The Allocation of Inorganic Nitrogen (↑1↑5NH↓4[superscript]+) to Soil, Microbial and Plant Biomass in an Arctic Salt Marsh [microform]
The Allocation of Inorganic Nitrogen (↑1↑5NH↓4[superscript]+) to Soil, Microbial and Plant Biomass in an Arctic Salt Marsh [microform]

Author: Kate M. (Kate Margaret) Buckeridge

Publisher: Library and Archives Canada = Bibliothèque et Archives Canada

Published: 2004

Total Pages: 214

ISBN-13: 9780612951976

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This study has demonstrated, through the shared distribution of a single resource (15NH4+), that plants and soil microbes compete for inorganic N in a N-limited system. At La Perouse Bay, soil microorganisms out-compete plants for this resource, but their competitive advantage is dampened relative to microorganisms in other Arctic ecosystems by the effects of goose grazing that promote plant growth via the addition of faeces. There is a seasonal displacement of N allocation, as microbes continue to mineralize and slowly immobilize nitrogen in the winter. Loss of vegetation, as a result of goose grubbing, has led to changes in soil characteristics, including high salinity and low redox potentials. These edaphic conditions may dampen N-uptake by soil microorganisms in these disturbed soils. Seasonal and grazing effects interact to contribute to a large potential N loss from these soils, although this is minimized by the apparent abiotic fixation of inorganic N.

Nitrogen Fertilization Enhances Soil Organic Carbon Accumulation by Improving Photosynthetic C Assimilation and Root Exudation Efficiency in a Salt Marsh
Nitrogen Fertilization Enhances Soil Organic Carbon Accumulation by Improving Photosynthetic C Assimilation and Root Exudation Efficiency in a Salt Marsh

Author: juanyong li

Publisher:

Published: 2023

Total Pages: 0

ISBN-13:

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Although salt marshes cover only a small area of the Earth, their contribution to long term carbon (C) burial is comparable to C sinks in many more dominant terrestrial ecosystem types. Continuous nitrogen (N) loading alters plant growth and subsequently has the potential to impact soil organic carbon (SOC) accumulation in salt marshes. However, there is presently little information concerning the input and allocation of photosynthesized C in plant-soil-microbial systems. This knowledge gap hampers the quantification of C fluxes and the clarification of the mechanisms controlling the C budget under N loading in salt marsh ecosystems. To address this, we conducted an N fertilization field observation combined with a five hour 13C-pulse labeling experiment in a salt marsh dominated by Suaeda. salsa (S. salsa) in the Yellow River Delta, China. N fertilization increased net 13C assimilation of S. Salsa by 177.37%, which was primarily allocated to aboveground biomass and SOC. However, N fertilization had little effect on 13C allocation to belowground biomass. Correlation analysis showed that 13C incorporation in soil was significantly and linearly correlated with 13C incorporation in shoots rather than in roots both in a 0N (0 g N m-2 yr-1) and +N (20 g N m-2 yr-1) group. The results suggest that SOC increase under N fertilization was mainly due to an increased C assimilation rate and more efficient downward transfer of photosynthesized C instead of root lysate and detritus. In addition, N fertilization strongly improved the 13C amounts in the chloroform-labile SOC component by 315%. However, the absolute increment of newly fix 13C mainly existed in the form of residual SOC, which had more tendency for burial in the soil. Thus, N fertilization enhanced SOC accumulation although C loss increased via belowground respiration. These results have important implications for predicting the carbon budget under further human-induced N loading.

Dynamics of Carbon and Nitrogen in a Southern California Salt Marsh
Dynamics of Carbon and Nitrogen in a Southern California Salt Marsh

Author: Theodore Paul Winfield

Publisher:

Published: 1980

Total Pages: 182

ISBN-13:

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This study explores three functional aspects of the salt marsh-estuarine ecosystem in the Tijuana Estuary (southern California): primary productivity of the salt marsh vascular plants, organic carbon cycle, and inorganic nitrogen cycle. The productivity study was designed to test the hypothesis that the salt marsh vascular plants in the Tijuana Estuary are not as productive as those in eastern coastal marshes. Spartina foliosa was found to be the most productive individual species in terms of dry weight and carbon, but succulent plant species as a group contributed more to the overall vascular plant productivity. On a dry weight basis net above-ground primary productivity (NAPP) averaged 0.8kg/m('2)/yr which was approximately 240g C/m('2)/yr. Carbon productivity of vascular plants was low in comparison to Atlantic and Gulf of Mexico marshes, and differences were attributed to the more saline soils of southern California. Standing dead biomass and litter averaged over the total marsh surface were constant throughout the study period. The decomposition rate of selected grass species was slower than that for succulent species and the decomposition rate for all plant material varied with elevation, being faster in the tidal creeks and slowest in the upper marsh. The organic carbon study was designed to provide data on the quality and quantity of the various forms of organic carbon being transported to and from the marsh surface in the tidal waters. The data were used in conjunction with those generated from the productivity study to evaluate the hypothesis that the Tijuana Estuary salt marsh exports a substantial amount (45-50%) of the organic carbon produced and that a major portion of the export is as particulate organic carbon (POC). The concentration of POC, dissolved organic carbon (DOC), ATP and chlorophyll a was measured in water samples collected periodically during a tidal cycle each month. Organic carbon was exported as DOC (40-110g C/m('2)/yr) and showed a slight import of POC (5-6g C/m('2)/yr). POC was mainly detrital carbon as opposed to biomass carbon. The Tijuana Estuary salt marsh exports substantially less than 50% of its NAPP, and export is in the dissolved form as opposed to particulate. Results of this and other recent studies suggest that a re-evaluation of salt marsh carbon flow models is needed. The purpose of the inorganic nitrogen study was to document the distribution of ammonium, nitrate and nitrite in the tidal waters draining the Tijuana Estuary salt marsh and to evaluate the tidal waters as a source of nitrogen for salt marsh vegetation. The inorganic nitrogen cycle was characterized by the annual import of ammonium and slight annual export of nitrate. Ammonium was found to be the dominant form of inorganic nitrogen except in the late spring when nitrate was dominant. Inorganic nitrogen import totalled 1.1 - 2.16g N/m('2)/yr. The import of inorganic nitrogen accounted for 28% of the nitrogen required by salt marsh vascular plants, but only 6% of the combined productivity of vascular plants and benthic algae. Nitrogen regeneration processes within the salt marsh are important in meeting the nitrogen needs of salt marsh vegetation.

Salt Marsh Nitrogen Analysis
Salt Marsh Nitrogen Analysis

Author: Thomas M. Leschine

Publisher:

Published: 1979

Total Pages: 64

ISBN-13:

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A five compartment schematic model of the flow of nitrogen through Great Sippewissett Marsh is presented. Flows are described in terms of annual inputs, outputs and intercompartmental transfers of nitrogen. The nitrogen in all forms occurring in the marsh is considered, though dissolved organic nitrogen is disaggregated from the total flow. A computer aided input - output analysis is performed on the model to assess the degree to which nitrogen inputs to the marsh surface are linked to nitrogen outputs in the form of net growth in marsh shellfish. In this way the effects of both direct and indirect flows linking the two compartments involved are considered. The analysis is done to assess the likelihood that a large scale application of fertilizer to the marsh surface will signjficantly enhance shellfish growth in marsh tidal creeks. While no definitive answer to this question can be given, it is argued that the present level of understanding of the marsh nitrogen cycle does not support an expectation that shellfish growth will be enhanced. This argument is supported by a comparative analysis which shows a strong likelihood that Spartina growth is enhanced by fertilization, an effect which has already been observed.

Fungal Succession and Carbon Quality as Drivers of Nitrogen Removal Capacity in a Constructed Salt Marsh
Fungal Succession and Carbon Quality as Drivers of Nitrogen Removal Capacity in a Constructed Salt Marsh

Author: Sommer Faith Starr

Publisher:

Published: 2020

Total Pages: 152

ISBN-13:

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Coastal wetlands mitigate excess nutrient inputs by acting as important sites of denitrification. Despite their role in removing excess nitrogen, coastal wetland area has declined by more than 50% in the 20th century, representing a potential loss of ecosystem service. To restore lost function, managers have devoted much effort to salt marsh restoration and construction. However, constructed marshes have lower function than natural marshes even with similar plant biomass. I conducted two experimental studies to 1) compare nitrogen (N) cycling rates between constructed and natural marshes, and 2) to assess microbial biomass/activity and carbon (C) quality differences as potential factors influencing the return of N cycling in constructed Gulf of Mexico salt marshes. In the first experiment, sediment was collected from a constructed and natural marsh and treated with inhibitors to isolate bacterial and fungal contributions to total denitrification. The constructed marsh had 3x lower total denitrification, 4x lower sediment fungal biomass and lower fungal denitrification than the natural marsh. Increased process rates following microbial inhibition in the natural marsh indicate the occurrence of microbial competition for nitrate. These results suggest that fungi and bacteria contribute differently to rates of incomplete denitrification between natural and constructed marshes and that constructed marshes have lower fungal biomass than natural marshes. In the second experiment, sediment was incubated for 19 days in ~149L aquaria and treated with labile or recalcitrant C under ambient or high nitrate conditions. Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates and microbial biomass were measured at three points during the incubation, and overlying water was sampled every two days for nutrient concentrations. Both denitrification and DNRA rates were similar between marshes, and labile C additions increased DNRA by more than 12x and reduced the ratio of denitrification to DNRA by as much as 22x. Nutrient concentrations were similar between marshes. Both fungal and bacterial biomass were lower in the constructed marsh. Collectively, the results of these experiments highlight that constructed marshes can reach functional recovery after 30 years and remove N as effectively as reference marshes, despite differences in microbial biomass and starting C and N stocks.

Underground Biomass Dynamics and Substrate Selective Properties of Atlantic Coastal Salt Marsh Plants
Underground Biomass Dynamics and Substrate Selective Properties of Atlantic Coastal Salt Marsh Plants

Author: John L. Gallagher

Publisher:

Published: 1977

Total Pages: 142

ISBN-13:

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An intensive study was made of the dynamics of the underground portion of selected salt marsh plants along the U.S. Atlantic Coast. The plants studied included: Borrichia frutescens, Carex paleacea, Distichlis spicata, Eleocharis obtusa, Juncus gerardi J. roemerianus, Phragmites communis, Salicornia virginica, Spartina alterniflora, S. bakeri, S. cynosuroides, S. patens, and Sporobolus virginicus. The study provides information applicable to marsh development on dredged material, particularly methodologies that can be used for determining which marsh plants will be likely to do well on various kinds of dredged material and when a marsh, which has been established on dredged material, approaches natural conditions. The overall study focuses on: an investigation of underground biomass dynamics; characterization of soils supporting the salt marsh plants; and experimentation on the substrate selective properties of several of the marsh plants studied. The following topics are included: underground biomass profiles and dynamics in Atlantic coastal marshes; comparison of some tidal marsh soils along the Atlantic Coast; response of salt marsh plant stands to a pulse of ammonium nitrate; salt marsh plant growth on three types of dredged material; and a bioassay approach to studying marsh plant root growth in natural soil and dredged material.