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Author: Daehyun Kim
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Biogeographic patterns across a landscape are developed by the interplay of environmental processes operating at different spatial and temporal scales. This research investigated dynamics of salt marsh vegetation on the Skallingen salt marsh in Denmark responding to environmental variations at large, medium, and fine scales along both spatial and temporal spectrums. At the broad scale, this research addressed the importance of wind-induced rise of the sea surface in such biogeographic changes. A new hypothetical chain was suggested: recent trends in the North Atlantic Oscillation index toward its positive phase have led to increased storminess and wind tides on the ocean surface, resulting in increased frequency, duration, and magnitude of submergence and, hence, waterlogging of marsh soils and plants, which has retarded ecological succession. At the mid-scale, spatial patterns of vegetation and environmental factors were examined across tidal creeks. Sites closer to tidal creeks, compared to marsh interiors, were characterized by the dominance of later-successional species, higher bulk density, and lower nutrient contents and electrical conductivity. This finding implies that locations near creeks have experienced a better drainage condition than the inner marshes, which eventually facilitated the establishment of later-successional plants that are intolerant to physical stress. At the micro-scale, this research examined how the extent and mode of facilitation and competition vary for different combinations of plant species along physical gradients. Both positive and negative relationships were spatially manifested to a greater degree on the low marsh than on the mid marsh. This insight extends our current knowledge of scale-dependent interactions beyond pioneer zones to higher zones. On the low marsh, different types of bivariate point pattern (i.e., clustered, random, and regular) were observed for different combinations of species even at similar spatial scales. This finding implies that it is difficult to generalize at which scales competition and facilitation occur. To conclude, this research stresses the need for a holistic approach in future investigations of salt marsh biogeography. For example, based on results of this current research, it would be meaningful to develop a comprehensive simulation model that incorporates salt marsh ecology, geomorphology, and hydrology observed across scales.
Author: Daehyun Kim
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Biogeographic patterns across a landscape are developed by the interplay of environmental processes operating at different spatial and temporal scales. This research investigated dynamics of salt marsh vegetation on the Skallingen salt marsh in Denmark responding to environmental variations at large, medium, and fine scales along both spatial and temporal spectrums. At the broad scale, this research addressed the importance of wind-induced rise of the sea surface in such biogeographic changes. A new hypothetical chain was suggested: recent trends in the North Atlantic Oscillation index toward its positive phase have led to increased storminess and wind tides on the ocean surface, resulting in increased frequency, duration, and magnitude of submergence and, hence, waterlogging of marsh soils and plants, which has retarded ecological succession. At the mid-scale, spatial patterns of vegetation and environmental factors were examined across tidal creeks. Sites closer to tidal creeks, compared to marsh interiors, were characterized by the dominance of later-successional species, higher bulk density, and lower nutrient contents and electrical conductivity. This finding implies that locations near creeks have experienced a better drainage condition than the inner marshes, which eventually facilitated the establishment of later-successional plants that are intolerant to physical stress. At the micro-scale, this research examined how the extent and mode of facilitation and competition vary for different combinations of plant species along physical gradients. Both positive and negative relationships were spatially manifested to a greater degree on the low marsh than on the mid marsh. This insight extends our current knowledge of scale-dependent interactions beyond pioneer zones to higher zones. On the low marsh, different types of bivariate point pattern (i.e., clustered, random, and regular) were observed for different combinations of species even at similar spatial scales. This finding implies that it is difficult to generalize at which scales competition and facilitation occur. To conclude, this research stresses the need for a holistic approach in future investigations of salt marsh biogeography. For example, based on results of this current research, it would be meaningful to develop a comprehensive simulation model that incorporates salt marsh ecology, geomorphology, and hydrology observed across scales.
Author: Duncan M. FitzGerald
Publisher: Cambridge University Press
ISBN: 1107186285
Category : Nature
Languages : en
Pages : 499
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Book Description
A multidisciplinary review of salt marshes, describing how they function and respond to external pressures such as sea-level rise.
Author: Akana Noto
Publisher:
ISBN:
Category :
Languages : en
Pages : 151
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Book Description
Interactions among members of ecological communities often vary spatially in response to environmental differences. Yet interactions can also vary spatially as a result of biotic factors such as differences in species traits or variation in other species interactions. It is necessary to understand the conditions under which each of these drivers of variation has an effect in order to predict how species interactions will be affected both by changes in the environment and in biotic communities. In this thesis, I explore mechanisms that may cause species interactions to vary across space at local, regional and continental scales in salt marsh plant communities. Chapter 1 investigates the relationship between the environment (means and variability) and community diversity and stability in time-series data from the east and west coasts of North America. Chapter 2 experimentally investigates the effect of sea-level rise on species interactions within a marsh. Chapter 3 seeks to understand geographic variation in plant interactions among six sites spanning the California coast. Chapter 4 uses a common garden experiment to test whether spatial variation in species interactions are driven by differences among plant populations or the environment. Finally, Chapter 5 describes geographic patterns of variation in herbivore pressure to determine whether herbivory drives regional differences in interactions among plants. I found that changes in mean conditions, including sea level, can affect community diversity, stability and strength of species interactions. Environmental variability only affects community stability and diversity when it is relatively large, so increases in variability with climate change may cause plant community dynamics to become affected by both variability and means. Species interactions vary geographically along the west coast, but unlike on the east coast, do not show consistent trends with latitude. Rather, interaction strengths may differ due to trait variation among plant populations and differences in herbivore pressure. My thesis demonstrates that environmental conditions and local factors, including intraspecific phenotypic variation and herbivory, both determine the nature of species interactions in salt marshes, and that the west coast of North America shows geographic patterns in interactions that are distinct from those found on the east coast.
Author: Kevan Bauer Moffett
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
A large fraction of coastal wetlands worldwide have been severely impacted by development, resulting in among the highest losses of any wetland type. Necessary improvements in restoration and management of coastal wetlands require a better scientific understanding of the underlying plant-water interactions, or ecohydrology. This research developed a new conceptual model of intertidal salt marsh ecohydrology to define the relative roles of: tidal flooding, groundwater flow, vegetation zonation, and plant water uptake. Spatial and temporal variations in plant-water interactions were observed over three years at a field site in the Palo Alto Baylands, California. Three-dimensional numerical simulations of the coupled surface water and unsaturated groundwater flow and evapotranspiration (ET) at the site were used to explore the links between marsh vegetation and hydrology. /// Vegetation zonation is one of the most distinctive properties of salt marshes, yet had not been combined with physics-based hydrologic analysis prior to this research. Statistical analysis showed that vegetation zones at the field site were not correlated with traditional proxies for hydrologic influences such as elevation and distance-to-channel. Vegetation zonation was strongly correlated with a metric describing the spatial patterns of tidally-induced changes in salt marsh soil saturation and salinity. This metric was developed based on time-lapse imaging of bulk soil electrical conductivity and a new geophysical analysis method, Quantitative Differential Electromagnetic Induction imaging (Q-DEMI). /// Spatial variations in vegetation water use within and among vegetation zones were investigated in detail using centimeter-resolution thermal infrared (TIR) remote sensing. Well-established latent heat models were adapted to use spatially-variable canopy stomatal resistances. The detailed stomatal resistance maps were determined from the TIR data in a biophysically realistic manner by a new method. In principle, the stomatal resistance mapping method is applicable at scales from leaves (such as in this study) to landscapes. /// The dynamics of plant-water interactions originating at the leaf scale were also detectable in marsh-scale eddy covariance and meteorological field data. Alternating daytime tidal flooding and exposure shifted the marsh surface energy balance: from similar to a well-watered lawn during flooding, to similar to a sparse crop during exposure. The net ecosystem exchange of carbon dioxide was also temporarily suppressed in proportion to flood depth and duration, further indicating close plant-water coupling in the intertidal salt marsh environment. /// These spatial and temporal plant-water interactions occur within a larger context governed by the tidal regime and coastal groundwater flow. Continuous measurements of groundwater potential characterized marsh groundwater dynamics and provided evidence of sediment heterogeneity at the field site. In three dimensional, coupled groundwater-surface water simulations, the sediment heterogeneity affected both the balance between creek bank and interior marsh hydrologic processes and the spatial distribution of groundwater-surface water exchange. In the field, similar groundwater discharge zones were located in the tidal channels by fiber-optic distributed temperature sensing (DTS). The DTS data also provided the first description of the salt marsh benthic thermal regime, a system co-dominated by groundwater discharge and an ephemeral "tidal thermal blanket." /// Spatial variability in ET and rooting depth due to vegetation zonation were incorporated into a numerical model to represent the ecohydrologic system. The zonally-distributed ET and rooting depths caused notable spatial variations in hydrologic conditions in the marsh root zone, including significant variations in unsaturated pressure head and soil saturation. Modest control of salt marsh water table depth by vegetation following flooding tides was simulated throughout the field site, in accord with the prevailing conceptual model of salt marsh plant-water interactions. The simulations also suggested four additional classes of ecohydrologic dynamics apparent under conditions of prolonged marsh exposure. The four new classes of ecohydrological behavior were distinguished by combinations of relatively high or low soil permeability and high or low ET rate. Together, patterns in vegetation and soil permeability thus created distinctive "ecohydrological zones." In some cases, the contrast among such ecohydrological zones caused upward and downward groundwater flow regions to be spatially juxtaposed, suggesting future research into soil biogeochemistry at these sites may be interesting. /// In summary, a new conceptual model of salt marsh ecohydrology is based on a definition of "ecohydrological zones" as the relevant unit of structure and function within the salt marsh ecohydrological system. Distinctive ecohydrological zones are created by hydraulic interactions between groundwater, vegetation, and the atmosphere. The specific nature of each zone depends both on the soil hydraulic properties resulting from the local geomorphological history and on the plant water uptake and transpiration governed by each plant species' unique physiology. The set of ecohydrological zones within a salt marsh are nested, in turn, within a coarser hydrologic system structure imposed by the tidal regime and larger intertidal groundwater flow system.
Author: Giovanni Coco
Publisher: Ed. Universidad de Cantabria
ISBN: 8486116775
Category : Education
Languages : en
Pages : 206
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Book Description
Libro de abstracts del congreso celebrado en Santander en junio de 2013.
Author: Arnas Palaima
Publisher: Univ of California Press
ISBN: 0520274296
Category : Business & Economics
Languages : en
Pages : 288
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Book Description
The San Francisco Bay, the biggest estuary on the west coast of North America, was once surrounded by an almost unbroken chain of tidal wetlands, a fecund sieve of ecosystems connecting the land and the Bay. Today, most of these wetlands have disappeared under the demands of coastal development, and those that remain cling precariously to a drastically altered coastline. This volume is a collaborative effort of nearly 40 scholars in which the wealth of scientific knowledge available on tidal wetlands of the San Francisco Estuary is summarized and integrated. This book addresses issues of taxonomy, geomorphology, toxicology, the impact of climate change, ecosystem services, public policy, and conservation, and it is an essential resource for ecologists, environmental scientists, coastal policymakers, and researchers interested in estuaries and conserving and restoring coastal wetlands around the world.
Author: M.P. Weinstein
Publisher: Springer Science & Business Media
ISBN: 0792360192
Category : Nature
Languages : en
Pages : 862
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Book Description
Tidal salt marshes are viewed as critical habitats for the production of fish and shellfish. As a result, considerable legislation has been promulgated to conserve and protect these habitats, and much of it is in effect today. The relatively young science of ecological engineering has also emerged, and there are now attempts to reverse centuries-old losses by encouraging sound wetland restoration practices. Today, tens of thousands of hectares of degraded or isolated coastal wetlands are being restored worldwide. Whether restored wetlands reach functional equivalency to `natural' systems is a subject of heated debate. Equally debatable is the paradigm that depicts tidal salt marshes as the `great engine' that drives much of the secondary production in coastal waters. This view was questioned in the early 1980s by investigators who noted that total carbon export, on the order of 100 to 200 g m-2 y-1 was of much lower magnitude than originally thought. These authors also recognized that some marshes were either net importers of carbon, or showed no net exchange. Thus, the notion of `outwelling' has become but a single element in an evolving view of marsh function and the link between primary and secondary production. The `revisionist' movement was launched in 1979 when stable isotopic ratios of macrophytes and animal tissues were found to be `mismatched'. Some eighteen years later, the view of marsh function is still undergoing additional modification, and we are slowly unraveling the complexities of biogeochemical cycles, nutrient exchange, and the links between primary producers and the marsh/estuary fauna. Yet, since Teal's seminal paper nearly forty years ago, we are not much closer to understanding how marshes work. If anything, we have learned that the story is far more complicated than originally thought. Despite more than four decades of intense research, we do not yet know how salt marshes function as essential habitat, nor do we know the relative contributions to secondary production, both in situ or in the open waters of the estuary. The theme of this Symposium was to review the status of salt marsh research and revisit the existing paradigm(s) for salt marsh function. Challenge questions were designed to meet the controversy head on: Do marshes support the production of marine transient species? If so, how? Are any of these species marsh obligates? How much of the production takes place in situ versus in open waters of the estuary/coastal zone? Sessions were devoted to reviews of landmark studies, or current findings that advance our knowledge of salt marsh function. A day was also devoted to ecological engineering and wetland restoration papers addressing state-of-the-art methodology and specific case histories. Several challenge papers arguing for and against our ability to restore functional salt marshes led off each session. This volume is intended to serve as a synthesis of our current understanding of the ecological role of salt marshes, and will, it is hoped, pave the way for a new generation of research.
Author: Jan de Leeuw
Publisher:
ISBN: 9789061640769
Category : Salt marsh plants
Languages : en
Pages : 177
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Book Description
Author: Duncan M. FitzGerald
Publisher: Cambridge University Press
ISBN: 1316946835
Category : Science
Languages : en
Pages : 499
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Book Description
Salt marshes are highly dynamic and important ecosystems that dampen impacts of coastal storms and are an integral part of tidal wetland systems, which sequester half of all global marine carbon. They are now being threatened due to sea-level rise, decreased sediment influx, and human encroachment. This book provides a comprehensive review of the latest salt marsh science, investigating their functions and how they are responding to stresses through formation of salt pannes and pools, headward erosion of tidal creeks, marsh-edge erosion, ice-fracturing, and ice-rafted sedimentation. Written by experts in marsh ecology, coastal geomorphology, wetland biology, estuarine hydrodynamics, and coastal sedimentation, it provides a multidisciplinary summary of recent advancements in our knowledge of salt marshes. The future of wetlands and potential deterioration of salt marshes is also considered, providing a go-to reference for graduate students and researchers studying these coastal systems, as well as marsh managers and restoration scientists.
Author: Sergio Fagherazzi
Publisher: American Geophysical Union
ISBN:
Category : Nature
Languages : en
Pages : 284
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Book Description
Located between sea and land, salt marshes are complex environments that provide critical ecosystem functions, such as production of organic material and nutrient cycling. This book examines the geomorphology of salt marshes with emphasis on the interaction between landscape and biota.
