Greenhouse Gas Fluxes Vary Between Phragmites Australis and Native Vegetation Zones in Coastal Wetlands Along a Salinity Gradient

Martin, Rose M.; Moseman‐Valtierra, Serena

doi:10.1007/s13157-015-0690-y

Cited by 63 publications

(62 citation statements)

References 44 publications

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“…CH 4 oxidation in our pots is likely limited due to low CH 4 production (Megonigal & Schlesinger, ). Invasive P. australis generally supports higher CH 4 emissions than native communities in brackish marshes (Mozdzer & Megonigal, ; Martin & Moseman‐Valtierra, ; Mueller et al ., ). However, most of the CH 4 produced is vented to the atmosphere through P. australis stems and likely bypasses oxidation at the soil surface (Armstrong et al ., ; Brix et al ., , ).…”

Section: Methodsmentioning

confidence: 99%

An invasive wetland grass primes deep soil carbon pools

Bernal

Megonigal

Mozdzer

2016

Global Change Biology

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Understanding the processes that control deep soil carbon (C) dynamics and accumulation is of key importance, given the relevance of soil organic matter (SOM) as a vast C pool and climate change buffer. Methodological constraints of measuring SOM decomposition in the field prevent the addressing of real-time rhizosphere effects that regulate nutrient cycling and SOM decomposition. An invasive lineage of Phragmites australis roots deeper than native vegetation (Schoenoplectus americanus and Spartina patens) in coastal marshes of North America and has potential to dramatically alter C cycling and accumulation in these ecosystems. To evaluate the effect of deep rooting on SOM decomposition we designed a mesocosm experiment that differentiates between plant-derived, surface SOM-derived (0-40 cm, active root zone of native marsh vegetation), and deep SOM-derived mineralization (40-80 cm, below active root zone of native vegetation). We found invasive P. australis allocated the highest proportion of roots in deeper soils, differing significantly from the native vegetation in root : shoot ratio and belowground biomass allocation. About half of the CO produced came from plant tissue mineralization in invasive and native communities; the rest of the CO was produced from SOM mineralization (priming). Under P. australis, 35% of the CO was produced from deep SOM priming and 9% from surface SOM. In the native community, 9% was produced from deep SOM priming and 44% from surface SOM. SOM priming in the native community was proportional to belowground biomass, while P. australis showed much higher priming with less belowground biomass. If P. australis deep rooting favors the decomposition of deep-buried SOM accumulated under native vegetation, P. australis invasion into a wetland could fundamentally change SOM dynamics and lead to the loss of the C pool that was previously sequestered at depth under the native vegetation, thereby altering the function of a wetland as a long-term C sink.

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Section: Methodsmentioning

confidence: 99%

An invasive wetland grass primes deep soil carbon pools

Bernal

Megonigal

Mozdzer

2016

Global Change Biology

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“…In salt marshes not subjected to eutrophication, N is limiting (Valiela & Teal, ) and so N 2 O fluxes generally are small. N 2 O emissions were found to be negligible at high and low marsh elevations of several southern New England salt (Martin & Moseman‐Valtierra, ; Moseman‐Valtierra et al., ) and brackish (Martin & Moseman‐Valtierra, , ) marshes receiving low N loads.…”

Section: Introductionmentioning

confidence: 99%

“…Great Sippewissett Marsh sediment CO 2 emissions have been previously reported (10–13 mmol m −2 s −1 ) (Howes et al., ). Carbon dioxide produced in salt marsh soils is frequently exceeded by photosynthetic CO 2 uptake during the growing season (Martin & Moseman‐Valtierra, , , ; Moseman‐Valtierra et al., ), and emissions are small during cooler months (Martin & Moseman‐Valtierra, ).…”

Section: Introductionmentioning

confidence: 99%

Long‐term nutrient addition increases respiration and nitrous oxide emissions in a New England salt marsh

Martin

Wigand

Elmstrom

et al. 2018

Ecology and Evolution

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Salt marshes may act either as greenhouse gas (GHG) sources or sinks depending on hydrological conditions, vegetation communities, and nutrient availability. In recent decades, eutrophication has emerged as a major driver of change in salt marsh ecosystems. An ongoing fertilization experiment at the Great Sippewissett Marsh (Cape Cod, USA) allows for observation of the results of over four decades of nutrient addition. Here, nutrient enrichment stimulated changes to vegetation communities that, over time, have resulted in increased elevation of the marsh platform. In this study, we measured fluxes of carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N2O) in dominant vegetation zones along elevation gradients of chronically fertilized (1,572 kg N ha−1 year−1) and unfertilized (12 kg N ha−1 year−1) experimental plots at Great Sippewissett Marsh. Flux measurements were performed using darkened chambers to focus on community respiration and excluded photosynthetic CO 2 uptake. We hypothesized that N‐replete conditions in fertilized plots would result in larger N2O emissions relative to control plots and that higher elevations caused by nutrient enrichment would support increased CO 2 and N2O and decreased CH 4 emissions due to the potential for more oxygen diffusion into sediment. Patterns of GHG emission supported our hypotheses. Fertilized plots were substantially larger sources of N2O and had higher community respiration rates relative to control plots, due to large emissions of these GHGs at higher elevations. While CH 4 emissions displayed a negative relationship with elevation, they were generally small across elevation gradients and nutrient enrichment treatments. Our results demonstrate that at decadal scales, vegetation community shifts and associated elevation changes driven by chronic eutrophication affect GHG emission from salt marshes. Results demonstrate the necessity of long‐term fertilization experiments to understand impacts of eutrophication on ecosystem function and have implications for how chronic eutrophication may impact the role that salt marshes play in sequestering C and N.

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“…GHG fluxes were calculated using the volume of chamber and area of the footprint (Martin & Moseman‐Valtierra, ). The ideal gas law (PV = nRT) was used to calculate the gas concentration rate of change over time with the measured air temperature and atmospheric pressure (Martin & Moseman‐Valtierra, ). Porewater salinity was collected from a depth of 20–30 cm using a sipper and measured in the field using a calibrated refractometer.…”

Section: Methodsmentioning

confidence: 99%

Pond Excavation Reduces Coastal Wetland Carbon Dioxide Assimilation

et al. 2020

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Coastal wetlands comprise important global carbon sinks; however, anthropogenic disturbance accompanied with accelerating sea level rise threaten their continued survival. In this study, we quantified habitat disturbance to salt marshes in Barnegat Bay, New Jersey, resulting from the construction of ponds for mosquito control. Geographic object‐based image analysis of high‐resolution four‐band aerial imagery revealed that over 7,000 ponds were constructed in the marsh complex with pond densities as high as 290 ponds per km2. Physical disturbance from pond creation and sediment dispersal extended to over 17% of the bay's tidal wetlands. By tracking recolonization of vegetation, we estimated that it took 5 years for 51% vegetation recovery and 10 years for 69% recovery, with complete recover (100%) not expected for more than 50 years. This suggests that efforts to extend the lifespan of drowning coastal wetlands through sediment additions might disrupt carbon dioxide assimilation, as effects of disturbance persist. Focusing on greenhouse gas exchange, our work found that areas of marsh vegetation contribute to carbon assimilation (−42 g C · m−2 · year−1), while ponds and areas of bare peat created by pond excavation were associated with carbon emissions (44 and 125 g C · m−2 · year−1, respectively). These results suggest that the conversion of wetlands to ponds—which is a significant driver of coastal wetland loss worldwide—may convert coastal wetlands from greenhouse gas sinks to sources. Additionally, quantifying the area of vegetation within a marsh (vs. bare ground or open water) is important for quantifying their greenhouse gas mitigation function.

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Greenhouse Gas Fluxes Vary Between Phragmites Australis and Native Vegetation Zones in Coastal Wetlands Along a Salinity Gradient

Cited by 63 publications

References 44 publications

An invasive wetland grass primes deep soil carbon pools

An invasive wetland grass primes deep soil carbon pools

Long‐term nutrient addition increases respiration and nitrous oxide emissions in a New England salt marsh

Pond Excavation Reduces Coastal Wetland Carbon Dioxide Assimilation

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