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Snowball Earth termination by destabilization of equatorial permafrost methane clathrate
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The start of the Ediacaran period is defined by one of the most severe climate change events recorded in Earth history—the recov- ery from the Marinoan ‘snowball’ ice age, ,635 Myr ago (ref. 1). Marinoan glacial-marine deposits occur at equatorial palaeolati- tudes2, and are sharply overlain by a thin interval of carbonate that preserves marine carbon and sulphur isotopic excursions of about 25 and 115 parts per thousand, respectively3–5; these deposits are thought to record widespread oceanic carbonate precipitation during postglacial sea level rise1,3,4. This abrupt transition records a climate system in profound disequilibrium3,6 and contrasts shar- ply with the cyclical stratigraphic signal imparted by the balanced feedbacks modulating Phanerozoic deglaciation. Hypotheses accounting for the abruptness of deglaciation include ice albedo feedback3, deep-ocean out-gassing during post-glacial oceanic overturn7 or methane hydrate destabilization8–10. Here we report the broadest range of oxygen isotope values yet measured in mar- ine sediments (225% to 112%) in methane seeps in Marinoan deglacial sediments underlying the cap carbonate. This range of values is likely to be the result of mixing between ice-sheet-derived meteoric waters and clathrate-derived fluids during the flushing and destabilization of a clathrate field by glacial meltwater. The equatorial palaeolatitude implies a highly volatile shelf permafrost pool that is an order of magnitude larger than that of the present day. A pool of this size could have provided a massive biogeochem- ical feedback capable of triggering deglaciation and accounting for the global postglacial marine carbon and sulphur isotopic excur- sions, abrupt unidirectional warming, cap carbonate deposition, and a marine oxygen crisis. Our findings suggest that methane released from low-latitude permafrost clathrates therefore acted as a trigger and/or strong positive feedback for deglaciation and warming. Methane hydrate destabilization is increasingly suspected as an important positive feedback to climate change11–13 that coincides with critical boundaries in the geological record14,15 and may represent one particularly important mechanism active during conditions of strong climate forcing.
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Snyder Snyder 1969.pdf
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SIM-SPA
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Social Science at the Wildland-Urban Interface: a Compendium of Research Results to Create Fire-Adapted Communities
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Over the past decade, a growing body of research has been conducted on the human dimensions of wildland fire. Building on a relatively small number of foundational studies, this research now addresses a wide range of topics including mitigation activities on private lands, fuels reduction treatments on public land, community impacts and resident behaviors during fire, acceptance of approaches to postfire restoration and recovery, and fire management policy and decisionmaking. As this research has matured, there has been a recognition of the need to examine the full body of resulting literature to synthesize disparate findings and identify lessons learned across studies. These lessons can then be applied to fostering fire-adapted communities—those communities that understand their risk and have taken action to mitigate their vulnerability and increase resilience.
This compendium of social science research findings related to fire-adapted communities has resulted from a project funded by the Joint Fire Science Program (JFSP). As part of these efforts, the research team reviewed more than 200 publications of research results. Then the team convened a workshop with 16 scientists with extensive experience in the human dimensions of fire management issues. Workshop participants evaluated collective findings and discussed their application to support fire management activities. In addition to this compendium, project outputs were: 1) a synthesis of published literature specific to eight management questions identified by the JFSP, 2) a list of future research needs, 3) a bibliography, including abstracts, with accompanying subject area guide, and 4) a video featuring the experiences of agency personnel and community leaders in successful collaborative fire planning settings. This video is accompanied by a field guide for use by agency managers to more effectively participate in building fire-safe communities.
In the sections that follow, we describe our approach to completing this review and present key findings from the literature. Our discussion is organized around five major topical areas: 1) homeowner/community mitigation, 2) public acceptance of fuels treatments on public lands, 3) homeowner actions during a fire, 4) postfire response and recovery, and 5) wildland fire policy and planning. The compendium concludes with a presentation of management implications and a bibliography of all material in this review.
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Societal challenges in understanding and responding to regime shifts in forest landscapes
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2 excerpts: "The degradation of seminatural landscapes at regional scales, whereby essential functional capabilities and biotic elements are permanently lost as a result of altered disturbance regimes, is a widespread phenomenon."
and "Salvage logging of burned or windthrown forests not only eliminates critical structural legacies from predisturbance stands but can disrupt natural regenerative processes, as noted below (10, 11)."
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Soil food web properties explain ecosystem services across European land use systems
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Intensive land use reduces the diversity and abundance of many soil biota, with consequences for the processes that they govern and the ecosystem services that these processes underpin. Relationships between soil biota and ecosystem processes have mostly been found in laboratory experiments and rarely are found in the field. Here, we quantified, across four countries of contrasting climatic and soil conditions in Europe, how differences in soil food web composition resulting from land use systems (intensive wheat rotation, extensive rotation, and permanent grassland) influence the functioning of soils and the ecosystem services that they deliver. Intensive wheat rotation consistently reduced the biomass of all components of the soil food web across all countries. Soil food web properties strongly and consistently predicted processes of C and N cycling across land use systems and geographic loca- tions, and they were a better predictor of these processes than land use. Processes of carbon loss increased with soil food web properties that correlated with soil C content, such as earthworm biomass and fungal/bacterial energy channel ratio, and were greatest in permanent grassland. In contrast, processes of N cycling were explained by soil food web properties independent of land use, such as arbuscular mycorrhizal fungi and bacterial channel biomass. Our quantification of the contribution of soil organisms to processes of C and N cycling across land use systems and geographic locations shows that soil biota need to be included in C and N cycling models and highlights the need to map and conserve soil biodiversity across the world.
soil fauna | modeling | soil microbes | nitrogen
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Soil for Water
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Learn more about NCAT’s Soil for Water project, working to capture and hold more water in the soil.
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Soil Health
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Soil Health Institute
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The Soil Health Institute is a non-profit whose mission is to safeguard and enhance the vitality and productivity of soil through scientific research and advancement. The Institute works with its many stakeholders to identify gaps in research and adoption; develop strategies, networks and funding to address those gaps; and ensure beneficial impact of those investments to agriculture, the environment and society.
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Soil organic matter turnover is governed by accessibility not recalcitrance
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Mechanisms to mitigate global climate change by sequestering carbon (C) in different ‘sinks’ have been proposed as at least temporary measures. Of the major global C pools, terrestrial ecosystems hold the potential to capture and store substantially increased volumes of C in soil organic matter (SOM) through changes in management that are also of benefit to the multitude of ecosystem services that soils provide. This potential can only be realized by determining the amount of SOM stored in soils now, with subsequent quantification of how this is affected by management strate- gies intended to increase SOM concentrations, and used in soil C models for the prediction of the roles of soils in future climate change. An apparently obvious method to increase C stocks in soils is to augment the soil C pools with the longest mean residence times (MRT). Computer simulation models of soil C dynamics, e.g. RothC and Century, partition these refractory constituents into slow and passive pools with MRTs of centuries to millennia. This partition- ing is assumed to reflect: (i) the average biomolecular properties of SOM in the pools with reference to their source in plant litter, (ii) the accessibility of the SOM to decomposer organisms or catalytic enzymes, or (iii) constraints imposed on decomposition by environmental conditions, including soil moisture and temperature. However, con- temporary analytical approaches suggest that the chemical composition of these pools is not necessarily predictable because, despite considerable progress with understanding decomposition processes and the role of decomposer organisms, along with refinements in simulation models, little progress has been made in reconciling biochemical properties with the kinetically defined pools. In this review, we will explore how advances in quantitative analytical techniques have redefined the new understanding of SOM dynamics and how this is affecting the development and application of new modelling approaches to soil C.
Keywords: C isotopes, decomposition, recalcitrance, soil C models, soil microorganisms, soil organic matter
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