140 research outputs found
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Understanding the Diversity and Community Structure of Bdelloid Rotifer Soil Communities.
Rotifers, though very important to the microbial food-web and energy flux of a system, are still poorly understood in terms of their taxonomy and geographical distributions. Rotifers pose problems for taxonomists and evolutionary biologists due to the difficulties associated with isolation, identification and enumeration of organisms that have few distinguishing morphological characters. This lack of morphological information and their extreme abundance of micro-invertebrates make identification of rare, or even common cryptic, taxa a large and unwieldy task as only painstaking microscopy can be used to identify synapomorphies. To overcome these problems I made use of environmental DNA sequencing to perform large- scale surveys of bdelloid rotifer communities. The goal of this study was to describe the diversity and distribution of bdelloid rotifer communities as they relate to space, soil environment, and co-occurring bacterial communities. I found that bdelloid rotifers are significantly limited in their dispersal capabilities on the order of 100 meters, despite historically being viewed as having easy-to-disperse propagules. Although dispersal limitation is a significant contributor to the diversity structure of bdelloid communities, its influence constitutes much less of an effect than local biogeochemistry. In contrast, co-occurring bacterial communities are less affected by both dispersal limitation and local habitat. However, both bdelloid rotifer and bacterial communities share patterns of diversity between three ecologically distinct sites within the Niwot Ridge LTER. Comparisons of the diversity and distribution of microscopic animal communities to bacterial communities have been anecdotal, and have not made direct comparisons among samples, as done here. Analyses comparing soil invertebrate communities to co- occurring microbial communities remain in their infancy, indicating that more inclusive concepts and theories are needed to explain observed patterns of distribution and diversity
Influence of Spatially Variable Instrument Networks on Climatic Averages
Copyright 1991 by the American Geophysical Union.Instrument networks for measuring surface air temperature (T) and precipitation (P) have varied considerably over the last century. Inadequate observingâstation locations have produced incomplete, uneven, and biased samples of the spatial variability in climate and, in turn, terrestrial and global scale averages of T and P have been biased. New highâresolution climatologies [Legates and Willmott, 1990a; 1990b] are intensively sampled and integrated to illustrate the effects of these nontrivial sampling biases. Since station networks may not represent spatial climatic variability adequately, their ability to represent climate through time is suspect
Impacts of Climate Change on the State of Indiana: ensemble future projections based on statistical downscaling
Using an ensemble of 10 statistically downscaled global climate model (GCM) simulations, we project future climate change impacts on the state of Indiana (IN) for two scenarios of greenhouse-gas concentrations (a medium scenario--RCP4.5, and a high scenario--RCP 8.5) for three future time periods (2020s, 2050s, 2080s). Relative to a 1971-2000 baseline, the scenarios project substantial changes in temperature for IN, with a change in the annual ensemble mean temperature for the 2080s RCP8.5 scenario of about 5.6 °C (10.1 °F). Such changes also indicate major changes in extreme temperatures. For southern IN, the number of days with daily maximum temperatures above 35 °C (95 °F) is projected to be about 100 days per year for the 2080s RCP8.5 scenario, as opposed to an average of 5 days for the historical baseline climate. Locations in northern IN could experience 50 days per year above 35 °C (95 °F) for the same conditions. Energy demand for cooling, as measured by Cooling Degree Days (CDD), is projected to increase nearly fourfold in response to this extreme warming, but heating demand as measured by Heating Degree Days (HDD) is projected to decline by 30%, which would result in a net reduction in annual heating/cooling energy demand for consumers. The length of the growing season is projected to increase by about 30 to 50 days by the 2080s for the RCP8.5 scenario, and U.S. Department of Agriculture hardiness zones are projected to shift by about two half zones throughout IN. By the 2080s, all GCM simulations for the RCP8.5 scenario show higher annual precipitation (P) over IN. Projected seasonal changes in P include a 25-30% increase in winter and spring P by the 2080s for the RCP8.5 scenarios and a 1-7% decline in summer and fall P (although there is low model agreement in the latter two seasons). Rising temperatures are projected to result in systematic decreases in the snowfall-to-rain ratio from Nov-Mar. Snow is projected to become uncommon in southern IN by the 2080s for the RCP8.5 scenario, and snowfall is substantially reduced in other areas of the state. The combined effects of these changes in T, P, and snowfall will likely result in increased surface runoff and flooding during winter and spring
Natural and Managed Watersheds Show Similar Responses to Recent Climate Change
Changes in climate are driving an intensification of the hydrologic cycle and leading to alterations of natural streamflow regimes. Human disturbances such as dams, land-cover change, and water diversions are thought to obscure climate signals in hydrologic systems. As a result, most studies of changing hydroclimatic conditions are limited to areas with natural streamflow. Here, we compare trends in observed streamflow from natural and human-modified watersheds in the United States and Canada for the 1981â2015 water years to evaluate whether comparable responses to climate change are present in both systems. We find that patterns and magnitudes of trends in median daily streamflow, daily streamflow variability, and daily extremes in human-modified watersheds are similar to those from nearby natural watersheds. Streamflow in both systems show negative trends throughout the southern and western United States and positive trends throughout the northeastern United States, the northern Great Plains, and southern prairies of Canada. The trends in both natural and human-modified watersheds are linked to local trends in precipitation and reference evapotranspiration, demonstrating that water management and land-cover change have not substantially altered the effects of climate change on human-modified watersheds compared with nearby natural watersheds
Indianaâs Past & Future Climate: A Report from the Indiana Climate Change Impacts Assessment
Indianaâs climate is changing. Temperatures are rising, more precipitation is falling and the last spring frost of the year has been getting steadily earlier. This report from the Indiana Climate Change Impacts Assessment (IN CCIA) describes historical climate trends from more than a century of data, and future projections that detail the ways in which our climate will continue to change
Analyzing the discharge regime of a large tropical river through remote sensing, ground-based climatic data, and modeling
This study demonstrates the potential for applying passive microwave satellite sensor data to infer the discharge dynamics of large river systems using the main stem Amazon as a test case. The methodology combines (1) interpolated ground-based meteorological station data, (2) horizontally and vertically polarized temperature differences (HVPTD) from the 37-GHz scanning multichannel microwave radiometer (SMMR) aboard the Nimbus 7 satellite, and (3) a calibrated water balance/water transport model (WBM/WTM). Monthly HVPTD values at 0.25° (latitude by longitude) resolution were resampled spatially and temporally to produce an enhanced HVPTD time series at 0.5° resolution for the period May 1979 through February 1985. Enhanced HVPTD values were regressed against monthly discharge derived from the WBM/WTM for each of 40 grid cells along the main stem over a calibration period from May 1979 to February 1983 to provide a spatially contiguous estimate of time-varying discharge. HVPTD-estimated flows generated for a validation period from March 1983 to February 1985 were found to be in good agreement with both observed arid modeled discharges over a 1400-km section of the main stem Amazon. This span of river is bounded downstream by a region of tidal influence and upstream by low sensor response associated with dense forest canopy. Both the WBM/WTM and HVPTD-derived flow rates reflect the significant impact of the 1982â1983 El Niño-;Southern Oscillation (ENSO) event on water balances within the drainage basin
HRM and innovation:looking across levels
Studies are starting to explore the role of HRM in fostering organizational innovation but empirical evidence remains contradictory and theory fragmented. This is partly because extant literature by and large adopts a unitary level of analysis, rather than reflecting on the multi-level demands that innovation presents. Building on an emergent literature focused on HRMâs role in shaping innovation, we shed light on the question of whether, and how, HRM might influence employeesâ innovative behaviours in the direction of strategically important goals. Drawing upon institutional theory, our contributions are three-fold: to bring out the effect of two discrete HRM configurations- one underpinned by a control and the other by an entrepreneurial ethos, on attitudes and behaviours at the individual level; to reflect the way in which employee innovative behaviours arising from these HRM configurations coalesce to shape higher-level phenomena, such as organizational-level innovation; and to bring out two distinct patterns of bottom-up emergence, one driven primarily by composition and the other by both composition and compilation
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