Factors Affecting Accumulation or Loss of Macroorganic Matter in Salt Marsh Sediments

Hackney, Courtney T.

doi:10.2307/1938385

Cited by 44 publications

(27 citation statements)

References 15 publications

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“…The range of decay coefficients we measured (0 to 0.376 yr −1 ) was slightly lower than ranges of decay measured elsewhere in the mid-Atlantic for S. alterniflora and Juncus roemerianus roots and rhizomes (0.11 to 0.51 yr −1 ) (Blum and Christian, 2004) and for newly senescent P. australis and S. patens litter (0.25 to 0.57 yr −1 ) (Windham, 2001), suggesting that our experimental approach captured the well-documented decline in decay rates across the continuum from fresh litter to SOM. Our results are consistent with previous work in salt marshes that indicates decomposition rates are not strongly related to flooding duration and soil redox potential (Valiela et al, 1982;Hackney, 1987;Blum, 1993;Blum and Christian, 2004). Moreover, Blum (1993) concludes that the insensitivity means that differences in organic matter accumulation between high and low marsh areas must be explained by differences in root production rather than differences in decay.…”

Section: Discussionsupporting

confidence: 92%

“…Responses in salt marshes are also variable. Nyman and DeLaune (1991), for example, measured reduced soil respiration rates in more flooded environments, but several authors have concluded that flooding frequency and redox potential play only minor roles in determining organic decay rates (Valiela et al, 1982;Hackney, 1987;Blum, 1993;Blum and Christian, 2004). Such a conclusion is perhaps surprising when viewed in the context of experiments conducted in terrestrial ecosystems.…”

Section: Introductionmentioning

confidence: 99%

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The impact of sea-level rise on organic matter decay rates in Chesapeake Bay brackish tidal marshes

et al. 2013

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The balance between organic matter production and decay determines how fast coastal wetlands accumulate soil organic matter. Despite the importance of soil organic matter accumulation rates in influencing marsh elevation and resistance to sea-level rise, relatively little is known about how decomposition rates will respond to sea-level rise. Here, we estimate the sensitivity of decomposition to flooding by measuring rates of decay in 87 bags filled with milled sedge peat, including soil organic matter, roots and rhizomes. Experiments were located in field-based mesocosms along 3 mesohaline tributaries of the Chesapeake Bay. Mesocosm elevations were manipulated to influence the duration of tidal inundation. Although we found no significant influence of inundation on decay rate when bags from all study sites were analyzed together, decay rates at two of the sites increased with greater flooding. These findings suggest that flooding may enhance organic matter decay rates even in water-logged soils, but that the overall influence of flooding is minor. Our experiments suggest that sea-level rise will not accelerate rates of peat accumulation by slowing the rate of soil organic matter decay. Consequently, marshes will require enhanced organic matter productivity or mineral sediment deposition to survive accelerating sea-level rise

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

The impact of sea-level rise on organic matter decay rates in Chesapeake Bay brackish tidal marshes

et al. 2013

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“…Moreover, more detailed studies at this site (Blum, 1993), and elsewhere (e.g. Valiela et al, 1982Valiela et al, , 1984Bertness, 1985;Hackney, 1987) indicate that soil moisture and/or redox potential is not a strong determinant of decomposition rates in tidal marshes. Although we acknowledge that other environmental variables may be at play, we therefore conclude that the steady increase in decay rate through time is the result of warming.…”

Section: Resultsmentioning

confidence: 63%

Enhanced decomposition offsets enhanced productivity and soil carbon accumulation in coastal wetlands responding to climate change

2011

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Abstract. Coastal wetlands are responsible for about half of all carbon burial in oceans, and their persistence as a valuable ecosystem depends largely on the ability to accumulate organic material at rates equivalent to relative sea level rise. Recent work suggests that elevated CO 2 and temperature warming will increase organic matter productivity and the ability of marshes to survive sea level rise. However, we find in a series of preliminary experiments that organic decomposition rates increase by about 20% per degree of warming. Our measured temperature sensitivity is similar to studies from terrestrial systems, three times as high as the response of salt marsh productivity to temperature warming, and greater than the productivity response associated with elevated CO 2 in C 3 marsh plants. Although the experiments were simple and of short duration, they suggest that enhanced CO 2 and warmer temperatures could actually make marshes less resilient to sea level rise, and tend to promote a release of soil carbon. Simple projections indicate that elevated temperatures will increase rates of sea level rise more than any acceleration in organic matter accumulation, suggesting the possibility of a positive feedback between climate, sea level rise, and carbon emissions in coastal environments.

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“…The prescence of living roots may also have had an effect on root decay in the periodically flooded treatment. Hackney (1987) suggested that living roots alter the chemical environment of the soil and may, therefore, accelerate decay of soil organic matter. In the mesocosms, the litter bags were buried at least 0,5 m from the nearest cypress seedlings, so roots in the litter bags were not initially in contact with living roots.…”

Section: Biotic Environmentmentioning

confidence: 99%

“…Fine roots represent a large and dynamic portion of belowground biomass, soil delritus, and nutrient capital; however, there have been few studies in which root decomposition or turnover have been measured (Waid 197,~, McGinty 1976, Hackney and de la Cr~ 1980, Harris et al 1980, Brinson et al 1981, McClaugherty et al 1982, Ellison et al 1986, Hackney 1987, Tupacz 1988, Gallagher 1988. In a periodically flooded wetland, fluctuating water levels are likely to have significant effects on belowground ecosystem dynamics (Dickson andBroyer 1972, Reddy andPatrick 1975).…”

Section: Introductionmentioning

confidence: 99%

Cypress root decomposition in experimental wetland mesocosms

1989

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Two forested wetland mesocosms containing organic soil (a sapric histosol) and cypress seedlings were constructed in the rhizotron facility at the University of Georgia's Savannah River Ecology Laboratory. A different hydroperiod (continuous versus periodic) was designed and implemented for each mesocosm. A vertical litter bag technique was used to measure cypress root decomposition rates in the mesocosms, Rapid leaching losses followed by 6 months o fno mass loss occurred in both mesoco sms. During the final 9 months of the study, roots in the periodically flooded mesocosm began to significantly decompose while those in the continuously flooded mesocosm remained unchanged. Inhibited decay was correlated with reduced redox potential, oxygen, and pH, but the delayed response to changes in these factors suggests that the coupling between root decomposition and the abiotic environment is not tight. The prescence of living cypress roots could explain more rapid decay near the surface of the periodically flooded mesocosm. In general, nutri en ts were higher in concentration and amount in the periodically flooded decomposing roots but lower in the soil water. Net accumulations of N occurred in the periodically flooded roots. These patterns indicate that periodically flooded ecosystems should have more conservative nutrient cycles thancontinuously flooded systems. In general, mesocosms appear to provide a useful experimental approach to the study of belowground ecosystem processes.

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Factors Affecting Accumulation or Loss of Macroorganic Matter in Salt Marsh Sediments

Cited by 44 publications

References 15 publications

The impact of sea-level rise on organic matter decay rates in Chesapeake Bay brackish tidal marshes

The impact of sea-level rise on organic matter decay rates in Chesapeake Bay brackish tidal marshes

Enhanced decomposition offsets enhanced productivity and soil carbon accumulation in coastal wetlands responding to climate change

Cypress root decomposition in experimental wetland mesocosms

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