Classification of the riparian vegetation of the montane and subalpine zones in western Colorado

A classification of the riparian vegetation of part of western Colorado was developed by cluster analysis and ordination of 115 samples of relatively undisturbed vegetation. The classification of plant associations contains five montane riparian forests, three subalpine riparian forests, four lower subalpine willow carrs, three upper subalpine willow carrs, and one subalpine wetland.     

Dam-site selection by beavers in an eastern Oregon basin

We compared physical and vegetative habitat characteristics at 14 dam sites occupied by beaver ( Castor Canadensis ) with those at 41 random unoccupied reaches to identify features important to dam-site selection in the Long Creek basin, Grant County, Oregon. Stream reaches with dams were shallower and had a lower gradient than unoccupied reaches. Beaver did not build dams at sites with a rock substrate. Bank slopes at occupied reaches were not as steep as those at unoccupied reaches; and occupied stream reaches had greater tree canopy cover, especially of thinleaf alder ( Alnus tenuifolia ), than did unused reaches. A discriminant model using transformations of bank slope, stream gradient, and hardwood cover classified all beaver dam sites correctly and 35 of 41 random sites as unoccupied sites. The 6 misclassified sites had rock substrates. We also tested four habitat suitability models for beaver in this basin. Three models produced significantly different ( P < .05) scores between occupied and random unoccupied reaches, suggesting that they might have some utility for this region.     

In memoriam: William Wallace Newby (1902-1977)

W. W. Newby, professor of biology at the University of Utah from 1927 to 1971, was renowned as a great teacher and a clear and forceful writer and for his meticulous research in invertebrate embryology. Ancillary skills were counseling (especially of premedical students), illustrating, wood crafting, and paper preserving. Some of his writings pertained to the history of research in the biological sciences at the University of Utah. His specialty areas in teaching were embryology and genetics, and he served as chairman of the Department of Genetics and Cytology from the year of its creation in 1948 until 1962. The most outstanding example of his research pertained to the early embryology of the echiuroid worm Urechis caupo . &nbsp;&nbsp;&nbsp;     

Spatial pattern and interference in pi?on-juniper woodlands of northwest Colorado

The local spatial arrangement of the coniferous trees Pinus edulis and Juniperus osteosperma was mapped in two woodland stands and measured in two shrub-dominated stands in the semiarid Piceance Basin of northwest Colorado. In the woodlands, small trees were often clumped, while medium and large trees were either randomly or uniformly dispersed. Significant regressions were obtained between a tree?s basal area or canopy area and the area of its Dirichlet domain (the region closer to it than to any other tree). Both findings from the woodland stands accord with results obtained by other workers in other vegetation. Like earlier workers, we interpret these patterns to indicate density-dependent mortality and density-dependent depression of growth rates among the trees in the woodlands. In contrast, the trees in the shrub-dominated stands are located at random with respect to each other. However, they are strongly associated with shrub cover. Apparently tree seeds arrive in these stands primarily by long-distance dispersal, and the establishment of seedlings is more likely in the shade of shrubs.     

Relationship between environmental and vegetational parameters for understory and open-area communities

Ten individuals from each of four tree species were selected, and their associated understory and adjacent open-area communities were sampled for both environmental and vegetational parameters, including light intensity, pH, litter depth, soil depth, and percentages of exposed rock, litter cover, living cover, shrubs, forbs, grasses, and annuals. The four tree species were ponderosa pine, Rocky Mountain juniper, Gambel oak, and snowbrush ceanothus. The study site was in the lower Uinta Mountains about 10 miles east of Kamas, Utah. Correlations among the various biotic and abiotic parameters were examined. The interplay of these factors in differentiating the understory and open-area communities is discussed. &nbsp;     

Two new species of Aurealcaulis (Osmundaceae) from northwestern New Mexico

Two new osmundaceous species, Aurealcaulis moorei and A. bransonii , are described from the San Juan Basin of northwestern New Mexico. The area from which they were collected is uncertain, but it is presumed they came from the Lower Eocene San Jose Formation near Angel Peak, southeast of Bloomfield, New Mexico. The species are characterized by having a heterogeneous ( A. moorei ) to homogeneous ( A. bransonii ) pith, non- or partial closure of their leaf gaps, exarch protoxylem clusters, formation of their C-shaped leaf traces by fusion of two segments from adjacent xylem strands in their inner cortices, relatively low numbers of traces in their cortices (16-22 in A. moorei , 15-19 in A. bransonii ), roots arising from lateral margins of these segments, sclerenchymatous outer cortex that connects with the sclerotic ring of the petiolar vascular strand, crenate ( A. moorei ) or interrupted ( A. bransonii ) sclerenchyma lining the adaxial concavity of their petiole strands, and leaf bases that may or may not contain one, occasionally two, sclerotic cellular masses in their stipular wings in A. moorei and 6-8 more or less aligned masses in A. bransonii . They are compared with other osmundaceous taxa, particularly A. crossii Tidwell & Parker of Paleocene age. Because of variations in these new species, Aurealcaulis Tidwell & Parker is slightly emended to accept species of this genus with heterogeneous or homogeneous piths, protoxylem becoming endarch in the leaf traces, petiolar vascular strands formed by fusion of segments from the xylem strands in the inner cortex, outer cortex, or outside the stem, and the occurrence or nonoccurrence of sclerenchyma in the adaxial concavity of their petiolar vascular stands and in their stipular wings. The paleoecological conditions under which these species of Aurealcaulis grew are also considered.     

Algae of Devils Hole, Nevada, Death Valley National Park

We examined algal flora in the aquatic system of Devils Hole, Nevada. The water is seasonally warm, near neutral in pH, and rich in dissolved carbonate, indicative of deeply circulating groundwater flowing through carbonate rock. Most algae were benthic, with only a few planktonic representatives. Eighty-four terminal identifications in 44 genera were recorded, with diatoms and blue-green algae the most speciose groups. Diatoms were major contributors to the grazing food web. Large, mat-forming filamentous algae have an important influence on the physicochemical and general structure of the benthic substrates in Devils Hole.     

Oreohelices of Utah, II. Extant status of the Brian Head mountainsnail, Oreohelix parawanensis Gregg, 1941 (Stylommatophora: Oreohelicidae)

The Brian Head mountainsnail, Oreohelix parawanensis , is reported for the 1st time as a living species, and for the 1st time its habitat is described. Preliminary determination of the very limited distribution of this species (≤ 2.3 ha inhabited in ～ 11 ha overall area) is presented. Morphometric data previously had been reported only for the holotype and for 1 topotype; measurements from 37 new specimens as well as 20 paratypes are provided here, and these data show that the lost holotype was not typical of the species. Sizes of reproductive snails and of embryos are also reported.     

Natural enemy assemblages on native and reseeded grasslands in southwestern Montana: a family-level analysis

We conducted a 2-year survey, using sweep sampling and family-level taxon identification, of the predatory and parasitoid insects on grassland sites in the Gallatin Valley of southwestern Montana. The 25 sites were divided into 4 habitat classes: 2 native habitat types ( Stipa comata/Bouteloua gracilis and Festuca idahoensis/Agropyron spicatum ) and 2 that had been reseeded with either crested wheatgrass ( Agropyron cristatum ) or smooth brome ( Bromus inermis ). Our major goal was to make quantitative comparisons of the abundance of insects among native and reseeded habitats. Of 51 families in 5 insect orders identified, 7 Hymenoptera (Encyrtidae, Braconidae, Ichneumonidae, Pteromalidae, Eulophidae, Scelionidae, and Torymidae), 3 Hemiptera (Lygaeidae, Nabidae, and Reduviidae), 1 Coleoptera (Coccinellidae), and 1 Diptera (Asilidae) comprised 90% of the natural enemies sampled. Ordination analyses provided no strong evidence that the 4 habitat classes contained distinct overall natural enemy communities. However, contiguous native and reseeded sites usually had relatively different overall natural enemy assemblages, suggesting that vegetation was often a more important correlate of community composition than was close spatial proximity of sites. Furthermore, several common families exhibited differential abundances across habitat classes in one or both years. For example, in 1989, Eulophidae, Pteromalidae, and Torymidae were more abundant on native Festuca/Agropyron sites, whereas Encyrtidae and Nabidae were more abundant on Festuca/Agropyron sites reseeded with Bromus inermis . Although analyses of insect assemblages classified to the family level provide somewhat limited information on functional ecological differences among habitats, they allow one to survey a broad array of taxa to identify focal groups for future conservation and land management studies.