Nitrogen cycling and ecosystem exchanges in a Virginia tidal freshwater marsh

Neubauer, Scott C.; Anderson, Iris C.; Neikirk, Betty Berry

doi:10.1007/bf02696019

Cited by 47 publications

(35 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One possibility is that hydrologic allothonous inputs of nitrogen and phosphorus are sufficient to obscure differences in plant demand between the CO 2 treatments. However, there is evidence to suggest that plant production in some tidal marshes is not regulated by allothonous nutrient inputs (Neubauser et al 2005). A second possibility is that soil organic matter mineralization rates are relatively high at elevated CO 2 due to increased decomposition or 'priming' effects (Wolf et al 2007), causing a simultaneous increase in nitrogen and phosphorus mineralization.…”

Section: Nutrient Dynamicsmentioning

confidence: 99%

Elevated CO2 affects porewater chemistry in a brackish marsh

et al. 2009

View full text Add to dashboard Cite

As atmospheric CO 2 concentrations continue to rise and impact plant communities, concomitant shifts in belowground microbial processes are likely, but poorly understood. We measured monthly porewater concentrations of sulfate, sulfide, methane (CH 4 ), dissolved inorganic carbon and dissolved organic carbon over a 5-year period in a brackish marsh. Samples were collected using porewater wells (i.e., sippers) in a Schoenoplectus americanus-dominated (C 3 sedge) community, a Spartina patensdominated (C 4 grass) community and a mixed (C 3 and C 4 ) community within the marsh. Plant communities were exposed to ambient and elevated (ambient ? 340 ppm) CO 2 levels for 15 years prior to porewater sampling, and the treatments continued over the course of our sampling. Sulfate reduction was stimulated by elevated CO 2 in the C 3 -dominated community, but not in the C 4 -dominated community. Elevated CO 2 also resulted in higher porewater concentrations of CH 4 and dissolved organic carbon in the C 3 -dominated system, though inhibition of CH 4 production by sulfate reduction appears to temper the porewater CH 4 response. These patterns mirror the typical divergent responses of C 3 and C 4 plants to elevated CO 2 seen in this ecosystem. Porewater concentrations of nitrogen (as ammonium) and phosphorus did not decrease despite increased plant biomass in the C 3 -dominated community, suggesting nutrients do not strongly limit the sustained vegetation response to elevated CO 2 . Overall, our data demonstrate that elevated CO 2 drives changes in porewater chemistry and suggest that increased plant productivity likely stimulates microbial decomposition through increases in dissolved organic carbon availability.

show abstract

Section: Nutrient Dynamicsmentioning

confidence: 99%

Elevated CO2 affects porewater chemistry in a brackish marsh

et al. 2009

View full text Add to dashboard Cite

show abstract

“…less nitrogen is leaving the marsh system than entering, is governed by the balance of loss processes (gaseous emissions of nitrous oxide and dinitrogen, and tidal export) and processes which import and retain nitrogen within the system (nitrogen fixation, precipitation, tidal imports, plant uptake, recycling, and accretion) (White and Howes, 1994b;Mitch and Gosselink, 2000). While particulate deposition (sedimentation), plant nitrogen uptake and denitrification are generally reported to be the most important sinks for watershed derived nitrogen in (tidal freshwater) wetlands (Bowden, 1986;Hansson et al, 2005;Neubauer et al, 2005), methodological restrictions have limited our understanding of interactions between the various marsh compartments and of the functioning of these ecosystems as a whole. The Scheldt estuary (Belgium -The Netherlands) is a macrotidal, heterotrophic, low-oxygen, nutrient-rich system (Soetaert et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Nitrogen assimilation and short term retention in a nutrient-rich tidal freshwater marsh – a whole ecosystem <sup>15</sup>N enrichment study

et al. 2007

View full text Add to dashboard Cite

Abstract. An intact tidal freshwater marsh system (3477 m 2 ) was labelled by adding 15 N-ammonium as a tracer to the flood water inundating the ecosystem. The appearance and retention of 15 N-label in different marsh components (leaves, roots, sediment, leaf litter and invertebrate fauna) was followed over 15 days. This allowed us to elucidate the direct assimilation and dependence on creek-water nitrogen on a relatively short term and provided an unbiased assessment of the relative importance of the various compartments within the ecosystem. Two separate experiments were conducted, one in spring/early summer (May 2002) when plants were young and building up biomass; the other in late summer (September 2003) when macrophytes were in a flowering or early senescent state.Nitrogen assimilation rate (per hour inundated) was >3 times faster in May compared to September. On both occasions, however, the results clearly revealed that the less conspicuous compartments such as leaf litter and ruderal vegetations are more important in nitrogen uptake and retention than the prominent reed (Phragmites australis) meadows. Moreover, short-term nitrogen retention in these nutrient rich marshes occurs mainly via microbial pathways associated with the litter and sediment. Rather than direct uptake by macrophytes, it is the large reactive surface area provided by the tidal freshwater marsh vegetation that is most crucial for nitrogen transformation, assimilation and short term retention in nutrient rich tidal freshwater marshes. Our results clearly revealed the dominant role of microbes in initial nitrogen retention in marsh ecosystems.

show abstract

“…The global contribution of methane from TFWs is unknown, but it is hypothesized to be negligible because of their limited area and competition with iron reduction (8,11). However, the contrasting oxic and anoxic environments in TFWs support coupling of nitrification and denitrification, making these habitats important N sinks (12). Only a few studies have examined microbial community composition related to these processes in TFWs (10), and to our knowledge, no study has compared microbial composition between natural and restored TFWs.…”

mentioning

confidence: 99%

Site History and Edaphic Features Override the Influence of Plant Species on Microbial Communities in Restored Tidal Freshwater Wetlands

Prasse

Baldwin

Yarwood

2015

Appl Environ Microbiol

View full text Add to dashboard Cite

Restored wetland soils differ significantly in physical and chemical properties from their natural counterparts even when plant community compositions are similar, but effects of restoration on microbial community composition and function are not well understood. Here, we investigate plant-microbe relationships in restored and natural tidal freshwater wetlands from two subestuaries of the Chesapeake Bay. Soil samples were collected from the root zone of Typha latifolia, Phragmites australis, Peltandra virginica, and Lythrum salicaria. Soil microbial composition was assessed using 454 pyrosequencing, and genes representing bacteria, archaea, denitrification, methanogenesis, and methane oxidation were quantified. Our analysis revealed variation in some functional gene copy numbers between plant species within sites, but intersite comparisons did not reveal consistent plantmicrobe trends. We observed more microbial variations between plant species in natural wetlands, where plants have been established for a long period of time. In the largest natural wetland site, sequences putatively matching methanogens accounted for ϳ17% of all sequences, and the same wetland had the highest numbers of genes coding for methane coenzyme A reductase (mcrA). Sequences putatively matching aerobic methanotrophic bacteria and anaerobic methane-oxidizing archaea (ANME) were detected in all sites, suggesting that both aerobic and anaerobic methane oxidation are possible in these systems. Our data suggest that site history and edaphic features override the influence of plant species on microbial communities in restored wetlands. Diverse soil microbial communities, capable of using numerous metabolic processes to generate energy and assimilate nutrients, mediate key wetland functions. Although recent studies have described microbial community composition and functional gene abundances related to land use, vegetation, and environmental factors (1-3), structure-function relationships in freshwater wetland soils are not well understood. Biogeochemical activities are regulated not only by the size of the microbial biomass but also by the presence, distribution, and abundance of functional guilds (4). Therefore, functional gene markers can provide valuable insight into key biogeochemical processes and their relationships to site properties (5, 6). Given that the underlying mechanisms of major nutrient cycles are related to microbial taxonomic diversity, it is surprising that relatively few studies have described both microbial composition and functional group abundance in freshwater wetlands, a biogeochemical hot spot of carbon (C) and nitrogen (N) cycling.Tidal freshwater wetlands (TFWs) are located in the upper reaches of estuaries along the coastlines of the U.S. Atlantic Ocean, the Gulf of Mexico, and elsewhere, where salinity is low (typically Ͻ0.5 ppt) (7-9). Unlike saline wetlands that tend to produce large quantities of hydrogen sulfide, the main C mineralization pathways in TFWs include methanogenesis (7,8,10) and, depending on miner...

show abstract

Nitrogen cycling and ecosystem exchanges in a Virginia tidal freshwater marsh

Cited by 47 publications

References 52 publications

Elevated CO2 affects porewater chemistry in a brackish marsh

Elevated CO2 affects porewater chemistry in a brackish marsh

Nitrogen assimilation and short term retention in a nutrient-rich tidal freshwater marsh – a whole ecosystem <sup>15</sup>N enrichment study

Site History and Edaphic Features Override the Influence of Plant Species on Microbial Communities in Restored Tidal Freshwater Wetlands

Contact Info

Product

Resources

About

Nitrogen cycling and ecosystem exchanges in a Virginia tidal freshwater marsh

Cited by 47 publications

References 52 publications

Elevated CO2 affects porewater chemistry in a brackish marsh

Elevated CO2 affects porewater chemistry in a brackish marsh

Nitrogen assimilation and short term retention in a nutrient-rich tidal freshwater marsh – a whole ecosystem &lt;sup&gt;15&lt;/sup&gt;N enrichment study

Site History and Edaphic Features Override the Influence of Plant Species on Microbial Communities in Restored Tidal Freshwater Wetlands

Contact Info

Product

Resources

About

Nitrogen assimilation and short term retention in a nutrient-rich tidal freshwater marsh – a whole ecosystem <sup>15</sup>N enrichment study