"Wetlands"

Arnold, Jeffrey G.;Allen, Peter M.;Morgan, David S.

doi: 10.1672/0277-5212(2001)021[0167:HMFDAC]2.0.CO;2pmid: N/A

Abstract The Trinity River Mitigation Bank was proposed to develop and use a mature, contiguous, diverse riparian corridor along the West Fork of the Trinity River near Dallas, Texas, USA. In the proposed wetland design, water would be diverted from Walker Creek as necessary to maintain wetland function. Therefore, assessment of the magnitude and continuity of the flow from Walker Creek was paramount to successful wetland operation. The Soil and Water Assessment (SWAT) model was used to assess whether the sustained flow (storm flow and base flow) from the Walker Creek Basin could maintain the proposed bottomland wetland ecosystem. For this study, SWAT was modified to allow ponded water within the prescribed wetland to interact with the soil profile and the shallow aquifer. The water budget was prepared for the wetland based on a three-step process. First, data required to run the model on Walker Creek, including soils, topographic, land-use, and daily weather data were assembled. Next, data required to validate the model were obtained. Since stream flow was not available at the proposed site, flow from a nearby watershed with similar soils, land use and topography were used. In the final step, the model was run for 14 years and compared to the measured water balance at the nearby watershed. The model results indicate that the wetland should be at or above 85 percent capacity over 60 percent of the time. The wetland did not dry up during the entire simulated time period (14 years) and reached 40 percent capacity less than one percent of the time during the simulation period. The advantages of the continuous simulation approach used in this study include (1) validation of wetland function (hydroperiod, soil water storage, plant water uptake) over a range of climatic conditions and (2) the ability to assess the long-term impact of land-use and management changes.

Windham, Lisamarie

doi: 10.1672/0277-5212(2001)021[0179:COBPAD]2.0.CO;2pmid: N/A

Abstract The recent expansion of Phragmites australis (common reed) from the marsh-upland interface into high marsh zones provides an opportunity to assess the impact of individual plant species on biomass production and decomposition in salt marshes. Seasonal harvests of aboveground and belowground biomass demonstrate that annual production of P. australis is approximately three times greater for aboveground biomass, two times greater for belowground biomass, and 30% lower in root: shoot ratio than neighboring populations of S. patens. Whole-plant litter (stems and leaves) also decomposes at a much slower annual rate for P. australis (k=0.25) than S. patents litter (k=0.57). By crossing litter type with site of litter decomposition, I found these plant species to influence decay rates through litter type and not through their effects on marsh surface conditions (e.g., temperature, sedimentation rates). Based on these calculations, annual rates of carbon accumulation in the peat of high marshes are likely to increase 5-fold once P. australis becomes established due to its greater rates of biomass production and residence time in infrequently flooded brackish marshes.

Wetzel, Paul R.;van der Valk, Arnold G.;Toth, Louis A.

doi: 10.1672/0277-5212(2001)021[0189:ROWVOT]2.0.CO;2pmid: N/A

Abstract The composition of seed banks of areas on the drained Kissimmee River floodplain (Florida, USA) that are currently pasture and formerly had been wet prairie, broadleaf marsh, and wetland shrub communities was compared to that of seed banks of areas that have extant stands of these communities. The species composition of the seed banks of existing wet prairie and former wet prairie sites were the most similar, with a Jaccard index of similarity of 55. Existing and former broadleaf marsh and wetland shrub communities had Jaccard indices of 38 and 19, respectively. Although existing and former wet prairie seed banks had nearly the same species richness, species richness at former broadleaf marsh and wetland shrub sites was higher than at existing sites. Mean total seed densities were similar in existing and former wet prairies (700 to 800 seeds m2). However, seed densities in former broadleaf marsh and wetland shrub sites were significantly greater than in comparable existing communities (>4,900 seeds m2 at former sites versus 200 to 300 in existing communities). The higher seed densities in former broadleaf marsh and wetland shrub sites was due to over 4,000 seeds m2 of Juncus effusus in their seed banks. Half of the species that characterize wet prairies were found in the seed banks at former and existing wet prairie sites. At existing broadleaf marsh and wetland shrub sites, most of the characteristic species were found in their seed banks. However, only one characteristic broadleaf species was found in the seed banks of the former broadleaf marsh sites, and no characteristic wetland shrub species were found in the seed banks of the former wetland shrub sites. The seeds of only two non-indigenous species were found in the seed banks of former wetland communities at very low densities. For all three vegetation types, but particularly for the broadleaf marsh and wetland shrub sites, re-establishment of the former vegetation on the restored floodplain will require propagule dispersal from off-site sources.

Farnsworth, Elizabeth J.;Ellis, Donna R.

doi: 10.1672/0277-5212(2001)021[0199:IPLLSA]2.0.CO;2pmid: N/A

Abstract Conflicting interpretations of the negative impacts of invasive species can result if inconsistent measures are used among studies or sites in defining the dominance of these species relative to the communities they invade. Such conflicts surround the case of Lythrum salicaria (purple loosestrife), a widespread exotic wetland perennial. We describe here a 1999 study in which we quantified stand characteristics of L. salicaria and associated vegetation in arrays of 30 1-m2 plots in each of five wet meadows in Connecticut, USA. We explored linear and non-linear relationships of above-ground plant biomass, stem density, and indices of species richness, diversity, and composition to gradients of L. salicaria dominance, including stem density, percent cover, and biomass. Species richness, other diversity metrics, and stem density of other species were not significantly correlated with the density or percent cover of L. salicaria stems. The relative importance values (number of quadrats in which they were found) of co-occurring species in low-density L. salicaria quadrats were significantly correlated with their relative importance in high-density L. salicaria quadrats, indicating that only modest shifts in abundance occurred as L. salicaria increased in density. No individual species were consistently associated with or repelled by the presence of L. salicaria across sites. In contrast to density and diversity features, however, the total biomass of species other than L. salicaria was significantly, negatively correlated with the total biomass of L. salicaria at each site surveyed. Lythrum salicaria in pure, dense stands maintained a greater above-ground standing biomass on invaded sites than uninvaded vegetation of similar physiognomy. This study demonstrates that hypotheses about L. salicaria effects can vary depending upon the ecological metric that is examined. Where one-time, correlative studies are the most feasible option, data taken on a range of metrics—especially biomass—should be taken to inform us about mechanisms by which L. salicaria invades and predominates in wetlands.

Verhoeven, Jos T. A.;Whigham, Dennis F.;van Logtestijn, Richard;O’Neill, Jay

doi: 10.1672/0277-5212(2001)021[0210:ACSONA]2.0.CO;2pmid: N/A

Abstract This paper describes a study of nutrient dynamics in 12 tidal and non-tidal freshwater riverine wetlands in The Netherlands, Belgium, and Maryland (USA). The purpose of the study was to investigate the relationships between nutrient cycling processes in riverine wetlands that were geographically separated, that were dominated by different types of vegetation, and that had different hydrodynamics. We also compared restored and natural riverine wetlands. The results showed distinct differences in interstitial water chemistry between the sites in Maryland and Europe. No such regional differences were found in the soil variables, except for soil phosphorus, which was higher in The Netherlands. Soil organic matter, total nitrogen and phosphorus content, and bulk density were higher in tidal freshwater wetland soils. Forested wetland soils had higher organic matter and total nitrogen and lower bulk density and total phosphorus than soils from wetlands dominated by herbaceous species. Restored wetlands had lower soil organic matter and total soil nitrogen and phosphorus than similar types of natural riverine wetlands. There were no differences in nutrient-related process rates nor plant nutrient concentrations in tidal versus non-tidal riverine wetlands. Lower nitrogen and phosphorus concentrations in plants at the restored sites suggest that nutrient uptake by vegetation may be poorly coupled to rates of nutrient cycling during early stages of vegetation development. A principal components analysis of the data identified groupings of soil and water variables that were similar to those that had been previously identified when we applied the same methods to peatlands that were also geographically widely separated. Results of the study demonstrate that the techniques that we have been using are robust and repeatable. They are especially useful for making general comparisons of nitrogen and phosphorus cycling, when there are limitations on the number of wetland that can be sampled. The approach that we have developed may also be used to calibrate and refine nutrient cycling models that are incorporated into wetland assessment procedures.

Euliss, Ned H.;Mushet, David M.;Johnson, Douglas H.

doi: 10.1672/0277-5212(2001)021[0223:UOMTIC]2.0.CO;2pmid: N/A

Abstract We evaluated the use of macroinvertebrates as a potential tool to identify dry and intensively farmed temporary and seasonal wetlands in the Prairie Pothole Region. The techniques we designed and evaluated used the dried remains of invertebrates or their egg banks in soils as indicators of wetlands. For both the dried remains of invertebrates and their egg banks, we weighted each taxon according to its affinity for wetlands or uplands. Our study clearly demonstrated that shells, exoskeletons, head capsules, eggs, and other remains of macroinvertebrates can be used, to identify wetlands, even when they are dry, intensively farmed, and difficult to identify as wetlands using standard criteria (i.e., hydrology, hydrophytic vegetation, and hydric soils). Although both dried remains and egg banks identified wetlands, the combination was more useful, especially for identifying drained or filled wetlands. We also evaluated the use of coarse taxonomic groupings to stimulate use of the technique by nonspecialists and obtained satisfactory results in most situations.

Nair, Vimala D.;Graetz, Donald A.;Reddy, K. Ramesh;Olila, Oscar G.

doi: 10.1672/0277-5212(2001)021[0232:SDIPMC]2.0.CO;2pmid: N/A

Abstract Soil characteristics of a wide variety of created wetlands were compared to those of native wetlands in phosphate-mined areas from central and north Florida, USA. Criteria selected for evaluation of soil samples from 184 sites included soil compaction, bulk density, organic matter (carbon) and nitrogen content, C∶N ratio, and available and total nutrient contents. Organic matter accumulation, one of the indicators of a functional wetland, increased across transects going from uplands toward the center of the wetlands, and with wetland age. The organic matter accumulation rate in the AO and A1 horizons was 320 g m2yr−1. Native wetlands had significantly greater organic matter accumulation, both in the litter and mineral soil surface. The C∶N ratio of the soil organic matter decreased with created wetland age and approached values commonly found in wetland soils (15–25). Bulk density decreased with increasing organic matter content in the created wetlands, and low bulk density soils appeared to support better vegetative growth. Based on the above-mentioned parameters, reclaimed wetlands are slowly developing into “typical” wetlands; the rate of development could possibly be increased by minimizing soil compaction, incorporation of organic matter, or by fertilization.

Lesica, Peter;Miles, Scott

doi: 10.1672/0277-5212(2001)021[0240:TGATNM]2.0.CO;2pmid: N/A

Abstract Tamarisk (Tamarix spp.), an introduced shrub or small tree, has invaded riparian areas throughout the western United States. Tamarisk invasion has been studied extensively in the Southwest, but there is little information on its performance at the northern margin of its naturalized range. We measured the canopy cover, density, height and age of tamarisk and plains cottonwood (Populus deltoides) in 50 plots at 25 sites along the Bighorn, Powder, and Yellowstone rivers in southeast Montana near the northern edge of tamarisk’s western North American range. Tamarisk commonly formed thickets on open, low terraces and along over-flow channels but was less dense beneath a cottonwood canopy. Tamarisk stems routinely died back to the ground, and the oldest live stems were generally much younger than the plants. Tamarisk 30 to 40 years old in our study area usually attained heights of only 4 m or less. Height and number of live stems of tamarisk plants were 16% and 44% lower respectively under a tall cottonwood canopy. Cottonwood grows faster than tamarisk, eventually shading it and causing its decline. We believe that tamarisk will be only an understory shrub in most eastern Montana riparian forests, declining as cottonwoods form a closed canopy. Minimizing the spread of tamarisk in riparian areas in Montana can best be accomplished by managing for cottonwood.

Richburg, Julie A.;Patterson, William A.;Lowenstein, Frank

doi: 10.1672/0277-5212(2001)021[0247:EORSAP]2.0.CO;2pmid: N/A

Abstract Kampoosa Bog in Stockbridge, Massachusetts, USA is a 70-ha wetland comprised of calcareous basin fen and red maple swamp bordered, in part, by roads including the Massachusetts Turnpike. High salt concentrations in the ground water (due to the application of deicing salts on the Turnpike) and Phragmites australis colonies appear to be impacting the native vegetation at this site. Sodium and chloride concentrations at Kampoosa Bog are generally below previously published threshold levels for impacting vegetation, although such levels vary by species and in relation to other environmental stress conditions. Giant reed (Phragmites), a salt-tolerant invasive species, invaded the northern portion of the wetland adjacent to the Turnpike and a gas pipeline sometime after they were built in the 1950s. By 1998, Phragmites had formed dense colonies that continued to spread across the wetland, which supports several state-listed rare plant and animal species. High salt concentrations (Na+ > 112 mg/L, Cl >54 mg/L) are present up to 300 meters from the Turnpike. Phragmites colonies occur in areas with high and low salt concentrations, and the species abundance is not well-correlated with elevated salt levels. Although high salt concentrations and Phragmites abundance do not seem to produce an interaction effect on the vegetation of the wetland, the graminoid fen community is impacted by both factors separately. We attribute decreases in the abundance of species between invaded and non-invaded areas to the presence of Phragmites. In the graminoid fen, we attribute decreases in both community measures (richness, evenness, and overall cover) and individual species abundances to high salt concentrations.

Pujol, Juan A.;Calvo, José F.;Ramírez-Díaz, Luis

doi: 10.1672/0277-5212(2001)021[0256:SGGAOA]2.0.CO;2pmid: N/A

Abstract In this paper, some issues of the autoecology of Halocnemum strobilaceum (a rare succulent halophyte that occurs in southeastern Spain) are examined, particularly the germination process and the first stages of plant development. In regards to germination, this species shows the general pattern of halophytes under increased salt stress (reduced germination and germination rate). What stands out is the extreme salt tolerance of H. strobilaceum seeds. The stimulation of root length by the presence of salt probably plays an important role in avoiding salt stress at surface-level soils, within salt concentrations where germination still occurs. Halocnemum strobilaceum typically accumulates Na+ ions, which, combined with Cl−, contributes to the internal osmotic potential. The accumulation of both ions clearly increases with an increase in salinity stress. In contrast, accumulation of K+, Mg2+, and Ca2+ decreases with an increase in salinity stress. Glycinebetaine contents are approximately 100 times greater than proline contents, although their contribution was significant only if cell compartmentalization was considered. The accumulation of ions along with the osmoprotective compounds glycinebetaine and proline allows seedlings to mantain a lower internal osmotic potential than that of the growth medium, which is necessary for water uptake in saline soils.