723 research outputs found
Amphibian diversity in Amazonian flooded forests of Peru
No full textGlobal biodiversity is currently facing the sixth mass extinction, with extinction rates at least 100 times higher than background levels. The Amazon Basin has the richest amphibian fauna in South America, but there remain significant gaps in our knowledge of the drivers of diversity in this region and how amphibian assemblages are responding to environmental change.
Surveys were conducted in the Pacaya-Samiria National Reserve (PSNR) in Amazonian Peru, with a view to (1) comparing assemblage structure on floating meadows and adjacent terrestrial habitats; (2) determining the predictors of diversity in these habitats; and (3) exploring the effects of disturbance and seasonal flooding on diversity measures. Eighty-one species of amphibians have been recorded in these habitats since 1996 representing 11 families and three orders. In 2012-2013 22 anuran species used the floating meadow habitat, of which 10 were floating meadow specialists. These specialists were predominantly hylids which breed on floating meadows all the year round. Floating meadows therefore host an assemblage of species which is different to that found in adjacent terrestrial areas which are subject to seasonal flooding. Floating meadows enhance the amphibian diversity of the region, and rafts of vegetation that break away and disperse frogs downstream may explain the wide distribution of hylids within the Amazon Basin.
Fourteen different reproductive modes were represented within the 54 anuran species observed. The number of reproductive modes present was influenced by localised disturbance and seasonal flooding. Diversity increased in the low water period, with hylids breeding in temporary pools. When the forest is inundated most species disperse away from the flood waters.
Disturbance, habitat change, emerging diseases and climate change would likely lead to changes in species composition and assemblage structure rather than wholescale extinctions. However, further studies are needed to evaluate long-term consequences of synergistic environmental change
Patterns of carbon and nitrogen accumulation in seagrass (Posidonia oceanica) meadows of the Eastern Mediterranean Sea
No full textThe variability in stocks and accumulation rates of organic carbon (Corg), nitrogen (N), and carbonate (CaCO3) was studied in fifteen Posidonia oceanica meadows spread throughout the South Aegean Sea (Greece). In addition, the abiotic and biotic drivers determining the pattern of variability in the accumulation rates were assessed by exploring the influence of sediment characteristics, seagrass traits, and environmental settings. The meadows supported on average (±STDEV) 14.6 ± 5.0 kg Corg m−2, 0.47 ± 0.17 kg N m−2, and 249 ± 210 kg CaCO3 m−2 in the top meter of their sediments, with mean accumulation rates over the last 500 years of 33.6 ± 23.6 g Corg m−2 yr−1, 1.00 ± 0.62 g N m−2 yr−1, and 405 ± 336 g CaCO3 m−2 yr−1 across sites. A redundancy analysis (RDA) explained 70% of the variation in Corg, N, and CaCO3 accumulation rates, with three sediment characteristics (i.e., sediment Corg:N and Corg:Cinorg ratios and P. oceanica contribution to the sediment Corg pool) emerging as the primary set of factors shaping the accumulation of matter, followed by seagrass traits (i.e., leaf biomass and rhizome elongation) and environmental variables (i.e., suspended organic matter). The high degree of variability within the region emphasizes the need for fine-scale assessments to understand the local conditions influencing sequestration. Our findings underscored the critical role of seagrass meadows in carbon and nitrogen sequestration in the region, urging conservation efforts to protect these ecosystems and prevent potential losses of stored carbon and nitrogen following seagrass degradation
Conservation and ecological restoration of Rocky Mountain subalpine meadows: vegetation responses to tree encroachment
No full textOver the past century tree encroachment has occurred in North American subalpine meadows. Causes of tree establishment have been related to climate influences and exclusion of fire, but very few studies have looked at the consequence of tree encroachment on meadow vegetation. Within the southern Canadian Rocky Mountains, Waterton Lakes National Park and Castle Special Management Area,
14 meadows were randomly selected at wet and dry sites. Nonmetric multidimensional scaling showed that species composition changed during the transition of open meadow to forest for both wet and dry habitats. There were no significant differences in these two management areas in terms of conifer encroachment and the effects on meadow species. Results of this study show that conifer encroachment has increased over the last century with the consequences of loss in meadow species through a decrease in abundance, richness and diversity. Wet sites were significantly more sensitive to conifer encroachment than dry sites. The greatest
inhibitory effects of trees on meadow vegetation within the ecotone occurred when trees were 54-72 years old for wet sites and 77-112 years old for dry sites. Ecological restoration of these meadows is important for ongoing habitat conservation, maintaining species and landscape diversity and ecosystem resilience
A Program of Study for 21st Century Clarinet Techniques Featuring Five New Compositions for Unaccompanied Clarinet
No full textabstract: As clarinet students progress in their studies, there comes a point at which many are assigned to perform contemporary repertoire that is either overplayed due to accessibility and use in pedagogy, or includes difficult extended techniques like microtones, multiphonics, and more. This project identifies a “gap” in unaccompanied clarinet repertoire and seeks to expand this repertoire by outlining a program of study featuring five newly commissioned unaccompanied clarinet solos through which students can learn both traditional and untraditional techniques. Each of the first four works focus on one aspect of clarinet technique—musicality, the altissimo register, microtones, and multiphonics, respectively—and the final work is a culmination of all these techniques. Included in this document is biographical information for each composer, program notes, a brief description, and a performance guide for each piece. Additionally, each work was recorded by the author and included with this document.Dissertation/ThesisPerformer: Olivia Meadows, Composer: Zachary BushPerformer: Olivia Meadows, Composer: Josh GottryPerformer: Olivia Meadows, Composer: Kurt MehlenbacherPerformer: Olivia Meadows, Composer: Spencer BrandPerformer: Olivia Meadows, Composer: Eric P. MandatDoctoral Dissertation Music 201
Corresponding Author's Institution: Yakama Nation
No full textAbstract: Local and landscape environmental attributes have been strongly linked to community and population patterns. While landscape context appears to be complementary to local characteristics, the relative importance of local and landscape scales varies according to taxonomic groups. We examined the relative influence of both local and landscape factors on butterfly communities in montane meadows of northeastern California. The strongest patterns in the community were related to three variables. Total butterfly richness and abundance was negatively related to a single landscape variable, the cover of big sagebrush vegetation in the matrix surrounding meadows. The species richness and abundance of meadow specialist butterflies, and the abundance of a single meadow specialist species, Plebejus podarce, was positively related to a single local variable, the cover of obligate wetland plants within meadows. The abundance of Speyeria mormonia and Colias eurytheme, and the abundance of Coenonympha tullia ssp. ampelos and Satyrium behrii were respectively, positively and negatively related to elevation. Local factors explained more o
Carbon and nitrogen stocks and accumulation rates in seagrass meadows (Posidonia oceanica) of the Eastern Mediterranean Sea [Dataset]
No full textThe dataset contains Posidonia oceanica sediment core characteristics (core length, compression during coring and age), sediment variables (granulometry, dry bulk density, organic carbon and nitrogen content) and elemental stocks and accumulaion rates (organic carbon, nitrogen and carbonate). The cores were collected in 15 study sites along the South Aegean Sea (Eastern Mediterranean Sea, Greece).Peer reviewe
Comparison of water velocity profiles through morphologically dissimilar seagrasses measured with a simple and inexpensive current meter
No full textThe influence of seagrass morphology on water flow was studied by measuring water velocity profiles through natural seagrass meadows. An array of eight solid-state electronic current meters was used to obtain profiles through meadows of Amphibolis griffithii (Cymodoceaceae), a seagrass which possesses a profusely-branched erect stem with terminal leaf clusters, and two strap-like seagrasses, Posidonia australis and P. sinuosa (Posidoniaceae). Significant differences were observed in the shapes of velocity profiles of the different seagrass species; in particular, a region of high water velocity was observed beneath the leafy canopy of Amphibolis, but not in the Posidonia canopy. There is a strong correlation between the water velocity profile of Amphibolis plants and the distribution of leaf biomass, highlighting the influence of the 'stem-and-leaf cluster' morphology on the velocity profile. The unusual velocity profile of Amphibolis has implications for the ecology of these ecosystems, and sediment stability in particular. The solid-state electronic current meters used in this study were found to be an effective and inexpensive means of measuring water velocity profiles in seagrass canopies
The changing face of the Constantia Valley a temporal study of land use change in a heritage landscape
No full textIncludes bibliographical references.The study of land use change and urban morphology requires a multi-layered approach. Case studies are needed to gain an understanding of the local factors that are driving land use change and forming urban landscapes. This study will provide a temporal perspective on land use change in the Constantia Valley, a high income suburb on the outskirts of Cape Town. It will contextualise the efforts to conserve its heritage and, furthermore, attempt to explain the factors underlying the observed changes in the urban form. This study, through the use of Geographic Information System (GIS) mapping and a series of interviews, examines how and why the urban form of the Constantia Valley has changed. Finally, based on the findings the possible future urban form of Constantia will be considered
Local competition and metapopulation processes drive long-term seagrass-epiphyte population dynamics
No full textIt is well known that ecological processes such as population regulation and natural enemy interactions potentially occur over a range of spatial scales, and there is a substantial body of literature developing theoretical understanding of the interplay between these processes. However, there are comparatively few studies quantifying the long-term effects of spatial scaling in natural ecosystems. A key challenge is that trophic complexity in real-world biological communities quickly obscures the signal from a focal process. Seagrass meadows provide an excellent opportunity in this respect: in many instances, seagrasses effectively form extensive natural monocultures, in which hypotheses about endogenous dynamics can be formulated and tested. We present amongst the longest unbroken, spatially explict time series of seagrass abundance published to date. Data include annual measures of shoot density, total above-ground abundance, and associated epiphyte cover from five Zostera marina meadows distributed around the Isles of Scilly, UK, from 1996 to 2011. We explore empirical patterns at the local and metapopulation scale using standard time series analysis and develop a simple population dynamic model, testing the hypothesis that both local and metapopulation scale feedback processes are important. We find little evidence of an interaction between scales in seagrass dynamics but that both scales contribute approximately equally to observed local epiphyte abundance. By quantifying the long-term dynamics of seagrass-epiphyte interactions we show how measures of density and extent are both important in establishing baseline information relevant to predicting responses to environmental change and developing management plans. We hope that this study complements existing mechanistic studies of physiology, genetics and productivity in seagrass, whilst highlighting the potential of seagrass as a model ecosystem. More generally, this study provides a rare opportunity to test some of the predictions of ecological theory in a natural ecosystem of global conservation and economic val
Pulling Back the Veil: The Characterization and Habitability of Enshrouded Worlds
No full textThesis (Ph.D.)--University of Washington, 2016-08This dissertation explores global atmospheric haze and cloud layers and shows that they are not impenetrable barriers to information about the lower atmosphere and surface environment of planets. Uncovering techniques to probe beneath these aerosol decks can reveal a wealth of knowledge about planetary environments that would otherwise be inaccessible. Hazes themselves may reveal much more than they conceal because photochemical haze layers can constrain important planetary processes and characteristics such as atmospheric redox state, surface gas source fluxes, planetary habitability, and possibly even signs of life. The spectral consequences of global aerosol decks can be significant. Unfortunately, based on historical efforts to understand cloud- and haze-covered solar system worlds, we know there is a high potential for spectral misinterpretation of globally-enshrouded worlds (e.g. Kuiper 1944). Therefore, understanding how to properly interpret the remote observables of enshrouded exoplanets will be important to future exoplanet characterization efforts that will lack the advantage of ground-truthing within our lifetimes. In the first section of this dissertation, I discuss sub-cloud observations of the closest globally-enshrouded planet: Venus. Venus has near-infrared spectral windows observable on the planet's nightside that allow remote sensing of thermal radiation emanating from below the cloud and haze deck. We observed Venus with the Apache Point Observatory 3.5m telescope TripleSpec spectrograph (R = 3500, λ=0.96-2.47 μm) on 1-3 March 2009 and on 25, 27, 30 November and 2-4 December 2010. With these observations and synthetic spectra generated with the Spectral Mapping and Atmospheric Radiative Transfer (SMART) model, I produced the first simultaneous maps of cloud opacity, acid concentration, water vapor (H2O), hydrogen chloride (HCl), carbon dioxide (CO), carbonyl sulfide (OCS), and sulfur dioxide (SO2) abundances in the Venusian sub-cloud atmosphere. Water measured at wavelengths near 1.18 μm (near-surface) averages 29±2 ppm (2009) and 27±2 ppm (2010), and measured near 1.74 μm (15-30 km) averages 33±2 ppm (2009) and 32±2 ppm (2010). Water in both of these altitude ranges is spatially homogeneous. Water measured near 2.4 μm (30-45 km) averages 34±2 ppm (2009) and 33±3 ppm (2010) and is spatially inhomogeneous and variable. Estimates retrieved from measurements of HCl near 1.74 μm indicate mixing ratios near 0.41±0.04 ppm (2009) and 0.42±0.05 ppm (2010). CO and OCS, (2.3-2.5 μm; 30-45 km in altitude), are spatially inhomogeneous and appear to be anticorrelated. CO (35 km) averages 25±3 ppm (2009) and 22±2 ppm (2010). OCS (36 km) averages 0.44±0.10 ppm (2009) and 0.57±0.12 ppm (2010). SO2 measurements indicate average mixing ratios near 140±37 ppm (2009) and 126±32 ppm (2010). Many species display a hemispherical dichotomy in their distributions, and there is considerable spatial variability suggesting active processes with conservation between species. The most variable regions are just below the Venus cloud deck, and these may be related to changes in atmospheric circulation or virga events. While Venus may be the closest current example of a world covered by haze and cloud, Earth itself may have hosted a global organic haze early in its history. This is significant because recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions. However, past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. My study of hazy early Earth presents simulations of a habitable, yet dramatically different phase of Earth's history, when the atmosphere contained a Titan-like, organic-rich haze. Prior work has claimed that a haze-rich Archean Earth (3.8-2.5 billion years ago) would be frozen due to the haze's cooling effects (e.g. Haqq-Misra et al. 2008). However, no previous studies have self-consistently taken into account climate, photochemistry, and fractal hazes. Using coupled climate-photochemical-microphysical simulations, I demonstrate that hazes can cool the planet's surface by about 20 K, but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ~5 at 200 nm) even with the fainter young sun. I find that optically thicker hazes are self-limiting due to their self-shielding properties, preventing catastrophic cooling of the planet. Hazes may even enhance planetary habitability through UV shielding via their broad UV absorption signature, which can reduce surface UV flux by about 97% compared to a haze-free planet, and potentially allow for survival of land-based organisms at 2.6-2.7 billion years ago. Hazy Archean Earth is the most alien world for which we have geochemical constraints on environmental conditions, providing a useful analog for similar habitable, anoxic exoplanets. To examine how organic haze may impact exoplanet habitability, I compared the production of fractal organic haze on Archean Earth-analog planets around several spectral types of stars: the sun at 2.7 billion years ago and at present day; the highly flaring M3.5V dwarf AD Leo; the M4V dwarf GJ 876; a modeled quiescent M dwarf; the K2V star ε Eridani; and the F2V star σ Boötis. In my simulations, planets orbiting stars with the highest or lowest UV fluxes did not form haze. Low UV-stars are unable to drive the photochemistry needed for haze formation. High UV stars generate photochemical oxygen radicals that halt the buildup of this haze. Hazes can impact planetary habitability via UV shielding and surface cooling, but this cooling seems unimportant for hazy M dwarf planets because the bulk of the M dwarf spectral energy arrives at longer infrared wavelengths where organic hazes are relatively transparent. I simulated hazy planet spectra for these exoplanet-analogs in reflected light, thermal emission, and transit transmission and found that the spectral features of organic hazes should be detectable with future telescopes. For 10 transits of a hypothetical Archean-analog planet orbiting GJ 876 observed by the James Webb Space Telescope (JWST) over 0.8 - 14 μm, haze, methane and carbon dioxide are detectable assuming photon-limited noise levels. For direct imaging of a planet at 10 pc using a coronagraphic 10-meter class ultraviolet-visible-near infrared telescope, a shortwave haze absorption feature would be strongly detectable at >12 σ in 200 hours. The apparent prevalence of hazy worlds in the known exoplanet population and in our solar system suggests that the impact of haze on planetary habitability and spectra are crucial to consider for future characterization of terrestrial exoplanets. The impact of haze on habitability may have been far-reaching, and haze in the Archean could even have impacted the evolution of photosynthetic pigments because the spectrum of light reaching the planet's surface would have been reddened. I explore the consequences of this and show the spectrum of photons at the Earth's surface beneath a haze. In addition to haze, other types of UV shields would have been present in the Archean. I present spectra at several depths under water with and without dissolved Fe(II), a UV shielding compound that may have been in the Archean oceans. UV-tolerant phototrophs like Chloroflexus aurantiacus could have received a survivable level of UV irradiance under a haze and 10 cm of water containing 5 ppm dissolved Fe(II). With haze and other types of biochemical, chemical and physical UV shields, such organisms may have been protected even directly at the planet's surface. Besides UV shielding and possible impacts on photosynthesis, there are other ways that an Archean haze the evolving biosphere were connected. Any haze in Archean Earth's atmosphere would have been strongly dependent on biologically-produced methane, and hydrocarbon haze may be a novel type of spectral biosignature on planets with substantial levels of CO2. On planets with high levels of biogenic organic sulfur gases, photochemistry involving these gases can drive haze formation at lower CH4/CO2 ratios than methane photochemistry alone, providing another means to argue for biological activity on a haze-rich planet
- …
