Kenneth G. Gerow

Effort Needed to Estimate Species Richness in Small Streams on the Great Plains in Wyoming

Abstract Our objective was to define the sampling effort needed with electrofishing gear or seines to capture all of the fish species present in sampling reaches on small streams of the Great Plains. The study was conducted because of recent interest in assessing the status of fishes in small streams of the Great Plains, which have lacked information that would enable sampling protocols to be developed. Based on the wetted widths (2–11 m) of sampling reaches, we defined the sampling effort needed to capture 90% and 100% of the fish species present. For electrofishing gear, sampling three 50-m-long units of the stream assured capture of 90% of the fish species present, and sampling four 50-m-units assured capture of 100%. When seines were used, sampling of four 50-m-long units captured 90% of the fish species present, and six 50-m-long units assured capture of 100%. As wetted width increased, the length of stream that needed to be sampled remained relatively constant; accordingly, the surface area of strea...

Changes in cytoplasmic volume are sufficient to drive spindle scaling.

Scaling Spindle Size The difficulty of modulating cell size in vivo has made it hard to test hypotheses for organelle size scaling during development. To this end, Hazel et al. (p. 853) and Good et al. (p. 856) developed microfluidic systems in which cytoplasmic extracts are encapsulated in compartments with definable size. The size of mitotic spindles assembled within cell-free extracts scaled with the volume of the compartment within which the spindle assembled. The findings suggest that the diminished availability of cytoplasmic components, notably tubulin, concomitant with cell size reduction, prescribes a smaller spindle size. Microfluidic techniques reveal how mitotic spindle size is regulated by titratable cytosolic factors. The mitotic spindle must function in cell types that vary greatly in size, and its dimensions scale with the rapid, reductive cell divisions that accompany early stages of development. The mechanism responsible for this scaling is unclear, because uncoupling cell size from a developmental or cellular context has proven experimentally challenging. We combined microfluidic technology with Xenopus egg extracts to characterize spindle assembly within discrete, geometrically defined volumes of cytoplasm. Reductions in cytoplasmic volume, rather than developmental cues or changes in cell shape, were sufficient to recapitulate spindle scaling observed in Xenopus embryos. Thus, mechanisms extrinsic to the spindle, specifically a limiting pool of cytoplasmic component(s), play a major role in determining spindle size.

Statistical Issues in Resource Selection Studies with Radio-Marked Animals

Publisher Summary Radiotelemetry studies of animals are designed to provide insights into resource selection so that managers can obtain, protect, and restore resources used by animals. A common approach to study resource selection using radiotelemetry data involves a comparison of resource use to resource availability. Resource selection occurs when resources are used disproportionately to availability. This chapter provides a review of the study designs, statistical issues, and analytical techniques used to study resource selection and provide practical guidance for biologists, resource managers, and others conducting studies of resource selection via radiotelemetry. It also focuses on statistical issues of scale, techniques for defining resource use and availability, pooling observations, independence of relocations, and variable and model selection and how these factors affect inference in resource selection studies. In most cases, the goal of a resource selection study is to make statistical inferences to a population of animals the radio-marked sample is assumed to represent. This is achieved by considering the radio-marked animal as the experimental unit to avoid pseudoreplication, thus reducing dependency problems when individual relocations are treated as experimental units.

Municipal solid waste generation in Kathmandu, Nepal

Waste stream characteristics must be understood to tackle waste management problems in Kathmandu Metropolitan City (KMC), Nepal. Three-stage stratified cluster sampling was used to evaluate solid waste data collected from 336 households in KMC. This information was combined with data collected regarding waste from restaurants, hotels, schools and streets. The study found that 497.3 g capita(-1) day(-1) of solid waste was generated from households and 48.5, 113.3 and 26.1 kg facility(-1) day(-1) of waste was generated from restaurants, hotels and schools, respectively. Street litter measured 69.3 metric tons day(-1). The average municipal solid waste generation rate was 523.8 metric tons day(-1) or 0.66 kg capita(-1) day(-1) as compared to the 320 metric tons day(-1) reported by the city. The coefficient of correlation between the number of people and the amount of waste produced was 0.94. Key household waste constituents included 71% organic wastes, 12% plastics, 7.5% paper and paper products, 5% dirt and construction debris and 1% hazardous wastes. Although the waste composition varied depending on the source, the composition analysis of waste from restaurants, hotels, schools and streets showed a high percentage of organic wastes. These numbers suggest a greater potential for recovery of organic wastes via composting and there is an opportunity for recycling. Because there is no previous inquiry of this scale in reporting comprehensive municipal solid waste generation in Nepal, this study can be treated as a baseline for other Nepalese municipalities.

Impacts of Exotic Annual Brome Grasses (Bromus spp.) on Ecosystem Properties of Northern Mixed Grass Prairie

Abstract Annual brome grasses, Bromus japonicus and B. tectorum, are common exotic plants in the northern mixed grass prairies of North America. As annuals, the bromes die following seed set in late spring, creating a functional difference between them and native perennial grasses because perennials continue to maintain live shoots into the summer and root systems throughout the year. Our objective was to investigate how this functional difference alters ecosystem properties over the growing season, including soil moisture content, quantity of plant biomass, litter accumulation and aboveground litter decomposition. We conducted an experiment in which the annual bromes were removed from treatment plots to compare with adjacent reference plots. While this experiment served as a direct test for brome impacts, observational plots also were sampled to determine if impacts were apparent in an unmanipulated system. A litter bag experiment was conducted to evaluate impacts of brome grasses on decomposition. Experimental removal of brome grasses led to more biomass both above- and belowground at the end of the growing season, and high brome observational plots averaged 28% less aboveground biomass and 40% less belowground biomass than low brome plots. In contrast, removal of brome grasses did not produce a consistent impact on soil moisture content between sites or among months, and none of measurable impacts from the removal experiment were significant in the observational study. Bromes slowed decomposition of aboveground litter at both sites. However, the overall impact on litter accumulation was only significant at one site, where brome removal reduced surface litter in the latter half of the growing season and high brome observational plots averaged 36% more litter than low brome plots. This study demonstrates how the brome functional type alters several properties in an ecosystem traditionally dominated by perennial grasses.

A digital land cover map of Wyoming, USA: a tool for vegetation analysis

Abstract. A Landsat Thematic Mapper (TM) based digital land cover map has been created for the state of Wyoming, USA, at moderate spatial (l-km2 minimum mapping unit) and high typal (41 land cover types) resolution as part of the Wyoming Gap Analysis Program (WGAP). This map presents opportunities for regional characterization of land cover, especially vegetation, and for examination of ecological phenomena that manifest themselves over large areas. Using the digital land cover data, we describe Wyoming vegetation and examine positions of three prominent physiognomic transitions in Wyoming: the elevation of upper and lower treeline, and the position of the biogeographic boundary between shruband grass-dominated vegetation. By area, the three leading land cover types in Wyoming are Artemisia tridentata ssp. wyomingensis sagebrush (33.4 %), mixed grass prairie (17.5 %) and Pinus contorta forest (6.5 %). Average upper-treeline elevation in Wyoming is 2947 m, and decreases with increasing latitude at an average rate of about 0.5 m/km, less than the rate of about 0.9 m/km reported by Peet (1978) for a gradient from Mexico to Canada. Lower-treeline occurs at an average elevation of 2241 m, and decreases with increasing latitude and with southerly aspect. In Wyoming, shrub-dominated communities are more likely to occur than grass-dominated communities as summer precipitation decreases below 282 mm. All of these relationships are subtle, and it appears that for particular areas, local factors are more important than regional climatic trends in explaining the position of phytogeographic boundaries.

An evaluation of a mammalian predator, Martes americana, as a disperser of seeds

Effective animal dispersers of fruit seeds have been primarily considered to be herbivorous birds and bats. To evaluate the seed-dispersal efficacy of a mammalian predator, we studied the American marten (Martes americana) as a disperser of two blueberries (Vaccinium alaskaense, V. ovalifolium) and salmonberry (Rubus spectabilis) on Chichagof Island, Alaska, by combining data on movement speed and gut-passage speed. Martens traveled a median distance of 133 m in 0-1 h and 501 m in 4-5 h. Median gut-passage time for V. alaskaense was 4.1 h and for R. spectabilis was 4.6 h. Median dispersal distances for both berry species were estimated to be about 500 m. In old-growth stands, V. ovalifolium seeds cleansed of pulp did not germinate differently than seeds cleansed of feces, suggesting that the marten gut does not harm germination. Vaccinium spp. seeds germinated better if cleansed of feces than if inside intact berries, indicating that passage through the gut of a marten improves germination over fruit fall alone. For V. alaskaense in old growth, seeds cleansed of feces germinated less than seeds cleansed of pulp, but still had high (41%) germination rates. We conclude that American martens move ingested seeds long distances, some of the highest reported for a mammal. This efficacy is in part due to the predatory adaptations of martens. Predators may have heretofore unrecognized value in shaping landscape patterns of berry-producing plants.

Temporal Variation in Trout Populations: Implications for Monitoring and Trend Detection

Abstract We summarized the temporal variation in populations of inland trout Salmo, Salvelinus, and Oncorhynchus spp. from streams in North America and determined the statistical power to detect trends over time. The coefficients of variation in abundance averaged 49% (SD = 27%; range = 15-108%) over time for all ages of trout. Temporal variation was lower when more age-classes were monitored, but whether abundance or biomass was more variable differed among populations. Detecting population trends was difficult when using the traditional α = 0.05 criterion. For example, detecting a 5% annual decline with good power (1 - β ≥ 0.80) would require about 20 years if only one site were monitored. Even when α was relaxed to 0.20, 15 years were required to detect a 5% annual decline when the variation was average. Using a network of sites improved the ability to detect changes: A 5% annual decline at α = 0.05 could be detected in 10 years when 30 sites were monitored. For high-value populations, it may require r...

Introduced Lake Trout Produced a Four-Level Trophic Cascade in Yellowstone Lake

Abstract Introduction of lake trout Salvelinus namaycush into a system can add a trophic level, potentially affecting organisms at lower trophic levels. Similar to many lakes and reservoirs in the western United States, lake trout were introduced into Yellowstone Lake, Wyoming. Previous studies showed that lake trout reduced the population and altered the size structure of native Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri in Yellowstone Lake, but we sought to determine the degree to which lake trout predation changed lower trophic levels. We predicted that the structure of lower trophic levels would change in conformance with trophic cascade theory because Yellowstone cutthroat trout consume zooplankton. We compared zooplankton and phytoplankton assemblages between the period when Yellowstone cutthroat trout were abundant and the period after they declined. As predicted by trophic cascade theory, zooplankton biomass shifted from being dominated by copepods before lake trout introduction to ...

A New Method to Compute Standard-Weight Equations That Reduces Length-Related Bias

Abstract We propose a new method for developing standard-weight (W s) equations for use in the computation of relative weight (W r) because the regression line–percentile (RLP) method often leads to length-related biases in W s equations. We studied the structural properties of W s equations developed by the RLP method through simulations, identified reasons for biases, and compared W s equations computed by the RLP method and the new method. The new method is similar to the RLP method but is based on means of measured weights rather than on means of weights predicted from regression models. The new method also models curvilinear W s relationships not accounted for by the RLP method. For some length-classes in some species, the relative weights computed from W s equations developed by the new method were more than 20 W r units different from those using W s equations developed by the RLP method. We recommend assessment of published W s equations developed by the RLP method for length-related bias and use ...