagebrush plant communities. Studies assessing understory response following cutting have been limited to early successional stages and have not evaluated the effects of western juniper debris on plant succession. Cutting western juniper produces a large amount of debris which is commonly left on site, occupying a significant portion of treated areas. This study evaluated successional dynamics spanning 13 years after western juniper cutting. Four 0.45-ha blocks were selected on Steens Mountain in southeastern Oregon. Western juniper cover averaged 26% and mature tree density averaged 250 trees · ha⁻¹. Blocks were cut in late summer 1991. Understory standing crop, cover, and density were compared among 3 locations: old canopy litter mats (canopy), interspace, and area underneath cut western juniper (debris). In the interspace, perennial grasses increased in cover and in standing crop relative to other functional groups. In canopy and debris locations, species composition shifted in the 6th year after cutting as annual grass cover, density, and standing crop increased. However, by 2003, perennial grass biomass was 2 times greater than annual grass biomass in canopy and debris locations. Because annual grasses increased in areas of debris accumulation, managers need to be cognizant of western juniper treatments that create safe sites that are favorable to the establishment of weedy species. Retaining western juniper debris on this site did not increase establishment and growth of perennial grasses compared to the interspace. A shift in perennial grass dominance from Thurber's needlegrass (Achnatherum thurberianum [Piper] Barkworth) to bottlebrush squirreltail (Elymus hystrix [Nutt.] Smith) occurred in areas of debris accumulation. Our results demonstrated that long-term vegetation evaluations are necessary to properly assess management activities and disturbance.

Interactions between forest health variables and mensurational characteristics in an uneven-aged eastern Sierra Nevada mixed conifer stand were examined. The stand was located in the Lake Tahoe Basin on a site featuring a coarsely textured granitic soil and numerous rock outcrops. Its composition was dominated by California white fir (Abies concolor var. lowiana [Gord.] Lemm.), with Jeffrey pine (Pinus jeffreyi Grev. & Balf.) and sugar pine (Pinus lambertiana Dougl.) less prominent and incense-cedar (Libocedrus decurrens Torr.) and mountain alder (Alnus tenuifolia Nutt.) the most minor constituents. The majority of saplings and seedlings were white fir. The stand exhibited no evidence that its development had been influenced by fire and, overall, it consisted of numerous small trees accruing little radial growth. Nearly one-quarter of all standing stems pole size or larger were dead, with mortality concentrated in white fir. Forest-floor fuel accumulations were excessive, and coarse debris was especially prominent. A fir engraver beetle (Scolytus ventralis LeConte) epidemic in white fir contrasted against apparent endemic population levels of the Jeffrey pine (Dendroctonus jeffreyi Hopkins) and red turpentine (Dendroctonus valens LeConte) beetles in Jeffrey pine and of the mountain pine beetle (Dendroctonus ponderosae Hopkins) in sugar pine. The severity of fir engraver attack on white fir was weakly related to overall tree size and to the proportion of composition consisting of this host species, while in Jeffrey pine and sugar pine, bark beetle attacks were strongly correlated with the individual proportions of these 2 hosts. Across all species, basal area explained a substantial proportion of the variation in overall attack severity. We found light infestations of true fir dwarf mistletoe (Arceuthobium abietinum Engelm. ex Munz f. sp. concoloris) in white fir and western dwarf mistletoe (Arceuthobium campylopodum Engelm.) in Jeffrey pine, plus an early stage of infection by the white pine blister rust (Cronartium ribicola J.C. Fischer) in sugar pine. Collectively, this case study characterized and quantified many of the conditions, symptoms, and causative agents inherent in a decadent mixed conifer stand in the eastern Sierra Nevada.

Corbicula fluminea is well known as an invasive filter-feeding freshwater bivalve with a variety of effects on ecosystem processes. However, C. fluminea has been relatively unstudied in the rivers of the western United States. In June 2003, we sampled C. fluminea at 16 sites in the San Joaquin River watershed of California, which was invaded by C. fluminea in the 1940s. Corbicula fluminea was common in 2 tributaries to the San Joaquin River, reaching densities of 200 clams · m⁻², but was rare in the San Joaquin River. Biomass followed a similar pattern. Clams of the same age were shorter in the San Joaquin River than in the tributaries. Distribution of clams was different in the 2 tributaries, but the causes of the difference are unknown. The low density and biomass of clams in the San Joaquin River was likely due to stressful habitat or to water quality, because food was abundant. The success of C. fluminea invasions and subsequent effects on trophic processes likely depends on multiple factors. As C. fluminea continues to expand its range around the world, questions regarding invasion success and effects on ecosystems will become important in a wide array of environmental settings.

We report 4 incidents of large (hundreds to hundreds of thousands of individuals) mixed-species flights of predatory and scavenging aquatic Heteroptera and Coleoptera. The events occurred on normal (mostly clear, calm) autumn 2005 and spring 2006 late afternoons near Flagstaff, Arizona. Flight days were either near the full moon or in advanced waning lunar periods. At least 18 species were involved in the flights, with as many as 16 species (7 species of Heteroptera in 3 families, 9 species of Coleoptera in 2 families) in a single flight. Heteroptera (especially from the family Corixidae) were 2–4 orders of magnitude more numerous than Coleoptera. The diasporas plummeted, with much direct mortality, onto green metal roofs, and the largest event lasted more than 2 hours. Even after 2 days, uninjured individuals failed to resume their flights. The literature suggests that such flights occur for autumn movement to winter habitats or for location of springtime habitats for reproduction. The relative proportions of species in flocks were similar neither to the relative proportions in the region nor to those in nearby livestock watering tanks, indicating that the flights consisted of nonrandom assemblages of species. These events are rare or unique observations of coordinated movement of mixed predatory and scavenging invertebrate species.

We examined home range size of Black-backed Woodpeckers (Picoides arcticus) in burned ponderosa pine (Pinus ponderosa) / Douglas-fir (Pseudotsuga menziesii) forests of southwestern Idaho during 2000 and 2002 (6 and 8 years following fire). Home range size for 4 adult males during the post-fledging period was 115.6–420.9 ha using the 95% fixed-kernel method, and 150.4–766.1 ha using the 100% minimum convex polygon method. Smoothed bootstrap estimates (95%) were 130.0–521.9 ha. Home range sizes were significantly smaller 6 years after fire than 8 years after fire. Each male had from 2 to 8 areas of concentrated use within his home range. We provide recommendations for estimating area requirements of Black-backed Woodpeckers in post-fire ponderosa pine / Douglas-fir forests.

We provide the 1st documented accounts of the Mexican endemic rattlesnake Crotalus aquilus from the state of México. The new records extend the known distribution of the species into a region where it may be sympatric with the superficially similar C. triseriatus. Because these taxa have previously been subject to some taxonomic confusion, we performed a preliminary morphological comparison using individuals of both species obtained from proximal localities. Our analyses support the supposition that these taxa are morphologically distinct. The new localities for C. aquilus are situated in high valleys that have been extensively modified by human settlement and agriculture.

The weevil Scaphomorphus trivittatus (Say) was found in close association with Astragalus praelongus var. elliseae (Rydb.) and Astragalus asclepiadoides (Jones) in selenium-containing soils in Carbon County, Utah. The weevils fed on roots of the Astragalus species and formed soil cocoons, which were attached to the tap roots. The weevils pupated and developed into adults in these cocoons over the fall and winter and then emerged in the spring. The plants and soil cocoons contained highly elevated levels of selenium compared to the soils. The weevils, in contrast, differed little from the soils in selenium content.

Isocapnia mogila, a rare winter stonefly, is found in good numbers in Humboldt County, California. In the 50 years since this species was described, very few specimens were recorded from only 4 sites in California and Oregon. Emergence seems to be higher in the fall and early winter than in the late winter and spring.

A report of the cliff chipmunk (Tamias dorsalis) from the Sandia Mountains, New Mexico, was erroneous. The capture location of the specimen was actually the Rio Puerco drainage in Sandoval County. There are no records of the cliff chipmunk from the Sandia Mountains or elsewhere east of the Rio Grande.

Gray wolves (Canis lupus) were reintroduced into Yellowstone National Park in 1995–1996. In August 2004 we measured plant architecture of Geyer willow (Salix geyeriana) stems along three 100-m reaches of Blacktail Deer Creek in Yellowstone's northern elk (Cervus elaphus) winter range to evaluate changes in patterns of browsing and height growth following wolf reintroduction. Average browsing intensities (n = 3 stream reaches) of 100% in 1997 decreased to 0%–55% by 2003, whereas average stem heights of 25–74 cm in 1997 increased to 149–268 cm by 2003, indicating that willow height growth was inversely related to browsing intensity. In addition, average willow canopy cover over the streams increased from <5% in 1997 to 14%–73% in 2004. These findings were consistent with a hypothesis that increased willow heights following the 1995–1996 wolf reintroduction represent a trophic cascade involving wolves, elk, and deciduous woody vegetation.

Mountain beavers cache plants in neat piles above the ground near the entrances to their underground burrows, although the purpose of these hay piles remains controversial. We tested the hypothesis that drying plants in piles above ground may slow decay when the plants are stored underground. Predried plants and undried controls were placed in abandoned burrows. Plants that had been predried retained more green and decayed more slowly than undried controls. This experimental test supports the hypothesis that haying may extend the time during which plants are useful to mountain beavers.