203 research outputs found

    Fates of Eroded Soil Organic Carbon: Mississippi Basin Case Study

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    We have developed a mass balance analysis of organic carbon (OC) across the five major river subsystems of the Mississippi (MS) Basin (an area of 3.2 3 106 km2). This largely agricultural landscape undergoes a bulk soil erosion rate of ;480 t·km22·yr21 (;1500 3 106 t/yr, across the MS Basin), and a soil organic carbon (SOC) erosion rate of ;7 t·km22·yr21 (;22 3 106 t/yr). Erosion translocates upland SOC to alluvial deposits, water impoundments, and the ocean. Soil erosion is generally considered to be a net source of CO2 release to the atmosphere in global budgets. However, our results indicate that SOC erosion and relocation of soil apparently can reduce the net SOC oxidation rate of the original upland SOC while promoting net replacement of eroded SOC in upland soils that were eroded. Soil erosion at the MS Basin scale is, therefore, a net CO2 sink rather than a source.This paper is part of ongoing studies by the coauthors to determine the role of landscape erosion and deposition in material fluxes and biogeochemical cycling. Parts of this work have been supported by internal institutional support at CICESE, Emporia State University, Miami University College of Arts and Science, and the Kansas Geological Survey, and by a Kansas NASA EPSCoR grant awarded to R. W. Buddemeier and R. O. Sleezer.We thank the numerous individuals who contributed technical assistance or conceptual support to these efforts. Three reviewers have provided useful critical comments on versions of this manuscript. Of these, we would like to single out Jon Cole, who thoroughly grasped the big picture of what we were advancing and whose summary comment seems worth quoting: ‘‘The idea that soil erosion is a large net sink of atmospheric CO2 is very interesting, well supported by the arguments and data in this paper, and likely to be a huge controversy. This controversy is a good thing, as Martha Stewart might say.’

    Radiological Dispersal Device Shelter & Evacuation Technical Basis CalEMA RNER Framework Supplement

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    Improvised Nuclear Device Response Training Materials

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    Improvised Nuclear Device Technical Basis CalEMA RNER Framework Supplement

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    A modeling tool to evaluate regional coral reef responses to changes in climate and ocean chemistry

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    This is the published version.We developed a spreadsheet-based model for the use of managers, conservationists, and biologists for projecting the effects of climate change on coral reefs at local-to-regional scales. The COMBO (Coral Mortality and Bleaching Output) model calculates the impacts to coral reefs from changes in average SST and CO2 concentrations, and from high temperature mortality (bleaching) events. The model uses a probabilistic assessment of the frequency of high temperature events under a future climate to address scientific uncertainties about potential adverse effects. COMBO offers data libraries and default factors for three selected regions (Hawai’i, Great Barrier Reef, and Caribbean), but it is structured with user-selectable parameter values and data input options, making possible modifications to reflect local conditions or to incorporate local expertise. Preliminary results from sensitivity analyses and simulation examples for Hawai’i demonstrate the relative importance of high temperature events, increased average temperature, and increased CO2 concentration on the future status of coral reefs; illustrate significant interactions among variables; and allow comparisons of past environmental history with future predictions

    Changing geo-ecological functions of coral reefs in the Anthropocene

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    This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record The ecology of many coral reefs has changed markedly over recent decades in response to various combinations of local and global stressors. These ecological changes have important implications for the abundance of taxa that regulate the production and erosion of skeletal carbonates, and thus for many of the geo-ecological functions that coral reefs provide, including reef framework production and sediment generation, the maintenance of reef habitat complexity and reef growth potential. These functional attributes underpin many of the ecosystem goods and services that reefs provide to society. Rapidly changing conditions of reefs in the Anthropocene are likely to significantly impact the capacity of reefs to sustain these geo-ecological functions. Although the Anthropocene footprint of disturbance will be expressed differently across ecoregions and habitats, the end point for many reefs may be broadly similar: (a) progressively shifting towards net neutral or negative carbonate budget states; (b) becoming structurally flatter; and (c) having lower vertical growth rates. It is also likely that a progressive depth-homogenisation will occur in terms of these processes. The Anthropocene is likely to be defined by an increasing disconnect between the ecological processes that drive carbonate production on the reef surface, and the net geological outcome of that production, that is, the accumulation of the underlying reef structure. Reef structures are thus likely to become increasingly relict or senescent features, which will reduce reef habitat complexity and sediment generation rates, and limit reef potential to accrete vertically at rates that can track rising sea levels. In the absence of pervasive stressors, recovery of degraded coral communities has been observed, resulting in high net-positive budgets being regained. However, the frequency and intensity of climate-driven bleaching events are predicted to increase over the next decades. This would increase the spatial footprint of disturbances and exacerbate the magnitude of the changes described here, limiting the capacity of many reefs to maintain their geo-ecological functions. The enforcement of effective marine protection or the benefits of geographic isolation or of favourable environmental conditions (“refugia” sites) may offer the hope of more optimistic futures in some locations. A plain language summary is available for this article.Royal Societ

    Projected Changes to Growth and Mortality of Hawaiian Corals over the Next 100 Years

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    BACKGROUND: Recent reviews suggest that the warming and acidification of ocean surface waters predicated by most accepted climate projections will lead to mass mortality and declining calcification rates of reef-building corals. This study investigates the use of modeling techniques to quantitatively examine rates of coral cover change due to these effects. METHODOLOGY/PRINCIPAL FINDINGS: Broad-scale probabilities of change in shallow-water scleractinian coral cover in the Hawaiian Archipelago for years 2000-2099 A.D. were calculated assuming a single middle-of-the-road greenhouse gas emissions scenario. These projections were based on ensemble calculations of a growth and mortality model that used sea surface temperature (SST), atmospheric carbon dioxide (CO(2)), observed coral growth (calcification) rates, and observed mortality linked to mass coral bleaching episodes as inputs. SST and CO(2) predictions were derived from the World Climate Research Programme (WCRP) multi-model dataset, statistically downscaled with historical data. CONCLUSIONS/SIGNIFICANCE: The model calculations illustrate a practical approach to systematic evaluation of climate change effects on corals, and also show the effect of uncertainties in current climate predictions and in coral adaptation capabilities on estimated changes in coral cover. Despite these large uncertainties, this analysis quantitatively illustrates that a large decline in coral cover is highly likely in the 21(st) Century, but that there are significant spatial and temporal variances in outcomes, even under a single climate change scenario
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