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Microbial fuel cell (MFC) technology has shown great potential for harvesting energy from waste organic materials. Here, we explored the potential of MFC-based electricity generation from forest detritus, a large untapped biomass pool. Electricity generation from in situ MFCs and relevant environmental parameters (i.e., carbon sources and concentrations, temperature, water depth) in a seasonally flooded freshwater cypress-tupelo wetland were monitored intensively for two flooding periods. Current outputs ranged from 0 to 1.27 mA (mean of 0.40 mA for flooding period) and were highly sensitive to environmental changes, showing seasonal and diel dependences. Excluding the influence of heavy storms, drought, or wetland icing, current output was highly temperature-dependent dielly. Seasonally, current output gradually increased in the first 3–4 months (limited by temperature) and decreased slightly during the last 1–2 months (probably limited by carbon and nutrients) of both flooding periods. Litter extract of baldcypress (Taxodium distictum) with lower C/N ratio and aromatic content showed greater stable current outputs (0.57 mA) based on 50 mg l � 1 biological oxygen demand compared to extracts of water tupelo (Nyssa aquatica) and longleaf pine (Pinus palustris), suggesting that the current output of in situ MFCs could depend on the vegetation within a wetland. Our study highlights the potential application of MFC in generating green and sustainable electricity from forest biomass for powering remote sensors in wetland ecosystems.

Forests comprise approximately 37% of the terrestrial land surface and influence global water cycling. However, very little attention has been directed towards understanding environmental impacts on stand water use (S) or in identifying rates of S from specific forested wetlands. Here, we use sapflow techniques to address two separate but linked objectives: (1) determine S in four, hydrologically distinctive South Carolina (USA) wetland forests from 2009–2010 and (2) describe potential error, uncertainty and stand-level variation associated with these assessments. Sapflow measurements were made from a number of tree species for approximately 2–8 months over 2 years to initiate the model, which was applied to canopy trees (DBH > 10–20 cm). We determined that S in three healthy forested wetlands varied from 1.97–3.97 mm day−1 or 355–687 mm year−1 when scaled. In contrast, saltwater intrusion impacted individual tree physiology and size class distributions on a fourth site, which decreased S to 0.61–1.13 mm day−1 or 110–196 mm year−1. The primary sources of error in estimations using sapflow probes would relate to calibration of probes and standardization relative to no flow periods and accounting for accurate sapflow attenuation with radial depth into the sapwood by species and site. Such inherent variation in water use among wetland forest stands makes small differences in S (

Questions What are the general tree communities found in tidal freshwater swamps along four large coastal rivers in the southeastern United States (US)? How do these communities compare to other tidal freshwater swamps in the US and South America? Locations Tidal floodplains of major rivers along the Atlantic and Gulf coasts of the southeastern US: Savannah, Altamaha, Suwannee and Apalachicola Rivers. Methods An extensive survey of trees and shrubs was conducted to describe the communities from a range of tidal freshwater swamps. River basins studied include micro-tidal (Gulf coast) and meso-tidal (Atlantic coast) regimes, and study areas were located both near and distant to primary channels. A total of 128 plots (100 m2 each) were inventoried, distributed evenly over the Savannah and Altamaha Rivers along the Atlantic coast, and the Suwannee and Apalachicola Rivers along the Gulf coast. Multivariate statistics helped discern communities and the significant indicator species in each. Results Four general communities were characterized and named according to the strongest individual indicator species in each: Water Tupelo (Nyssa aquatica) Community, Swamp Tupelo (Nyssa biflora) Community, Dwarf Palmetto (Sabal minor) Community and Cabbage Palm (Sabal palmetto) Community. Conclusions Descriptions of most tidal freshwater swamps in the southeastern US fit within the communities described in this study. Because studies that make inferences between environmental drivers (e.g. salinity, hydroperiod, hurricanes) and specific community types are best applied to the same communities (but perhaps different river systems), this work provides a framework by which tidal freshwater forested wetlands can be accurately compared based on their tree communities. We suggest that, within the broad range of our inventories, the four communities described identify the primary associations that should be tracked within most tidal freshwater swamps of the US. However, we identify some river basins in the US that do not fit this construct. Diversity of major tree communities in tidal freshwater swamps outside the US is generally much lower (with the notable exception of Amazonian hardwood tidal varzea), as are basal area values.

Decomposition of site-specific litter mixtures was monitored for 100 wk in four Roodplaht communities: (i) a mixed oak community along the Cache River in central Arkansas, (ii) s sweetgum (Liquidambar styracijlua L.)-cherrybark oak (Quercwfalcata vwpagodaefolia ELI.) community along Iatt Creek in central Louisiana, (iii) a sweetgum-swamp tupelo [Nyssu sylvaticu var. bifroru (Walt.) Sarg.] community, and (iv) a laurel oak (Quercus luurifolia Michx.) commnnity along the Coosawhatchie River in southeastern South Carolina. Soil temperature, hydroperiod, and litter quality (C:N, C:P, N:P, fignin:N) were used to interpret differences in the rates of mass loss and nutrient dynamics. After 100 wk, litter mixtures retained 33, 18, 8, and 5% of original mass on the Cache, Coosawhatchie (laurel oak community), Coosawhatchie (sweetgum-swamp tupelo community), and Iatt floodplains, respectively, and these differences appeared related to hydroperiod. Decay rates were comparable to rates reported in similar floodplain environments. Net mineralization of both N and P was observed after 100 wk, but both elements accumulated in litter mixtures periodically. Differences in hydroperiod were observed among the four floodplain communities and decomposition of and nutrient mineralization from litter among them appeared to be inversely related to the number and duration of flood events. Litterbags containing leaf litter of a single-species (i.e., cherrybark oak) were also monitored on three of the four sites to compare decay rates and nutrient dynamics with the litter mixtures. On the Cache River floodplain, slower decay of poorer quality cherrybark oak litter suggested that titter quality drove decomposition under similar edaphic conditions.

Various aspects of water chemistry of a natural forested wetland were studied in order to determine the possibility of using the wetland for advanced wastewater treatment in Louisiana and to evaluate the wastewater effect on swamp water quality. The study was carried out by comparing treatment and control cypress-tupelo forests separated by a bottomland hardwood forest ridge. The treatment area (231 ha) received secondarily treated municipal wastewater at a rate of 6.3 x 10 6 L d -1 . The calculated hydraulic detention time of the wastewater was 120 d. Electrical conductivity (EC), pH, and concentrations of 5-d biological oxygen demand (BOD 5 ), dissolved oxygen (DO), solids, nutrients, and trace metals were monitored. Mean concentrations for the wastewater were 14.6 mg L -1 for total N and 2.5 mg L -1 for total P. The dominant form of N in the wastewater was NO 3 -N. The swamp system attenuated the NO 3 -N by 100%, total Kjeldahl nitrogen (TKN) by 69%, and total P by 66%. It appears that tertiary wastewater treatment was achieved due to the nutrient attenuations. Based upon our findings, we predict that the high N attenuation efficiency would enable the swamp to work well if the N loading rate were doubled. However, P removal was dependent on loading rate, hydraulic retention time, and temperature. The swamp was more efficient in treating wastewater during warm seasons than cool seasons. During the monitoring period, trace metals were not significantly increased in the swamp water because of very low concentrations in the wastewater.

It has been hypothesized that periodically flooded forests have higher rates of aboveground net primary production than upland forests and near-continuously flooded forests, but a competing hypothesis holds that the benefits of periodic inputs of nutrients and water may be diminished by stresses associated with anaerobic soils or drought. To test these hypotheses, we measured groundwater table depths and aboveground productivity in floodplain forests of South Carolina and Louisiana. We established paired plots on locally dry, intermediate, and wet topographic positions across three hydrologic transects in each state. These plots encompassed upland hardwood, bottomland hardwood, and cypress swamp forests. Measurements of leaf litterfall, wood production, and groundwater table depth were made in 1987 and 1988. We then used mean growing-season water depth (MWD) to group the plots into three classes: wet (>0 cm), intermediate (0 to -60 cm), and dry ( 25% dead stems) the slope of this line was 5 times greater (-24 gm-2yr- -cm- ). We conclude that the subsidy-stress hypothesis does not adequately describe patterns of NPP across Southeastern U.S. floodplain forests. Conditions of periodic flooding and flowing water do not often lead to high rates of productivity compared with upland forests. However, extensive flooding is nearly always a significant stress on forest productivity, particularly when the flooding regime has been recently perturbed through levee construc- tion or impoundment. Our data support a more complex interaction between subsidy and stress factors.

The highly dynamic, fine root component of forested wetland ecosystems has received inadequate attention in the literature. Characterizing fine root dynamics is a challenging endeavor in any system, but the difficulties are particularly evident in forested floodplains where frequent hydrologic fluctuations directly influence fine root dynamics. Fine root (≤3 mm) biomass, production, and turnover were estimated for three soils exhibiting different drainage patterns within a mixed-oak community on the Coosawhatchie River floodplain, Jasper County, South Carolina. Within a 45-cm-deep vertical profile, 74% of total fine root biomass was restricted to the upper 15 cm of the soil surface. Fine root biomass decreased as the soil became less well drained (e.g., fine root biomass in well-drained soil > intermediately drained soil > poorly drained soil). Fine root productivity was measured for 1 yr using minirhizotrons and in situ screens. Both methods suggested higher fine root production in better drained soils but showed frequent fluctuations in fine root growth and mortality, suggesting the need for frequent sampling at short intervals (e.g., monthly) to accurately assess fine root growth and turnover. Fine root production, estimated with in situ screens, was 1.5, 1.8, and 0.9 Mg ha -1 yr -1 in the well-drained, intermediately drained, and poorly drained soils, respectively. Results from minirhizotrons indicated that fine roots in well-drained soils grew to greater depths while fine roots in poorly drained soils were restricted to surface soils. Minirhizotrons also revealed that the distribution of fine roots among morphological classes changed between well-drained and poorly drained soils.

hardwood site (BLH) and 500 g dry wt/m2 for a baldcypress-water tupelo site (CT). Litter-fall was 574 g dry wt/m2/yr for BLH and 620 g dry wt/m2/yr for CT. Harvest samples within the two plots yielded 200 g dry wt/m2 and 20 g dry wt/m2 for BLH and CT, respectively. Minimum net primary production was calculated as the sum of the three: 1574 g dry wt/m2/ yr for BLH and 1140 g dry wt/m2/yr for CT. Maximum estimates of herbaceous production and insect consumption were made by using values from the literature. Estimated total net primary productivity was 1733 g dry wt/m2/yr for BLH and 1516 g dry wt/m2/yr for CT. Tree composition was determined by the point-centered quarter method. Relative frequency, relative density, absolute density, relative dominance, and importance value (IV) were calculated for the tree species along each transect. In the bottomland hardwood area many woody species exist with Acer rubrum var. drummondii (IV = 23.9) and Nyssa aquatica (IV = 18.4) the most dominant. In the baldcypress-water tupelo area, fewer woody species exist and Taxodium distichum (IV - 39.2) and N. aquatica (IV = 37.6) dominated. Comparison of productivity data from several southeastern swamps indicate that flowing water regimes tend to result in the highest swamp forest productivity.

Net primary productivity and community structure were studied at three adjacent swamp sites that were all once subject to seasonal flooding. Because of man-related activities one is now permanently flooded, and a second is managed on a summer-fall dry period and a winterspring flooded period. In the permanently flooded area such flood-intolerant trees as green ash are dying while shrubs and aquatic plants are increasing. Competition among overstory trees is reduced, enhancing growth of existing baldcypress and water tupelo trees. Total areal production, however, is low (887 gIm2/yr) because of fewer trees. Productivity in the managed area is high (1,780 gIm2/yr). The baldcypress-water tupelo community is being replaced by a swamp maple-ash community typical of bottomlands. In the natural swamp forest, baldcypress and water tupelo have remained dominant. Canopy closure has limited understory and aquatic growth but has also increased competition among overstory trees, resulting in a slow increase in basal area. Productivity is about 1,166 gIm2/yr. It is suggested that the flooding regime is an important controlling factor in each of the areas. SWAMP FORESTS are recognized as integral parts of wetland ecosystems, serving as habitats, spawning and nursery grounds, and sources of food for many organisms (Brown, Brinson and Lugo, 1979; Wharton and Brinson, 1979). Seasonal flooding and draining of swamps are vital to the maintenance of these functions. Recent studies have illustrated the high productivity of seasonally flooded swamp forests (Conner and Day, 1976; Mitsch and Ewel, 1979; Carter et al., 1973) and the export of large amounts of organic and inorganic nutrients from the swamp to downstream lake and marsh environments (Day, Butler and Conner, 1977; Kemp, 1978; Wharton and Brinson, 1979). In many wetlands the construction of canals, spoil deposits, embankments and impoundments associated with mining, timber, highway activities, and, in Louisiana, crawfish culture, has altered the flow of water. The purpose of this study was to compare plant community structure and productivity of three swamp areas with different flooding re1 Received for publication 20 February 1980; revision accepted 11 September 1980. Contribution No. LSU-CEL-79-17 of the Coastal Ecology Laboratory, LSU Center for Wetland Resources, Baton Rouge, La. This research was supported by the LSU Sea Grant College Program, a part of the National Sea Grant College Program maintained by the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. We would like to thank Ron Paille, Lynne Bowers, Paul Kemp, Steve Whipple, and John Day whose assistance and comments helped make this paper possible. gimes. Three major tree species, baldcypress (Taxodium distichum), water tupelo (Nyssa aquatica), and ash (Fraxinus sp.) are emphasized. MATERIALS AND METHODS-Study sitesThe Lac des Allemands swamp is located at the upper end of the Barataria Bay estuary, between the Mississippi River and Bayou Lafourche, La. (Fig. 1). During a routine examination of 1972 infrared false color imagery of this swamp, we noticed a 970-ha area that appeared white in comparison to the red and bluegreen of the other forested areas. Earlier imagery (December 1940 and March 1952) showed that extensive logging operations had occurred throughout the swamp, but the distinctive pattern of the 1972 imagery was not evident. Natural water flows through this swamp forest are northeast to southeast. However, the 970-ha site was found to be impounded and permanently flooded by water up to 1 m deep. Impoundment began when Louisiana Highway 20 was completed in 1930 along the western boundary, blocking overland flows from upstream. A natural ridge runs along the southeastern side of the area. The Vacherie Canal was dredged in 1955 along the northern boundary, and Bayou Chevreuil along the southern boundary in 1959, impounding the area with spoil deposits so that natural water flow has been altered for at least 20 yr. North of the permanently flooded area is a dense, healthy forest (320 ha). This area was isolated by construction of a board road in the