Marsh Plant Growth Research Articles

Promoting success in thin layer sediment placement: effects of sediment grain size and amendments on salt marsh plant growth and greenhouse gas exchange

Thin layer sediment placement (TLP) is used to build elevation in marshes, counteracting effects of subsidence and sea level rise. However, TLP success may vary due to plant stress associated with reductions in nutrient availability and hydrologic flushing or through the creation of acid sulfate soils. This study examined the influence of sediment grain size and soil amendments on plant growth, soil and porewater characteristics, and greenhouse gas exchange for three key U.S. salt marsh plants: Spartina alterniflora (synonym Sporobolus alterniflorus), Spartina patens (synonym Sporobolus pumilus), and Salicornia pacifica. We found that bioavailable nitrogen concentrations (measured as extractable NH4+‐N) and porewater pH and salinity were inversely related to grain size, while soil redox was more reducing in finer sediments. This suggests that utilizing finer sediments in TLP projects will result in a more reduced environment with higher nutrient availability, while larger grain sized sediments will be better flushed and oxygenated. We further found that grain size had a significant effect on vegetation biomass allocation and rates of gas exchange, although these effects were species‐specific. We found that soil amendments (biochar and compost) did not subsidize plant growth but were associated with increases in soil respiration and methane emissions. Biochar amendments were additionally ineffective in ameliorating acid sulfate conditions. This study uncovers complex interactions between sediment type and vegetation, emphasizing the limitations of soil amendments. The findings aid restoration project managers in making informed decisions regarding sediment type, target vegetation, and soil amendments for successful TLP projects.

Temporal and Spatial Variation in Vegetation Coverage and Its Response to Climatic Change in Marshes of Sanjiang Plain, China

Sanjiang Plain is the most extensive marsh distribution region in China. Marshes in this region can protect biodiversity, regulate climate, and provide habitats for wild animals and plants. The normalized difference vegetation index (NDVI) is a crucial indicator of vegetation coverage, which may reflect ecosystem structure and functional features. Clarifying the spatiotemporal change of marsh coverage and its climatic drivers is vital for observing and predicting vegetation change in Sanjiang Plain. Using meteorological dataand MODIS NDVI data from 2000 to 2020, we analyzed the spatiotemporal variation in marsh vegetation coverage and climatic change effects in Sanjiang Plain. We found that the growing season vegetation NDVI of marsh increased significantly at a rate of 0.011/decade, indicating that the marsh vegetation growth has obviously improved during the past 21 years. Furthermore, we found that the increase of minimum (Tmin) and maximum (Tmax) temperature in July can significantly promote the marsh plant growth, and increasing nighttime Tmin has a stronger impact on promoting the growth than increasing daytime Tmax in this month. In addition, the increase of daytime Tmax in August can promote the marsh vegetation growth, whereas the increasing precipitation in August was unfavorable for the growth in Sanjiang Plain.

Surface Water and Groundwater Interactions in Salt Marshes and Their Impact on Plant Ecology and Coastal Biogeochemistry

AbstractSalt marshes are highly productive intertidal wetlands providing important ecological services for maintaining coastal biodiversity, buffering against oceanic storms, and acting as efficient carbon sinks. However, about half of these wetlands have been lost globally due to human activities and climate change. Inundated periodically by tidal water, salt marshes are subjected to strong surface water and groundwater interactions, which affect marsh plant growth and biogeochemical exchange with coastal water. This paper reviews the state of knowledge and current approaches to quantifying marsh surface water and groundwater interactions with a focus on porewater flow and associated soil conditions in connection with plant zonation as well as carbon, nutrients, and greenhouse gas fluxes. Porewater flow and solute transport in salt marshes are primarily driven by tides with moderate regulation by rainfall, evapotranspiration and sea level rise. Tidal fluctuations play a key role in plant zonation through alteration of soil aeration and salt transport, and drive the export of significant fluxes of carbon and nutrients to coastal water. Despite recent progress, major knowledge gaps remain. Previous studies focused on flows in creek‐perpendicular marsh sections and overlooked multi‐scale 3D behaviors. Understanding of marsh ecological‐hydrological links under combined influences of different forcing factors and boundary disturbances is lacking. Variations of surface water and groundwater temperatures affect porewater flow, soil conditions and biogeochemical exchanges, but the extent and underlying mechanisms remain unknown. We need to fill these knowledge gaps to advance understanding of salt marshes and thus enhance our ability to protect and restore them.

Inoculating rhizome-propagated Sporobolus pumilus with a native mycorrhizal fungus increases salt marsh plant growth and survival

Salt marshes are ecosystems of significant ecological importance for coastal stability and fundamental roles in marine ecosystems. Salt marshes are declining due to anthropogenic and natural causes including sea level rise. Coastal restoration efforts have increased worldwide, but many fail in long-term coastal stability. We used a naturally occurring arbuscular mycorrhizal fungus (AMF) to test whether survival and early growth of the salt marsh grass Sporobolus pumilus (formerly Spartina patens) improved under simulated salt marsh conditions. Using a tidal mesocosm bench, we grew inoculated plants with varying AMF treatments under simulated tidal regimes to determine if AMF could aid in establishment of healthy Sporobolus communities. Rhizome-derived S. pumilus had greater survival and grew faster than seed-derived plants. Plants inoculated with propagated AMF consistently outperformed both sterile and native sediment controls in terms of plant survival and growth. Use of rhizome-derived Sporobolus inoculated with propagated Funneliformis geosporum showed the most promise in producing successful plant populations for salt marsh restoration. This may be due to plant life stage and improved plant nutrient status, allowing rhizome-derived plants to grow more quickly than seed-derived plants. Using these plants in future large-scale restoration may increase re-establishment of salt marsh ecosystems.

Increasing grazer density leads to linear decreases in Spartina alterniflora biomass and exponential increases in grazing pressure across a barrier island

Researchers now recognize that top-down as well as bottom-up forces regulate salt marsh primary production. However, how top-down forces vary with grazer density is still poorly resolved. To begin to address this void, we (1) surveyed grazing intensity in short-form Spartina alterniflora across Sapelo Island, Georgia (USA), and (2) removed varying densities of grazers from 13 sites over 2 yr. Our survey revealed a non-linear relationship between snail abundance and grazing intensity, with grazing scars per stem increasing exponentially with snail density. Further, there appeared to be a threshold at ~80 snails m-2, below which increasing snail density did not significantly increase grazing scars—potentially because snails target dead grass rather than live grass when competition with other snails is low. Increasing snail densities also exponentially reduced stem density within a plot, but only over 80 snails m-2. Our removal experiment showed that snails linearly decreased S. alterniflora biomass across a naturally representative range of snails (0-586 snails m-2) and that top-down control of short-form S. alterniflora was important at multiple sites across an island, with snail removal on average increasing primary production by 164%. Our results reveal that top-down control of short-form S. alterniflora is a common process across this intensively studied island, and that grazing scars increase non-linearly with snail density, while consumer effects on biomass increase linearly. Future models based on marsh plant growth (e.g. geomorphic evolution, primary production) should incorporate both the importance and functional form of grazer control to create more accurate carbon budgets and to better understand marsh network dynamics.

Response of a salt marsh plant to sediment deposition disturbance

Salt marshes (a type of coastal wetland with herbaceous plants) are one of the most productive ecosystems. The organic matter accumulated by plants, together with deposition of inorganic mineral sediments, contributes to vertical marsh growth and determines the marsh ability to cope with regional sea level rise. Deposition of mineral sediment, in turn, alters the growth of plant roots and shoots, and further marsh morphology and blue carbon storage. Based on mesocosm experiments simulating the sedimentation intensity, this paper examined the responses of Spartina alterniflora (a plant widely distributed in global salt marshes) to sediment deposition events (0–24 cm thicknesses). The plant height increased by 1.51 cm on average with 1 cm sediment deposition. New roots grew into the deposited sediment layers, resulting in a significant increase in the below-ground biomass. The below-ground biomass doubled with the treatment of 24 cm deposition thickness in comparison with that without deposition. The depth-dependent distribution of below-ground biomass changed from a monotonous (decreasing with soil depth) to a non-monotonic (increasing first and then decreasing) trend. This illustrates the growth of marsh plants in response to sediment deposition disturbance (similar to artificial or storm-induced sediment deposition) and have important implications for further investigations on marsh resiliency, blue carbon storage and marsh morphology.

Salt Marsh Migration into Lawns Revealed by a Novel Sediment-Based Approach

Upslope migration will be critical to the future survival and stability of tidal salt marshes in an age of accelerated sea-level rise, yet only a small number of studies have measured historic migration rates. We developed a new approach for reconstructing salt marsh migration that can be used even in situations where that migration would be undetectable by aerial photograph analysis, such as the growth of marsh plants under trees or the movement of marsh ecosystems into mowed lawns. Our approach involves identifying a wedge of salt marsh peat (overlying the pre-existing upland soil) through the presence of foraminifera and then dating that wedge using 137Cs. We demonstrate our approach by calculating migration rates (1963–2016) for two lawn-adjacent salt marshes along the Connecticut coast of Long Island Sound. Both marshes showed substantial migration over this time period, although vertical migration rates differed dramatically between the two sites, perhaps because of the differential influence of large storms. Further, we demonstrate that the presence of foraminifera (an unequivocal signal of tidal inundation) constitutes a more accurate indicator of the migration wedge than high organic content. Our relatively inexpensive approach could be used to assess migration rates at multiple sites in order to better understand the factors controlling marsh migration.

Salt Dynamics in Coastal Marshes: Formation of Hypersaline Zones

AbstractSalt is a key solute in salt marshes and under the influence of evapotranspiration can accumulate to a high concentration level in the marsh soil and precipitate in the solid form to become a significant stressor for plants, affecting marsh plant productivity and ecological zonation. Numerical simulations of coupled pore water flow and salt transport were conducted to examine how spring‐neap tides and evaporation combine to influence salt dynamics and distribution patterns in marshes. The salt pan formation was simulated with a sandy loam marsh soil subjected to a medium rate of potential evaporation. The critical condition for the salt pan formation was underpinned by hydraulic connection between the marsh surface and water table to sustain evaporation in the supratidal zone. Both low soil permeability and overly high potential evaporation were found to break the hydraulic connection. In this case, the surface soil salinity increased gradually over the intertidal zone to a maximum around the spring high tide mark followed by a rapid decrease to a lower constant level across the supratidal zone. This salinity distribution pattern has also been observed in the field. In both salt marshes with and without salt pans, excessive salt accumulated on the marsh surface due to evaporation was removed by tidally induced circulating flow and/or flow driven by density gradients associated with the accumulated salt. The salt dynamics and distribution patterns revealed here, especially the salt pan formation simulated for the first time, have important implications for studies of marsh plant growth and overall eco‐functions.

Restoration of Cordgrass Salt Marshes: Limited Effects of Organic Matter Additions on Nitrogen Fixation

The extensive loss of tidal marsh habitat surrounding the San Francisco Bay has led to numerous restoration projects to restore ecosystem function. Native cordgrass (Spartina foliosa) is important for sediment accumulation and nesting habitat for endangered California Ridgway’s Rail (Rallus obsoletus obsoletus), and because salt marshes are typically nitrogen-limited ecosystems, previous restoration studies in California have used nitrogen fertilizers to increase plant growth. This study compared the use of two low-nitrogen, high-carbon fertilizers (Macrosystis pyrifera (kelp) and sodium alginate) to stimulate N2-fixing bacteria inhabiting the S. foliosa rhizosphere in a historic and recently restored marsh in San Francisco Bay. Alginate increased N2-fixation, though there was no observed S. foliosa growth response. Kelp suppressed N2-fixation, and increased the foliar nitrogen content of Salicornia pacifica in mixed Spartina-Salicornia stands. The restored marsh had less than 0.5 μM phosphate in porewaters, suggesting phosphorus, not nitrogen, limits S. foliosa growth in this marsh. Alginate increased rates of N2-fixation and may promote plant growth in marshes exhibiting nitrogen limitation. Phosphate limitation was a surprise considering numerous previous studies indicate nitrogen as the primary limiting nutrient of tidal marsh plants. We recommend first assessing nutrient stoichiometry when considering manipulations to promote plant growth in restored marshes.

Combined effects of tides, evaporation and rainfall on the soil conditions in an intertidal creek-marsh system

Salt marshes, distributed globally at the land-ocean interface, are a highly productive eco-system with valuable ecological functions. While salt marshes are affected by various eco-geo-hydrological processes and factors, soil moisture and salinity affect plant growth and play a key role in determining the structure and functions of the marsh ecosystem. To examine the variations of both soil parameters, we simulated pore-water flow and salt transport in a creek-marsh system subjected to spring-neap tides, evaporation and rainfall. The results demonstrated that within a sandy-loam marsh, the tide-induced pore-water circulation averted salt build-up due to evaporation in the near-creek area. In the marsh interior where the horizontal drainage was weak, density-driven flow was responsible for dissipating salt accumulation in the shallow soil layer. In the sandy-loam marsh, the combined influences of spring-neap tides, rainfall and evaporation led to the formation of three characteristic zones, c.f., a near-creek zone with low soil water saturation (i.e., well-aerated) and low pore-water salinity as affected by the semi-diurnal spring tides, a less well-aerated zone with increased salinity where drainage occurred during the neap tides, and an interior zone where evaporation and rainfall infiltration regulated the soil conditions. These characteristics, however, varied with the soil type. In low-permeability silt-loam and clay-loam marshes, the tide-induced drainage weakened and the soil conditions over a large area became dominated by evaporation and rainfall. Sea level rise was found to worsen the soil aeration condition but inhibit salt accumulation due to evaporation. These findings shed lights on the soil conditions underpinned by various hydrogeological processes, and have important implications for further investigations on marsh plant growth and ecosystem functions.

富营养化对盐沼生态系统土壤有机碳库固定潜力影响机理研究进展

随着工农业的发展，沿海地区水体富营养化的程度加剧，严重威胁了海滨湿地生态系统的功能。本文综述了富营养化对盐沼外来植物竞争能力、盐沼植物群落演替、盐沼植物生长策略及沉积环境、盐沼植物对大气二氧化碳浓度增加的响应以及植物碳分配策略的影响等方面研究进展，总结了富营养化对盐沼的生态系统固碳潜力的效应及可能的作用机理，指出未来的研究方向。 With the development of human activities, more nitrogen and phosphorus are released into marine ecosystem, leading to heavier eutrophication, which threatens the function of the coastal wetland ecosystem. This paper reviewed the research progresses on the eutrophication affecting the salt marsh ecosystems including the effects of eutrophication on the alien plant competition ability, salt marsh plant community succession, salt marsh plant growth strategy and sedimentary environment, the responses of salt marsh plants to the atmospheric carbon dioxide concentration increase and the influence on plant carbon allocation strategy, discussed the effects of eutrophication on salt marsh soil organic carbon and its possible mechanism, and suggested the valuable research directions in this field.

Revisiting salt marsh resilience to sea level rise: Are ponds responsible for permanent land loss?

AbstractPonds are unvegetated rounded depressions commonly present on marsh platforms. The role of ponds on the long‐term morphological evolution of tidal marshes is unclear—at times ponds expand but eventually recover the marsh platform, at other times ponds never recover and lead to permanent marsh loss. Existing field observations indicate that episodic disturbances of the marsh vegetation cause the formation of small (1–10 m) isolated ponds, even if the vegetated platform keeps pace with relative sea level rise (RSLR) and that isolated ponds tend to deepen and enlarge until they eventually connect to the channel network. Here I implement a simple model to study the vertical and planform evolution of a single connected pond. A newly connected pond recovers if its bed lies above the limit for marsh plant growth or if the inorganic deposition rate is larger than the RSLR rate. A pond that cannot accrete faster than RSLR will deepen and enlarge, eventually entering a runaway erosion by wave edge retreat. A large tidal range, a large sediment supply, and a low rate of RSLR favor pond recovery. The model suggests that inorganic sediment deposition alone controls pond recovery, even in marshes where organic matter dominates accretion of the vegetated platform. As such, halting permanent marsh loss by pond collapse requires to increase inorganic sediment deposition. Because pond collapse is possible even if the vegetated platform keeps pace with RSLR, I conclude that marsh resilience to RSLR is less than previously quantified.

Potential effects of sea-level rise on plant productivity: species-specific responses in northeast Pacific tidal marshes

Coastal wetland plants are adapted to varying degrees of inundation. However, functional relationships between inundation and productivity are poorly characterized for most species. Determining species-specific tolerances to inundation is necessary to evaluate sea-level rise (SLR) effects on future marsh plant community composition, quantify organic matter inputs to marsh accretion, and inform predictive modeling of tidal wetland persistence. In 2 macrotidal estuaries in the northeast Pacific we grew 5 common species in experimental mesocosms across a gradient of tidal elevations to assess effects on growth. We also tested whether species abundance distributions along elevation gradients in adjacent marshes matched productivity profiles in the mesocosms. We found parabolic relationships between inundation and total plant biomass and shoot counts in Spartina foliosa and Bolboschoenus maritimus in California, USA, and in Carex lyngbyei in Oregon, USA, with maximum total plant biomass occurring at 38, 28, and 15% time submerged, respectively. However, biomass of Salicornia pacifica and Juncus balticus declined monotonically with increasing inundation. Inundation effects on the ratio of belowground to aboveground biomass varied inconsistently among species. In comparisons of field distributions with mesocosm results, B. maritimus, C. lyngbyei and J. balticus were abundant in marshes at or above elevations corresponding with their maximum productivity; however, S. foliosa and S. pacifica were frequently abundant at lower elevations corresponding with sub-optimal productivity. Our findings show species-level differences in how marsh plant growth may respond to future SLR and highlight the sensitivity of high marsh species such as S. pacifica and J. balticus to increases in flooding.

Nutrients and Abiotic Stress Interact to Control Ergot Plant Disease in a SW Atlantic Salt Marsh

Fil: Daleo, Pedro. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina

Field-Based Radiometry to Estimate Tidal Marsh Plant Growth in Response to Elevated CO2 and Nitrogen Addition

Plant growth is one of the most important variables to measure in long-term research plots, but the negative effects of labor-intensive and destructive sampling can restrict frequent assessment of plant biomass. Here, we used field-based, active radiometry to assess plant biomass in an ongoing, experimental manipulation of atmospheric CO2 and soil nitrogen availability in a tidal wetland. We compared the ability of several radiometric vegetation indices (VIs) to predict total plant biomass and that of two plant functional groups, sedges and grasses. All VIs estimated total biomass better in July than in October, when senescence had begun. All VIs correlated strongly and positively to grass biomass (average r = 0.83) and weakly or negatively to sedge biomass (r = −0.30). Modified soil-adjusted vegetation index (MSAVI2) performed well through space (average July total biomass r = 0.83) and time (across four sampling times r = 0.83) and predicted CO2 and nitrogen treatment effect sizes. In conjunction with conventional biomass measurements field-based, active radiometry provides (1) a frequent estimate of biomass that can reveal plant responses to environmental stimuli that would otherwise escape detection, and (2) a viable alternative to frequent destructive sampling for assessing growth of fine-stemmed species such as Spartina patens and Distichlis spicata.

Alginate Addition Influences Smooth Cordgrass (Spartina alterniflora) Growth and Macroinvertebrate Densities

In nitrogen-limited temperate marshes, increasing nitrogen availability via biological mechanisms such as N2 fixation and organic matter mineralization may lead to elevated marsh plant growth and macroinvertebrate densities. A polysaccharide, alginate, known to enhance microbial activity was added to sediment in a salt marsh (GA, USA) and the responses of the smooth cordgrass, Spartina alterniflora, and densities of common macroinvertebrates with important roles in nutrient cycling and energy flow through detrital systems were examined. Plant characteristics and macroinvertebrate densities were measured over portions of two growing seasons between July 2007 and July 2008. Spartina alterniflora stem densities increased in the alginate treatment compared to controls after six weeks of exposure, and this difference was evident throughout the second growing season. Differences in plant heights emerged during the second growing season. Positive effects on Geukensia demissa densities occurred during both growing seasons, Littoraria irrorata densities were elevated relative to controls only in the second growing season, and no differences were observed for Uca pugnax. This potential for increased marsh productivity following carbon amendments may be useful in developing plans for salt marsh recovery.

Effects of mud fiddler crabs (Uca pugnax) on the recruitment of halophyte seedlings in salt marsh dieback areas of Cape Cod (Massachusetts, USA)

AbstractThe effects of bioturbation by the mud fiddler crab (Uca pugnax) on salt marsh seedling recruitment were investigated experimentally in this study. Burrowing and foraging activity caused a large amount of soil disturbance, which in turn negatively impacted the establishment of seedlings. Either seeds did not germinate or seedlings were uprooted or buried. Although the majority of the published literature suggests a positive influence of Uca spp. on salt marsh plant growth, at high densities they have the potential to hinder the re‐colonization of areas made bare by previous disturbance. This study illustrates the perhaps underappreciated role that bioturbators can have on vegetation patterns in salt marshes and other ecosystems.

Grazer facilitation of fungal infection and the control of plant growth in south‐western Atlantic salt marshes

Summary 1 While great effort has been made in documenting the processes that drive plant-induced susceptibility after herbivore attack and it is widely accepted that herbivores can facilitate plant diseases, the relative importance of this interaction in controlling plant growth in natural systems remains largely unexplored. 2 In south-western Atlantic salt marshes, we investigated the importance of disease after herbivory by examining: (i) whether or not a herbivorous crab facilitates disease (i.e. fungus infection) in marsh plants (Spartina alterniflora and S. densiflora) when clipping off small portions of leaves and (ii) the separate and interactive effects of crab grazing but fungal infection in controlling marsh plant growth. 3 Our results show that crab grazing facilitates fungal infection in Spartina leaves. A factorial field experiment shows that both direct crab herbivory and fungal infection strongly suppress plant production (by more than 50%). 4 Synthesis. These experimental results demonstrate that fungal infection following herbivory attack can decrease salt marsh plant production and that increased disease susceptibility can be a fundamental factor in controlling plant production in natural ecosystems, even in cases where herbivores do not directly inoculate the pathogen but only damage plant tissue.

Effects of exogenous nitrogen on freshwater marsh plant growth and [formula omitted] fluxes in Sanjiang Plain, Northeast China

Field management strongly affected the emission of N 2 O and plant growth from freshwater marshes. Nitrous oxide ( N 2 O ) fluxes, leaf area, plant height and above ground biomass were investigated under four N treatments (0, 6, 12 and 24 g NH 4 NO 3 – N m - 2 ) in the freshwater marshes of Sanjiang Plain, Northeast China. The average growing season N 2 O flux was 0.065 ± 0.037 , 0.086 ± 0.111 , 0.141 ± 0.186 , 0.445 ± 0.491 mg m - 2 h - 1 , respectively, the above-ground biomass was 201 ± 49 , 252 ± 40 , 290 ± 47 , 954 ± 115 g m - 2 , respectively, the plant height was 66.25 ± 20.99 , 71.91 ± 16.18 , 73.55 ± 16.59 , 84.14 ± 27.07 cm , respectively. Exogenous nitrogen had a significant impact on N 2 O fluxes and plant growth. Compared to the non-fertilization treatment, the average growing season N 2 O flux in fertilization increased by 32%, 113%, 581%, respectively, the above-ground biomass increased by 26%, 44%, 375%, respectively, while the plant height increased by 8.5%, 11% and 27%, respectively. A quadratic relationship between the nitrogen applied rate and N 2 O fluxes, and a non-linear positive correlation between the nitrogen and above-ground biomass were found, while the relationship between the N 2 O flux and the above-ground biomass was significantly linear positive correlated after nitrogen application, so was the plant height. It was proposed that the exogenous nitrogen gives rise to considerable N 2 O emissions from freshwater marshes and a large fraction of N 2 O was emitted to the atmosphere via the transpiration stream within the Deyeuxia angustifolia plants, which provides some quantificational data on the relationship between the nitrogen, N 2 O fluxes and marsh plant growth.

Anthropogenic Sulfur Effects on Marshland Sulfate Sources

Human activity can have measurable impacts on sulfur levels in the world's water bodies. Atmospheric sulfur dioxide pollution and the resulting acid rain increases freshwater sulfate levels, and individual pollution sources deposit organic sulfur compounds in river sediments. Since the affected water bodies can be the primary sources of sulfur in adjacent marsh environments, anthropogenic pollution may influence the sulfur cycling of nearby marshes. Appropriate levels of plant-available sulfur are necessary for plant growth in marshes, though too much sulfur can damage plants. Saline marshes are often high-sulfur environments due to the steady sulfur inputs that come from seawater present in saline estuaries. Sulfur content is more variable in less saline environments, where primary inputs are rainfall and freshwater runoff. The link between human activity and sulfur levels in marsh soils has not yet been established, since research has not clearly demonstrated the effects of human activity on sulfur in saline water bodies and has generally not sought to link water-body sulfur levels to plant-available sulfur levels or area marsh health.