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.     

Winter habitats and foods of Blue Grouse in the Sheeprock Mountains, Utah

Winter habitat use and food habits of Blue Grouse ( Dendragapus obscurus ) were studied in an isolated Utah desert mountain range that contained little typical Douglas-fir ( Pseudotsuga menziesii ) winter habitat. Habitat use was concentrated in the Douglas-fir and pinyon ( Pinus edulis )-juniper ( Juniperus spp. ) habitat. Douglas-fir and pinyon pine were the most consumed foods. Other foods that represented >15% of the composition of an individual fecal sample were limber pine ( Pinus flexilis ), mahogany ( Cercocarpus ledifoliu ), juniper, and an Anteunaria-Cirsium type. The breadth in winter diet indicates that Blue Grouse may successfully occupy other habitats when typical winter habitat is scarce.     

Effects of arthropods on root:shoot ratio and biomass production in undisturbed and modified mountain shrub habitats

In 1987 the effects of arthropods on root:shoot ratios and biomass production were examined in southeastern Wyoming mountain shrub habitats that were undisturbed or had undergone conventional shrub management by mowing, burning, or herbicide application during the previous year. In habitats with and without shrub canopy, treatment with insecticides generally increased foliage biomass and consistently decreased root biomass, regardless of the shrub management practice. In open areas the effects of insecticide treatments on the root and shoot biomass were relatively greater in undisturbed plots than in any of the managed plots. With only one exception, the root:shoot ratio increased following application of insecticide.     

Monitoring with a modified Robel pole on meadows in the central Black Hills of South Dakota

This study using a modified Robel pole was conducted in the central Black Hills, South Dakota. The objectives were to test the relationship between visual obstruction readings and standing herbage, develop guidelines for monitoring, and estimate sample size. The relationship between visual obstruction and standing herbage was linear with 2 segments in a piecewise model. Regression coefficients were highly significant ( P ≤ 0.001). Standard error of the estimate for a single mean was 373 kg ? ha –1 . Herbage ranged from 89 to 3821 kg ? ha –1 with a mean of 1416 kg ? ha –1 . The average number of visually obstructed bands was 6.4 and ranged from 0.21 to 20.4. Cluster analyses grouped the visual obstruction readings into 3 management categories: short, medium, and tall. A minimum of 3 transects (20 stations per transect) is recommended for monitoring areas ≤259 ha (1 section) to be within 20% of the mean at 80% confidence. The protocol developed to monitor standing herbage is accurate, precise, and easy to apply. This tool provides pertinent information for managers to develop guidelines based on the bands and/or standing herbage for monitoring livestock and wildlife use.     

Distribution of a thermal endemic minnow, The desert dace ( Eremichthys acros ), and observations of impacts of water diversion on its population

Population status surveys were performed from 1987 to 1996 for desert dace ( Eremichthys acros , a cyprinid endemic to several small thermal springs in Soldier Meadow, Humboldt County, Nevada, where the species occupies 7 spring areas in a single valley. Because spring distributions are patchy and all areas are not linked by surface flow, each area comprises a more-or-less isolated population, although irrigation practices or high runoff may occasionally link several of them. Although limited to thermal springpools and outflows, desert dace were found in temperatures ranging from 37° C near spring sources to 13° C in downstream areas. Between May 1988 and October 1989, most of the discharge from a major spring outflow was diverted from its natural channel into an irrigation ditch than in the channel. Reduced fish numbers still persist (1996), even though the affected site has been relatively undisturbed since 1989. To improve desert dace habitat and increase populations, irrigation diversion should be discontinued and water returned to the original channel. Continued protection and increased habitat preservation for desert dace are recommended because of their limited distribution, apparently restricted habitat requirements, and the potential for environmental disruption in the area.     

Opportunistic feeding in Sceloporus horridus from Jalisco, Mexico

Based on a sample of 17 adult specimens of Sceloporus horridus taken near Autlan, Jalisco, Mexico in May 1974 just before and just after the first rainfall of the year, we present the first published data on the food habits of this lizard. Important prey item taxa were Homoptera, Coleoptera, Hymenoptera, Orthoptera, and Isoptera. The absence of Homoptera and Orthoptera, and the concomitant greater relative importance of Isoptera and Hymenoptera in the diet after the rain than before indicates opportunistic feeding by S. horridus. Our data suggest that reproduction in this lizard is probably initiated soon after the first rains in late spring.     

Some aspects of succession in the spruce-fir forest zone of northern Utah

A site in the Rocky Mountain subalpine forest zone with which a series of hypotheses concerning ecosystem succession was tested is characterized. Succession from herb-dominated meadows to climax forests of Engelmann spruce and subalpine fir can follow at least four identified pathways. After fire, spruce and fir may reinvade a site directly, follow invasion by aspen, or follow invasion by lodgepole pine, the pathway depending on a combination of physical and biotic factors. In other cases, succession begins with long-established meadows which do not owe their existence to fire. In this latter pathway, aspen invades meadows by suckering and changes the environment near the soil surface so as to facilitate establishment of the climax tree species. The biota and soils of four characteristic seral stages (meadow, aspen, fir, spruce-fir) in this latter pathway are described.     

New Nevada entities and combinations in Eriogonum (Polygonaceae)

New species and varieties of the plant genus Eriogonum (Polygonaceae) that occur in Nevada are proposed. Eriogonum tiehmii and E. ochrocephalum var. alexanderae are endemic to Nevada, and E. lewisii is restricted to extreme northeastern Nevada and adjacent Utah. These entities belong to the subgenus Eucycla. Two varieties of E. umbellatum (of the subgenus Oligogonum) are proposed. The first, var. juniporinum , is found in eastern Nevada and in the desert ranges of southeastern California. The second is var. furcosum , which is restricted to the Sierra Nevada. One new combination is also proposed: E. nudum var. gramineum .