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Because of their proximity to oceanic waters, freshwater tidal forests are susceptible to impacts from future climate change and sea level rise. These wetlands are historically understudied and we conducted our study to improve the understanding of structural changes in forested wetlands as they become tidally influenced. Using 20 forested stands a...
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... Due to their low elevation, tidal influence, and limited tolerance for salinity, these species-rich ecosystems are threatened by climate change, especially saltwater intrusion [2]. Prior studies have documented rapid rates of forest-to-marsh transition in TFF affected by sea level rise [3][4][5][6], but even intermittent pulses of salinity from tropical storms can have adverse effects on forest health [7]. ...
... The importance of TFF ecosystems is widely recognized [2,[8][9][10], but TFF remain understudied compared to salt marshes or non-tidal riparian ecosystems [1,2,7,[11][12][13]. Doyle et al. [1] suggest that TFF are understudied because they have been altered or destroyed by human activities such as logging and drainage prior to scientific study, and continued management for flood control, navigability, and wildlife habitat have prevented large areas of TFF from regenerating. ...
... At each plot center, we recorded a general site description, took photographs, and measured canopy coverage using a canopy densiometer (Forest Densiometers, Marianna, FL, USA). Following the methodology of Anderson et al. [7], for all trees greater than 2.5 cm in diameter at breast height (DBH), we measured height using a laser hypsometer (Nikon Inc., Melville, NY, USA) and DBH with a diameter tape, identified them by species where possible, and assessed whether their crown reached the canopy. ...
Situated in the transitional zone between non-tidal forests upstream and tidal freshwater marshes downstream, tidal freshwater forests (TFF) occupy a unique and increasingly precarious habitat due to the threat of saltwater intrusion and sea level rise. Salinization causes tree mortality and forest-to-marsh transition, which reduces biodiversity and carbon sequestration. The Altamaha River is the longest undammed river on the United States East Coast and has extensive TFF, but there have been only limited field studies examining TFF along the entire gradient of salinity and flooding. We surveyed thirty-eight forest plots on the Altamaha River along a gradient of tidal influence, and measured tree species composition, diameter, and height. Hierarchical clustering and indicator species analysis were used to identify TFF communities. The relationship of these communities to elevation and river distance was assessed using non-metric multidimensional scaling (NMDS). We identified six significantly different forest communities: Oak/Hornbeam, Water Tupelo, Bald Cypress/Tupelo, Pine, Swamp Tupelo, and Bald Cypress. Both elevation and river distance were significantly correlated with plot species composition (p = 0.001). Plots at the downstream extent of our study area had lower stem density, basal area, and species diversity than those further upstream, suggesting saltwater intrusion. This study demonstrates the importance of and need for thorough and robust analyses of tidal freshwater forest composition to improve prediction of TFF response to sea level rise.
... The coastal forests of the mid-Atlantic and southern New England states are commonly a mix of deciduous hardwoods and evergreen conifers with the species composition dependent upon the site level soil moisture gradient and coarser scale latitudinal gradients in species ranges [28][29][30]. The drier upland end of the gradient in these forests are dominated by a diversity of oaks (including white (Quercus alba), southern red (Q. ...
... virginiana), and shortleaf (P. echinata)) [29]. The wetter end of the gradient is dominated by red maple (Acer rubrum), black gum (Nyssa sylvatica), American Holly (Ilex opaca), loblolly pine (at southern end of region), pitch pine (in the central portion of the region), and Atlantic White Cedar (Chamaecyparis thyoides) [29]. ...
... echinata)) [29]. The wetter end of the gradient is dominated by red maple (Acer rubrum), black gum (Nyssa sylvatica), American Holly (Ilex opaca), loblolly pine (at southern end of region), pitch pine (in the central portion of the region), and Atlantic White Cedar (Chamaecyparis thyoides) [29]. The transition zone between the salt marsh and adjacent forest is often consists of common reed (Phragmites australis, henceforth referred to as Phragmites), marsh elder (Iva frutescens), highbush blueberry (Vaccinium corymbosum), and eastern red cedar (Juniperus virginiana) [29]. ...
A number of studies have documented coastal forest dieback as a historical and ongoing process across the Northeast US region. To further develop a current understanding of the state of knowledge, review adaptation and response measures available to land managers, and to identify research and management needs, we conducted a literature review, interviewed experts, and convened a workshop bringing together scientists and land managers. A synthesis of the above suggests that the most important proximate mechanisms driving coastal forest dieback in the Northeast US are sea level rise-induced changes in the groundwater table in concert with increased saltwater inundation related to storm surges. What sets our conceptual model apart from prior work is the greater emphasis placed on the role of rising fresh groundwater levels in increasingly stressing the forest vegetation and decreasing regeneration potential. Episodic storm surges often exceed the salinity or saturation tolerances of existing trees leading to a wave of mortality that leaves the site inhospitable to subsequent regeneration. Maintaining functioning coastal forests across the Northeast US will require that the marsh and forest ecosystems be considered as an integrated unit when determining an appropriate adaptation response. With a better understanding of each of the sea level rise-induced mechanisms at work in these ecosystems, managers may be better prepared for the changes ahead and facilitate proactive adaptation strategies. Easements or buyouts are vital to ensure that there is ample space for the marsh and upland systems to migrate landward together. Forward thinking land use planning is needed to promote the “no net loss” of both marsh and coastal forest ecosystems to ensure the continued provision of their vital services to society.
... Tidal freshwater forested wetlands (TFFWs) are unique forested wetland ecosystems whose structure is a result of flooding, salinity, and topographical gradients [1][2][3][4]. Aboveground net primary productivity (ANPP) of forested wetlands is greatest in areas with seasonal hydrology [5,6]. TFFWs also have relatively high primary productivity, likely due to the hydrological pulsing these systems experience from tides [7,8]. ...
... Global climate change has the potential to impact the ability of TFFWs to sequestration [14]. Greenhouse and field studies have documented the effects of increased salinity on freshwater systems (e.g., [15][16][17]), reporting decreases in productivity, tree death, and conversion to other community types [4,[18][19][20][21]. It is forecast that climate change will cause sea level rise rates to increase, as well as cause changes in local precipitation and watershed runoff [22,23]. ...
... TFFW along the Atlantic and Gulf coasts occur in low lying areas which makes them susceptible to upland runoff, tidal flooding, saltwater intrusion, and other global climate change phenomena [64]. These forests are readily impacted by slight changes in salinity as a result of rising sea level [3,4,50,[65][66][67]. While porewater salinity decreased during this study, it rarely fell below 1 ppt and only in the areas furthest from the where tidal exchange occurs (Figures 1 and 2). ...
Rising sea levels and increasing salinity are impacting coastal forests of the Southern U.S. Forest productivity and composition was studied from 2014 to 2020 in paired plots (20 × 25-m) along a porewater salinity gradient (0, 0.8, 2.6, 4.6 PSU). Aboveground net primary productivity was estimated by summing annual litterfall and woody growth. In addition, voucher specimens for each vascular plant species were collected. Productivity differed in forest communities across the salinity gradient averaging 1081, 777, 694, and 613 g m−2 yr−1 in fresh, low-salt, mid-salt, Freshwater forest communities and high-salt sites, respectively. The vascular flora consisted of 144 species within 121 genera and 57 families. Although salinity in Strawberry Swamp is currently declining, it hasn’t reached levels low enough to reverse the loss of forested wetlands. With projections of continuing sea level rise and increasing salinity intrusions, tree regeneration and growth will continue to decline as the forest transitions into marsh.
... Larger diameters and taller trees occurred in sites within projected SLR inundation areas, whereas grasses were dominant and tree stands were more dense in high-salinity soils. Many studies have described gradients in vegetation structure and composition along tidal gradients, as well as observations in the variability of stem densities of trees, dominant understorey growth form and the abundance of seedlings in TFFWs in the eastern US (Baldwin 2007;Anderson et al. 2013;Johnson and Simenstad 2015;Liu et al. 2017). In these wetlands, dense stands of smaller trees tend to occur in tidal areas (Anderson et al. 2013). ...
... Many studies have described gradients in vegetation structure and composition along tidal gradients, as well as observations in the variability of stem densities of trees, dominant understorey growth form and the abundance of seedlings in TFFWs in the eastern US (Baldwin 2007;Anderson et al. 2013;Johnson and Simenstad 2015;Liu et al. 2017). In these wetlands, dense stands of smaller trees tend to occur in tidal areas (Anderson et al. 2013). Keith and Scott (2005) also note denser stands of melaleucas and eucalypts in disturbed or regrowth areas of coastal floodplain wetlands in New South Wales, Australia. ...
... However, a hydrological-salinity gradient explains some patterns in vegetation structure and composition. TFFWs in the southern US are similarly structured along a tidal gradient of differing salinity and flooding (Mitsch and Gosselink 2015c), reflected by variation in vegetation structure, species richness and diversity and tree regeneration (Baldwin 2007;Krauss et al. 2009;Anderson et al. 2013;Liu et al. 2017). Within subtropical Australia, dominant CFW canopy species shift along landward elevational gradients, reflecting changes in salinity and flooding (Grieger et al. 2019). ...
Coastal freshwater wetlands (CFWs) are among the most understudied wetlands globally and are highly vulnerable to projected climate changes. To address CFW knowledge gaps in south-east Queensland, Australia, we surveyed the floristic composition and structure of wooded CFWs and explored variation in vegetation patterns in relation to selected environmental drivers. Understorey and shrub assemblages were surveyed using a cover-class scale and stem counts for tree species abundance. Vegetation structure attributes (stem density, basal area) were calculated from survey data. Redundancy analysis was used to investigate drivers of vegetation structure and the species composition of each stratum. Vegetation structure patterns were associated with gradients of rainfall, soil moisture, salinity and pH. Understorey species composition was associated with wallum wetland species, native perennial grass and herb species, and vegetation patterns of the canopy. Common CFW species, namely Melaleuca quinquenervia and Eucalyptus tereticornis, dominated tree assemblage variation. Overall, CFW vegetation exhibited strong associations with gradients of salinity, rainfall, groundwater dependence and disturbance. Alterations to key drivers of vegetation pattern with future climate changes are likely to markedly influence the composition, structure and function of CFW vegetation communities. Action is therefore required to maintain CFW vegetation communities and ecological function in these diverse and unique wetland systems.
... Morella cerifera (wax myrtle) was limited to the lower stations of the study rivers (ER2-6 and SMR1-3). As a mid-story shrub or small tree, this species may benefit from decreased tree basal area and increased light penetration that commonly occurs as forested wetlands transitioning from non-tidal to tidal (Cormir et al. 2013, Anderson et al. 2013. For TFFWs in South Carolina, Liu et al. (2017) noted that M. cerifera seemed particularly well suited to tidal conditions and increased in density with increased salinity. ...
Tidal freshwater forested wetlands (TFFWs) commonly occur along coastal rivers; however, sea level rise and changes to river discharge may impact these wetlands. Information that characterizes the hydrology and salinity regime of the TFFW zone is needed to assess risk and predict future viability. A combination of field data and modeling were used to characterize TFFW hydrology, salinity, and vegetation along two distributaries (the East River and St. Marks River) of the Apalachicola River in west Florida, USA. Six gaging stations were established (three per river) roughly equidistant along the TFFW tidal gradient to monitor salinity and water levels at the river-wetland interface. Eighteen 500-m2 forest survey stations (nine per river) were also established roughly equidistant between (and including) the upper and lower gaging stations to measure canopy trees (> 2.54 cm DBH) and calculate species importance values (IV200). Field measures, along with other monitoring and model data, were used to develop a 30-year salinity record (1985–2015) for each gaging station based on an artificial neural network (ANN) model. Optimal ANN models for each TFFW gaging station were selected based on Akaike’s Information Criteria, and 30-year mean daily salinity was interpolated to all forest survey stations based on river distance. Important input variables for the ANN models included daily Apalachicola River discharge, Apalachicola Bay tidal stage, and bay salinity, among others. Based on 30-year salinity models, mean daily salinity ranged between 0.30 and 0.63 ppt at the downriver stations of East and St. Marks Rivers, respectively, to 0.14 and 0.14 ppt at the upriver stations, respectively. Results showed a predictable reduction in mean salinity and salinity ranges further upriver at both rivers; however, the St. Marks River showed a distinct inflection point in reduced salinity compared with the East River. Evaluating tree species IV200, there was a shift to species indicative of non-tidal conditions midway up the study reach of the St. Marks River while tidal species remained prominent throughout the East River study reach. Comparison of salinity, tidal reach, and species IV200 for each river suggests hydrology may be the most important contributor to the downriver extent of TFFWs while salinity may be an important driver of TFFW community composition.
... The water tends to be slightly acidic and low in nutrients (Cho, 2011). Freshwater tidal forests are typically associated with high-flow river systems with gradual elevation gradients and generally mark the inland limit of tidal influence in estuarine ecosystems (Anderson, Lockaby, and Click, 2013). Taxodium distichum (Bald Cypress), Taxodium ascendens (Pond Cypress), and Nyssa aquatica (Water Tupelo) are typical of the Mississippi Cypress-Tupelo swamp (Cho, 2011). ...
... While shorelines have retreated and channels have widened throughout much of the estuary, marsh vegetation has in large part failed to migrate inland as expected under conditions of gradual salinification from SLR ( Figure 2, Figure 3, and Table 1). Species composition and forest structure in this transitional zone is sensitive to changes in tidal influence (Anderson, Lockaby, and Click, 2013). Thus, species diversity and turnover can be high, in part due to annual fluctuations in salinity, which can encourage the growth of salt-tolerant vegetation (Anderson, Lockaby, and Click, 2013). ...
... Species composition and forest structure in this transitional zone is sensitive to changes in tidal influence (Anderson, Lockaby, and Click, 2013). Thus, species diversity and turnover can be high, in part due to annual fluctuations in salinity, which can encourage the growth of salt-tolerant vegetation (Anderson, Lockaby, and Click, 2013). In their examination of hydrological patterns in the forested wetlands of the Apalachicola River, Florida, Anderson and Lockaby (2012) found tidal freshwater swamps to exist within a narrow water level range of 620 cm of the ground surface, and at salinities of less than 0.5 ppt. ...
Waldron, M.C.B.; Carter, G.A., and Biber, P.D., 2021. Using aerial imagery to determine the effects of sea-level rise on fluvial marshes at the mouth of the Pascagoula River (Mississippi, USA). Journal of Coastal Research, 37(2), 389–407. Coconut Creek (Florida), ISSN 0749-0208.Coastal marshes provide valuable ecosystem services yet are increasingly vulnerable to sea level rise (SLR).To facilitate a better understanding of how fluvial marshes along the Gulf of Mexico coast are responding to regional SLR of around 3.7 mm per year, this study used aerial imagery to map land cover at the mouth of the Pascagoula River at 20-year intervals, beginning in 1955 and ending in 2014. High-resolution land cover maps were created for each image date based on a maximum likelihood classification scheme using spectral and textural image features. This marsh ecosystem, at the mouth of the largest free-flowing river by volume in the contiguous United States, should be more resilient to sea level rise than other Gulf Coast marshes, with little restriction to sediment supply and relatively low subsidence rates measured nearby. However, the results of this study show that marsh area declined by 1073 ha (17.5%) and rates of marsh conversion to open water increased over the studied time period. Although modeling studies indicate that coastal marshes worldwide may persist under accelerated SLR, these observations suggest that marsh extent in the sediment-rich Pascagoula River Estuary will continue to decline, signifying vulnerability among other marsh ecosystems along the northern Gulf of Mexico coast.
... Many freshwater wetland plants are well adapted to variable hydrologic regimes, but tend to be strongly and negatively impacted by salinity (Flynn et al. 1995;Neubauer 2013;Sutter et al. 2014;Herbert et al. 2015). Increased saline groundwater intrusion and increased periods of saltwater inundation have already led to large-scale changes in vegetation community structure, including tree mortality, in many American tidal freshwater marshes (Leck and Simpson 1995;Baldwin et al. 2001;Anderson et al. 2013). Changes in hydrology also drive shifts in coastal wetland vegetation composition, with both floods and droughts reducing species richness and abundance (Baldwin et al. 2001). ...
... Of the seedlings investigated in this study, M. quinquenervia and E. tereticornis were observed to be less tolerant of saline flooding, with seedling mortality recorded in almost all saltwater-flooded seedlings and detrimental effects on growth and biomass recorded, even under short pulses of saline flooding. The ongoing effect of saline water intrusion and rising sea levels has been widely recorded for tidal freshwater forests of southern USA, with many authors noting reductions in species diversity, productivity and regeneration (Krauss et al. 2009;Anderson et al. 2013;Xijun et al. 2017). Widespread tree mortality events and reduced seedling regeneration have also been recorded in US tidal freshwater forests experiencing saltwater intrusion and rising sea levels (Doyle et al. 2007;Anderson et al. 2013;Xijun et al. 2017), which have resulted in a transition to tidal marsh or saltmarsh habitat (Krauss et al. 2009;Anderson et al. 2013). ...
... The ongoing effect of saline water intrusion and rising sea levels has been widely recorded for tidal freshwater forests of southern USA, with many authors noting reductions in species diversity, productivity and regeneration (Krauss et al. 2009;Anderson et al. 2013;Xijun et al. 2017). Widespread tree mortality events and reduced seedling regeneration have also been recorded in US tidal freshwater forests experiencing saltwater intrusion and rising sea levels (Doyle et al. 2007;Anderson et al. 2013;Xijun et al. 2017), which have resulted in a transition to tidal marsh or saltmarsh habitat (Krauss et al. 2009;Anderson et al. 2013). A similar fate could be predicted for coastal freshwater wetlands in Southeast Queensland, with a reduction in regeneration capacity from both the soil seed bank and reduced seedling survival. ...
Coastal freshwater wetlands are amongst the world’s most modified but poorly researched ecosystems and some of the most vulnerable to climate change. Here, we examine vegetation resilience in coastal wetlands of subtropical Australia to altered salinity and flooding regimes likely to occur with climate change. We conducted field surveys and glasshouse experiments to examine plant diversity and regeneration responses of understorey and canopy species across four habitats. Vegetation composition, but not richness, varied between seaward and inland habitats while soil seed bank diversity was greatest in more inland sites. Experimental salinity and flooding treatments strongly influenced emergence from seed banks with most species germinating under fresh, waterlogged conditions and very few in saline treatments. Composition of emerging seedling assemblages was similar across habitats and treatments but differed considerably from the extant vegetation, indicating a relatively minor role of soil seed banks in sustaining current vegetation structure in this wetland. An exception to this was Sporobolus virginicus (marine couch) which was common in both the vegetation and seed banks suggesting a high capacity for this species to re-establish following disturbances. Seedlings of dominant canopy species also reacted strongly to increased salinity treatments with decreased survivorship recorded. Overall, our findings suggest a high probability of constrained vegetation regeneration in this wetland in response to key projected climate change disturbances with implications for vegetation diversity at a landscape scale including declines in the extent and diversity of more landward vegetation communities and expansion of salt-tolerant marshes dominated by Sporobolus virginicus.
... Community composition of canopy species differs between non-tidal floodplain forest and TFFW (Anderson and Lockaby 2011a). Smaller trees, more shrubs, more herbaceous cover, and less wood production and litterfall are found in tidal than non-tidal freshwater floodplain forests (Brinson et al. 1984;Anderson et al. 2013). TFFW also have lower concentrations of N and phosphorus (P) in tree leaves and more P limitation than non-tidal floodplain forest (Anderson and Lockaby 2011b). ...
Sea-level rise is pushing freshwater tides upstream into formerly non-tidal rivers. This tidal extension may increase the area of tidal freshwater ecosystems and offset loss of ecosystem functions due to salinization downstream. Without considering how gains in ecosystem functions could offset losses, landscape-scale assessments of ecosystem functions may be biased toward worst-case scenarios of loss. To stimulate research on this concept, we address three fundamental questions about tidal extension: Where will tidal extension be most evident, and can we measure it? What ecosystem functions are influenced by tidal extension, and how can we measure them? How do watershed processes, climate change, and tidal extension interact to affect ecosystem functions? Our preliminary answers lead to recommendations that will advance tidal extension research, enable better predictions of the impacts of sea-level rise, and help balance the landscape-scale benefits of ecosystem function with costs of response.
... Tidal freshwater forested wetlands (TFFW) ecosystems provide an opportunity for understanding the unique structuring of freshwater forests along hydroperiod, salinity, and microtopographical gradients (Williams et al., 1999;Morris et al., 2002;Craft et al., 2009;Anderson et al., 2013). TFFW with seasonal hydrology are generally more productive than their stagnant or drained counterparts (Conner andDay, 1976, 1992). ...
... Tidal freshwater forested wetlands of the southeastern United States are experiencing an increase in salinity intrusions as a result of rising sea level (Craft et al., 2009;Cormier et al., 2013;Anderson et al., 2013). In this study, low-saline and mid-saline sites had similar water depth, but the level was significantly lower than in the high-saline site. ...
Tidal freshwater forested wetlands (TFFW) of the southeastern United States are experiencing increased saltwater intrusion mainly due to sea-level rise. Inter-annual and intra-annual variability in forest productivity along a salinity gradient was studied on established sites. Aboveground net primary productivity (ANPP) of trees was monitored from 2013 to 2015 on three sites within a baldcypress (Taxodium distichum) swamp forest ecosystem in Strawberry Swamp on Hobcaw Barony, Georgetown County, South Carolina. Paired plots (20 × 25-m) were established along a water salinity gradient (0.8, 2.6, 4.6 PSU). Salinity was continuously monitored, litterfall was measured monthly, and growth of overstory trees ⩾10 cm diameter at breast height (DBH) was monitored on an annual basis. Annual litterfall and stem wood growth were summed to estimate ANPP. The DBH of live and dead individuals of understory shrubs were measured to calculate density, basal area (BA), and important values (IV). Freshwater forest communities clearly differed in composition, structure, tree size, BA, and productivity across the salinity gradient. The higher salinity plots had decreased numbers of tree species, density, and BA. Higher salinity reduced average ANPP. The dominant tree species and their relative densities did not change along the salinity gradient, but the dominance of the primary tree species differed with increasing salinity. Baldcypress was the predominant tree species with highest density, DBH, BA, IV, and contribution to total ANPP on all sites. Mean growth rate of baldcypress trees decreased with increasing salinity, but exhibited the greatest growth among all tree species. While the overall number of shrub species decreased with increasing salinity, wax myrtle (Morella cerifera) density, DBH, BA, and IV increased with salinity. With rising sea level and increasing salinity levels, low regeneration of baldcypress, and the invasion of wax myrtle, typical successional patterns in TFFW and forest health are likely to change in the future.
... Mature nontidal palustrine forested wetlands have been noted to yield lower values for woody stem species and, more notably, herbaceous species (Warren et al., 2006;Anderson et al., 2013). Though PNWL was subjected to a logging event in the early 1950's which removed all old growth trees, the wetland has grown to support trees comparable in size to several natural palustrine forested (PFOs) in the southeastern US (Anderson et al., 2013). ...
... Mature nontidal palustrine forested wetlands have been noted to yield lower values for woody stem species and, more notably, herbaceous species (Warren et al., 2006;Anderson et al., 2013). Though PNWL was subjected to a logging event in the early 1950's which removed all old growth trees, the wetland has grown to support trees comparable in size to several natural palustrine forested (PFOs) in the southeastern US (Anderson et al., 2013). ...
... These results parallel the concept of natural "hydrarch succession" where autogenic and allogenic woody species grow to dominate the system and outcompete understory plants for sunlight, resulting in a reduced number of herbaceous species (Warren et al., 2006;Anderson et al., 2013;Deberry 2006). Consequently, the understory of the PNWL was found to support a number of shade tolerant species including Lizard's tail (Saururus cernuus), Stinging nettle (Urtica dioica), False nettle (Boehmeria cylindrica), and Arrow arum (Peltandra virginica) (Plant Fact Sheet, 2002;Newcomb, 1977). ...
According to USEPA’s “No Net Loss,” memorandum, wetlands must be created in compensation for any unavoidable impacts resulting from development. Ideally, each individual constructed wetland should become functionally comparable to its natural predecessor. Three constructed non-tidal palustrine forested wetlands (PFO) and one natural PFO were compared based on vegetative proliferation and soil physiochemical characteristics in the Virginia Piedmont and Coastal Plain provinces. Vegetation parameters included woody stem counts, a list of total wetland flora, Basal Area (BA), and Diameter at Breast Height (DBH) measurements. Soils were flooded using synthetic-enriched freshwater (with naturally occurring concentrations of NH4-N and PO4-P) for 72 hours and measured for N exchange/release and P sorption/desorption, in order to approximate biogeochemical nutrient cycling as a result of prolonged inundation.
All wetland soils released N (2.65-13.6 mg NH4-N/m2). P sorption/desorption ranged from -4.35 mg PO4-P/m2 (desorption) to 16.6 mg PO4-P/m2 (sorption). The natural wetland (PNWL) supported significantly larger trees (DBH=13.1±9.86 cm) (BA=9.93 cm2 ha-1) (p<0.0001) than constructed sites, the lowest density of woody stems (1102 ws ha-1), the lowest species richness (SR=14), while also containing the most phosphorus and percent OM through a depth of 30 cm. Overall, the 19 year old SMWL (Spotsylvania Mitigated Wetland) differed significantly from PNWL with a higher density of predominantly small trees (4095 ws ha-1) (p=0.046) (DBH=0.99±0.96 cm) and sandy entisols which show a drastic reduction in soil quality with depth.
Underdeveloped, anthropogenically altered soils (udorthents) found in SMWL and intense beaver activity have likely limited success for this constructed PFO (Palustrine Forested Wetland). NH4-N release in these wetlands was presumed to be the result of significant microbial N-fixation under anaerobic flood conditions. Findings suggest that special attention be paid to initial soil conditions during construction and underline the complexity of flood-induced nutrient cycling in wetlands especially relevant as sea level rise and increased precipitation may result in more flood-prone wetlands in many transitional fluvial systems.
