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Soil Organic Carbon, Nitrogen, and Phosphorus as Indicators of Recovery in Restored Spartina Marshes
Abstract
Carbon:Nitrogen ratio indicates complete recovery of waterquality improvement functions in a Georgia marsh after 42 years.
... SOM and sediment N content are the good proxy to understand the energy flow (carbon content) and nutrients (N concentrations) cycles of ecosystems (Craft et al. 2003). There are evidences that N limited the salt marsh above-ground biomass, and therefore succession of vegetation in the restored or created marshes depends on the accumulated N contents in the soil and plant biomass (Van Wijnen and Bakker 1999;Craft 2001). Being a detritusbased ecosystem, salt marsh SOM serves as a food for heterotrophic organisms including deposit-feeding invertebrates and to fuel microbial process like de-nitrifications (through providing labile fractions of the carbon) (Craft 2001). ...
... There are evidences that N limited the salt marsh above-ground biomass, and therefore succession of vegetation in the restored or created marshes depends on the accumulated N contents in the soil and plant biomass (Van Wijnen and Bakker 1999;Craft 2001). Being a detritusbased ecosystem, salt marsh SOM serves as a food for heterotrophic organisms including deposit-feeding invertebrates and to fuel microbial process like de-nitrifications (through providing labile fractions of the carbon) (Craft 2001). ...
... Macrobenthic density in constructed marsh requires 5-25 years to reach equivalence to natural marsh (Craft et al. 1999(Craft et al. , 2003. Besides, SOM in restored marsh requires about 15 years to achieve equivalent level of that measured in the natural marshes; however, N content of the sediment requires 30 years to achieve equivalent level of that measured in the natural marsh (e.g., Craft 2001). Similarly, restored marshes require more than 30 years to reach the same level of sediment diatom similarity as natural marshes (Craft et al. 2003). ...
Coastal wetlands including salt marshes are among the most productive ecosystems on Earth. They are known for improving the quality of coastal water and provisioning coastal fisheries. However, this ecosystem is under potential threat due to urban coastal land reclamation, limited sediment supply, increased nutrient/eutrophication, and sea level rise. Therefore, restoration efforts to protect the degraded salt marsh habitat are considerably increasing worldwide. In this paper, we present an overview of salt marsh restoration techniques and success indicators. Published scientific literature in English language was collected by searching the most relevant keywords from popular search engines, namely, Google Scholar, Scopus, and Mendeley to get the information about salt marsh restoration techniques and success indicators. This study comprehensively reviewed data from 78 peer-reviewed papers. Results indicated that much of the salt marsh was restored through assisted abiotic strategies (e.g., recovery of tidal exchange, managed realignment, and sediment level amendment). A total of 214 indicators were found, spanning over six major ecological attributes such as structural diversity, ecosystem functions, physical conditions, species composition, external exchange, and absence of threat. Author keywords analysis revealed several hotspots for recent research (e.g., 16 s rRNA, fungi, microbial communities, carbon accumulation, and blue carbon). This paper proposes a model for restoring degraded salt marsh, as well as tracking their success. The information presented here will assist the marine ecosystem restoration practitioners in getting a comprehensive understanding of salt marsh restoration success evaluation.
... Studies comparing CWs and RWs to NWs have examined differences in vegetation communities (Heaven et al. 2003, Spieles 2005, physical and chemical soil properties (Bishel-Machung et al. 1996, Craft 2001, Bruland et al. 2003, Bruland and Richardson 2005a, Bruland and Richardson 2006, hydrology (Zampella and Laidig 2003), and biological communities (Hannaford 1998, King et al. 2000. ...
... Thus the use of reference wetlands is based on the underlying assumptions that NWs represent high levels of functioning and that wetlands sharing similar soil properties, hydrology characteristics, vegetation community, or environmental conditions, function in a similar or equivalent manner (Brinson and Rheinhardt 1996, Stolt et al. 2000, Zampella and Laidig 2003. Numerous variables have been used when evaluating the success of CWs and RWs, with measurements of vegetation being most common (Galatowitsch and van der Valk 1996, Kentula 2000, followed by soils (Stolt et al. 2000, Craft 2001, Bruland and Richardson 2004, hydrology (Ashworth 1997), and macrofauna (Brown and Batzer 2001). In this study, a quantitative investigation and inventory of coastal lowland Hawaiian wetlands, I will assess vegetation community composition and soil chemical and physical properties of NWs, RWs, and CWs in Hawaii. ...
... Given the important role that soils play in the biogeochemical processes that occur in wetlands, the measurement of soil properties has become more common when evaluating wetland mitigation projects. Soil properties, such as soil organic matter (SOM), nutrient content, and particle-size distribution have been shown to reflect the wetland environment and have thus been used to evaluate and compare mitigation and reference wetlands (Craft et al. 1988, Bishel-Machung et al. 1996, Shaffer and Ernst 1999, Stolt et al. 2000, Craft 2001, Bruland and Richardson 2004, Bruland and Richardson 2005a, Bruland and Richardson 2006. ...
... Phosphorus pools ranged from a low of 70 ± 6 g/m 2 in the impounded marsh to a high of 154 ± 19 g/m 2 in the Phragmites marsh. Nutrient pools in the four marshes were higher than the ranges recorded for natural saltwater cordgrass marshes along the Atlantic coast of the United States (620-4,160 g C/m 2 ; 38-270 g N/m 2 ; 12-88 g P/m 2 ; Craft, 2001) and may reflect greater inputs of sediments and nutrients in stormwater from the highly urbanized watershed. ...
... frutescens (499 ± 77 g/m 2 /yr) and impounded (335 ± 33 g/m 2 /yr) marshes (Table 4). Our values are within the range (160-2670 g/m 2 /yr) reported for natural Atlantic coast saltwater cordgrass marshes (Craft, 2001). High mineral accumulation in the S. alterniflora marsh relative to the other marshes reflects the high bulk density and low carbon content of the soil that results from greater sediment inputs to the marsh. ...
... Nitrogen accumulation exhibited a similar pattern, ranging from 5.9 g/m 2 /yr in the impounded marsh to 10.4 g/m 2 /yr in the Phragmites marsh. Carbon and nitrogen accumulation rates are consistent with rates reported for natural Atlantic coast saltwater cordgrass marshes (21-215 g C/m 2 /yr; 1.3-11 g N/m 2 /yr; Craft, 2001). Phosphorus accumulation rates were highest in the S. alterniflora marsh (2.76 g/m 2 /yr) and lowest in the impounded marsh (0.91±0.09 g/m 2 /yr). ...
An impounded estuarine marsh scheduled for restoration in 2003 and three nearby unimpounded marshes (Spartina alterniflora, S. patens/Iva frutescens, and Phragmites australis) in highly urbanized NY/NJ Harbor were studied to assess the impact of impoundment on marsh structure and function and to identify trajectories of ecosystem change following removal of the levee. Aboveground biomass was greater in the Phragmites and S. alterniflora marshes (706–809 g/m2) as compared to the S. patens/I. frutescens and impounded marshes (378–588 g/m2). Macro-organic matter (0–30 cm) was similar across all marshes (7452–9212 g/m2). The S. patens/Iva frutescens marsh had the lowest aboveground biomass, but contained more plant species (2.8 species/0.25 m2) and greater species diversity (H = 1.33) than the other marshes (1.3–2.0 species/0.25 m2, H = 0.16–0.78). Rates of sediment and nutrient accumulation were lower in the impounded marsh (335 g sediment/m2/yr, 97 g C/m2/yr, 6.5 g N/m2/yr, and 0.9 g P/m2/yr) than in the reference marshes (422–1515 g sediment/m2/yr; 111–160 g C/m2/yr; 7–10 g N/m2/yr; 1.6–2.8 g P/m2/yr). Our results indicate that the impounded marsh does not contain the high species diversity of the high marsh, nor does it provide the same level of functions as naturally inundated marshes. Reintroduction of tidal inundation to the impounded marsh will enhance water quality benefits and favor development of S. alterniflora salt marsh community structure.
... In excess of 4000 impediments to tidal flow have been identified, of which approximately one third have potential for estuarine wetland rehabilitation (Williams and Watford, 1997). Even though it is not completely clear how this potential rehabilitation would affect carbon sequestration, successful rehabilitation projects in the US indicate some recovery of the carbon stores of tidal wetlands following reintroduction of tidal flows (Craft, 2001). ...
... The vertical accretion rates of the disturbed Site 1 substrates (Fig. 2a) were substantially higher than those at Site 2 (Fig. 2b). This trend is in agreement with studies of rehabilitated estuarine wetlands in Long Island (Anisfield et al., 1999) and Georgia (Craft, 2001), US, where the higher rates were attributed to higher sediment availability due to tidal reinstatement. At Site 1, removal of culverts for reintroduction of tidal flows in 1995 increased flow conveyance capacity by a factor of 30 leading to remobilization of sediment from newly incised creek channels and deposition within vegetated areas, resulting in a net increase in vertical accretion at both saltmarsh and mangrove sites. ...
... Site 1 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 carbon reported elsewhere (Craft, 2001), where initially high vertical accretion rates in rehabilitated sites drive an asymptotic increase in soil carbon stores. These findings support the potential for substantial gains in carbon sequestration associated with reinstatement of tidal flows to degraded estuarine wetlands in a relative short time scale. ...
The aim of this work was to quantify the soil carbon storage and sequestration rates of undisturbed natural wetlands and disturbed wetlands subject to restriction of tidal flow and subsequent rehabilitation in an Australian estuary. Disturbed and undisturbed estuarine wetlands of the Hunter estuary, New South Wales, Australia were selected as the study sites for this research. Vertical accretion rates of estuarine substrates were combined with soil carbon concentrations and bulk densities to determine the carbon store and carbon sequestration rates of the substrates tested. Relationships between estuary water level, soil evolution and vertical accretion were also examined. The carbon sequestration rate of undisturbed wetlands was lower (15% for mangrove and 55% for saltmarsh) than disturbed wetlands, but the carbon store was higher (65% for mangrove and 60% for saltmarsh). The increased carbon sequestration rate of the disturbed wetlands was driven by substantially higher rates of vertical accretion (95% for mangrove and 345% for saltmarsh). Estuarine wetland carbon stores were estimated at 700–1000 Gg C for the Hunter estuary and 3900–5600 Gg C for New South Wales. Vertical accretion and carbon sequestration rates of estuarine wetlands in the Hunter are at the lower end of the range reported in the literature. The comparatively high carbon sequestration rates reported for the disturbed wetlands in this study indicate that wetland rehabilitation has positive benefits for regulation of atmospheric carbon concentrations, in addition to more broadly accepted ecosystem services.
... Here, we adapted the methods used by Moritsch et al. (2021) and assumed that carbon sequestration rates of restored ecosystems will be the same of mature ecosystems after 20 years (Craft, 2001;Osland et al., 2012;Marbà et al., 2015), with ecosystems between 0 and 20 years since restoration sequestering carbon at a conservatively estimated lower rate compared to mature ecosystems. Therefore, we used a percentage of carbon sequestration in mature ecosystems as sequestration rates for recently restored (i.e., 45% and 56% for mangrove forests and tidal marshes, respectively), and 10-years-old (i.e., 45% and 80% for mangrove forests and tidal marshes, respectively) restored ecosystems based on assessments in the published literature (Craft, 2001;Meyer et al., 2008;Adams et al., 2012;Osland et al., 2012;Marbà et al., 2015). ...
... Here, we adapted the methods used by Moritsch et al. (2021) and assumed that carbon sequestration rates of restored ecosystems will be the same of mature ecosystems after 20 years (Craft, 2001;Osland et al., 2012;Marbà et al., 2015), with ecosystems between 0 and 20 years since restoration sequestering carbon at a conservatively estimated lower rate compared to mature ecosystems. Therefore, we used a percentage of carbon sequestration in mature ecosystems as sequestration rates for recently restored (i.e., 45% and 56% for mangrove forests and tidal marshes, respectively), and 10-years-old (i.e., 45% and 80% for mangrove forests and tidal marshes, respectively) restored ecosystems based on assessments in the published literature (Craft, 2001;Meyer et al., 2008;Adams et al., 2012;Osland et al., 2012;Marbà et al., 2015). ...
There is a growing interest in including blue carbon ecosystems (i.e., mangroves, tidal marshes and seagrasses) in climate mitigation programs in national and sub-national policies, with restoration and conservation of these ecosystems identified as potential activities to increase carbon accumulation through time. However, there is still a gap on the spatial scales needed to produce carbon offsets comparable with terrestrial or agricultural ecosystems. Here, we used the Coastal Blue Carbon InVEST 3.7.0 model to estimate future net carbon sequestration in blue carbon ecosystems along Australia's Great Barrier Reef (hereafter GBR) catchments, considering different management scenarios (i.e., reintroduction of tidal exchange through the removal of barriers, sea level rise, restoring low lying land) at three different spatial scales: whole GBR coastline, regional (14,000–16,300 ha), and local (335–370 ha) scales. The focus of the restoration (i.e., tidal marshes and/or mangroves) was dependent on data availability for each scenario. Furthermore, we also estimated the monetary value of carbon sequestration under each management scenario and spatial scale assessed in the study. We found that large scale restoration of tidal marshes could potentially sequester an additional ∼800,000 tonnes of CO2e by 2045 (potentially generating AU$12 million based on the average Australia carbon price), with greater opportunities when sea level rise is accounted for in the modelling. Also, we found that regional and local projects would generate up to 23 tonnes CO2e ha⁻¹ by the end of the crediting period. Our results can guide future decisions in the blue carbon market and financing schemes, however, the return on investment is dependent on the carbon price and funding scheme available for project implementation.
... As part of this, the chronosequence approach with respect to ecosystem histories has proved crucial for assessing the recovery process of ecosystem functions and in determining the critical http://dx.doi.org/10.1016/j.ecoleng.2017.04.027 0925-8574/© 2017 Elsevier B.V. All rights reserved. factors involved in site restoration (Craft, 2001;Craft et al., 2003;Ballantine and Schneider, 2009;Erwin, 2009). Specifically, the recovery characteristics of soil carbon and nitrogen accumulation appear to be driven strongly by the establishment of vegetation, the development of heterotrophic activity, hydrological processes and sediment deposition (Craft et al., 2003;Ballantine and Schneider, 2009;Sheng et al., 2015). ...
... Regardless of planting approach, the stocks of SOC and SN increased with the age of the communities in both the muddy and silty sites. This observation is consistent with other examples of restored salt marshes (Craft, 2001;Craft et al., 2003;Henry and Twilley, 2013;Keller et al., 2015). It is generally hypothesized that SOC and SN accumulation is facilitated by vegetation restoration and that the consequent biomass input and the above-ground and below-ground biomass litter are the main sources of organic matter input into the soil in terrestrial ecosystems (Laganière et al., 2010;Zhao et al., 2015;Deng et al., 2016). ...
As part of research into the re-establishment of the native species Scirpus mariqueter in the salt marshes of the Yangtze Estuary, the roles of revegetation mode (planting density), site characteristics (sediment texture and hydrological regime) and community age (recently restored and mature marshes) in the storage of soil organic carbon (SOC) and nitrogen (SN) were examined. In recently restored marsh characterized by muddy sediments with moderate sediment accretion, vegetation growth and SOC and SN storage increased along with the increase in planting densities and the SOC storage was 1.14–1.52 times greater than that in non-vegetated plots after two years of revegetation. The SOC storage under a high planting density equated to approximately 75% of the carbon stock in the mature marsh. However, the increase in SOC storage was much less in those sites characterized by silty sediments than that in sites with muddy sediment, even when a high planting density was applied. This is attributed to a lower rate of sediment deposition and inhibition of below-ground root growth, which was found to be strongly correlated with carbon and nitrogen stocks in the soil. Additionally, the main rooting system of S. mariqueter and SOC and SN storage were concentrated in the top ∼20 cm in the recently restored marshes. These results demonstrate that successful vegetation restoration plays a key role in determining SOC and SN storage within a salt marsh. The restoration of native S. mariqueter for SOC and SN stocks is most effective when conducted in muddy sediments with good sedimentation rates and using a high planting density. In contrast, costs will be higher and recovery time longer in silty (or sandy) sediments, due to their poorer conditions for plant growth and significantly lower rates of carbon and nitrogen accumulation.
... The conversion of wetlands to agricultural land has had a significant negative impact on water quality and storage in most parts of the world, including New Zealand (Gosselink et al. 1990;Patrick 1994;Bernert et al. 1999;Brinson & Malvárez 2002). International research shows that restoring vegetation and hydrology in natural wetlands can improve both water purification and storage functions (Turner & Lewis 1997;Pfadenhauer & Grootjans 1999;Craft 2001;Bruland et al. 2003;Hansson et al. 2005;Meyer et al. 2008), but we were unable to find similar studies from New Zealand. Nevertheless, effects on water quality and storage are likely to be similar where natural wetlands are restored in New Zealand, providing that climatic factors and hydrological regimes are broadly comparable to those studied elsewhere (Chris Tanner, NIWA, Hamilton, pers. ...
... Levett et al. (1985) looked at litterfall and its macronutrient concentrations in native and exotic forests in New Zealand, but got variable results and few consistent differences between forest types. International studies show that if land protection enables natural recovery of previously degraded vegetation, nutrient cycling systems can be restored (Toky & Ramakrishnan 1983;Brown & Lugo 1990;Hughes et al. 1999;McDonald & Healey 2000;Craft 2001). Active replanting schemes may have the same effect, but we did not find any studies that measured this. ...
Ecosystem services are the benefits people obtain from ecosystems, such as clean air, fresh water, and the pollination of crops. The aim of this literature review was to find empirical data illustrating the ways in which conservation land and conservation management activities affect ecosystem services. The widely-held belief that natural ecosystems-such as those found on conservation land in New Zealand-provide a range of ecosystem services is generally supported by the literature. International studies show that natural vegetation can decrease air pollution, regulate local air temperatures, improve water quality, reduce shallow soil erosion, and retain natural nutrient cycles. It can also be beneficial for pest control and pollination on agricultural land. Wetlands can improve water quality and can play a role in drought and flood mitigation. Seagrasses, saltmarsh vegetation, and mangroves can reduce the height and force of waves and play a role in flood protection. In addition, maintaining biodiversity preserves genetic libraries and future options for discoveries of valuable biological compounds. The few studies investigating the effects of conservation management activities on ecosystem services indicate that restoring vegetation can improve water quality and water storage functions, can reverse soil degradation on a local scale, and can restore plant-insect interactions. Additionally, removing some invasive plant species can increase water yield. Unfortunately, very few studies of ecosystem services have been conducted in New Zealand to date, and only some of the international results are likely to be applicable under New Zealand conditions, Accordingly, while conservation is probably beneficial for a range of ecosystem services in New Zealand, the scarcity of local data makes it difficult to ascertain where and when, and to what extent, the majority of those benefits transpire.
... Flux tower marshes A and B were in relatively undisturbed marshes 1. 5 km from each other, c. 620 m north and southeast of an eddy covariance carbon flux tower operated by the Georgia Coastal Ecosystems Long-Term Ecological Research (GCE-LTER) project on Sapelo Island, GA. Flux tower marsh B was in a lower elevation area with greater tidal creek density than flux tower marsh A. UGAMI marsh, adjacent to the University of Georgia Marine Institute also on Sapelo Island, was a formerly impounded marsh that experienced altered hydrological cycles (Craft, 2001). The Skidaway marsh was on Skidaway Island, GA, just south of Savannah, GA, in a more urbanized watershed. ...
Spatiotemporal patterns of Spartina alterniflora belowground biomass (BGB) are important for evaluating salt marsh resiliency. To solve this, we created the BERM (Belowground Ecosystem Resiliency Model), which estimates monthly BGB (30‐m spatial resolution) from freely available data such as Landsat‐8 and Daymet climate summaries.
Our modeling framework relied on extreme gradient boosting, and used field observations from four Georgia salt marshes as ground‐truth data. Model predictors included estimated tidal inundation, elevation, leaf area index, foliar nitrogen, chlorophyll, surface temperature, phenology, and climate data. The final model included 33 variables, and the most important variables were elevation, vapor pressure from the previous four months, Normalized Difference Vegetation Index (NDVI) from the previous five months, and inundation.
Root mean squared error for BGB from testing data was 313 g m ⁻² (11% of the field data range), explained variance ( R ² ) was 0.62–0.77. Testing data results were unbiased across BGB values and were positively correlated with ground‐truth data across all sites and years ( r = 0.56–0.82 and 0.45–0.95, respectively).
BERM can estimate BGB within Spartina alterniflora salt marshes where environmental parameters are within the training data range, and can be readily extended through a reproducible workflow. This provides a powerful approach for evaluating spatiotemporal BGB and associated ecosystem function.
... Kaolinite, montmorillonite, vermiculite, illite, chlorite, quartz, feldspar, plagioclase, gibbsite, and metahalloysite are found at saltwater-marsh sites in Sapelo Island, Georgia (Letzsch 1986), and the carbon to nitrogen ratio (C/N) of the sediments sampled from these sites is 13.7±0.6 (per g) on average (Craft 2001). ...
Saltwater marshes or salt marshes are capable of providing to fauna and flora a biologically desirable environment while operating as a sink for sequestering large amounts of heavy metals. Salt marshes have the highest value of net primary productivity among terrestrial and wetland ecosystems and are adversely impacted and threatened by land-use change. Preservation and restoration practices for salt marshes require well-established databases characterizing these coastal areas based on vegetation, soil, and water. This study uses field-based experiments to characterize the native halophytic species and pore-water properties found along the Georgia coast. In addition, laboratory-based experiments were carried out to identify texture, bulk density, carbon to nitrogen (C/N) ratio, trace elements, and the mineralogy of the hydric soils of eight salt marshes located along Georgia’s shoreline. A greenhouse experiment was conducted to evaluate the growth of four predominant salt marsh vegetation types (Spartina alterniflora, Juncus roemerianus, Schoenoplectus tabernaemontani, and Borrichia frutescens) in eight engineered soil mixtures that approximate the physical and chemical properties of salt marsh soils, along with two controls providing baselines for growth in potting soil, as well as growth in the material specified in the current GDOT construction specifications for restoration of disturbed salt marshes. The results demonstrate that growth rates of halophytes depend on salinity of pore-water and soil constituents and properties such as texture, bulk density, organic matter, and mineralogy. Further, resulting statistical analyses reveal a correlation among salt marsh–predominant vegetation types and pore water redox potential. Also, percent organic matter and fine content of salt marsh soils are statistically significant drivers of soil bulk density.
... Blue carbon projects will need to consider local conditions and ecosystem services provided by the freshwater wetlands created by the earlier implementation of tidal barrages (Abbott et al., 2020). In addition, we need to highlight that the restoration of carbon sequestration in areas in which coastal wetlands migrate landward or are recently restored usually can take years (Craft, 2001;Osland et al., 2012;Marbà et al., 2015;Ewers Lewis et al., 2019). In general, ecosystem services take years to decades to re-establish and the consequences of sea level rise on the wetland community composition could lead to potential benefits for carbon sequestration (e.g., mangrove encroachment into tidal marshes) (Rogers et al., 2019a;Lovelock and Reef, 2020) but could also lead to trade-offs for other ecosystem services including biodiversity (Traill et al., 2011). ...
Australia’s Great Barrier Reef (GBR) catchments include some of the world’s most intact coastal wetlands comprising diverse mangrove, seagrass and tidal marsh ecosystems. Although these ecosystems are highly efficient at storing carbon in marine sediments, their soil organic carbon (SOC) stocks and the potential changes resulting from climate impacts, including sea level rise are not well understood. For the first time, we estimated SOC stocks and their drivers within the range of coastal wetlands of GBR catchments using boosted regression trees (i.e., a machine learning approach and ensemble method for modelling the relationship between response and explanatory variables) and identified the potential changes in future stocks due to sea level rise. We found levels of SOC stocks of mangrove and seagrass meadows have different drivers, with climatic variables such as temperature, rainfall, and solar radiation, showing significant contributions in accounting for variation in SOC stocks in mangroves. In contrast, soil type accounted for most of the variability in seagrass meadows. Total SOC stock in the GBR catchments, including mangroves, seagrass meadows and tidal marshes, is approximately 137 Tg C, which represents 9‐13% of Australia’s total SOC stock while encompassing only 4‐6% of the total extent of Australian coastal wetlands. In a global context, this could represent 0.5‐1.4% of global SOC stock. Our study suggests that landward migration due to projected sea level rise has the potential to enhance carbon accumulation with total carbon gains between 0.16‐0.46 Tg C and provides an opportunity for future restoration to enhance blue carbon.
... In these scenarios, we assumed ecosystems between 0 and 20 years post-restoration (tidal reconnection) sequester carbon at a fraction of the rate of an undisturbed ecosystem (Table S2; Craft, 2001;Marbà et al., 2015;Osland et al., 2012). We assigned sequestration rates to restored ecosystems (Table S2) at the appropriate intervals corresponding to the years since a given 100 × 100 m square of landscape became inundated. ...
Restoring and protecting “blue carbon” ecosystems - mangrove forests, tidal marshes, and seagrass meadows - are proposed actions for increasing global carbon sequestration. To improve understanding of which management actions produce the greatest gains in sequestration, we used a spatially explicit model to compare carbon sequestration and its economic value over a broad spatial scale (2500 km of coastline in southeastern Australia) for four management scenarios: (1) Managed Retreat, (2) Managed Retreat Plus Levee Removal, (3) Erosion of High Risk Areas, (4) Erosion of Moderate to High Risk Areas. We found that carbon sequestration from avoiding erosion-related emissions (abatement) would far exceed sequestration from coastal restoration. If erosion were limited only to the areas with highest erosion risk, sequestration in the non-eroded area exceeded emissions by 4.2 million Mg CO2 by 2100. However, losing blue carbon ecosystems in both moderate and high erosion risk areas would result in net emissions of 23.0 million Mg CO2 by 2100. The removal of levees combined with managed retreat was the strategy that sequestered the most carbon. Across all time points, removal of levees increased sequestration by only an additional 1 to 3% compared to managed retreat alone. Compared to the baseline erosion scenario, the managed retreat scenario increased sequestration by 7.40 million Mg CO2 by 2030, 8.69 Mg CO2 by 2050, and 16.6 million Mg CO2 by 2100. Associated economic value followed the same patterns, with large potential value loss from erosion greater than potential gains from conserving or restoring ecosystems. This study quantifies the potential benefits of managed retreat and preventing erosion in existing blue carbon ecosystems to help meet climate change mitigation goals by reducing carbon emissions.
... We assumed that carbon sequestration rates of restored ecosystems will be the same mature ecosystems after 20 years (Craft, 2001;Osland et al., 2012;Marbà et al., 2015), with ecosystems between 0-20 years since restoration sequestering carbon at a lower rate compared to mature ecosystems. Therefore, we used a percentage of carbon sequestration in mature ecosystems as sequestration rates for recently restored (45% and 56% for mangroves and saltmarshes, respectively) and 10-years-old (45% and 80% for mangroves and saltmarshes, respectively) restored ecosystems (Craft et al., 1999;Meyer et al., 2008;Adams et al., 2012;Osland et al., 2012;Marbà et al., 2015). ...
... The range of C:N ratios observed in the region highlights the need for additional data collection, especially within expanding un-vegetated marsh features. For example, Craft (2001) utilized fluctuations in C:N ratios to evaluate changes in soil conditions over time following marsh establishment. A similar approach may prove useful for investigating the stability and trajectory of un-vegetated pannes occurring within the marsh platform. ...
Coastal salt marshes consist of a mosaic of vegetated and open water features, which naturally evolve and change over time. However, the rapid expansion of open water areas has been associated with marsh degradation and there is a growing need for detailed studies as coastal wetlands continue to degrade under increasing rates of sea level rise and related stressors. Yet, few studies investigate soil physicochemical and biogeochemical properties within different marsh landscape features, which could provide insight into mechanisms of the formation and expansion of open water areas. The current study compared wetland soil physical and microbial properties observed in vegetated areas with shallow open water areas called pannes, identifying a number of significant differences. Panne soils possessed lower bulk density, total C, N, P, SOC, DOC, and SRP compared with vegetated marsh areas, suggesting a shift in nutrient pools as vegetated areas transition into shallow open water features. Panne features also displayed significantly lower microbial pool sizes and processing rates than vegetated marsh soils, suggesting reduced capacity for nutrient processing in open water areas. Further, extractable NH4-N was highest in the panne soils suggesting that the absence of macrophytes decreased N uptake in open water areas. Also related to the lack of vascular plants, extractable DOC in pannes averaged less than half the concentration found in vegetated marsh areas, despite a smaller difference in soil total C. Results underscore the importance of incorporating heterogeneous landscape soil conditions when evaluating marsh degradation and considering potential restoration activities.
... Soil quality in restored and created (including mitigation) wetlands has also received considerable attention as the basis for indicators to determine project success (e.g., Bishel-Machung 1996;Shaffer and Ernst 1999;Craft 2001;Fennessy et al. 2008;see Chapter 18). Numerous studies across diverse regions and wetland types have shown that restored and created sites have lower organic C content and nutrient availability. ...
... With the exception of the 1-yr-old constructed marsh, which had the highest rate of P accumulation (5 gm 2 /yr), P accumulation in constructed and natural marshes was Ͻ2 g·m Ϫ2 ·yr Ϫ1 . Rates of N and P accumulation measured in our marshes are within the range reported for other natural, constructed, and restored salt marshes (Craft et al. 1999, Craft 2001. ...
Ecological attributes were measured along a chronosequence of 1- to 28-yr- old, constructed Spartina alterniflora marshes to identify trajectories and rates of ecosystem development of wetland structure and function. Attributes related to biological productivity and diversity (Spartina, epiphytic and sediment algae, benthic invertebrates), soil devel- opment (sediment deposition, organic C, N, P, organic matter quality), and microbial pro- cesses (C mineralization) were compared among eight constructed marshes and eight paired natural reference marshes. Most ecological attributes developed in a predictable manner over time, and most achieved equivalence to natural marshes 5-15 yr after marsh construc- tion. An exception was soil organic C and N pools (0-30 cm) that, after 28 yr, were significantly lower in constructed marshes. Development of habitat structure (Spartina stem height and density) and biodiversity (algae and invertebrates) developed concurrently with functional characteristics such as biomass, chlorophylla, and invertebrate density. Processes related to hydrology, sediment deposition and soil C and N accumulation, developed almost instantaneously with the establishment of Spartina, and young (1- to 3-yr-old), constructed marshes trapped sediment and sequestered N at higher rates than comparable reference marshes. Development of heterotrophic activity (C mineralization, invertebrate density) was strongly linked to surface (0-10 cm) soil organic C content. Ecosystem development of constructed (and natural) salt marshes depended on a minimum of 100 g N/m2 (0.05- 0.1% N) to support emergent vegetation and 1000 g C/m2 (0.5-1% C) to sustain the het-
Coastal saltmarshes are found globally, yet are 25%–50% reduced compared with their historical cover. Restoration is incentivised by the promise that marshes are efficient storers of ‘blue’ carbon, although the claim lacks substantiation across global contexts. We synthesised data from 431 studies to quantify the benefits of saltmarsh restoration to carbon accumulation and greenhouse gas uptake. The results showed global marshes store approximately 1.41–2.44 Pg carbon. Restored marshes had very low greenhouse gas (GHG) fluxes and rapid carbon accumulation, resulting in a mean net accumulation rate of 64.70 t CO2e ha−1 year−1. Using this estimate and potential restoration rates, we find saltmarsh regeneration could result in 12.93–207.03 Mt CO2e accumulation per year, offsetting the equivalent of up to 0.51% global energy- related CO2 emissions—a substantial amount, considering marshes represent <1% of Earth's surface. Carbon accumulation rates and GHG fluxes varied contextually with temperature, rainfall and dominant vegetation, with the eastern coasts of the USA and Australia particular hotspots for carbon storage. While the study reveals paucity of data for some variables and continents, suggesting need for further research, the potential for saltmarsh restoration to offset carbon emissions is clear. The ability to facilitate natural carbon accumulation by saltmarshes now rests principally on the action of the management-policy community and on financial opportunities for supporting restoration.
Tidal marshes are common in temperate regions of the world. They are characterized by mixing of seawater and freshwater and by hydrologic pulsing driven by the astronomical tides and are among the most productive of wetlands, supporting high levels of plant and animal biomass. Many tidal marshes have been lost to shoreline development and urbanization and, sometimes, agriculture. Efforts to restore them consist of reintroducing tidal inundation by removing fill, dikes, levees, and tide gates and by managed realignment where coastal defenses are removed and marsh vegetation is allowed to reestablish. Because of the vigorous energy associated with tidal inundation, reestablishment of vegetation by natural colonization or seeding is slow and planting is often required. Development of heterotrophic food webs depends on establishing good coverage of vegetation and accumulation of soil organic matter and nitrogen (N). Keys to successful restoration include selecting sites with large tidal range to support a wide expanse of vegetation, gentle slope to limit waterlogging, and enhancing connectivity by creating tidal creeks and abundant vegetated edge to facilitate access and use by nekton and wading birds.
Land-use change has altered the ability of wetlands to provide vital services such as nutrient retention. While compensatory practices attempt to restore degraded wetlands and their functions, it is difficult to evaluate the recovery of soil biogeochemical functions that are critical for restoration of ecosystem services. Using solution 31P Nuclear Magnetic Resonance Spectroscopy, we examined the chemical forms of phosphorus (P) in soils from wetlands located across a land-use gradient. We report that soil P diversity, a functional attribute, was lowest in farmland, and greatest in native wetlands. Soil P diversity increased with age of restoration, indicating restoration of biogeochemical function. The trend in soil P diversity was similar to documented trends in soil bacterial taxonomic composition but opposite that of soil bacterial diversity at our study sites. These findings provide insights into links between ecosystem structure and function and provide a tool for evaluating the success of ecosystem restoration efforts.
Isles Dernieres is a transgressive barrier island arc in southeast Louisiana associated with the Bayou Grand Caillou headland of the Lafourche delta complex, which was abandoned 600 to 800 years ago. During the past two decades Trinity and Whiskey Islands have been eroding at rates of >18 m/y, and East Island has been eroding at a rate of 11.8 m/y. The Isles Dernieres Barrier Island Stabilization Project, implemented in 1998, dredged material from various sites in the bay behind the barriers for dune and marsh restoration of East, Trinity, and Whiskey Islands. The 1998 restoration increased the overall height and width of the islands but marsh habitat has not developed on the restored material behind the barriers. This study characterizes the physical and chemical properties of soil from restored and natural back-barrier salt marsh on Isles Dernieres to determine the restoration timeframe in which restored marsh soils develop to conditions more similar to natural marsh soils. Additionally, the goal is to identify the soil properties in restored marsh that could be modified to enhance back-barrier marsh habitat. Laboratory analyses of 60 cores from four different vegetation density classes in restored marsh and nine cores from natural marshes included bulk density, soil moisture content, grain size, sorting, pH, conductivity, total carbon, and total nitrogen. Vegetation density in restored marshes had no significant effect on soil properties, with the exception of bulk density. Marsh type had a significant effect on all measured soil properties. Variations in the soil properties of restored and natural back-barrier salt marsh are primarily the result of differences in soil texture and elevation.
Wetland condition can be severely altered as a result of a change in hydrology. In this study, we examined several soil-based
methods to quantify and assess changes in salt marsh condition as a result of tidal restriction. Soil properties were compared
between two tidally restricted and two (paired) unrestricted salt marshes. Organic horizon morphology provided a qualitative
metric of marsh peat decomposition. Quantitative measures of the degree of decomposition included stable plant fragment content
and bearing capacity. Soil pH provided simple metrics of changes in soil chemistry. Bulk density was measured to estimate
marsh peat collapse and soil organic matter content provided a measure of carbon dynamics. Neither marsh showed significant
differences in soil organic matter or bulk density relative to their paired reference marsh. In contrast, soil pH, stable
plant fragment content, and bearing capacity were significantly different between restricted and reference marshes. With the
exception of incubation pH, these soil properties can be simply and rapidly measured in the field to quantify physical, chemical,
and biological changes in the wetland condition of salt marshes as a result of tidal restriction. Further studies should be
conducted to develop a rapid protocol for measuring incubation pH in the field.
KeywordsReference sites–Tidal marshes–Tidal restriction–Wetland condition
To assess attributes of algal assemblages as indicators of salt marsh restoration, we chose eight pairs of salt marshes in
North Carolina, USA, each pair with one restored marsh (from 1 to 28 years old) and a nearby existing salt marsh. Algae on
both Spartina alterniflora and sediments (sediment algae) were collected in each marsh during spring and summer 1998 for assaying algal biomass (dry
mass (DM), ash free dry mass (AFDM), chl a content, algal biovolume), algal species composition and diversity, and gross primary production. An attribute restoration
ratio was calculated by dividing attribute values from each restored marsh by values from a paired reference marsh. Controlling
for regional variation in reference marshes substantially increased precision in relations between attributes and the increase
in age of restored marshes. The organic matter restoration ratio of sediments increased with age of restored marshes in both
spring and summer. The algal biomass restoration ratios of epiphytes, calculated with algal biovolume and chl a, increased with restored marsh age in summer but not during spring. Biomass of sediment algae was not related to marsh age.
The species diversity of sediment algae in summer showed an asymptotic relationship with sediment nutrient concentration.
The similarity of diatom species composition between paired restored and reference sites increased with age of restored marshes
during spring and summer. Primary production by epiphytic and sediment algae in summer showed site-specific changes and did
not change consistently with marsh age. Algal biomass, algal diversity, and diatom species composition during summer were
positively correlated with sediment nitrogen and phosphorus concentration. We concluded that other structural and functional
development of restored wetlands, especially nutrient storage in sediments, regulates algal species composition and algal
biomass accumulation, which can be used to evaluate salt marsh restoration.
The recent listing of saltmarsh in northern New South Wales, Australia, as an endangered ecological community has highlighted
the need to rehabilitate damaged saltmarsh and create new areas to offset losses. Land managers require scientific measurements
of the early stages of restoration for adaptive management but the interpretation of the data should account for environmental
factors. In this study of a degraded and rehabilitated subtropical saltmarsh on the east coast of Australia, measurements
of the changes in the soil microalgal community using chlorophyll a showed the differences between reference sites and treatment sites. Analyses of across-site variables showed that solar radiation,
rainfall, and tidal inundation influenced microalgal growth, highlighting the importance of seasonal studies. Microalgal abundances
showed relationships with developing site variables such as percentage soil moisture, total organic carbon, and total nitrogen.
MDS analyses using chlorophyll a showed that the restoration sites were progressing towards, but were not equivalent to the reference state in the short time
since restoration (two years) despite the fast growth rates of soil algae.
Wetland restoration is increasingly used as a strategy both to address historical wetland losses and to mitigate new wetland impacts. Research has examined the success of restored wetlands for avifaunal habitat, plant biodiversity, and plant cover; however, less is known about soil development in these systems. Soil processes are particularly important as soil organic matter (SOM), cation exchange capacity (CEC), and other properties are directly linked to wetland functions such as water quality improvement. This research compared soil development processes and properties of 30 palustrine depressional wetlands of four different age classes (approximately 5, 14, 35, and 55 years since restoration) located in central New York (USA). Five natural wetlands were used as references. This chronosequence included wetlands 27 years older than previously conducted studies, making it the longest reported database available. Replicated soil cores from each site were analyzed for SOM, bulk density (D(b)), CEC, and concentrations of nutrients and other chemical constituents. Decomposition rate and aboveground plant and litter biomass were measured as key contributors to soil development. The results indicate that some soil properties critical for water quality functions take decades or centuries to reach natural reference levels. Of particular importance, in the top five centimeters of soil, SOM, D(b), and CEC achieved <50% of reference levels 55 years after restoration. Soil development processes in these depressional wetlands appear to be driven by autochthonous inputs and by internal processes such as litter decomposition and are not accelerated in the initial phase of development by allochthonous inputs as has been documented in coastal salt marshes and riverine floodplains. While monitoring generally focuses on the initial establishment phase of restored ecosystems, our findings indicate that the later autogenic phase strongly influences development trajectories for important wetland soil properties. Therefore, the role of different successional phases in determining long-term trajectories of ecosystem development should be considered in restoration design, research, and monitoring. This research highlights areas for improving the field of restoration through understanding of successional processes, increased efforts to jump-start soil development, longer-term monitoring programs, and greater focus on soil components of restored wetlands.
Tidal marsh profiles from various locations around Chesapeake Bay were dated using 210Pb geochronology. These soils, which were classified as Typic and Terric Sulfihemists, Typic and Histic Sulfaquents, and Histic Hydraquents, were characterized with respect to bulk density, organic matter content, S and Fe speciation, and pyrite content. These characteristics were interpreted in the context of marsh accretionary activity and soil forming processes. Rates of vertical accretion ranged between 0.35 and 0.75cm yr -1, indicating that the marshes examined are keeping pace with published rates of sea level rise. -from Authors
Dredge material from the Gulf Intracoastal Waterway near Galveston, Tex., was used as a substrate material in the construction of an experimental intertidal salt marsh. Chemical and physical properties of dredge substrate samples at 270 sites were monitored over a 16‐month period. Cation exchange capacity (CEC), extractable phosphorus (P), total Kjeldahl nitrogen (TKN), NH 4 ‐N, and organic matter increased from 3.0 to 7.4 meq/100 g, 24 to 96 µg P/g, 85 to 296 µg N/g, 3.0 to 9.9 µg N/g, and 0.2 to 0.5%, respectively. No significant increases in N and P were observed in the substrate due to fertilization.
A separate study comparing substrate properties of the experimental marsh to three natural marshes demonstrated that organic matter, TKN, and NH 4 ‐N concentrations in the experimental marsh were lower. Organic matter, TKN, and NH 4 ‐N in the experimental marsh substrate averaged 0.6%, 260 µg N/g, and 5.4 µg N/g compared to 2.3%, 650 µg N/g, and 12.1 µg N/g, respectively, for the three natural marshes. Within each of the four marsh sites extreme spatial heterogeneity of chemical and physical properties was apparent.
Psammaquents, Sulfihemists, and Sulfaquents were found in the tidal marshes of Hernando (Gulf Coast) and Duval (Atlantic Coast) counties, in Florida. They were saline and near neutral in pH and, with the exception of the Psammaquents, contained higher levels of S (2.66–5.19%). Hernando County soils were shallow over limestone and much sandier than those in east Florida. Duval County soil clays were primarily montmorillonite, mica, and kaolinite but Hernando County soil clays were mostly vermiculite‐chlorite intergrade and kaolinite‐metahalloysite. Except for one of the Psammaquents, the soils contained relatively high levels of organic matter (7.8–28.9% organic C) and extractable bases. Juncus roemerianus Scheele is the principal plant in these marshes. The bulk density of the organic soil layers ranged from 0.13 to 0.36 g/cm ³ , whereas that of the clayey layers was 0.16 to 0.25 g/cm ³ .
Plant succession was investigated on sand waste heaps produced by kaolin mining in central Cornwall. It was found that relatively even aged, monospecific stands of vegetation were frequently present. The principal colonists were woody leguminous plants which, in some situations, were superceded by a massive growth of rhododendrons (Rhododendron ponticum) or native woodland species. Where legumes were absent, the waste was slowly colonised by Calluna vulgaris and other heathland species.
The age structure of the vegetation was negatively and significantly correlated (r=−0.71) with the moisture deficit (evapotranspiration minus rainfall) during the spring and early summer. Drought, limited seed availability, and low nitrogen levels in the waste material are factors which contribute to the development of monospecific, even-aged legume communities of Ulex europaeus, Sarothamnus scoparius and Lupinus arboreus.
Measurements were made of biomass and litter in five plant communities and nitrogen levels were determined in the soil/plant system within these communities and also in the soil of a woodland which had developed on sand waste. The low productivity and low rate of nitrogen accumulation in a stand of Calluna vulgaris contrasted with stands of the three woody legumes. Gorse (Ulex europaeus) accumulated nitrogen most rapidly and appeared to have preceded invasion by Rhododendron ponticum and transition to native woodland. Within the woodland and rhododendron thicket the soil nitrogen levels approached those characteristic of temperate climax woodland.
The data indicate that the course of plant succession and the rate of soil development are strongly influenced by the biological properties of the colonising species. These processes are accelerated considerably following the invasion of woody legumes. re]19760512