Comparative ecology of Sarcobatus baileyi and Sarcobatus vermiculatus in estern California

Greasewood ( Sarcobatus ) is a succulent-leaved, halophytic shrub of North American origin. The genus comprises 2 species: Sarcobatus baileyi and Sarcobatus vermiculatus. Sarcobatus vermiculatus is common throughout much of western North America, but S. baileyi is much more limited in distribution and was previously thought to be endemic to Nevada. Here we document and describe a S. baileyi population in eastern California, comparing its morphology and ecology to an adjacent S. vermiculatus population. Morphologically, S. baileyi is smaller in stature but produces larger seeds; however, fewer S. baileyi seeds germinated and survived a 20-day laboratory incubation compared to seeds of S. vermiculatus. Sarcobatus baileyi has higher leaf Na concentrations and operates at much lower plant water potentials than S. vermiculatus under field conditions; however, no significant differences were observed between the 2 species in long-term water-use efficiency as measured by leaf δ13C. Leaf Na concentrations were very low in both species. Overall, these species differ greatly in a number of traits that are consistent with the upland, nonphreatophytic character of S. baileyi, which is in stark contrast to the phreatophytic character of S. vermiculatus. Both species, however, are very salt tolerant and have low leaf N concentrations, indicating the low nutrient availability and the potentially high salinity of their extreme habitats. Further investigation of comparable desert ridge environments should be conducted to determine the extent of S. baileyi in eastern California, and common garden comparisons of the 2 species should be conducted to compare their ecophysiological traits. El ";greasewood” ( Sarcobatus ) es un arbusto halofítico de origen norteamericano con hojas suculentas. El género consta de dos especies: Sarcobatus baileyi y Sarcobatus vermiculatus. Aunque S. vermiculatus es común en gran parte del oeste de Norteamerica, S. baileyi tiene una distribución mucho más limitada. Se pensaba anteriormente que S. baileyi era endémico a Nevada, pero aquí documentamos y describimos una población en el este de California, comparando su morfología y ecología con las de una población adyacente de S. vermiculatus. Morfológicamente, S. baileyi es más pequeña de altura, pero produce semillas más grandes. Sin embargo, menos semillas de S. baileyi germinaron y sobrevivieron a una incubación en laboratorio de 20 días, comparado con S. vermiculatus. Sarcobatus baileyi opera con potenciales de agua mucho más bajos que los de S. vermiculatus en condiciones de campo y tiene mayores concentraciones de Na en sus hojas. No obstante, no se observaron diferencias significativas en la eficiencia del uso de agua a largo plazo, medida en términos de δ13C entre las 2 especies. Las concentraciones de N en las hojas fueron muy bajas en ambas especies. En general, estas especies difieren mucho en varios rasgos que son consistentes con el carácter no freatofítico de S. baileyi de tierras altas, el cual contrasta claramente con el carácter freatofítico de S. vermiculatus. Ambas especies, sin embargo, son bastante tolerantes a la sal y tienen concentraciones bajas de N en hojas, lo cual indica la baja disponibilidad de nutrientes y la potencial alta salinidad en sus hábitats extremos. Investigaciones adicionales en ambientes comparables de bordes desérticos deberán llevarse a cabo para determinar la extensión S. baileyi en el este de California, además de comparaciones de las dos especies en jardín para comparar sus rasgos ecofisiológicos.     

Effects of convict cichlids on growth and recruitment of White River springfish

Observations of changes in population density of native White River springfish ( Crenichthys baileyi ) in Pahranagat Valley led to the following hypothesis: introduced convict cichlids ( Cichlasoma nigrofasciatum ) cause reduced growth and recruitment; cover reduces the magnitude of the effect. The hypothesis was tested by establishing sympatric and allopatric groups of the two species in experimental aquaria with and without cover. Change in volume (= mass) and length of the two species over a three-month period in spring 1986 and 1987 was measured and analyzed using 2 × 2 factorial analyses. Convict cichlids caused reduced growth and eliminated recruitment of springfish under the experimental conditions. Cover did not influence growth but positively affected recruitment of springfish in allopatry. It is likely that a portion of the reduced springfish population densities in nature can be attributed to adverse effects from introduced cichlids.     

Suitability of shrub establishment on Wyoming mined lands reclaimed for wildlife habitat

Restoring coal mined land to pre-mining shrub cover, density, height, community composition, and diversity to renew wildlife habitat quality is a priority for reclamation specialists. Long-term shrub reestablishment success on reclaimed mined land in Wyoming and suitability of these lands for wildlife habitat are unknown. Fourteen reclaimed study sites, 10 yr old or older, were selected on 8 mines in Wyoming to evaluate shrub reestablishment and wildlife habitat value for antelope ( Antilocapra americana ) and sage grouse ( Centrocercus urophasianus ). Five sites were categorized as fourwing saltbush ( Atriplex canescens ) sites and 9 as fourwing saltbush/big sagebrush ( A. canescens/Artemisia tridentata spp. wyomingensis ) sites. Published data describing antelope and sage grouse-preferred habitat requirements in sagebrush-grassland steppe ecosystems were used to evaluate shrub community value of sampled sites for wildlife habitat. Mean shrub canopy cover, density, and height for fourwing saltbush sites were 5.8%, 0.23 m -2 , and 41.6 cm, respectively, compared to 5.6%, 0.61 m -2 , and 31.1 cm for fourwing saltbush/big sagebrush sites. Two fourwing saltbush and 4 fourwing saltbush/big sagebrush sites provided sufficient cover for antelope, while 2 fourwing saltbush and 4 fourwing saltbush/big sagebrush sites were adequate for sage grouse. Only 1 fourwing saltbush/big sagebrush site provided high enough shrub densities for sage grouse. One fourwing saltbush and 7 fourwing saltbush/big sagebrush sites provided ample shrub heights for antelope, while 1 fourwing saltbush and 8 fourwing saltbush/big sagebrush sites were sufficient for sage grouse. One fourwing saltbush and 1 fourwing saltbush/big sagebrush site provided enough grass, forb, and shrub composition for antelope, while no site in either reclamation type was satisfactory for sage grouse. Shrub diversity was 3 times higher for fourwing saltbush/big sagebrush sites (0.984) than for fourwing saltbush sites (0.328). Individually, sites seeded with multiple shrub species had higher canopy cover, density, and diversity compared with single-species shrub seedings. Achieving premining shrub cover, density, height, community composition, and diversity within existing bond-release time frames is unrealistic, considering that some native shrublands require 30-60 yr to reach maturity.     

Plant age/size distributions in black sagebrush ( Artemisia nova ): effects on community structure

The demography of black sagebrush ( Artemisia nova Nelson) was investigated in the Buckskin Mountains of western Nevada to determine patterns of stand renewal in sagebrush communities currently free from wildfires. Biomass sampling was conducted to develop growth classes that reflected apparent age of the shrubs. The density of black sagebrush plants was twice that of basin big sagebrush ( A. tridentata ssp. tridentata Nutt.) in adjacent communities on contrasting soils (2.2 versus 1.1 plants per m 2 ). Black sagebrush accumulated only 75% as much woody biomass as big sagebrush. Regression equations were developed and tested for predicting total woody biomass, current annual growth (CAG), and leaf weight of black sagebrush plants. Apparent age classes were developed both for the black sagebrush plants and the sub-canopy mounds on which they grew. Discriminant analysis was used to test this classification system. Plant succession, apparently controlled by nitrate content of the surface soil, appeared to eliminate the successful establishment of black sagebrush seedlings on the mounds. After the shrubs die, the mounds eventually deflate. We propose that mounds reform around shrub seedlings, but because seedling establishment is so rare in these communities, this could not be verified.     

Environmental effects on Common Snipe winnowing and calling (activity)

Our objective was to clarify the effects of 10 identified variables on snipe activity (winnowing and calling) by demonstrating correlations between the variables and snipe activity. We monitored snipe at 2 study areas in southwestern Montana and northwestern Wyoming at all hours of the day and night during the 1996 and 1997 breeding seasons. We measured 10 variables at established points along transects that were situated through the middle of each study site (8 study sites total). A total of 1200 monitoring periods were conducted throughout the course of this study. Effects of each factor on snipe activity were considered by examining general trends in each factor's graphical representation. Our results identified 6 factors (season, time of day, lunar cycle, solar radiation, wind speed, and temperature) that are associated with snipe activity. Snipe were most active early in the breeding season during 2 twilight periods during the first and last quarters of the lunar cycle. Low solar radiation levels, wind speeds, and temperatures were also most ideal conditions for snipe activity. All 6 factors should be considered when attempting to detect, survey, or estimate snipe populations.     

Diets of young Colorado squawfish and other small fish in backwaters of the Green River, Colorado and Utah

We compared diet of young-of-year Colorado squawfish ( Ptychocheilus lucius ), an endangered cyprinid, with diets of other fish Rhinichthys osculus, Catostomus discobolus, and C. latipinnts , and nonnative Cyprinella lutrensis, Notropis stramineus, Pimephales promelas, Ictalurus punctatus, and Lepomis cyanellus. For each species, diet varied with size and between upper and lower river reaches but not between seasons for fish of similar size. Larval chironomids and ccratopogonids were principal foods of most fishes. Copepods and cladocerans were important in diets of P. lucius L. cyanellus Catostomus discobolus was the only species that ate moderate amounts of algae. Fish (all larvae) were in digestive tracts of only 10 P. lucius (21-73 mm TL), about 1% of P. lucius analyzed. High diet overlap occurred between some size-reach groups of P. lucius and C. lutrensis, R. osculus, C. latipinnis, I. punctatus, and L. cyanellus . Potential for food competition between young-of-year P. lucius and other fishes in backwaters appeared greatest with the very abundant C. lutrensis .     

Distribution of sculpins in the Clearwater River Basin, Idaho

The distributions of Cottus bairdi, C. rhotheus, and C. beldingi exhibited a highly significant positive degree of association. Conversely, the distribution of C. confusus exhibited a highly significant negative association with the distributional complex, C. bairdi, C. rhotheus, and C. beldingi. These species of sculpins can be grouped into two assemblages; one based on the distribution of C. confusus and the other based on the combined distributions of the other three species. The factor or factors limiting the downstream distribution of C. confusus or the upstream distribution of the other three species could not be positively identified. However, we hypothesize that competition between C. confusus and one or more members of the C. bairdi, C. rhotheus and C. beldingi complex is involved. In the area of overlapping distributions among C. bairdi, C. rhotheus, and C. bairdi we hypothesize that resource partitioning is occurring. However, the data did not allow evaluation of this hypothesis.        

Temporal activity patterns of Dipodomys ordii population

Temporal activity patterns for Dipodomys ordii were generally bimodal during the summer, with the highest peak occurring during early predawn hours when conditions were optimum for water conservation. Removal of dominant members in the population resulted in a substantial shift in the activity pattern to increased activity during the evening hours.     

Breeding behavior of the Plumbeous Vireo in New Mexico

The Plumbeous Vireo ( Vireo plumbeus ) is a poorly studied songbird species that breeds within the interior western United States and Mexico. We studied the breeding behavior of Plumbeous Vireos within pinyon-juniper habitats in northeastern New Mexico in 1996 and 1997. Over both years we located and monitored 40 nests and conducted behavioral observations throughout the nesting cycle. From these observations we described and compared basic behavioral traits of male and female vireos during their nest-building, egg-laying, incubation, and nestling stages, and their response to potential predators near the nest. Male vireos displayed potential nest sites to females, but the females selected the site to be used and built most of the nest. Vireos often did not initiate egg-laying until 2-3 d after nest completion. The female tended to incubate eggs and brood nestlings more than the male, but both parents contributed equally in provisioning the young. Brown-headed Cowbirds ( Molothrus ater ) parasitized 77% of nests in 1996, 63% in 1997, and parasitism was the primary cause of nest failure in this population. The conspicuousness of vireos around the nest, particularly during the nest-building stage, may contribute to high parasitism levels. Vireo aggression near the nest may also act as a cue to help cowbirds locate nests.     

Pocket gophers ( Thomomys talpoides ) in successional stages of spruce-fir forest in Idaho

This study examined (1) the relative abundance of the pocket gopher ( Thomomys talpoides ) in four successive stages (1–10, 11–39, 40–79, and 80+ years following disturbance) of spruce-fir forest; (2) the relationship between number of gopher sign (mounds and earth plugs) with gopher density; and (3) a method of sampling pocket gopher populations using a 500 by 4 m strip transect. The number of gopher mounds was significantly correlated with the number of earth plugs. Data were pooled and a categorical log linear analysis used to test for significant differences in pocket gopher sign between the four successive stages. The 1–10 and the 80+ -year-old sites had significantly more gopher sign than the 11–39 and the 40–79 year-old sites. No significant differences were found between the 11–39 and the 40–79-year-old sites, or between the 1–10 and the 80+ -year-old sites. The difference in population densities may be due to understory vegetation differences between the successional stages. There was a significant correlation between amount of gopher sign and gophers caught in each of the study sites. This indicates that counts of pocket gopher sign may be used to estimate pocket gopher density. The strip transect is recommended as the most appropriate method when sampling heterogeneous habitats or when there is cause to suspect gopher populations may be aggregated within the area rather than spaced randomly or regularly.