Resuspension of bottom sediments by waves and tidal currents was investigated in three characteristic environments of middle
Chesapeake Bay (shallow platform, deep platform, and main channel). In the shallow near shore platform wind waves frequently
resuspended significant amounts of sediment, some of which was transported offshore. In both the shallow and adjacent deep
platform regions, tidal currents were too weak (<20 cm cm/sec) to resuspend bottom sediments. In the main channel, peak current
velocities were substantially stronger (40 cm/sec), but were still not competent to erode the bottom. The stability of the
bottom in this area is related to the activities of the benthic organisms which are influenced by seasonal anoxia.
University of Maryland Center for Environmental and Estuarine Studies (CEES) Contribution No. 1572. 相似文献
Vertical accretion rates were determined for brackish marshes in an estuarine tributary on the Eastern Shore of Chesapeake
Bay. These rates determined on the basis of the peak phase of early European settlement as recorded in pollen spectra of the
marsh sediments range between 0. 18 to 0.74 cm yr−1 over approximately the last 194 years and generally decrease down the estuary. More recent accretion rates (estimated from
changes in pine pollen concentration) appear to have accelerated, exceeding the present local rate of sea level rise. The
implications for using estuarine marsh accretion rates as surrogates for changes in sea level are discussed. 相似文献
Summary In palaeomagnetism it is usually assumed that the distribution of directions of natural remanent magnetization at a site is Fisherian. This assumption is used here for an analysis of dispersion on a sphere when only inclination (and not declination) of NRM directions is known. By this method, in spite of the lack of declination data, the mean inclination and precision of the parent Fisherian population are estimated, together with the probable errors in these estimates. The method is tested against known Fisherian populations and is then used for dealing with data from borecores, where the way-up of cores and dip of the hole are known, but the azimuth of cores is not. Uses of the information derived from this analysis include estimations of age of NRM, support for palaeomagnetic data from surface studies, and comparison of dispersion of the palaeomagnetic field with that of the present geomagnetic field. 相似文献
Carbon markets and climate finance payments are being used to incentivize the mitigation of CO2 arising from anthropogenic land-use change in forests, marine ecosystems, and lowland grasslands. However, no such consideration has been given to how these ‘carbon finance incentives’ might be applied to mountain grasslands and shrublands, ecosystems that contain a substantial amount of carbon. These incentives amount to more than US$350 billion per annum and could potentially support underfunded natural resource management (NRM) activities, which are urgently needed to address numerous stressors impacting these important ecosystems. In the mountain context, NRM activities could include adaptive grazing management, sustainable cropping, ecosystem preservation, ecosystem restoration, and engineered soil conservation measures. This article investigates the stressors, challenges, and priorities related to the NRM of carbon stocks in mountain grasslands and shrublands; why carbon markets and climate finance have not yet been utilized in this context; and, what is required to position mountain-based NRM activities as eligible for carbon finance incentives. Using surveys and interviews triangulated with a systematic literature review, the study found that carbon finance incentives are not well understood, both amongst mountain-focused experts and in the literature. The study also found the required technical methodologies, policy frameworks, and data to be largely undeveloped. This article proposes a top-down conceptual policy framework that can be used to develop key ‘enabling factors’ with the view of extending the eligibility of carbon markets and climate finance to NRM activities undertaken in mountain grasslands and shrublands in the same way that has been afforded to other ecosystems.
Policy relevance
This is the first study to explicitly highlight the important role that the mountain grasslands and shrublands might play in international climate policy, and how carbon finance mechanisms might support better NRM in these areas. It is also the first to investigate why these incentives have not been adopted thus far. The article concludes by proposing a novel top-down ‘carbon incentive enabling’ framework that could be driven by governments and mountain development focused organizations so as to capture some of the opportunities offered by carbon-based incentives, and help meet international climate policy objectives. 相似文献
Managed aquifer recharge (MAR) is a tool available to water-resources managers that assists agencies to secure water supplies and protect aquifers and groundwater-dependent ecosystems in the face of climate change and growing water demand. Yet few natural-resources managers have access to a coordinated set of policies that enable the potential benefits of MAR to be fully realised in urban and rural areas. This paper reviews contemporary Australian water-resource policies and systematically applies a refined set of ‘robust separation of rights’ principles based on secure entitlements, annual allocations and end-use obligations to guide the coordination of policies specific to each of the four operational processes central to MAR schemes: source water harvesting, aquifer recharge, recovery of stored water and end use. Particular attention is given to the formulation of policies relating to the recovery of water, including the feasibility for market exchange of permanent and temporary rights to recover recharged water, as these have the potential to greatly expand the role of MAR. Aquifer characteristics, existing groundwater extractions and potential third party effects need to be taken into account in determining both recovery entitlements and annual allocations. A transitional pathway to implement novel MAR policies is suggested. 相似文献