Comparison between plant species in bushy-tailed woodrat middens and in the habitat

Bushy-tailed woodrats ( Neotoma cinera ) collect vegetation and store it in middens. We asked to what extent plant species collected by woodrats reflect the array of species growing in the habitat. Species composition of plant clippings at 20 bushy-tailed woodrat middens in central Colorado were compared to vegetation growing within 30 m of the dens. Amount of overlap between midden and habitat species was low (28-49%) when all taxa were included; however, if only woody taxa were considered, overlap was 71-89%. Sorensen's Index of Similarity exhibited a like pattern; the index increased markedly if only woody taxa were included. Only one plant species not found within 30 m of a den occurred in significant amounts of the middens. Bushy-tailed woodrats collected a wide array of species but were more selective the greater the habitat plant diversity. Results of this and other studies indicate the concordance between midden contents and habitat vegetation decreases with increasing habitat plant diversity. Ancient woodrat middens are nonetheless useful to paleontologists seeking to reconstruct past vegetation associations in woody vegetation is well represented in middens.     

Abundance,species richness and diversity of the orb-weaving spider families Araneidae,Nephilidae and Tetragnathidae in natural habitats in Trinidad,West Indies

This study examined the biodiversity of orb-weaving spiders in natural habitats in Trinidad, a continental island with a northern South American fauna. Forty-six localities were sampled, classified into seven formations (representing vegetation structure) and 16 habitat types (based on plant species composition), using visual search and sweep-netting methods, resulting in a total of 1225 individuals of 57 species. Abundance and species richness were significantly related to formation but not habitat type, while both factors influenced species diversity, evenness and dominance. Gamma (γ) diversity had a larger component of β than α diversity did, indicating that between-habitat differences are a substantial part of regional diversity in orb-weaving spiders in Trinidad.     

Vegetation, soils, and hydrogeomorphology of riparian patch types of a dryland river

From a landscape perspective, riparian corridors can be viewed as mosaics of vegetation patches. We delineated 10 patch types within the floodplain of the San Pedro River (Arizona) on the basis of physiognomy, dominant overstory species, and tree size class; and we assessed differences in hydrogeomorphology, vegetation structure, plant species richness, and soil chemistry and texture. Patches of tamarisk ( Tamarix ), an introduced species, fell within the continuum of variation shown by other patch types in the landscape mosaic. Among the tree-dominated types, cottonwood-willow ( Populus-Salix ) and tamarisk patches were inundated more frequently than mesquite ( Prosopis ) patches, while cottonwood-willow patches had shallower groundwater than tamarisk or mesquite patches. Due to the wetter conditions, cottonwood-willow patches had a high relative abundance of wetland and exotic species in the understory. Tamarisk patches and wet shrublands ( Baccharis salicifolia—Salix exigua ) had high woody stem densities while cottonwood-willow patches had dense canopy cover. In association with differences in canopy cover, cottonwood-willow patches had low herbaceous species richness but high woody species richness, while tamarisk patches had high herbaceous and low woody species richness. Soil electrical conductivity, silt content, organic matter content, and available phosphorus increased from young to old stands of both tamarisk and cottonwood-willow, often resulting in greater differences between patches of different size/age class than between patches with different dominant species. Surface soil salinity (electrical conductivity) was low in all patches, including those dominated by tamarisk. Nitrate was abundant in soils of tamarisk patches (perhaps reflecting their high clay content) and wet shrubland patches. Dry shrublands ( Hymenoclea-Ericameria ) and wet shrublands were similar to young forest patches in having coarse soils with little organic matter.     

Plant composition and erosion potential of a grazed wetland in the salmon river subbasin, Idaho

Wetlands are dynamic habitats with many unique, important functions including filtering sediments and providing diverse habitats for fish and wildlife. Wetlands in the western United States are particularly important because they offer habitat for a number of protected runs of endangered fish species. Historically, livestock grazing has altered wetland and riparian area form and function by facilitating exotic species invasions, altering spatial heterogeneity of vegetation, and increasing erosion. In this study we examined vegetation structure and erosion potential in a wetland meadow exposed to unregulated grazing along Deer Creek in the Salmon River subbasin, Idaho. We characterized the vegetation composition and structure within the study area and attempted to assess potential erosion conditions using the Revised Universal Soil Loss Equation (RUSLE), an empirical approach developed by the U.S. Department of Agriculture—Agricultural Research Service (USDA-ARS). We found no significant spatial variability in species richness and noted a moderate number of exotic species in the total plant composition. Plant cover was higher near slightly entrenched banks, indicating that uncontrolled livestock were primarily occupying gently sloped streambanks and the interior of the meadow. Based on current vegetation composition and RUSLE results, uncontrolled grazing may be negatively impacting the study area. If uncontrolled grazing were excluded or carefully managed in the wetland meadows of the upper portion of the Deer Creek watershed, a reduction in excess sediments to Deer Creek may occur.     

Comparisons of the alpine bird communities across habitats and between autumn and winter in the mid‐Yalong Zangbo River valley,Tibet

The extreme alpine environment around the mid‐Yalong Zangbo River on the Tibetan plateau supports a unique avifauna. To understand the structure and habitat selection of this poorly known bird assemblage, we quantified abundance of the birds in four representative types of vegetation and a human settlement inside a shrub‐covered alpine valley (29°27′N, 91°40′E, 4000–5200 m a.s.l.) in the Lhasa mountains, Tibet, from September 2004 to January 2005. A total of 40 species of birds was recorded, six of which were summer breeders, one vagrant autumn migrant, 29 permanent residents, and four local wintering migrants. Latitudinally migrating taxa were absent. Of the 33 wintering species, 70% were alpine specialists. Patterns of distribution of species and individuals differed across habitats. The highest bird species richness was found in Rose–Barberry shrub where vegetation was most complex, and fruiting and seeding plants abundant. From autumn to winter, birds tended to aggregate in the human settlement for foods supplemented by local Buddhists; as a consequence this habitat contained the highest individual density. In terms of trophic guilds, plant‐eating birds were predominant in composition (65.8–75.8%) and numerically abundant (89.8–96.7%) in all the habitats. We concluded that vegetation diversity and food supply significantly influence species composition and individual abundance of the alpine bird community. For long‐term survival of the unique bird assemblage, we argue for protection of the shrub vegetation as it is difficult to regenerate in the harsh high‐altitude conditions.     

Factors controlling structural and floristic variation of riparian zones in a mountainous landscape of the western United States

We examined landscape patterns in the physical conditions and vegetative composition of montane riparian zones to identify their most important sources of variation. Information on plant species cover and on physical characteristics that occur at coarse, medium, and fine scales was collected for 144 riparian plots located throughout the Lake Tahoe Basin, which straddles the California-Nevada border in the western United States. Constrained and unconstrained ordination analyses were used to identify the most important correlates of physical form and plant species composition. Through multivariate analysis of environmental variables (principal components analysis), vegetation data (detrended correspondence analysis), and the combined relationship between the environmental and vegetation data (canonical correspondence analysis), we consistently found that the greatest variation occurred along a gradient of decreasing valley width, decreasing stream sinuosity, and increasing stream slope. Although surface characteristics reflected a 2nd important source of variation in physical conditions, plant species distribution was not strongly correlated with riparian surface conditions. Strong correlations among physical variables that occur at different scales, such as between valley form and geofluvial surface and between geofluvial surface and surface conditions, support the use of a physically based hierarchical framework for organizing riparian zones within the landscape. Such a hierarchical framework would be useful for interpreting patterns in riparian structure and process at different scales and could be applied to riparian zones in other mountain landscapes of the western United States and elsewhere. Moreover, our finding that riparian plant species composition is most strongly correlated with environmental variables that occur at coarse to moderate scales, most of which can be derived from existing data, supports the idea that modeling montane riparian community distribution using topographic and remotely sensed data could be useful; however, a large degree of species variation, unexplained by the variables we collected, indicates that other variables, perhaps disturbance regime, should be included in such a venture. Nomenclature: Hickman (1993).     

Natural variability of vegetation, soils, and physiography in the bristlecone pine forest of the Rocky Mountains

Pinus aristata Engelm. forest vegetation in Colorado was studied to determine vegetation composition and the relationship between vegetation and environment. Species percent cover, tree size class, and environmental variables were recorded for 49 plots. Previously collected data for 4 plots form New Mexico were included. Environmental variables included latitude, longitude, elevation, slope, aspect, topographic position, parent material, percent rock cover, mean rock size, litter depth, estimated plot age class, and evidence of anthropogenic disturbance. Soils were analyzed for texture, depth, and percent carbon and nitrogen. Pinus aristata foliage was analyzed for percent nitrogen and phosphorus. Direct and indirect gradient analyses (CANOCO) were used to determine environmental factors associated with community composition. Vegetation in P. aristata forests is influenced primarily by elevation and soil pH. Substrate, soil texture, topographic position, and geographic location are secondary factors. Six plant associations were identified using cluster analysis (listed in an elevational sequence from low to high): Pinus aristata/ Festuca arizonica Vasey, Pinus aristata / Festuca thurberi Vasey, Pinus aristata / Juniperus communis L., Pinus aristata / Vaccinium myrtilus L., Pinus aristata / Ribes montigenum McClatchie, and Pinus aristata / Trifolium dasyphyllum Torr. & Gray.     

Species composition, emergence, and habitat preferences of Trichoptera of the Sagehen Creek Basin, California, USA

An extensive study of larvae and adult Trichoptera of the Sagehen Creek basin. Sierra Nevada, California, USA, revealed 77 species representing 14 families and 41 genera. Twenty-six species were restricted to small water bodies (spring sources, seeps, spring streams, temporary ponds, and intermittent streams); 27 were restricted to Sagehen Creek, a second-order stream, and the mouths of two large spring streams. Similarity between species caught at black lights and those in emergence traps was 43%. There were two major peaks in adult emergence by species, midsummer and late summer-fall. A few species emerged during winter or throughout most of the year. The species composition of the community showed affinity with Oregon, the Great Basin, and the Rocky Mountains but very little similarity with the California Coast Range. Four of the most abundant species in the basin have very restricted distributions. Ecological separation of several groups of closely related species could be explained by major differences in larval habitats or by different emergence periods.     

Bryophytes on the calcareous soils of Mungo National Park, an arid area of southern central Australia

Bryophytes were found to be abundant as components of microbiotic soil crusts on the calcareous soils of Mungo National Park, an arid area of southern central Australia. Six sites that reflected differences in soils, topography, and vascular plant vegetation were studied. At each site bryophytes were abundant, both in terms of number of species present and percent ground cover. Number of species present did not differ significantly between sites, but percent bryophyte cover was lower at a site on sand dunes in mallee woodland and a site on a silcrete ridge than at the four other sites. Environmental factors (soil texture, pH, conductivity, nutrient status, vascular plant vegetation, light level, leaf litter, and fire frequency) appear to play a significant part in determining bryophyte distribution. Mosses that occur at Mungo are also widespread on calcareous substrates throughout arid southern Australia. Many of the bryophyte species present at Mungo also occur on limestones in high rainfall areas of eastern Australia. Environmental factors favoring bryophytic soil crusts in arid Australia are also present on limestones in high rainfall areas of eastern Australia and may account for tile presence of many arid zone bryophyte species on limestones. In Australia there appears to be a relationship between rainfall and the ratios of acrocarpous to pleurocarpous mosses, and thallose to leafy liverworts. Recognition of calcareous soils, widespread in arid areas of southern Australia, may be possible by assessing a combination of characteristics of bryophyte assemblages.     

Prey selection by Australian wasps of the genus Cerceris (Hymenoptera,Sphecidae)

Prey records are presented for 17 Australian species of the digger wasp genus Cerceris. Collectively beetles of 10 families were found to serve as prey. Several species appear to be specialists, taking only members of certain genera or subfamilies, while others accept members of several families. It is common to find several species nesting together in areas of suitable substrate. In such areas it is evidently to the advantage of all species either to specialize to ‘share’ the available beetle prey or to become generalists, taking advantage of whatever beetles of suitable size are abundant in the surrounding vegetation.     

Response of winterfat ( Ceratoides lanata ) communities to release from grazing pressure

Sixteen study sites were established in grazed and ungrazed stands of winterfat in Kane County, Utah. The area is located within the winter range of cattle and along U.S. Highway 89 between Kanab, Utah, and Page, Arizona. Road construction in 1957 dissected several winterfat communities, and following fencing part of the communities were released from grazing. Differences in species composition, vegetation, and soil characteristics between grazed and ungrazed sites were assessed. Major differences in site characteristics appeared due to the influence of winter grazing by cattle. Winterfat and Indian ricegrass showed increased cover on the nongrazed sites following release from grazing pressure. Winterfat also showed significant negative interspecific association patterns with all major species.     

Distribution and ecological characteristics of Lewisia longipetala (Piper) Clay, a high-altitude endemic plant

Lewisia longipetala (Piper) Clay is a high-altitude endemic found in the northern Sierra Nevada. The characteristics of 12 sites with L. longipetala , which represent all known populations, were studied to define habitat requirements of the species. Meso- and microscale characteristics of the habitat were examined, including characteristics of the associated plant community. Average plant size and plant density of L. longipetala were also determined for each population. Similar measurements were made on 6 populations of Lewisia pygmaea (A. Gray) Robinson, a more common Lewisia . Populations of L. longipetala that had larger plants and higher plant density were associated with gently sloped, north-facing sites that were near large, persistent snowbanks and had low vegetative cover. Plant species associated with populations of L. longipetala were similar among the 12 sites and were indicative of mesic, rocky alpine sites. These types of plant communities found near persistent snowbanks are often termed snow-bed vegetation. In contrast, L. pygmaea was found to be less site specific. Lewisia pygmaea was found adjacent to or interspersed with L. longipetala at 5 sites, but was found in areas associated with a higher percentage of herbaceous cover and a wider variety of species. This integration of ecological community information for L. longipetala populations contributes to the interim management and long-term monitoring of this species by providing needed information concerning its habitat and environmental specificity.     

Breeding behaviour and mating success of Phyllomedusa rohdei (Anura,Hylidae) in south‐eastern Brazil

Observations on the courtship behaviour, mating behaviour and mating success of a leaf‐frog, Phyllomedusa rohdei, population were conducted in a temporary flooded site of the Atlantic Forest, south‐eastern Brazil. We did not find any influence of size and body weight on male mating success across three scales: seasonal, nightly chorus and local groups (males found within 1?m of a mated pair). In addition, no evidence was found that female Phyllomedusa rohdei exhibit overt mate choice. The formation of mated pairs in P. rohdei occurred because males moved toward the females, rather than reverse. The only variable that was significantly related to male mating success was the number of nights of participation in chorus activity. Besides calling tactics, males showed active searching behaviour. There was no evidence of size‐ and mass‐assortative mating, and a high percentage of fertilization at all size and mass ratios of males and females was observed. Clutches in this species are produced in the same manner found in others members of Phyllomedusa; a purse‐like nest is made over water by folding a leaf around the egg mass (embryos and fluid‐filled capsules). Finally, we supply a list of several studies that examined the relationship between size or mass ratios of males and females in amplexus and its influence on fertilization rate, and show that size‐assortative mating in anurans is inconsistent (present in some species but not in other).     

Leafhopper assemblages on native and reseeded grasslands in southwestern Montana

Using sweep samples, we surveyed leafhoppers (Homoptera: Cicadellidae) on grassland sites in the Gallatin Valley of Montana during 1988 and 1991. We sampled 12 sites representing 2 habitat types defined by their dominant plant species in an undisturbed state ( Stipa comata / Bouteloua gracilis and Festuca idahoensis / Agropyron spicatum ). At half of the sites the native plant communities were present, whereas the remainder had been reseeded with either Agropyron spicatum (to replace the S. comata / B. gracilis assemblage ) or Bromus inermis (to replace the F. idahoensis / A. spicatum assemblage). We found at least 66 species of leafhoppers among 44,428 adults collected. Seven taxa comprised 83% of all individuals collected: Doratura stylata (26%), Ceratagallia spp. (18%), Endria inimica (17%), Orocastus perpusillus (7%), Sorhoanus spp. (6%), Athysanella spp. (5%), and Psammotettix lividellus (4%). Sites with similar vegetation had broadly similar leafhopper assemblages, and assemblages differed most between the relatively xeric Stipa comata / Bouteloua gracilis sites and the more mesic sites dominated by Bromus inermis . The composition of a leafhopper assemblage at a site tended to be more similar to those on noncontiguous sites with the same overall vegetation than to those on contiguous sites with different vegetation. These patterns are likely related to the fact that many Cicadellidae are host specialists. In fact, variation in abundance of some of the most common leafhopper taxa on our sites was correlated with the percent cover of their known host plants. Our analyses of the leafhopper assemblages generally support the contention that terrestrial plant associations are among the more useful indicators of insect community composition.     

Riparian vegetation along the middle Snake River, Idaho: zonation, geographical trends, and historical changes

A baseline study was conducted on an 83-km free-flowing reach of the Snake River between Swan Falls Dam and the Idaho-Oregon border. The research had 2 components: (1) field characterization and inventory of existing riparian flora, vegetation, and environment (soils, topography, streamflow), and (2) determination and mapping, using a geographic information system, of historic changes in riparian vegetation based on a time series (1938-39, 1957, 1969, 1987) of aerial photographs. The flora was diverse, with 185 species of vascular plants identified, 63 of which were exotics. Vegetation was structured vertically along the riverbank gradient into lifeform-defined habitat types: emergent, riparian shrub-forb, tree, transitional grass-shrub, and upland. Riverbank seepage, probably of agricultural origin, blurred zonation patterns on some sites and added species to the overall flora. Upstream-downstream differences existed in the physical characteristics and vegetation of river subreaches. Coverage of riparian woodland, island riparian and total riparian vegetation, and area of islands increased since the 1930s, with the greatest changes in the 1969-1987 interval. Possible contributing facts were (1) significant declines in annual minimum flows since the 1950s, (2) decreases in peak flows following the completion of Swan Falls Dam and some upstream dams since the 1920s, (3) introduction and spread of exotic tree species ( Elaeagnus angustifolia and Tamarix spp.) and (4) possible effects of intensive agriculture on river sediment load and soil nutrients. The introduction and proliferation of purple loosestrife ( Lythrum salicaria ) could have considerable future effects on vegetation-channel dynamics in the middle Snake River.     

Insects and spiders on snowfields in the Cairngorms,Scotland

Summary

An account is given of seven collections of insects and spiders made in summer 1979 on snowfields above 1100m elevation in the Cairngorm mountains, Scotland. In one comprehensive collection 278 recently deposited animals representing 35 species were obtained in 25 m²; the other collections were selective. A high proportion of the roughly 700 specimens obtained have been identified. They represent at least 130 species, including 12 species of Araneae and 34 species each of Coleoptera, Hymenoptera and Diptera. Only 10 species are known to be restricted to ‘montane’ environments and it is concluded that the composition of fallout on mountain snowfields, both in Britain and elsewhere, reflects mainly the nature of the vegetation, and thus of the insect communities, in upwind areas at lower elevations. The discussion concerns the significance of fallout as a resource for high altitude communities and as a manifestation of long-distance migration and potential gene flow among populations of terrestrial arthropods.     

Anuran assemblage in a rice field agroecosystem in the Pantanal of central Brazil

Agricultural practice is an important factor that threatens biodiversity. However, modified habitats such as irrigated rice fields could serve as potential refuges for several species of amphibians. This study describes the composition of an anuran assemblage in an irrigated rice field system in the Pantanal floodplains of central Brazil. The low species richness found in rice fields and neighbouring habitats can be interpreted as resulting from the structural limitations of a modified environment. Flooding occurs for longer periods than in natural areas and leads to a lack of dry space, hindering the presence of terrestrial anuran species. Furthermore, the absence of herbaceous vegetation and shrubs in cultivated fields prevents the establishment of species of large tree frog. A positive correlation was found between rainfall and richness, although the abundance of some species did not fit this relationship. The present study suggests that only anuran species that are generalists and highly resilient will survive as the natural wetlands are transformed into irrigated rice plantations.     

Diet and feeding behaviour of the Neotropical parrot snake (Leptophis ahaetulla) in northern Brazil

Specimens (289) of Leptophis ahaetulla from northern Brazil and western Maranhão were examined for the composition of stomach contents. Most prey items were tree frogs, especially those of the family Hylidae (90%). Most of the anurans identified belong to the Scinax ruber species group (27%) and Scinax sp. (25%). Prey size was significantly related to snake length but not to head length. There was no significant difference related to sex in either case. Both sexes preyed on small to medium‐sized items (3–10% of snake snout–vent length). Leptophis ahaetulla seems to manipulate captured prey before ingestion since most of the prey items (83.6%) were swallowed head‐first. Leptophis ahaetulla is primarily diurnal and semi‐arboreal, inhabits disturbed and undisturbed forest, and forages primarily on the ground and in fallen vegetation, where its prey items are likely to be found at rest.     

Effects of prescribed fall burning on a wetland plant community, with implications for management of plants and herbivores

An important contemporary challenge for adaptive resource management is assessing both the direct and indirect effects of management activities by designing appropriate monitoring programs and sound analysis methods. Here we evaluate the effects of prescribed fall burning on a wetland plant community that is managed primarily for spring-migrating geese. During late fall in 2 consecutive years, we burned vegetation in 4 replicate blocks (2.3 ha each) that traversed a natural moisture and associated vegetation gradient. We used ordination, gradient analysis, and contingency table analysis to evaluate how annual changes in relative abundance of plants were affected by burning as well as other important ecological factors. Burning increased species diversity of plants, especially in the 2 wetter vegetation zones, but had no effect on species richness or on the proportion of native plant species. Wetland plant species responded to prescribed burning independently, and their response often differed by vegetation zone and with annual variation in flooding. Burning enhanced the abundance of native foxtail barley ( Hordeum jubatum ) and reduced the abundance of introduced swamp timothy ( Crypsis shoenoides ). Saltgrass ( Distichlis spicata ), a native plant species, was usually less abundant following burning, although the level of response was different for each of the 3 vegetation zones. Two other introduced plant species, quackgrass ( Elytrigia repens ) and reed canarygrass ( Phalaris arundinaceae ), were less abundant after fall burning, especially when spring flooding was more extensive. Wild geese using the experimental blocks for feeding clearly preferred burned sites, suggesting that fall burning can enhance wetland use by geese during spring. Given that simple manipulations such as burning and flooding of a wetland system may often produce complex results, we suggest that on-going management schemes be regularly evaluated with field experiments such as those conducted in this study.     

Bird use of riparian vegetation along the Truckee River, Califonia and Nevada

The Truckee River in California and Nevada is subject to diverse water regimes and a corresponding variety of flow rates. Original riparian vegetation has been altered by these variable flow rates and by a variety of human uses resulting in loss of native riparian vegetation from its historic extent. We conducted bird surveys along the Truckee River during spring 193 to (1) determine relationships between birds and the present vegetation; (2) determine the importance of different vegetation types to sensitive bird species that have declined recently in the western United States due to competition from exotic plant species, cowbird ( Molothrus ater ) parasitism, reduction in nesting habitat, or other unidentified reasons; and (3) establish a monitoring program and collect baseline data for future comparisons. The most frequently detected bird species throughout the study was the Brown-headed Cowbird. The greatest number of bird species (98 of 116) was found in the native mixed willow ( Salix spp.) riparian scrub vegetation type. We recommend protecting the remaining native riparian vegetation types for bird habitat along the Truckee River.