A comparison of riparian condition and aquatic invertebrate community indices in central Nevada

The importance of maintaining healthy riparian communities to sustain natural stream processes and function is well documented. Land management agencies in the West are currently developing methods to assess and monitor riparian community condition to adapt land use practices that would better protect rangeland ecosystems. To determine whether these methods also provide an indication of abiotic and biotic stream condition, we compared the classification system of riparian communities developed by the U.S. Forest Service (USFS) to physical parameters of stream condition and to aquatic invertebrate community assemblages. Thirty-three sites in 19 different streams of the Toiyabe Range in central Nevada were measured for water quality, substrate characteristics, and fish abundance and diversity. We sampled aquatic invertebrates and calculated community indices based on environmental tolerance levels, taxonomic diversity, and abundance of sensitive taxa. USFS personnel classified these sites by dominant riparian plant community type (meadow, willow, or aspen) and ecological status (low, moderate, or high) using plant abundance data, rooting depth, and soil infiltration to determine similarities to potential natural communities. Riparian condition indices as well as community diversity were significantly correlated to proportions of fine and small-diameter substrate in streambeds. Accumulation of silt was significantly related to plant community type, with meadow sites expressing highest proportions. Further examinations indicated that 2 of 6 invertebrate community indices were significantly related to ecological status, with highest diversity levels occurring mainly in willow- and aspen-dominated sites in moderate ecological condition. Nevertheless, we show that several other environmental variables, including substrate characteristics, dissolved oxygen, water temperature, and species richness of fish communities, were more strongly and consistently related to invertebrate assemblage patterns. Our results demonstrate that information on aquatic invertebrates and stream condition could augment the existing riparian classification system and provide useful monitoring tools to more thoroughly examine ecosystem health in rangelands.     

A sagebrush community type classification for mountainous northeastern Nevada rangelands

Vegetation characteristics of 15 sagebrush community types identified on the Humboldt National Forest, northeastern Nevada, are described. A total of 218 plant species were found over the 372 relatively undisturbed rangeland communities sampled. The dominant plant families encountered were the Asteraceae (45 taxa), Poaceae (32 taxa), Scrophulariaceae (14 taxa), and the Fabaceae (12 taxa). Average annual dry weight production of the community types ranged from about 400 kg/ha/yr on types with Artemisia nova as the dominant sagebrush species to 1,200 kg/ha/yr on some A. tridentata ssp. vaseyana community types. A general increase in species richness and vegetation plus litter ground cover was observed within community types as the dominant sagebrush species changed from A. nova to A. arbuscula to A. longiloba to A. tridentata spp. tridentata to A. tridentata ssp. vaseyana . Major differences in plant species production and constancy exist between the sagebrush community types studied.     

Vegetation characteristics of mountainous northeastern Nevada sagebrush community types

Vegetation characteristics of 15 sagebrush community types identified on the Humboldt National Forest, northeastern Nevada, are described. A total of 218 plant species were found over the 372 relatively undisturbed rangeland communities sampled. The dominant plant families encountered were the Asteraceae (45 taxa), Poaceae (32 taxa), Scrophulariaceae (14 taxa), and the Fabaceae (12 taxa). Average annual dry weight production of the community types ranged from about 400 kg/ha/yr on types with Artemisia nova as the dominant sagebrush species to 1,200 kg/ha/yr on some A. tridentata ssp. vaseyana community types. A general increase in species richness and vegetation plus litter ground cover was observed within community types as the dominant sagebrush species changed from A. nova to A. arbuscula to A. longiloba to A. tridentata spp. tridentata to A. tridentata ssp. vaseyana . Major differences in plant species production and constancy exist between the sagebrush community types studied.     

Beetles from the environs of Lake Powell in southern Utah and northern Arizona

Sixty-eight species of beetles of 14 families were collected in pit traps in 12 major vegetative communities during environmental monitoring studies in the summers of 1971 to 1973 in southern Utah and northern Arizona. Seasonal and plant community differences and correlations in population and composition were noted for the 16 sites studied. Highest populations and the most species were found in a grass community, but occurred in different months in each of the three years. Lowest populations were found in a Coleogyne community, and fewest species in an Artemisia- grass community.     

Factors linked to temporal and spatial variation in the metazoan parasite communities of green jack Caranx caballus (Günther 1868) (Pisces: Carangidae) from the Pacific coast of Mexico

ABSTRACT

Biotic or abiotic factors responsible for temporal or spatial variation in metazoan parasite communities of the green jack Caranx caballus were studied over a nine-year period using samples collected at locations along the south-central Pacific coast of Mexico. A total of 708 fish were collected from six locations between December 2009 and October 2017. Thirty-two parasite species were identified: three Monogenea, nine Digenea, two Cestoda, five Nematoda, eight Copepoda, and three Isopoda. At the component community level, parasite species richness varied significantly from seven (Zihuatanejo 2016) to 18 (Acapulco Bay 2011). The component communities and infracommunities of C. caballus exhibited a similar pattern: low species numbers, low diversity, and dominance by a single species (mainly the monogenean Pseudomazocraes selene or the digenean Bucephalus varicus). Parasite community structure and species composition varied between locations and/or sampling years. The main factors responsible for these variations were host traits such as feeding behaviour and body size, the occurrence of a set of distinctive parasite species, and possible variations in the availability of infected prey between locations.     

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.     

Naturalization and habitat relationships of bitter nightshade ( Solanum dulcamara ) in central Utah

Ten plant communities containing bitter nightshade ( Solanum dulcamara ) were studied and the ecology and naturalizing relationships of bitter nightshade in central Utah area were investigated. Biotic and abiotic factors from each area were statistically analyzed. The data indicated that bitter nightshade was negatively correlated (P       

Macrobenthic communities in water bodies and streams of Svalbard,Norway

Diversity of macrobenthic communities was studied from water bodies and streams of Spitsbergen, Svalbard archipelago, Norway. In total 162 quantitative samples from different regions of Spitsbergen were analysed in relation to environmental variables. Macrobenthic communities were found on all kinds of substrates (except for the periglacial zone), representing a wide range of biological communities: solid-bottom, soft-bottom, macrophytes and small brook associated. However, taxonomical structure is very simplified, with particular dominance of the Chironomidae family. Chironomid larvae dominated highly in diversity, abundance and biomass. Overall macrobenthic communities were characteristic, with remarkable dominance of one species and general omnipresent taxonomical scarcity (average 2.8 species per sample). In total we found 30 taxa. We distinguished 16 types of macrobenthis communities, with characteristic dominance of different taxa: chironomids (11 types), oligochaete Enchytraeidae family (3), caddisfly Apatania zonella (1) and gammarid amphipod Gammarus setosus (1). Regarding environmental variables, temperature and pH had the most significant influence on the abundance of macrobenthic organisms. It is hypothesized that the structural convergence of different types of communities is their common response to extreme high Arctic living conditions. On the other hand, different chironomids may dominate in the same habitats and water bodies. This gives the effect of lower average similarity of communities and high β-diversity.     

The influence of habitat features on amphibian distribution in Northeastern Greece

Environmental and isolation variables relating to abundance of breeding amphibians, species richness and community structure at different spatial scales were examined in the Dadia-Lefkimi-Soufli Forest National Park, Evros, Greece. Logistic regression and a generalized linear model were used to relate several habitat characteristics to species occurrence and species richness. The community structure responses to breeding-pond features were examined at four spatial scales using canonical correspondence analysis (CCA). The richest communities live in low-altitude ponds, with stony or clay bottoms, high solar exposure and abundant submerged and floating vegetation. The CCA models were significant (p < 0.005) and revealed the influence of altitude, percentage of field and broadleaf forest coverage, and number of water bodies on amphibian species assemblages at all four spatial scales. There is a specific need for holistic management of amphibians that will consider habitat connectivity, particularly between aquatic and terrestrial habitats, at a larger, more interconnected scale.     

Influence of soil and site characteristics on Palouse prairie plant communties

The structure of grassland communities can vary widely in response to heterogeneous habitat variables. In this study we document plant communities, soil types, and site characteristics for 12 Palouse prairie remnants in southeastern Washington and northern Idaho. We used general linear models to test the predictive value of 6 biophysical variables (slope, aspect, distance from edge, edge type, vegetation structure, and soil type) on 3 plant community metrics: species richness, Simpson’s diversity index, and the dominance of exotic species. From full models including all variables, we used Akaike’s information criterion (AIC) to select the best model for each metric. Aspect and vegetation structure were significant predictors of species richness ( R 2 = 0.08) and diversity ( R 2 = 0.09), while aspect, soil type, distance from edge, and edge type (type of adjacent matrix habitat) influenced the dominance of exotic species ( R 2 = 0.28). Additional soil sampling determined that the depth to a restrictive layer also had significant impacts on the dominance of exotic species ( R 2 = 0.31). This study confirms that biophysical characteristics influence Palouse prairie plant communities and may help set research and conservation priorities for isolated and uninventoried remnants.     

Vegetative and edaphic factors affecting abundance and distribution of small mammals in southeast Oregon

The relationships between vegetative and edaphic habitat factors and the local distribution and abundance of small mammals on Malheur National Wildlife Refuge, Harney County, Oregon, were examined between July 1973 and June 1975. Of 16 species of small mammals captured, deer mice ( Peromyscus maniculatus ), montane voles ( Microtus montanus ), Great Basin pocket mice ( Perognathus parvus ), and least chipmunks ( Eutamias minimus ) comprised 90.1 percent of the individuals. The physiognomy of the vegetation was a factor in the distribution of rodent species other than deer mice. Pocket mice and chipmunks were restricted to the communities dominated by sagebrush ( Artemisia tridentata ) or greasewood ( Sarcobatus vermiculatus ). Population densities of pocket mice and chipmunks were significantly related to edaphic factors such as soil depth, texture, and strength, which may have affected the construction and stability of burrows. Montane voles occurred only in marsh or grassland communities. Population densities of voles were directly correlated with the amount of cover and inversely correlated with its patchiness. Deer mice were the most common species encountered and occurred in all but the grassland communities. The density of this species was related to vegetative or edaphic factors only seasonally or in certain habitats, and few generalizations could be made.     

Forest-floor treatments in Arizona ponderosa pine restoration ecosystems: no short-term effects on plant communities

Leaf litter accumulation during fire exclusion and increases in tree density in postsettlement southwestern Pinus ponderosa forests may limit the establishment of understory vegetation. We performed an experiment in P. ponderosa forests of northern Arizona to ascertain plant community responses to forest-floor scarification and Oi removal on thirty-six 100-m 2 plots overlaid on an existing ecological restoration experiment that involved tree thinning and prescribed burning. Constrasting with findings from many other forest types, forest-floor treatments had no effect on community diversity or composition during the 2-year experiment. S?rensen similarities were as high as 97% between posttreatment years within treatments; and successional vectors also provided little indication that treatments may appreciably affect longer-term successional trajectories. Lack of response to these fairly drastic treatments is surprising given these forests' exceptionally heavy Oi horizons and large proportions of conifer litter. Apparently shading, belowground competition for water or nutrients, or other tree-associated factors more strongly limit understory communities than does leaf litter. Based on sparse A-horizon seed banks averaging &#60;300 seeds ? m –2 and limited aboveground vegetation, we hypothesize that seed shortages, particularly for native perennials, also partly precluded a treatment response. Because extensive unvegetated areas at these restoration sites may be colonized by exotics, conservative management strategies could include testing the seeding or outplanting of desirable native species as an option for filling unoccupied microsites. Reporting of "no treatment effect" experiments such as this one is important to avoid biasing meta-analyses, as is future research to clarify combinations of factors limiting understory communities. Increased understanding of these limiting factors may lead to identification of other treatments that promote recovery of native species during ecological restoration in this region.     

Water stress and hybridization between Quercus gambelii and Quercus grisea

The historical and environmental forces involved in determining the geographic location of plant hybrid zones have long been of interest. Often hybrid zones appear to be intimately tied to the environment, yet because many abiotic factors covary it is often difficult to understand which are truly the most important in maintaining the position and structure of a hybrid zone. This study uses empirical data and modeling analyses to examine whether abiotic factors are responsible for the location and structure of an oak ( Quercus ) hybrid zone and, if so, which factors are the most important. Specifically, leaf trait measurements and ecological niche models were used to test the hypothesis that water availability plays a primary role in promoting and maintaining the location of hybridization between 2 species. Leaf trait analyses and ecological niche models both supported the hypothesis that water availability determines the location and structure of the hybrid zone. These findings lend support for the general importance of environmental factors in determining hybrid zone location and structure. Furthermore, they demonstrate how functional trait analyses and predictive ecological niche models can be used in future hybrid zone research.     

Spatial patterns of plant communities and differential weathering in Navajo National Monument, Arizona

Vegetation patterns in Navajo National Monument, Arizona, were studied over a five-year period from 1977 to 1981. Twelve distinct plant community types occur within the boundaries of the park. These communities are characterized and the dominant plant species of each are recorded. The relationships of parent material, soils, and moisture to plant communities are also discussed. It appears that discrete communities occupy soils of different characteristics, particularly with respect to amount of weathering of parent material. &nbsp;&nbsp;&nbsp;     

Potential impacts of logging on intertidal infaunal communities within the Kitimat River estuary

ABSTRACT

Efficiently evaluating industrial activities plays an essential role in determining the extent to which human–ecosystem interactions may lead to species loss, disrupted community dynamics, and degraded ecosystems. Intertidal habitats offer a unique opportunity in this regard, as they are species rich ecosystems that exhibit rapid community turnover and pronounced responses to ecological disturbances. In an attempt to use these dynamic communities to identify the impact storage of harvested logs is having on the Kitimat River estuary, surveys evaluating the biotic and abiotic conditions within surrounding mudflats were conducted. The intertidal mudflats of the Kitimat River Estuary varied spatially and temporally, and with differences in the infaunal community, as well as the abiotic sediment conditions between reference mudflats, and mudflats potentially impacted by logging activities. While these differences were pronounced, we cannot at this time link these differences to the logging activities at impacted sites. We also observed evidence that suggests that the infaunal community of these intertidal mudflats have changed substantially since the 1970s, with the establishment of a community of polychaetes, as well as the appearance of the invasive clam Mya arenaria, and the invasive Cumacea Nippoleucon hinumensis. Beyond contrasting impacted and reference mudflats, the current health of these mudflats, as indicated by the infaunal community assemblage, is currently unclear. More research is required to determine if organic enrichment has occurred at these habitats, as well as to further elucidate the current health of these intertidal mudflats.     

Ant assemblages in intact big sagebrush and converted cheatgrass-dominated habitats in Tooele County, Utah

Biological invasions are one of the greatest threats to native species in natural ecological systems. One of the most successful invasive species is Bromus tectorum L. (cheatgrass), which is having marked impacts on native plant communities and ecosystem processes. However, we know little about the effects of this invasion on native animal species in the Intermountain West. Because ants have been used to detect ecological change associated with anthropogenic land use, they seem well suited for a preliminary evaluation of the consequences of cheatgrass-driven habitat conversion. In our study, we used pitfall traps to assess ant community assemblages in intact sagebrush and nearby cheatgrass-dominated vegetation. Ant abundance was about 10-fold greater in cheatgrass-dominated plots than in sagebrush plots. We also noted differences in diversity and evenness between habitat types at both the species and the functional-group levels of organization. At the species level, Shannon’s diversity index was greater in sagebrush plots than in cheatgrass-dominated plots. However, at the functional-group level, Simpson’s and Shannon’s diversity indices and the Brillouin evenness index were greater in cheatgrass-dominated plots than in sagebrush plots. Further, common species / functional groups tended to be more abundant while less common species / functional groups tended to be less abundant in cheatgrass-dominated plots compared to intact sagebrush plots. Patterns appear to be at least partially related to resource availabilities. This initial survey of ant communities from intact-native and altered vegetation types may be indicative of similar trends of biodiversity shifts throughout the Intermountain West where cheatgrass has successfully replaced native species. We also discuss the implications of ant communities on land management activities, specifically in the context of aridland restoration.     

Habitat requirements for Erigeron kachinensis , a rare endemic of the Colorado Plateau

Erigeron kachinensis is a rare endemic of the Colorado Plateau in southeastern Utah. This perennial composite grows in small, isolated populations at seeps and alcoves arising along canyon walls in Cedar Mesa Sandstone substrates. Characteristics of six Erigeron kachinensis sites in Natural Bridges National Monument, San Juan County, Utah, were studied to determine habitat requirements for this species. Sites were analyzed with respect to geology, soil chemistry, physical properties, and vegetational characteristics. The alcoves studied were very saline, often with soil surfaces covered with a white crust of salt. Living cover was enhanced by perennially moist soils, diminished amounts of solar radiation, soil salinity, and above-average amounts of available soil phosphorus. Kachina daisy vegetative growth appears to be favored by these same abiotic factors. The most commonly associated plant species on E. kachinensis sites were Aquilegia micrantha, Calamagrostis scopulorum, Zigadenus vaginatus, and Erigeron kachinensis . These species and the daisy accounted for more than 75% of the total living cover in the alcoves studied. A principal components analysis procedure was developed for evaluating site suitability for Erigeron kachinensis . This daisy has been successfully introduced to a site selected using that model.     

Parasite community of the golden cownose ray Rhinoptera steindachneri Evermann and Jenkins 1891 (Chondrichthyes: Myliobatidae), in Acapulco Bay,Guerrero, Mexico

The parasite community of the ray Rhinoptera steindachneri from Acapulco Bay was examined and quantified; analyses were based on the sex of the host and the date of sampling. A total of 171 specimens of R. steindachneri were examined during July–August of 2010, and May and July of 2012. Twenty-one species of parasites were found: three species of Monogenea; eight adult and one larval species of Cestoda; one larval species of Nematoda; five species of Copepoda; two species of Isopoda; and one species of Hirudinea. Cestodes had the greatest species richness (43% of the total species), followed by the copepods (24%). Two species of cestode, Glyphobothrium sp. and Rhinebothrium sp., were collected only from adult rays. At the component community level, species richness showed statistically significant variation between 13 and 16 species, which is similar to previous reports for other species of rays. The parasite component communities and infracommunities of R. steindachneri exhibited similar patterns: high species number and low numerical dominance by a particular species of parasite. The differences of body size of male vs. female rays, and a change in diet and feeding behaviour with the age of R. steindachneri, are likely important factors in the structuring of their parasite communities.     

Tundra vegetation of three cirque basins in the northern San Juan Mountains, Colorado

The vegetation of three alpine cirque basins in the northern San Juan Mountains of southwestern Colorado was inventoried and analyzed for the degree of specificity shown by vascular plant communities for certain types of habitats identified as representative of the basins. A total of 197 vascular plant species representing 31 families was inventoried. Growth forms of all species were noted and a growth form spectrum for all of the communities was derived. The caespitose monocot and erect dicot growth forms are the most important growth forms among the community dominants. The most common growth form among all species is the rosette dicot. &nbsp;&nbsp; &nbsp;&nbsp;     

Habitat relationships of Glaux maritima in central Utah

Thirty-five study sites were established in the meadow communities surrounding Utah Lake in central Utah. The study sites ranged across several community types. Glaux maritima was found in all sites but varied as to its ecological importance in these communities. Sixteen soil factors were measured relative to the stands studied. Cover of Glaux maritima correlated with parts per million sodium and total soluble salts in the soil. No other factors correlated significantly with the cover of Glaux maritima. Glaux maritima occupied only those sites with high levels of moisture throughout the growing season. The high moisture levels came from springs, seeps, elevated water tables, and early seasonal inundation. High levels of Glaux maritima cover corresponded to low numbers of species in the habitat. &nbsp;&nbsp;