Ages and isotopic signatures of peat cores from a boreal landscape, Interior Alaska

To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate ~600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing season temperature record from Fairbanks. This concurrent wetland succession and reduced growth of black spruce trees indicates a step-wise ecosystem-level response to a change in regional climate. In 2001, fire was observed coincident with permafrost collapse and resulted in lateral expansion of the peatland. These observations and the peat profile suggest that future warming and/or increased fire disturbance could promote permafrost degradation, peatland expansion, and increase carbon storage across this landscape; however, the development of drought conditions could reduce the success of both black spruce and Sphagnum, and potentially decrease the long-term ecosystem carbon storage.

Surface Elevation Change Processes in the Snohomish River Estuary, Washington

Estuaries provide crucial ecosystem functions and contain significant socio-economic value. Within Washington State, estuaries supply rearing habitat for juvenile salmon during their transition period from freshwater to open sea. In order to properly manage wetland resources and restore salmon habitat, the mechanisms through which estuaries evolve and adapt to pressures from climate change, most notably eustatic sea level rise, must be understood. Estuaries maintain elevation relative to sea level rise through vertical accretion of sediment. This report investigates the processes that contribute to local surface elevation change in the Snohomish Estuary, conveys preliminary surface elevation change results from RTK GPS monitoring, and describes how surface elevation change will be monitored with a network of RSET-MH’s. Part of the tidal wetlands within the Snohomish River Estuary were converted for agricultural and industrial purposes in the 1800’s, which resulted in subsidence of organic soils and loss of habitat. The Tulalip Tribes, the National Oceanic and Atmospheric Administration (NOAA), Northwest Indian Fisheries Commission (NWIFC), and the Environmental Protection Agency (EPA) are conducting a large-scale restoration project to improve ecosystem health and restore juvenile salmon habitat. A study by Crooks et al. (2014) used 210Pb and carbon densities within sediment cores to estimate wetland re-building capacities, sediment accretion rates, and carbon sequestration potential within the Snohomish Estuary. This report uses the aforementioned study in combination with research on crustal movement, tidal patterns, sediment supply, and sea level rise predictions in the Puget Sound to project how surface elevation will change in the Snohomish Estuary with respect to sea level rise. Anthropogenic modification of the floodplain has reduced the quantity of vegetation and functional connectivity within the Snohomish Estuary. There have been losses up to 99% in vegetation coverage from historic extents within the estuary in both freshwater and mesohaline environments. Hydrographic monitoring conducted by NOAA and the Tulalip Tribe shows that 85% of the historic wetland area is not connected to the main stem of the Snohomish (Jason Hall 2014, unpublished data, NOAA). As vegetation colonization and functional connectivity of the floodplains of the Snohomish estuary is re-established through passive and active restoration, sediment transport and accretion is expected to increase. Under the Intergovernmental Panel on Climate Change (IPCC) “medium- probability” scenario sea level is projected to rise at a rate of 4.28 mm/year in the Puget Sound. Sea level rise in the Snohomish Estuary will be exacerbated from crustal deformation from subsidence and post-glacial rebound, which are measured to be -1.4 mm/year and -0.02 mm/year, respectively. Sediment accretion rates calculated by Crooks et al. (2014) and RTK GPS monitoring of surface elevation change of the Marysville Mitigation site from 2011-2014 measured vertical accretion rates that range from -48-19 mm/year and have high spatial variability. Sediment supply is estimated at 490 thousand tons/year, which may be an under-estimate because of the exclusion of tidal transport in this value. The higher rates of sediment accretion measured in the Snohomish Estuary suggest that the Snohomish will likely match or exceed the pace of sea level rise under “medium-probability” projections. The network of RSET-MH instruments will track surface elevation change within the estuary, and provide a more robust dataset on rates of surface elevation change to quantify how vertical accretion and subsidence are contributing to surface elevation change on a landscape scale.

Integration3

Thesis (Master's)--University of Washington, 2016-06

Modelling of different measures for improving removal in a stormwater pond

The effect of retrofitting an existing pond on removal efficiency and hydraulic performance was modelled using the commercial software Mike21 and compartmental modelling. The Mike21 model had previously been calibrated on the studied pond. Installation of baffles, the addition of culverts under a causeway and removal of an existing island were all studied as possible improvement measures in the pond. The subsequent effect on hydraulic performance and removal of. suspended solids was then evaluated. Copper, cadmium, BOD, nitrogen and phosphorus removal were,also investigated for that specific improvement measure showing the best results. Outcomes of this study reveal that all measures increase the removal efficiency of suspended solids. The hydraulic efficiency is improved for all cases, except for the case where the island is removed. Compartmental modelling was also used to evaluate hydraulic performance and facilitated a better understanding of the way each of the different measures affected the flow pattern and performance. It was concluded that the installation of baffles is the best of the studied measures resulting in a reduction in the annual load on the receiving lake by approximately 8,000 kg of suspended solids (25% reduction of the annual load), 2 kg of copper (10% reduction of the annual load) and 600 kg of BOD (10% reduction of the annual load).

Water quality in the Great Barrier Reef region: responses of mangrove, seagrass and macroalgal communities

Marine plants colonise several interconnected ecosystems in the Great Barrier Reef region including tidal wetlands, seagrass meadows and coral reefs. Water quality in some coastal areas is declining from human activities. Losses of mangrove and other tidal wetland communities are mostly the result of reclamation for coastal development of estuaries, e.g. for residential use, port infrastructure or marina development, and result in river bank destabilisation, deterioration of water clarity and loss of key coastal marine habitat. Coastal seagrass meadows are characterized by small ephemeral species. They are disturbed by increased turbidity after extreme flood events, but generally recover. There is no evidence of an overall seagrass decline or expansion. High nutrient and substrate availability and low grazing pressure on nearshore reefs have lead to changed benthic communities with high macroalgal abundance. Conservation and management of GBR macrophytes and their ecosystems is hampered by scarce ecological knowledge across macrophyte community types. (c) 2004 Elsevier Ltd. All rights reserved.

Aeration for plant root respiration in a tidal marsh

This paper investigates the tidal effects on aeration conditions for plant root respiration in a tidal marsh. We extend the work of Ursino et al. ( 2004) by using a two-phase model for air and water flows in the marsh. Simulations have been conducted to examine directly the link between the airflow dynamics and the aeration condition in the marsh soil. The results show that the effects of entrapped air on water movement in the vadose zone are significant in certain circumstances. Single-phase models based on Richards' equation, which neglect such effects, may not be adequate for quantifying the aeration condition in tidal marsh. The optimal aeration condition, represented by the maximum of the integral magnitude of tidally advected air mass ( TAAM) flux, is found to occur near the tidal creek for the four soil textures simulated. This may explain the observation that some salt marsh plant species grow better near tidal creeks than in the inner marsh areas. Our analyses, based on the two-phase model and predicted TAAM flux magnitude, provide further insight into the positive feedback'' mechanism proposed by Ursino et al. ( 2004). That is, pioneer plants may grow successfully near the creek where the root aeration condition is optimal. The roots of the pioneer plants can soften and loosen the rhizosphere soil, which increases the evapotranspiration rate, the soil porosity, and absolute permeability and weakens the capillary effects. These, in turn, improve further the root aeration conditions and may lead to colonization by plants less resistant to anaerobic conditions.

Early and mid Holocene tool-use and processing of taro (Colocasia esculenta), yam (Dioscorea sp.) and other plants at Kuk Swamp in the highlands of Papua New Guinea

Recent multidisciplinary investigations document an independent emergence of agriculture at Kuk Swamp in the highlands of Papua New Guinea. In this paper we report preliminary usewear analysis and details of prehistoric use of stone tools for processing starchy food and other plants at Kuk Swamp. Morphological diagnostics for starch granules are reported for two potentially significant economic species, taro (Colocasia esculenta) and yam (Dioscorea sp.), following comparisons between prehistoric and botanical reference specimens. Usewear and residue analyses of starch granules indicate that both these species were processed on the wetland margin during the early and mid Holocene. We argue that processing of taro and yam commences by at least 10,200 calibrated years before present (cal BP), although the taro and yam starch granules do not permit us to distinguish between wild or cultivated forms. From at least 6950 to 6440 cal BP the processing of taro, yam and other plants indicates that they are likely to have been integrated into cultivation practices on the wetland edge.

The water use rates of reedbed and wet woodland habitats

To create hydrologically sustainable wetlands, knowledge of the water use requirements of target habitats must be known. Extensive literature reviews highlighted a dearth of water-use data associated with large reedbeds and wet woodland habitats and in response to this field experiments were established. Field experiments to measure the water use rates of large reedbeds [ET(Reed)] were completed at three sites within the UK. Reference Crop Evapotranspiration [ETo] was calculated and mean monthly crop coefficients [Kc(Reed)] were developed. Kc(Reed) was less than 1 during the growing season (March to September), ranging between 0.22 in March and reaching a peak of 0.98 in June. The developed coefficients compare favourably with published data from other large reedbed systems and support the premise that the water use of large reedbeds is lower than that from small/fringe reedbeds. A methodology for determining water use rates from wet woodland habitats (UK NVC Code: W6) is presented, in addition to provisional ET(W6) rates for two sites in the UK. Reference Crop Evapotranspiration [ETo] data was used to develop Kc(W6) values which ranged between 0.89 (LV Lysimeter 1) and 1.64 (CH Lysimeter 2) for the period March to September. The data are comparable with relevant published data and show that the water use rates of wet woodland are higher than most other wetland habitats. Initial observations suggest that water use is related to the habitat’s establishment phase and the age and size of the canopy tree species. A theoretical case study presents crop coefficients associated with wetland habitats and provides an example water budget for the creation of a wetland comprising a mosaic of wetland habitats. The case study shows the critical role that the water use of wetland habitats plays within a water budget.

A method for the in-situ determination of the hydraulic conductivity of gravels as used in constructed wetlands for wastewater treatment

A new instrument and method are described that allow the hydraulic conductivities of highly permeable porous materials, such as gravels in constructed wetlands, to be determined in the field. The instrument consists of a Mariotte siphon and a submersible permeameter cell with manometer take-off tubes, to recreate in-situ the constant head permeameter test typically used with excavated samples. It allows permeability to be measured at different depths and positions over the wetland. Repeatability obtained at fixed positions was good (normalised standard deviation of 1–4%), and results obtained for highly homogenous silica sand compared well when the sand was retested in a lab permeameter (0.32 mm.s–1 and 0.31 mm.s–1 respectively). Practical results have a ±30% associated degree of uncertainty because of the mixed effect of natural variation in gravel core profiles, and interstitial clogging disruption during insertion of the tube into the gravel. This error is small, however, compared to the orders of magnitude spatial variations detected. The technique was used to survey the hydraulic conductivity profile of two constructed wetlands in the UK, aged 1 and 15 years respectively. Measured values were high (up to 900 mm.s –1) and varied by three orders of magnitude, reflecting the immaturity of the wetland. Detailed profiling of the younger system suggested the existence of preferential flow paths at a depth of 200 mm, corresponding to the transition between more coarse and less coarse gravel layers (6–12 mm and 3–6 mm respectively), and transverse drift towards the outlet.

Clogging in subsurface-flow treatment wetlands:measurement, modeling and management

This paper reviews the state of the art in measuring, modeling, and managing clogging in subsurface-flow treatment wetlands. Methods for measuring in situ hydraulic conductivity in treatment wetlands are now available, which provide valuable insight into assessing and evaluating the extent of clogging. These results, paired with the information from more traditional approaches (e.g., tracer testing and composition of the clog matter) are being incorporated into the latest treatment wetland models. Recent finite element analysis models can now simulate clogging development in subsurface-flow treatment wetlands with reasonable accuracy. Various management strategies have been developed to extend the life of clogged treatment wetlands, including gravel excavation and/or washing, chemical treatment, and application of earthworms. These strategies are compared and available cost information is reported. © 2012 Elsevier Ltd.

Clogging in subsurface-flow treatment wetlands:occurrence and contributing factors

Clogging is a major operational and maintenance issue associated with the use of subsurface flow wetlands for wastewater treatment, and can ultimately limit the lifetime of the system. This review considers over two decades of accumulated knowledge regarding clogging in both vertical and horizontal subsurface flow treatment wetlands. The various physical, chemical and biological factors responsible for clogging are identified and discussed. The occurrence of clogging is placed into the context of various design and operational parameters such as wastewater characteristics, upstream treatment processes, intermittent or continuous operation, influent distribution, and media type. This information is then used to describe how clogging develops within, and subsequently impacts, common variants of subsurface flow treatment wetland typically used in the U.S., U.K., France and Germany. Comparison of these systems emphasized that both hydraulic loading rate and solids loading rate need to be considered when designing systems to operate robustly, i.e. hydraulic overloading makes horizontal-flow tertiary treatment systems in the U.K. more susceptible to clogging problems than vertical-flow primary treatment systems in France. Future research should focus on elucidating the underlying mechanisms of clogging as they relate to the design, operation, and maintenance of subsurface flow treatment wetlands. © 2010 Elsevier B.V.

The L-31E Surface Water Rediversion Project Final Report: Implementation, Results, and Recommendations

Throughout the Biscayne Bay watershed, existing coastal wetland communities have been cut off from sheet flow for decades. With the expectation that reconnection of these wetlands to upstream water sources would alter existing hydrologic conditions and recreate a more natural sheet flow to Biscayne National Park, a demonstration project on freshwater rediversion was undertaken. The objectives of the project were to document the effects of freshwater diversion on: (a) swamp and nearshore water chemistry and hydrology; (b) soil development processes; (c) macrophyte and benthic algal community composition, structure and production; (d) abundance of epiphytic and epibenthic invertebrates; (e) zonation, production, and phenology of primary producers in the nearshore environment, and (f) exchanges of nutrients and particulates between nearshore and mangrove ecosystems.

The exchange of carbon, nitrogen, and phosphorus in dwarf and fringe mangroves of the oligotrophic southern Everglades

Water management has altered both the natural timing and volume of freshwater delivered to Everglades National Park. This is especially true for Taylor Slough and the C-111 basin, as hypersaline events in Florida Bay have been linked to reduced freshwater flow in this area. In light of recent efforts to restore historical flows to the eastern Everglades, an understanding of the impact of this hydrologic shift is needed in order to predict the trajectory of restoration. I conducted a study to assess the importance of season, water chemistry, and hydrologic conditions on the exchange of nutrients in dwarf and fringe mangrove wetlands along Taylor Slough. I also performed mangrove leaf decomposition studies to determine the contribution of biotic and abiotic processes to mass loss, the effect of salinity and season on degradation rates, and the importance of this litter component as a rapid source of nutrients. ^ Dwarf mangrove wetlands consistently imported total nutrients (C, N, and P) and released NO2− +NO3 −, with enhanced release during the dry season. Ammonium flux shifted from uptake to release over the study period. Dissolved phosphate activity was difficult to discern in either wetland, as concentrations were often below detection limits. Fluxes of dissolved inorganic nitrogen in the fringe wetland were positively related to DIN concentrations. The opposite was found for total nitrogen in the fringe wetland. A dynamic budget revealed a net annual export of TN to Florida Bay that was highest during the wet season. Simulated increases and decreases in freshwater flow yielded reduced exports of TN to Florida Bay as a result of changes in subsystem and water flux characteristics. Finally, abiotic processes yielded substantial nutrient and mass losses from senesced leaves with little influence of salinity. Dwarf mangrove leaf litter appeared to be a considerable source of nutrients to the water column of this highly oligotrophic wetland. To summarize, nutrient dynamics at the subsystem level were sensitive to short-term changes in hydrologic and seasonal conditions. These findings suggest that increased freshwater flow has the potential to lead to long-term, system-level changes that may reach as far as eastern Florida Bay. ^

Understanding anuran community dynamics in temporary wetlands: The interaction and importance of landscape and biotic processes

The major objective of this study was to determine the relative importance of landscape factors, local abiotic factors, and biotic interactions in influencing tadpole community structure in temporary wetlands. I also examined the influence of agricultural activities in South-central Florida by comparing tadpole communities in native prairie wetlands (a relatively unmodified habitat) at the Kissimmee Prairie Sanctuary (KPS) to tadpole communities in three agriculturally modified habitats found at MacArthur Agro-Ecology Research Center (MAERC). Environmental characteristics were measured in 24 isolated wetlands, and tadpoles were sampled using throw-traps and dipnets during the 1999 wet season (June–October). Landscape characteristics were expected to predominately influence all aspects of community structure because anurans associated with temporary wetland systems are likely to exist as metapopulations. Both landscape characteristics (wetland proximity to nearest woodland and the amount of woodland surrounding the wetland) and biotic interactions (fish predation) had the largest influence on tadpole community structure. Predatory fish influenced tadpole communities more than expected due to the ubiquity of wetlands, lack of topographic relief, and dispersal abilities of several fish species. Differences in tadpole community structure among habitat types were attributed to differences in woodland attributes and susceptibility to fish colonization. Furthermore, agricultural modification of prairie habitats in South-central Florida may benefit amphibian communities, particularly woodland-dwelling species that are unable to coexist with predatory fish. From a conservation standpoint, temporary wetlands proximal to woodland areas and isolated from permanent water sources appear to be most important to amphibians. In addition, the high tadpole densities attained in these wetlands suggest that these wetlands serve as biological hotspots within the landscape, and their benefits extend into the adjacent terrestrial matrix. Further research efforts are needed to quantify the biological productivity of these systems and determine spatial dynamics of anurans in surrounding terrestrial habitats. ^

Vegetation dynamics and their implications for the management of wetlands in the lowlands of Nepal

The maintenance of species richness is often a priority in the management of nature reserves, where consumptive use of resources is generally prohibited. The purpose of this research was to improve management by understanding the vegetation dynamics in the lowlands of Nepal. The objectives were to determine vegetation associations in relation to environments and human-induced disturbances that affect vegetation dynamics on floodplains, where upstream barrages had altered flooding patterns, and consumptive use of plant resources was influencing natural processes. Floodplain vegetation in relation to physical environments and disturbances were studied along transects, perpendicular to the course of the Mahakali River in the western Terai, Nepal. Forest structural changes were studied for three years in ten plots. A randomized split-block experiment with nine burning and grazing treatments was performed in seasonally flooded grasslands. A semi-structured questionnaire was used to assess people's socio-economic status, natural resource use patterns and conservation attitudes. ^ Elevation, soil organic matter, nitrogen, percentage of sand and grazing intensity were significant in delineating herbaceous vegetation assemblages, whereas elevation and livestock grazing were significant in defining forest type boundaries. On the floodplain islands, highly grazed Dalbergia sissoo-Acacia catechu forests were devoid of understory woody vegetation, but the lightly grazed D. sissoo-mixed forests had a well-developed second canopy layer, comprising woody species other than D. sissoo and A. catechu. In grasslands, species richness and biomass production were highest at intermediate disturbance level represented by the lightly grazed and ungrazed early-burned treatments. Ethnicity, education and resource use patterns were important in influencing conservation attitudes. A succession towards the mixed forests would occur in D. sissoo-dominated floodplain forests, where dams and barrages reduce flooding and associated fluvial processes, and if livestock grazing is stopped, as occasionally suggested by nature conservationists. In seasonally flooded grasslands, early burning with moderate grazing would enhance the species diversity and productivity. There is a need to implement a participatory integrated wetland management plan, to include community development, education and off farm income generation, to assure participatory conservation and management of wetlands in Nepal. ^