J. T. Morris- PhD
- Professor at University of South Carolina
J. T. Morris
- PhD
- Professor at University of South Carolina
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99
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Publications (99)
Different CO2 exchange pathways were monitored for a year in short- and tall-form Spartina alterniflora grasses in a southeastern USA salt marsh at North Inlet, South Carolina. The tall form of grass growing close to a creek under favorable conditions reached a higher standing biomass than the short form of grass growing in the interior marsh. Howe...
In the Sacramento–San Joaquin Delta (Delta), widespread drainage of historical wetlands has led to extensive subsidence and peat carbon losses, as well as high ongoing greenhouse gas (GHG) emissions. Large-scale wetland restoration and conversion to rice fields has the potential to mitigate these effects while conferring flood protection and creati...
The evolution of coastal wetlands is a complex process which is difficult to forecast, made more complicated by the addition of changing climatic conditions. Here, long term ecological and geomorphological data are coupled to geotechnical measurements at a coastal wetland in North Inlet estuary, South Carolina. The coupled methodology is presented...
Accompanying climate change and sea level rise, tidal marsh mortality in coastal wetlands has been globally observed that urges the documentation of high-resolution, 3D marsh inventory to assist resilience planning. Drone Lidar has proven useful in extracting the fine-scale bare earth terrain and canopy height. Beyond that, this study performed mar...
Heterotrophic activity, primarily driven by sulfate-reducing prokaryotes, has traditionally been linked to nitrogen fixation in the root zone of coastal marine plants, leaving the role of chemolithoautotrophy in this process unexplored. Here, we show that sulfur oxidation coupled to nitrogen fixation is a previously overlooked process providing nit...
A network of 15 Surface Elevation Tables (SETs) at North Inlet estuary, South Carolina, has been monitored on annual or monthly time scales beginning from 1990 to 1996 and continuing through 2022. Of 73 time series in control plots, 12 had elevation gains equal to or exceeding the local rate of sea-level rise (SLR, 0.34 cm/year). Rising marsh eleva...
Tidal marshes are dynamic environments providing important ecological and economic services in coastal regions. With accelerating climate change and sea level rise (SLR), marsh mortality and wetland conversion have been observed on global coasts. For sustainable coastal management, accurate projection of SLR-induced tidal inundation and flooding re...
A network of 15 Surface Elevation Tables (SET) at North Inlet estuary, SC, have been monitored on annual or monthly time scales beginning from 1990 to 1996. The initial elevations spanned a range from suboptimal to superoptimal relative to the vertical growth range of the dominant vegetation, Spartina alterniflora . Of 98 time series, 20 have eleva...
Symbiotic root microbiota are crucial for plant growth as they assist their hosts in nutrient acquisition. In the roots of coastal marine plants, heterotrophic activity in the rhizosphere by sulfate-reducing microorganisms has been linked to nitrogen fixation. In this study, we recovered 239 high-quality metagenome-assembled genomes (MAGs) from a s...
The frequency of salt marsh dieback events has increased over the last 25 years with unknown consequences to the resilience of the ecosystem to accelerated sea level rise (SLR). Salt marsh ecosystems impacted by sudden vegetation die-back events were previously thought to recover naturally within a few months to years. In this study, we used a 13-y...
Mangrove trees are invading saltmarshes at subtropical ecotones globally, but the consequences of this vegetation shift for ecosystem sustainability remain unknown. Using the Coastal Wetland Equilibrium Model (CWEM) to simulate vegetation survival and sediment accretion, we predict that black mangroves, Avicennia germinans, can build soil elevation...
Processed-based biogeochemical mathematical models are powerful tools that are increasingly being used to estimate potential carbon sequestration and greenhouse gas (GHG) impacts of management at a landscape level. These models can simulate some or all of the processes responsible for carbon sequestration and GHG emissions, which can relieve some o...
The frequency of salt marsh dieback events has increased over the last 25 years with unknown consequences to the resilience of the ecosystem to accelerated sea level rise (SLR). Salt marsh ecosystems impacted by sudden vegetation dieback events were previously thought to recover naturally within a few months to years. In this study, we provide evid...
Deltaic floodplains are highly vulnerable to relative sea level rise (RSLR) depending on the sediment supply from river channels that provides elevation capital as adaptation mechanism. In river channels where levees have restricted sediment supply to coastal deltaic floodplains, river sediment diversions have been proposed as a restoration strateg...
Coastal tidal marshes are essential ecosystems for both economic and ecological reasons. They necessitate regular monitoring as the effects of climate change begin to be manifested in changes to marsh vegetation healthiness. Small unmanned aerial systems (sUAS) build upon previously established remote sensing techniques to monitor a variety of vege...
Shrubs are invading into grasslands around the world, but we don’t yet know how these shrubs will fare in a warmer future. In ecotonal coastal wetland ecosystems, woody mangroves are encroaching into herbaceous salt marshes owing to changes in temperature, precipitation, and sediment dynamics. Increasing mangrove biomass in wetlands often increases...
This study reports an inventory of marsh dieback events from spatial and temporal perspectives in the North Inlet-Winyah Bay (NIWB) estuary, South Carolina (SC). Past studies in the Gulf/Atlantic coast states have reported acute marsh dieback events in which marsh rapidly browned and thinned, leaving stubble of dead stems or mudflat with damaged ec...
In 2014, a DNA‐based phylogenetic study confirming the paraphyly of the grass subtribe Sporobolinae proposed the creation of a large monophyletic genus Sporobolus, including (among others) species previously included in the genera Spartina, Calamovilfa, and Sporobolus. Spartina species have contributed substantially (and continue contributing) to o...
Coastal salt marshes are biologically productive ecosystems that generate and sequester significant quantities of organic matter. Plant biomass varies spatially within a salt marsh and it is tedious and often logistically impractical to quantify biomass from field measurements across an entire landscape. Satellite data are useful for estimating abo...
Rapid invasion of Spartina alterniflora into Chinese coastal wetlands has attracted much attention. Many field and remote sensing studies have examined the spatio-temporal dynamics of S. alterniflora invasion; however, spatially explicit quantitative analyses of S. alterniflora invasion and its underlying mechanisms at both patch and landscape scal...
Over 25% of Mississippi River delta plain (MRDP) wetlands were lost over the past century. There is currently a major effort to restore the MRDP focused on a 50-year time horizon, a period during which the energy system and climate will change dramatically. We used a calibrated MRDP marsh elevation model to assess the costs of hydraulic dredging to...
We measured methane emissions together with acetate, DMS, sulfate, and dissolved methane concentrations in pore waters from adjacent marsh plant communities in an oligohaline marsh of the Min River estuary, southeastern China-one community dominated by a native species, Cyperus malaccensis, the other by the exotic Spartina alterniflora. The objecti...
We evaluated the importance of both tidal inundation and nutrient fertilization as drivers of elevation change in coastal salt marshes. The three sites investigated occurred along a 9-km stretch of the Atlantic Intracoastal Water Way in Central North Carolina. Despite their close geographic proximity, the sites varied in tidal range, elevation with...
Reducing uncertainty in data inputs at relevant spatial scales can improve tidal marsh forecasting models, and their usefulness in coastal climate change adaptation decisions. The Marsh Equilibrium Model (MEM), a one-dimensional mechanistic elevation model, incorporates feedbacks of organic and inorganic inputs to project elevations under sea-level...
Climate change is altering sea level rise rates and precipitation patterns worldwide. Coastal wetlands are vulnerable to these changes. System responses to stressors are important for resource managers and environmental stewards to understand in order to best manage them. Thin layer sand or sediment application to drowning and eroding marshes is on...
Supporting data for the results.
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Coastal marshes are important ecosystems that provide an array of ecosystem services. With increasing sea level these marshes may negatively be impacted. Salinity is one variable that influences production within marshes. Gaining a better understanding of the major parameters that influence salinity will provide a better understanding of how marshe...
Among the solutions being proposed for reversing wetland loss in the Mississippi River Delta are the creation of diversions to reintroduce suspended sediment carried in the river. In areas of rapid relative sea-level rise, as in the Mississippi Delta, it is generally accepted that a supply of sediment in flood water and mineral sedimentation are cr...
Among the solutions being proposed for reversing wetland loss in the Mississippi River Delta are the creation of diversions to reintroduce suspended sediment carried in the river. In areas of rapid relative sea-level rise, as in the Mississippi Delta, it is generally accepted that a supply of sediment in flood water and mineral sedimentation are cr...
The coupling of geomorphological and ecological processes is critical for the maintenance or disappearance of salt marshes. Emergent macrophytes dampen wave- and tide-generated shear stresses, promoting sediment deposition and marsh formation. The complex interactions among marsh primary productivity, sea level, and sedimentation determine the equi...
Coastal landscapes are often dominated by extensive tidal flats. Tidal flats are characterized by near-horizontal topography and are typically depositional environments that store sediments transported by rivers and nearshore currents. These environments support a diverse biota that modifies the erosive characteristics of the substrate and mediates...
As the Gulf of Mexico recovers from the Deepwater Horizon oil spill, natural resource managers face the challenge of understanding the impacts of the spill and setting priorities for restoration work. The full value of losses resulting from the spill cannot be captured, however, without consideration of changes in ecosystem services--the benefits d...
1] Assumptions of a static landscape inspire predictions that about half of the world's coastal wetlands will submerge during this century in response to sea‐level acceleration. In contrast, we use simulations from five numerical models to quantify the conditions under which ecogeomorphic feed-backs allow coastal wetlands to adapt to projected chan...
Data from salt marshes in the U.S. Southeast show that long-term variations in salt marsh productivity and porewater salinity correlate strongly with mean water level (MWL). To understand how tidally-influenced groundwater flow might control these correlations, we developed process-based numerical models to assess the effect of variations in MWL on...
Sea level rise (SLR) has the potential to affect a variety of coastal habitats with a myriad of deleterious ecological effects and to overwhelm human settlements along the coast. SLR should be given serious consideration when more than half of the U.S. population lives within 50 miles of the coast. SLR effects will be felt along coastal beaches and...
The importance of groundwater flow for wetland zonation and productivity is particularly striking in salt marsh ecosystems, where tidally-influenced groundwater flow controls salinity in addition to saturation state and nutrient transport. Here we describe complex interactions between groundwater, rainfall, evapotranspiration and surface water in a...
Long-term storage of organic carbon in sediment is one of the key functions of coastal wetlands. Owing to the rise of sea level, a fraction of their primary production is buried annually. However, the productivity of tidelands and, hence, carbon accretion depend on their relative elevation within the tidal frame. It has been shown empirically that...
1] Plants are known to enhance sedimentation on intertidal marshes. It is unclear, however, if the dominant mechanism of enhanced sedimentation is direct organic sedimentation, particle capture by plant stems, or enhanced settling due to a reduction in turbulent kinetic energy within flows through the plant canopy. Here we combine several previousl...
We measured concentrations of dimethylsulfoniopropionate (DMSP) in Spartina alterniflora (Loisel.) in response to the plant hormones abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) to determine whether DMSP concentration is linked to any of their signaling pathways. DMSP concentrations were also measured in plants at a salt marsh d...
The rate of accretion on coastal salt marshes depends on feedbacks between flow, macrophyte growth, and sedimentation. Under favourable conditions, marsh accretion rates will keep pace with the local rate of sea level rise. Marsh accretion is driven by both organic and inorganic sedimentation; mineral rich marshes will need less organic sedimentati...
Because nitrogen and phosphorus are primary resources for plant, algal, and microbial production, increases in nutrient inputs
can markedly alter aquatic ecosystems. Coastal wetland plots at Belle W. Baruch Marine Field Laboratory (South Carolina, USA)
have been amended with nitrogen and phosphorus for ~20 years to determine the effects of nutrient...
Extensive vegetated marshes, and the channel networks that wind through them, provide a striking example of a geomorphic system in which physical and biological processes interact to facilitate stability in an environment characterized by fluctuations in sea level and sediment inputs. Moderate increases in inundation tend to enhance vegetation prod...
Sea-level rise and sedimentation interact to control productivity on coastal salt marshes since the mean sea level influences flood frequency. Irregularly flooded marshes are inundated during spring and storm tides and during extended periods of north-easterly winds. The weak and irregular inundation in marshes may effect rates of decomposition, or...
Bottom-up factors such as nutrient availability have long been thought to be the primary regulators of plant growth in salt
marshes. However, that paradigm has been challenged by investigations showing that grazing by the periwinkle snailLittoraria irrorata regulatesSpartina alterniflora growth through top-down forces. Our investigation was conduct...
Salt marshes accrete both organic and inorganic sediments. Here we present analytical and numerical models of salt marsh sedimentation that, in addition to capturing inorganic processes, explicitly account for above- and belowground organic processes including root growth and decay of organic carbon. The analytical model is used to examine the bias...
Marshes worldwide are actively degrading in response to increased sea level rise rates and reduced sediment delivery, though the growth rate of vegetation plays a critical role in determining their stability. We have compiled 56 measurements of aboveground annual productivity for Spartina alterniflora, the dominant macrophyte in North American coas...
Unlike freshwater wetlands, tidal salt marshes export significant dissolved reactive phosphorus (DRP) and ammonium to adjacent surface waters. Here we used long-term nutrient and salinity records from porewaters and tidal creeks collected at North Inlet, SC and numerical models of tidally-driven groundwater flow to investigate the role of tidal for...
Astronomically forced changes in the hydroperiod of a salt marsh affect the rate of marsh primary production leading to a biogeochemical cascade. For example, salt marsh primary production and biogeochemical cycles in coastal salt marshes are sensitive to the 18.6-year lunar nodal cycle, which alters the tidal amplitude by about 5 cm. For marshes t...
Tidal freshwater sections of the Cooper River Estuary (South Carolina) include extensive wetlands, which were formerly impounded
for rice culture during the 1,700s and 1,800s. Most of these former rice fields are now open to tidal exchange and have developed
into productive wetlands that vary in bottom topography, tidal hydrography and vegetation d...
Salt marshes dominate the intertidal zone in temperate latitudes and present some unique features pertaining to measurement of primary production. Several destructive harvest and non-destructive methods for quantifying salt marsh production are described. Allometric methods that account for stem turnover are the recommended approach. Field and labo...
This chapter studies random, steady state food webs of varying size and complexity (up to 2,000 species and 1.3 million connections) which were generated with and without ecologically realistic constraints. This chapter analyses trends in network metrics, such as ascendancy, developmental capacity, and throughput as functions of size and complexity...
Competitive interactions among marsh plant species are mediated by the influence of the vegetation on sediment accretion and modifications of the relative elevation of the marsh surface. A model described here demonstrates some of the feedbacks between physical processes like sediment accretion and biological processes such as those that determine...
We have developed a three dimensional model of tidal marsh accretion and channel network development that couples physical sediment transport processes with biomass productivity. A new, simplified, water routing technique facilitates application of the model over the large spatial and temporal scales necessary to address morphologic and biologic re...
A 1-D model for exploring the interaction between hydrodynamics, sedimentation, and plant community evolution on a salt marsh populated by Spartina alterniflora is developed. In the model tidally induced flows over marsh platforms are affected by S. alterniflora through drag forces. In general macrophyte characteristics are determined by a wide ran...
Extensive loss of global marshlands has been attributed to a combination of sea level rise, subsidence, erosion, and reduced sediment supply. Field and laboratory measurements indicate that in many marshes, vertical accretion rates are in equilibrium with sea level rise. Because vertical accretion rates appear to keep pace with sea level rise even...
Salt marsh ecosystems are maintained by the dominant macrophytes that regulate the elevation of their habitat within a narrow portion of the intertidal zone by accumulating organic matter and trapping inorganic sediment. The long-term stability of these ecosystems is explained by interactions among sea level, land elevation, primary production, and...
Wetland vegetation may be useful in the remediation of shallow contaminated aquifers. Mesocosm experiments were conducted to describe the regulatory mechanisms affecting trichloroethene (TCE) removal rates from groundwater by flood-adapted wetland trees at a contaminated site. TCE flux through baldcypress [Taxodium distichum (L) Rich] seedlings gro...
Results of a 12-yr study in an oligotrophic South Carolina salt marsh demonstrate that soil respiration increased by 795 g C m(-2) yr(-1) and that carbon inventories decreased in sediments fertilized with nitrogen and phosphorus. Fertilized plots became net sources of carbon to the atmosphere, and sediment respiration continues in these plots at an...
The purpose of this investigation was to determine whether tree-core analysis could be used to delineate shallow groundwater contamination by chlorinated ethenes. Analysis of tree cores from bald cypress [Taxodium distichum (L.) Rich], tupelo (Nyssa aquatica L.), sweet gum (Liquidambar stryaciflua L.), oak (Quercus spp.), sycamore (Platanus occiden...
In North Inlet, a tidally dominated salt-marsh estuary near Georgetown, South Carolina, the summer chlorophyll maximum correlates with an annual peak in ambient NH4+ concentration. This relationship suggests that phytoplankton population growth during the summer bloom is Limited by factors other than nutrient supply, because NH4+ is the major inorg...
The effects of sulfide on growth and dimethylsulfoniopropionate (DMSP) concentration in Spartina alterniflora were studied in greenhouse cultures. Spartina plants were maintained in sand-filled pots and supplemented with a balanced nutrient mixture and 1 g/1 of NaCl. After they were well established, plants were separated into four treatment groups...
Salinity can be used as a conservative tracer of porewater turnover in circumstances when evapotranspiration is great enough
to concentrate porewater salts in intertidal sediments. At two intertidal sites situated at mean high tide at North Inlet,
South Carolina, porewater drainage was estimated by this method to be 9.4 m−2 d−1 and 16.6 1 m−2 d−1,...
A two-chamber-system was used to study whole-plant gas exchange responses of Spartina alterniflora to long-term and transient salinity treatments over the range of 5 to 40 ppt NaCl. Lower photosynthetic rates, leaf water vapor conductances, belowground respiration rates, and higher aboveground respiration rates in plants adapted to 40 ppt NaCl were...
A two-chamber-system was used to study whole-plant gas exchange responses of Spartina alterniflora to long-term and transient salinity treatments over the range of 5 to 40 ppt NaCl. Lower photosynthetic rates, leaf water vapor conductances, belowground respiration rates, and higher aboveground respiration rates in plants adapted to 40 ppt NaCl were...
We studied the effects of oxygen (aerated versus O-2 depleted similar to 0.5 mg l(-1) O-2) and nitrate (none versus 10 mu mol l(-1)) on the ammonium uptake kinetics and adenylate pools in two wetland plants differing in their degree of flood tolerance (Phalaris arundinacea L. and Glyceria maxima (Hartm.) Holmb.). The study was performed as a random...
From the 1930s to 1990, the coastal zone of Louisiana lost an estimated 3,950 square kilometers, or 1,526 square miles, of wetlands (i.e., periodically flooded land containing emergent vegetation. This loss of wetlands resulted, for the most part, from
inundation or erosion of wetlands rather than from the draining or filling characteristic of many...
The extent to which Spartina alterniflora Loisel. fixes lacunar CO2 and utilizes dissolved inorganic carbon in the interstitial water of sediment was investigated, and the contribution of these two processes to total primary productivity was estimated and compared with photosynthesis in the leaf blades. Atmospheric CO2 is primarily fixed in the lea...
The extent to which Spartina alterniflora Loisel. excluded, secreted or accumulated the major seawater ions (Cl-, SO2-4, Na+, K+, Mg2+, and Ca2+) was investigated under varying salinity treatments. From a quantitative viewpoint, ion exclusion was most prominent and
accounted for 91–97% of the theoretical maximum ion uptake as a result of transpirat...
Higher pressure, up to several hundred pascal relative to ambient, is generated by hygrometric pressurization within the central hollow space of the stem in Spartina alterniflora. Dilution of oxygen and nitrogen by water vapor within the plant's internal gas space results in an influx of nitrogen and oxygen from the air and a net increase in the in...
A 70% reduction in freshwater discharge through the Cooper River Basin, South Carolina, has provided a unique opportunity
to study changes in estuarine plant communities in response to a system-wide increase in salinity. A one-dimensional tidal
prism mixing model was used to simulate the changes in the longitudinal salinity distribution which have...
The annual aboveground productivity of Spartina alterniflora in a South Carolina saltmarsh varies by a factor of two and correlates positively with anomalies in mean sea level during the growing season. Commercial landings of shrimp and Atlantic menhaden Brevoortia tyrannus from the SE US Atlantic and C Gulf of Mexico are positively correlated with...
(1) Salt-marsh microcosms containing the halophyte Spartina alterniflora were maintained in a greenhouse for 2 years. Microbial and plant activity were monitored monthly in microcosms given daily dosages of a hydrocarbon mixture containing hexane, heptane, octane, nonane, benzene, toluene, ethylbenzene and xylene that comprises about 15% of crude o...
The effects of sulfide concentration and hypoxia on NH"4^@?-uptake kinetics in Spartina alterniflora were examined in a laboratory culture experiment. Both factors significantly influenced the Michaelis-Menten parameters, V"m"a"x and K"m, which characterize the nitrogen uptake rate as a function of nitrogen concentration. Under oxygen-saturated con...
A model of vertical light distribution in plant canopies as a function of canopy biomass and solar angle was derived and fitted to measured light profiles from salt marsh communities of the grass Spartina alterniflora. The model accounted for 73–95% of the variability in light profiles from different canopies at different times of day. In a single...
Measurements of potential denitrification, by the acetylene block technique, and COâ production were made in sediment samples from cores taken to a depth of 185 m on Parris Island, SC. A significant denitrification potential in sediments overlying the Floridan aquifer and in the Floridan aquifer itself was found. Denitrification rates in subsurface...
Previously the growth of Spartina alterniflora has been found to be limited by nitrogen and correlated with sediment redox potential. In this study we have investigated a possible connection between these two factors. We have found that internal °2 transport is insufficient to saturate NH4+ uptake in short S. alterniflora in hydroponic culture. Rat...
Previously the growth of Spartina alterniflora has been found to be limited by nitrogen and correlated with sediment redox potential. In this study we have investigated a possible connection between these two factors. We have found that internal O2 transport is insufficient to saturate NH4⁺ uptake in short S. alterniflora in hydroponic culture. Rat...
A computer model was developed to integrate laboratory and field data concerning the N cycle in a tidal, freshwater marsh and river. The model links hydrodynamics to material transport and biotic processing. Preliminary results from the water transport model agree with observed tide height and salinity data collected over 24-hours. Using inorganic...
Feedbacks between plant biomass density and sedimentation maintain intertidal marshes in equilibrium with mean sea level (MSL).
Stable marshes exist at an elevation that is supraoptimal for the biomass density of marsh macrophytes. At this elevation,
biomass density is sensitive to changes in MSL, and adjustments in productivity and sedimentation r...
Goals: Tidal wetlands provide important ecosystem services (disturbance regulation, biological productivity, waste treatment) to the more than 50% of the world's population that lives in the coastal zone (Craft et al. 2009). They are highly susceptible to rising sea level caused by global warming and there is concern that they may not persist if se...
