scholarly journals Millennial-Scale Carbon Storage in Natural Pine Forests of the North Carolina Lower Coastal Plain: Effects of Artificial Drainage in a Time of Rapid Sea Level Rise

Land ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1294
Author(s):  
Maricar Aguilos ◽  
Charlton Brown ◽  
Kevan Minick ◽  
Milan Fischer ◽  
Omoyemeh J. Ile ◽  
...  

Coastal forested wetlands provide important ecosystem services along the southeastern region of the United States, but are threatened by anthropogenic and natural disturbances. Here, we examined the species composition, mortality, aboveground biomass, and carbon content of vegetation and soils in natural pine forests of the lower coastal plain in eastern North Carolina, USA. We compared a forest clearly in decline (termed “ghost forest”) adjacent to a roadside canal that had been installed as drainage for a road next to an adjacent forest subject to “natural” hydrology, unaltered by human modification (termed “healthy forest”). We also assessed how soil organic carbon (SOC) accumulation changed over time using 14C radiocarbon dating of wood sampled at different depths within the peat profile. Our results showed that the ghost forest had a higher tree density at 687 trees ha−1, and was dominated by swamp bays (Persea palustric), compared to the healthy forest, which had 265 trees ha−1 dominated by pond pine (Pinus serotina Michx). Overstory tree mortality of the ghost forest was nearly ten times greater than the healthy forest (p < 0.05), which actually contributed to higher total aboveground biomass (55.9 ± 12.6 Mg C ha−1 vs. 27.9 ± 8.7 Mg ha−1 in healthy forest), as the dead standing tree biomass (snags) added to that of an encroaching woody shrub layer during ecosystem transition. Therefore, the total aboveground C content of the ghost forest, 33.98 ± 14.8 Mg C ha−1, was higher than the healthy forest, 24.7 ± 5.2 Mg C ha−1 (p < 0.05). The total SOC stock down to a 2.3 m depth in the ghost forest was 824.1 ± 46.2 Mg C ha−1, while that of the healthy forest was 749.0 ± 170.5 Mg C ha−1 (p > 0.05). Carbon dating of organic sediments indicated that, as the sample age approaches modern times (surface layer year 2015), the organic soil accumulation rate (1.11 to 1.13 mm year−1) is unable to keep pace with the estimated rate of recent sea level rise (2.1 to 2.4 mm year−1), suggesting a causative relationship with the ecosystem transition occurring at the site. Increasing hydrologic stress over recent decades appears to have been a major driver of ecosystem transition, that is, ghost forest formation and woody shrub encroachment, as indicated by the far higher overstory tree mortality adjacent to the drainage ditch, which allows the inland propagation of hydrologic/salinity forcing due to SLR and extreme storms. Our study documents C accumulation in a coastal wetland over the past two millennia, which is now threatened due to the recent increase in the rate of SLR exceeding the natural peat accumulation rate, causing an ecosystem transition with unknown consequences for the stored C; however, much of it will eventually be returned to the atmosphere. More studies are needed to determine the causes and consequences of coastal ecosystem transition to inform the modeling of future coastal wetland responses to environmental change and the estimation of regional terrestrial C stocks and flux.

1980 ◽  
Vol 4 (2) ◽  
pp. 84-88 ◽  
Author(s):  
C. W. Ralston ◽  
D. D. Richter

Abstract Analysis of forest survey plot data for 16 coastal counties in North Carolina indicated substantial areas of very low productivity for pine growth were associated with two site types, savannas and pocosins, that are easily identified by aerial photo interpretation. Results indicate that the ready identifiability of such areas provides a rapid method for screening areas for soil test sampling and for making large-scale economic appraisals of sites where fertilizer investments might be worthwhile.


2006 ◽  
Vol 30 (4) ◽  
pp. 513-530 ◽  
Author(s):  
Jonathan D. Phillips ◽  
Michael C. Slattery

Coastal and marine sedimentary archives are sometimes used as indicators of changes in continental sediment production and fluvial sediment transport, but rivers crossing coastal plains may not be efficient conveyors of sediment to the coast. Where this is the case, changes in continental sediment dynamics are not evident at the river mouth. Stream power is typically low and accommodation space high in coastal plain river reaches, resulting in extensive alluvial storage upstream of estuaries and correspondingly low sediment loads at the river mouth. In some cases there is a net loss of sediment in lower coastal plain reaches, so that sediment input from upstream exceeds yield at the river mouth. The lowermost sediment sampling stations on many rivers are too far upstream of the coast to represent lower coastal plain sediment fluxes, and thus tend to overestimate sediment yields. Sediment which does reach the river mouth is often trapped in estuaries and deltas. Assessment of sediment flux from coastal plain rivers is also confounded by the deceptively simple question of the location of the mouth of the river. On low-gradient coastal plains and shelves, the location of the river mouth may have varied by hundreds of kilometers due to sea-level change. The mouth may also differ substantially according to whether it is defined based on channel morphology, network morphology, hydrographic or hydrochemical criteria, elevation of the channel relative to sea level, or the locus of deposition. Further, while direct continent-to-ocean flux may be very low at current sea-level stands, sediment stored in estuaries and lower coastal plain alluvium (including deltas) may eventually become part of the marine sedimentary package. The role of accommodation space in coastal plain alluvial sediment storage has been emphasized in previous work, but low transport capacity controlled largely by slope is also a crucial factor, as we illustrate with examples from Texas.


1980 ◽  
Vol 13 (2) ◽  
pp. 213-229 ◽  
Author(s):  
Thomas M. Cronin

AbstractMarine ostracodes from 50 localities were studied to determine the age and elevation of Pleistocene sea levels in the Atlantic coastal plain from Maryland to northern Florida. Using ostracode taxon and concurrent ranges, published planktic biostratigraphic, paleomagnetic, and radiometric data, ostracode assemblage zones representing early (1.8-1.0 my), middle (0.7-0.4 my), and late (0.3-0.01 my) Pleistocene deposition were recognized and used as a basis for correlation. Ostracode biofacies signifying lagoonal, oyster bank, estuarine, open sound, and inner sublittoral environments provided estimated ranges of paleodepths for each locality. From these data the following minimum and maximum Pleistocene sea-level estimates were determined for the southeastern coastal plain: late Pleistocene, 2–10 m from Maryland to northern Florida; middle Pleistocene, 6–15 m in northern South Carolina; early Pleistocene, 4–22 m in central North Carolina, 13–35 m in southern North Carolina, and 6–27 m in South Carolina. Climatically induced glacio-eustatic sea-level fluctuations adequately account for the late Pleistocene sea-level data, but other factors, possibly differential crustal uplift, may have complicated the early Pleistocene record.


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