Nonstructural carbohydrate and element pools in globemallow ( Sphaeralcea ): defoliation effects and seasonal trends

Globemallows ( Sphaeralcea spp.) are arid land forbs suitable for seeding with crested wheatgrass ( Agropyron cristatum [L.] Geartner). However, little is known about the quantitative role of total nonstructural carbohydrates (TNC) in relation to globemallow tolerance of grazing, or about seasonal dynamics of mineral elements. The objectives of this study were to compare TNC and element pools (concentration x biomass) in the roots, crowns, and shoots of clipped versus unclipped S. munroana (Dogl.) Spach. Seedlings of S. munroana were transplanted to a northern Utah field site in 1985. Interplanted crested wheatgrass provided uniform competitive background. One-half of the globemallows were clipped to 5 cm on 10 May 1986 when stems were elongating the root and crown TNC pools were low. The remaining globemallows were not clipped. Root, crown and shoot pools of TNC and elements (N, P, K, Ca, and MG) were determined on 1 May, 20 May, 7 June, 11 July, 22 September, and 5 November 1986, and 29 May 1987. Defoliation did not affect shoot weights during a 1-year period. Experiment-long TNC and element pools also were not affected by clipping. Results indicate that S. munroana shoot recovery from a single spring grazing during a 1-year period would not be impaired by low root and crown TNC pools, and that TNC stored in the roots and crowns would account for only 7% of the regrowth produced. Furthermore, TNC and element pools of roots and crowns were generally constant from May to September but increased from September to November. TNC and element pools in shoots increased from May to September and then generally declined by November. TNC Pools of roots and crowns declined during winter.     

Annotated inventory of invertebrate populations of an alpine lake and stream chain in Colorado

Benthic macroinvertebrates were collected during the ice-free season (1 July-20 October) over a five-year period from a chain of alpine lakes and intervening streams in the Green Lakes Valley (3,347-3,615 m) in Boulder County, Colorado. A list of taxa was developed for 1981 and 1982, with taxonomic additions for 1983- 1985 and comments on community structure, seasonal and elevational changes in species abundance, and noteworthy occurrences. A total of 111 taxa was collected, of which 84% occurred in streams, 58% being exclusively lotic. Dipterans composed 73-81% of total abundance in streams. The littoral benthic zone of lakes was predominantly trichopterans and dipterans, 44-60% and 24-39%, respectively. Numerically important organisms in various lakes and streams were chironomids, simuliids (particularly Metacnephia ), oligochaetes, and the bivalve Pisidium casertanum . An isolated lake and its outlet stream, with unique characteristics, were the sole locations of Gammarus lacustris (Amphipoda) and Glossiphonia complanata (Hirudinea). Manipulated lowering of a lake along the main drainage exposed abundant and luxuriant colonies of the bryozoan Fredericella sultana . This organism was found on 43% of all rocks sampled, a preponderance heretofore unknown for this, or any, ectoproct in alpine or arctic lakes.     

Ecological differences of C 3 and C 4 plant species from central Utah in habitats and mineral composition

Six study sites were established in each of three community life form types (grass, forb, and shrub) containing as dominants or subdominants either C 3 and/or C 4 plants. Soil and vegetation samples were analyzed for total nitrogen, phosphorus, magnesium, calcium, potassium, sodium, zinc, iron, copper, and manganese. Discriminant analysis and analysis of variance statistics were used to evaluate differences in mineral content of soils and plant tissues. C 4 plants in all study sites assimilated higher concentrations of potassium, iron, and calcium than did C 3 plants. Forbs in all sites contained the highest concentrations of minerals, followed by shrubs and grasses.     

Respiration characteristics differ among cheatgrass ( Bromus tectorum L.) populations

Cheatgrass ( Bromus tectorum L.) is a dominant weed that has increased the frequency of wildfire in the Great Basin since its introduction about 100 yr ago. This study examines characteristics of respiratory metabolism in several different populations. Seeds from 6 populations were germinated and metabolic heat rates (q) and dark respiration rates (R co2 ) of all seedlings were measured calorimetrically at 15° and 25° C or (for 3 populations) at 5° intervals from 5° to 35° C. Growth rates, substrate carbon conversion efficiencies, and Arrhenius temperature coefficients were calculated from the data. Results show that cheatgrass metabolism is most efficient at temperatures near 0° C; at temperatures above 20-25° C, efficiency goes to zero. Cheatgrass populations differ in their temperature dependencies of substrate carbon conversion efficiency and predicted growth rate. Measurements of respiratory heat and CO 2 rates as functions of temperature can be made relatively quickly and used to aid understanding of metabolic adaptation by invasive and native species to the environment.     

Movements and home ranges of San Joaquin kit foxes ( Vulpes macrotis mutica ) relative to oil-field development

We examined the effect of oil-field development on movements and patterns of spatial use of San Joaquin kit foxes ( Vulpes macrotis mutica ) on the Naval Petroleum Reserves in California (NPRC) in the San Joaquin Valley. To do this, we compared movements and home ranges of kit foxes from June 1984 to September 1985 in areas developed for petroleum production (30% of native habitat lost to production facilities) and areas with little development (3%). Distances traveled nightly by kit foxes did not differ between levels of petroleum development or between sexes ( P > 0.2). Mean length of nightly movements during breeding (14.6 km) was longer than during pup-rearing (10.7 km) and pup-dispersal (9.4 km) periods ( P = 0.01). Mean size of home ranges was 4.6 ± 0.4 ( s￣x ) km 2 ( n = 21) and did not differ between levels of petroleum development and sexes ( P > 0.2). Overlap of home ranges of foxes from the same social group (78 ± 4.3%) was greater than that of same-sex foxes (35 ± 7.8%) and males and females of different social groups (32 ± 8.0%, P P > 0.4). Despite extensive overlap of home ranges, kit foxes on NPRC maintained relatively exclusive core areas, particularly adjacent foxes of the same sex. Future studies should examine which levels of habitat conversion impact spatial use of kit foxes.     

Density and biomass of redband trout relative to stream shading and temperature in southwestern Idaho

Density and biomass of redband trout ( Oncorhynchus mykiss gairdneri ) relative to stream temperature were examined in headwater reaches of Big Jacks and Little Jacks Creeks in southwestern Idaho. Stream shading was greater (mean of 80% versus 46%) and solar insolation was lower (mean of 7.9 versus 15.1 mJ · m -2 · day -1 ) in Little Jacks Creek ( P P ≤ 0.07) but increased more rapidly and to higher levels (24° - 26° C) in Big Jacks Creek. Daily maximum water temperatures (23 km downstream of headwater springs) during July 1996 were lower in Little Jacks Creek (ranged from 18° to 22° C) than in Big Jacks Creek (20.2° to 26° C, P P -2 and 25.0 g · m -2 ) compared to Big Jacks Creek (0.3 fish · m -2 and 8.9 g · m -2 , P = 0.01). Trout density was negatively correlated with increases in water temperature ( P = 0.03) and solar insolation ( P = 0.09) in both streams. Trout biomass increased with stream shading and was negatively correlated with solar insolation ( P < 0.1). Warmer water temperatures in Big Jacks Creek were likely due to historical summerlong livestock grazing, which drastically reduced riparian shading.     

Winter nutritive content of black sagebrush ( Artemisia nova ) grown in a uniform garden

Winter crude protein content, in vitro digestibility, and productivity were determined for seven accessions of black sagebrush ( Artemisia nova ) grown in a uniform garden. No significant differences were detected among the accessions for any of these attributes. Mean crude protein was 6.8% of dry matter. Accessional range was from 5.8% to 7.3%. Mean in vitro digestion was 54.8% of dry matter; accessional range, 51.9% to 57.2%. Mean current year's growth (a measurement of productivity) was 4.3 cm; accessional range, from 3.7 to 5.1 cm. In comparison to other winter forages, black sagebrush ranks high for winter levels of crude protein and very high in winter digestible dry matter but low in productivity.     

Stand-level herbivory in an old-growth conifer forest canopy

Herbivory is an important ecological process in forest canopies but is difficult to measure, especially for whole stands. We used the Wind River Canopy Crane in Washington State to access 101 randomly-located sample points throughout the forest canopy. This provided a relatively quick and convenient way to estimate herbivory for a whole stand. The overall level of herbivory was estimated at 1.6% of leaf area. The distribution was strongly skewed to the lower canopy where broad-leafed species experienced higher levels of herbivory. Herbivory averaged 0.3% in conifers and 13.5% in broad-leafed species. Fully half of the sample points had no detectable herbivory. Herbivory in this old-growth conifer forest is among the lowest levels published for forests around the globe and may reflect the general levels of herbivory in temperate coniferous forests during nonoutbreak conditions. Our whole-stand estimate is the first attempt at measuring herbivory for an entire forest stand in the Pacific Northwest.     

Subspecies specificity of gall forms on Chrysothamnus nauseosus

Galls induced by tephritid flies (Diptera: Tephritidae) on Chrysothamnus nauseosus ssp. albicaulis, consimilis, graveolens, and salicifolius are useful in taxonomic identification of these subspecies in Utah. In this study, &ldquo;callus&rdquo; galls were found almost exclusively on ssp. albicaulis. &ldquo;Cotton&rdquo; galls were more frequent on ssp. consimilis and graveolens. &ldquo;Mace&rdquo; galls occurred on all four subspecies but were the only gall found on naturally occurring populations of ssp. salicifolius. Gall form specificity is not as well correlated with C. nauseosus subspecies in peripheral areas of the species range as in Utah. This decrease in specificity may be due to decreased competition for the host plant in outlying areas.