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Wetlands provide essential habitat for shorebirds, songbirds, and waterfowl. Invasive species can disrupt trophic interactions within wetlands by altering the arthropod assemblages on which birds rely. An invasive grass species, Phragmites australis (common reed), has invaded wetlands across North America, including those surrounding the Great Salt Lake, Utah, U.S.A. Phragmites outcompetes native vegetation and alters habitat for resident and migratory birds, yet how Phragmites affects arthropod assemblages is unclear. To address these knowledge gaps, this study investigated how arthropod assemblages differ between native and invasive vegetation in Great Salt Lake wetlands. We examined the arthropod assemblages found within three native habitats as well as in Phragmites-invaded areas. There were few differences in arthropod assemblages between Phragmites and two native habitats (hardstem bulrush, Schoenoplectus acutus and alkali bulrush, Bolboschoenus maritimus). Arthropod assemblages differed between Phragmites and the native Salicornia rubra (pickleweed), which differed markedly from the other plant species in structure, biomass, and related site conditions. Identifying how arthropods interact with Phragmites and native vegetation is critical to recognizing how to effectively manage wetlands for bird habitat. By gaining an understanding of these relationships, arthropod biomass, abundance, diversity, and assemblage composition could serve as assessment metrics for determining wetland management success.

Behavior of Columbian mammoths (Mammuthus columbi) is revealed by a newly discovered trackway at the Pleistocene locality of Fossil Lake, Oregon. Our 8 by 20 m excavation of the mammoth trackway found 117 tracks, including one 20-m-long adult trail, partial trackways of 3 additional adults, a yearling and a baby all heading generally west. The tracks are in the Marble Bluff biotite tuff (43.2 cal ka), which forms a surface horizon to the Pogani silty clay loam paleosol (Natrargid), with a cracked surface and a columnar-structured, subsurface (Bn) horizon, like soils under desert soda pans with alkali shrubland. Directly below is the Yada silty clay paleosol (Xeroll) with crumb textured surface (A) horizon like grassland soils. The Pasiwa loam (Psamment) is a thin brown siltstone, with sparse roots and burrows of lake-margin early successional vegetation. The Pui sandy loam (Aquent) is well-bedded tuff and sand (A) with subhorizontal calcareous rhizomes and adventitious roots, like those of lake-margin tule reeds (Schoenoplectus acutus). Columbian mammoths may have moved like modern elephants with infants in matriarchal groups through landscapes of sagebrush and grassland, and this trackway includes a limping female attended by concerned juveniles. Grassland paleosols common in the Fossil Lake Formation, are now rare in the same region, perhaps related to extinction of proboscidean and equine grazers.

Nitrogen (N) and Silicon (Si) availability can affect the vigor and resiliency of plant communities. The effects of N on plant growth has been investigated in multiple species and is understood to promote growth. Though it is generally understood that Si aids in plant functions such as stem strength enhancement and herbivory defense, the role Si has not been explored in many wetland plant species. Tidal wetland plants are often subjected to high wind and wave energy, which can cause breakage or collapse of stems. This body of research investigated the combined effects of Si and N regimes to reduce the occurrence of stem collapse through its influence on stem strength. We investigated the effects of Si and N concentration on the growth, morphology, and physiology of Schoenoplectus acutus and Schoenoplectus californicus, two species of macrophytes that are commonly used in freshwater tidal restoration plantings. Individuals of each species were grown hydroponically in four different nutrient combinations (low Si and low N, low Si and high N, high Si and low N, and high Si and high N). Results indicated that increased N concentrations promoted aboveground biomass production, whereas increased Si concentration enhanced stem strength and decreased the likelihood of stem collapse and herbivory. Plants receiving a high Si and low N nutrient combination exhibited the most robust stems. Our findings emphasize the importance of Si, as well as N, in Schoenoplectus spp. growth and highlight the potential applications for these nutrients in enhancing tidal marsh management.

Limited knowledge of seed dormancy break, germination requirements, and intraspecific variation of these traits hinders revegetation of many species targeted for restoration. We evaluated the importance of cold stratification and chemical scarification for breaking seed dormancy and the impact of soaking in water on germination for three globally distributed bulrush species. These species, Bolboschoenus maritimus (alkali bulrush), Schoenoplectus acutus (hardstem bulrush), and S. americanus (threesquare bulrush), form critical habitat in Great Salt Lake wetlands. For B. maritimus and S. acutus , we also evaluated variation in response to seed dormancy breaking treatments among geographically-distant seed sources. We found that both 180 days of cold, moist stratification or 48 hours of bleach scarification were effective for breaking seed dormancy for most seed sources of B. maritimus . For S. acutus , longer stratification lengths may result in consistently higher germination percentages, but 30 days of stratification may be of sufficient length for some source sites. For S. americanus , stratification improved germination in one experiment, but 20–60 percent of viable seed did not germinate in each experiment potentially due to a poor understanding of germination requirements. Soaking seeds in water under greenhouse conditions, improved the germination of all species when done after dormancy breaking treatments. Importantly, response to dormancy breaking treatment varied among source sites; intraspecific variation may account for unpredictable responses to dormancy breaking treatments. These findings can assist practitioners in crafting strategies to effectively break dormancy and germinate seeds of B. maritimus, S. acutus , and S. americanus .

In an effort to improve fish habitat in western irrigation reservoirs, germination of seeds of six wetland plant species was investigated in two separate experiments. In the first, seeds were stored overwinter at 3–4 °C either dry or wet. In spring, these groups were further divided into four constant temperature treatments (15, 20, 25, or 30 °C) and 3 fluctuating temperature treatments (low, moderate, high). Within each treatment, seeds from a subset of species ( Alisma gramineum, Schoenoplectus acutus, S. americanus ) were scarified using either bleach for 1 or 5 d or mechanical abrasion. Seeds were exposed to a 12 h photoperiod in Petri plates within germination chambers for 57 days. In the second experiment, photoperiod (12, 14, or 24 h light), water depth (0 or 4 cm; S. acutus only), temperature, and bleach pretreatment were further evaluated. Cold, wet storage (CWS) and bleach treatment significantly improved germination (84 to 100%) of A. gramineum and led to quicker germination. Bleach treatment for 5 days significantly increased germination (13%) for S. acutus at 15 °C. Temperature effects varied with species. Inundation of seeds significantly improved germination of S. acutus . For both Schoenoplectus species, germination was highest at daily fluctuating temperatures of 32–38 °C. Photoperiod effects were inconsistent. Polygonum pensylvanicum germination was only evaluated in the second experiment; maximum germination (54%) was under a diel cycle of 15–20 °C after 1 year of CWS. Based on the study, effects of temperature, temperature fluctuation, water depth, overwinter storage conditions, and scarification are sufficiently known to use the data for initiating seed pretreatment for habitat projects.

Author(s): Sloey, Taylor M.; Hester, Mark W. | Abstract: Liberty Island, California, is a historical freshwater tidal wetland that was converted to agricultural fields in the early 1900s. Liberty Island functioned as farmland until an accidental levee break flooded the area in 1997, inadvertently restoring tidal marsh hydrology. Since then, wetland vegetation has naturally recolonized part of the site. We conducted a seed bank assay at the site and found that despite a lack of germination or seedling recruitment at the site, the seed bank contained a diverse plant community, indicating that the site’s continuous flooding was likely suppressing germination. Additionally, the frequency of germinating seeds in the seed bank did not represent the dominant adult plant community. We conducted a cold stratification study to determine if this observed disparity could be explained by seed germination dynamics, and whether germination could be enhanced using a pre-germination cold exposure, particularly for species of concern for wetland restoration. The cold stratification study showed that longer durations of pre-germination cold enhanced germination in Schoenoplectus acutus, but reduced germination in Schoenoplectus californicus, and had no effect on Typha latifolia. Overall, germination of S. californicus and S. acutus was much lower than T. latifolia. Our findings suggest that seeding may not be an effective restoration technique for Schoenoplectus spp., and, to improve restoration techniques, further study is needed to more comprehensively understand the reproduction ecology of important marsh species.

For wetland restoration success to be maximized, restoration managers need better information regarding how the frequency, depth, and duration of flooding affect soil chemistry and the survival, growth, and morphology of targeted plant species. In a greenhouse study we investigated the impact of four different flooding durations (0 %, 40 %, 60 %, and 100 %) on soil physicochemistry and the responses of seedlings and adults of two species of emergent wetland macrophytes commonly used in restoration efforts (Schoenoplectus acutus and Schoenoplectus californicus). The longest flooding duration, which created more reducing soil conditions, resulted in significantly reduced survival of S. acutus adults (34 ± 21 % survival) and complete mortality of seedlings of both species. Schoenoplectus californicus adults exhibited higher flooding tolerance, showing little impact of flooding on morphology and physiology. A companion field study indicated that S. californicus maintained stem strength regardless of flooding duration or depth, supporting the greenhouse study results. This information serves to improve our understanding of the ecological differences between these species as well as provide restoration managers with better guidelines for targeted elevation and hydrologic regimes for these species in order to enhance the success of restoration plantings and better predict restoration site development.

The demand for an improved knowledge base for planning and management of tidal marsh restoration worldwide has become more fully recognized. In the Sacramento-San Joaquin Bay Delta, California, U.S.A., concerns have arisen about the degradation of the Delta and key ecosystem services. One restoration method proposed includes intentionally breaching levees that protect agricultural lands to re-establish a hydrology that encourages tidal marsh development. Our research investigated relevant constraints on vegetation establishment and expansion of key tidal marsh species. We transplanted three macrophyte species (Schoenoplectus acutus, Schoenoplectus californicus, and Typha latifolia) using two transplant types (rhizomes and adults) in locations that varied in hydrologic and edaphic conditions at Liberty Island, a post-levee breach tidal marsh restoration site. Two years of monitoring revealed that transplanted adults outperformed rhizomes. In addition, S. californicus exhibited greater survival and vegetation expansion. S. californicus vegetation expansion covered a maximum area of approximately 23 m2, which is two orders of magnitude (OOM) greater than the maximum area covered by S. acutus (approximately 0.108 m2) and three OOM greater than T. latifolia (approximately 0.035 m2). Results suggest that hydrologic regime and degree of soil compaction are influential in controlling vegetation establishment and expansion. Greater vegetation expansion occurred in transplant sites characterized by a deeper surface layer of non-compacted soil in conjunction with shorter durations of flooding. Information derived from this study is valuable to restoration planning in the Delta and other tidal marshes worldwide where these species occur, especially in terms of setting restoration goals and trajectories based on site-specific environmental characteristics.

Removal behavior of indigo carmine by Schoenoplectus acutus and Ni nanoscale oxides/Schoenoplectus acutus composite was determined. The characterization of both materials was done by TEM, SEM/EDS, DRX, and BET. Experimental data were best fitted to pseudo second order and Langmuir-Freundlich models for kinetics and isotherm, respectively; these results indicate a chemisorption mechanism on heterogeneous materials. Adsorption capacity of Ni nanoscale oxides/Schoenoplectus acutus composite was high in comparison with other adsorbents (760 mg/g). Adsorption of dye is not affected by pH (3 to 9). Metal nanoparticles supported on cheap and eco-friendly adsorbents are an alternative for the removal of dyes from wastewater.

Karyomorphological analysis of four species of Schoenoplectus (Cyperaceae) from north-central Mexico were carried out. Chromosome numbers ranged from 2n = 38 to 2n = 84. New records of counting are given for Schoenoplectus acutus var. occidentalis (2n = 38 and 2n = 84) and S. americanus (2n = 66). Intra-individual variation in chromosome number is reported for the first time for S. acutus, with a rare polyploid mixoploidy with a prevalence of cells with 2n = 38 (36 small + 2 compound, larger chromosomes) and a few cells with 2n = 84 small, dot-shaped chromosomes, this being the first record of polyploid mixoploidy for Cyperaceae. Mean length of the diploid set ranged from 51.5 μm (S. tabernaemontani) to 79.5 μm (S. acutus). The lowest average chromosome length for the dot-shaped chromosomes was 0.69 μm (S. acutus) and the highest 1.62 μm (S. tabernaemontani); the pair of large chromosomes in S. acutus reached 3.17 μm. A low interchromosomal asymmetry index (A2), 0.11 to 0.14 was found, very similar among ...

Climate change impacts, such as accelerated sea‐level rise, will affect stress gradients, yet impacts on competition/stress tolerance trade‐offs and shifts in distributions are unclear. Ecosystems with strong stress gradients, such as estuaries, allow for space‐for‐time substitutions of stress factors and can give insight into future climate‐related shifts in both resource and nonresource stresses. We tested the stress gradient hypothesis and examined the effect of increased inundation stress and biotic interactions on growth and survival of two congeneric wetland sedges, Schoenoplectus acutus and Schoenoplectus americanus. We simulated sea‐level rise across existing marsh elevations and those not currently found to reflect potential future sea‐level rise conditions in two tidal wetlands differing in salinity. Plants were grown individually and together at five tidal elevations, the lowest simulating an 80‐cm increase in sea level, and harvested to assess differences in biomass after one growing season. Inundation time, salinity, sulfides, and redox potential were measured concurrently. As predicted, increasing inundation reduced biomass of the species commonly found at higher marsh elevations, with little effect on the species found along channel margins. The presence of neighbors reduced total biomass of both species, particularly at the highest elevation; facilitation did not occur at any elevation. Contrary to predictions, we documented the competitive superiority of the stress tolerator under increased inundation, which was not predicted by the stress gradient hypothesis. Multifactor manipulation experiments addressing plant response to accelerated climate change are integral to creating a more realistic, valuable, and needed assessment of potential ecosystem response. Our results point to the important and unpredicted synergies between physical stressors, which are predicted to increase in intensity with climate change, and competitive forces on biomass as stresses increase.

a b s t r a c t A 15N-addition mesocosm experiment was used to study competition for nitrogen (N) between the aggressive cattail species Typha × glauca (T. latifolia × T. angustifolia) Godr. (hybrid cattail) and a suite of native plant species often found in marshes Typha invades. Plant uptake of 15 N released from labeled Typha and native-species litter was then measured in a pot experiment with new cohorts of two native plant species (Juncus balticus Willd. and Schoenoplectus acutus Muhlenberg ex Bigelow) grown with and without Typha. In both experiments, species differed in their above- and belowground uptake of 15N, with Typha outperforming the other species (1.7-5.0-times greater mean uptake, P =

Replacement of native macrophyte species with exotic or invasive ones affects the quality of detritus entering streams and can alter nutrient cycles and community structure in aquatic ecosystems. Decomposition of air-dried native hardstem bulrush (Schoenoplectus acutus), invasive southern cattail (Typha domingensis), and exotic common reed (Phragmites australis) were studied in an urban stream (Las Vegas, Nevada, USA) using litter bags. Samples were analyzed for dry mass, lignin, nutrients, trace elements, and macroinvertebrates. Litter type and sediment deposited on plant material influenced material loss. Trace elements arsenic and selenium increased in plant material to concentrations considered marginal for ecosystem contamination by exposure day 76. Mercury increases were inconsistent across plant species and did not exceed limits. Bulrush decomposed faster, and tended to have higher selenium concentrations, than did invasive southern cattail and exotic common reed. Macroinvertebrate communities colonizing litter bags were similar across plant litter types, but differed from mesh-only bags and samples collected with a kick-net. Macroinvertebrate exclusion resulted in significantly lower loss rates, but functional feeding groups such as shredders were not associated with decomposition differences. The caddisfly, Smicridea, physically modified stem material and aided in processing, but microbes appeared most important in biological material breakdown. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Assessment of emergent vegetation biomass can be time consuming and labor intensive. To establish a less onerous, yet accurate method, for determining emergent plant biomass than by direct measurements we collected vegetation data over a six-year period and modeled biomass using easily obtained variables: culm (stem) diameter, culm height and culm density. From 1998 through 2005, we collected emergent vegetation samples (Schoenoplectus californicus and Schoenoplectus acutus) at a constructed treatment wetland in San Jacinto, California during spring and fall. Various statistical models were run on the data to determine the strongest relationships. We found that the nonlinear relationship: $$ CB = {\beta _0}D{H^{{\beta _1}}}{10^\varepsilon } $$ , where CB was dry culm biomass (g m−2), DH was density of culms × average height of culms in a plot, and β0 and β1 were parameters to estimate, proved to be the best fit for predicting dried-live above-ground biomass of the two Schoenoplectus species. The random error distribution, e, was either assumed to be normally distributed for mean regression estimates or assumed to be an unspecified continuous distribution for quantile regression estimates.

Treatment wetlands (TWs) are widely used for treating domestic, agricultural, and industrial wastewater, stormwater runoff, and acid mine drainage; natural wetlands are also exposed to these pollutant sources. Currently, few plant species are used in the majority of TWs, and these are often non-native and/or weedy. We are working to identify native species for year-round use in cold-region TWs, particularly the Rocky Mountain region, and explore the basis of differences in performance. In studies presented here, we evaluated chemical oxygen demand (COD) removal from simulated wastewater in microcosms planted with monocultures of 19 species. Experiments were conducted over one year at seasonal temperatures of 4-24°C. With some species and in unplanted controls, COD removal declined at cold temperatures during dormancy, as expected with normal temperature dependence of microbial processes. However, COD removal was constant across seasons with the majority of species. Average COD removal exceeded 90% for Carex aquatilis, C. bebbii, C. praegracilis, C. utriculata, Schoenoplectus acutus, Juncus arcticus, J. torreyi, and Deschampsia cespitosa; of these, only S. acutus is widely used. In contrast, the widely used (and frequently invasive) species T. latifolia, P. australis, and P. arundinacea were somewhat less effective, with average COD removals of 84%, 74%, and 83%, respectively. Redox, sulfate, and root oxygen loss measurements suggest that plant-mediated oxygen transfer may explain the ability of some species to offset the effect of temperature on microbial processes and maintain high COD removal in all seasons. Results indicate that many non-weedy, regionally native species may be candidates for use in TWs or for rehabilitation of natural wetlands exposed to certain pollutants. In addition to the species we studied, other Obligate Wetland and Facultative Wetland species of the Cyperaceae and Juncaceae merit investigation.

Many species of waterbirds nest over-water in shallow lakes and marshes in the Northern Plains region of North America. High winds are common in this region and the resulting waves can cause significant loss of nesting platforms, yet the behavior of waves in these systems has not been well-studied. We used observational and experimental techniques to examine how Hardstem Bulrush (Schoenoplectus acutus Muhl.) impacts wave attenuation through its clonal growth characteristics. The predictable growth patterns influence nest placement and nesting success in colonial nesting grebes and other over-water nesting waterbirds. We constructed an artificial nesting colony to experimentally test how location with respect to wave-exposure affects nest structural integrity in grebes. Additional experiments with boat wakes confirmed the importance of emergent vegetation in attenuating waves caused by watercraft. Nests gain more protection from being placed on the lee side of a stand of vegetation than by having ...

Decomposition of senesced culm material of two bulrush species was studied in a surface-flow ammonia-dominated treatment wetland in southern California. Decomposition of the submerged culm material during summer months was relatively rapid (k = 0.037 day−1), but slowed under extended submergence (up to 245 days) and during fall and spring sampling periods (k = 0.009–0.014 day−1). Stepwise regression of seasonal data indicated that final water temperature and abundance of the culm-mining midge, Glyptotendipes, were significantly associated with culm decomposition. Glyptotendipes abundance, in turn, was correlated with water quality parameters such as conductivity and dissolved oxygen and ammonia concentrations. No differences were detected in decomposition rates between the bulrush species, Schoenoplectus californicus and Schoenoplectus acutus.

The modified k–C* first-order degradation model proposed by Kadlec and Knight [Kadlec, R.H., Knight, R.L., 1996. Treatment Wetlands. Lewis Publishers, Boca Raton, FL] was fit to 192 data sets of COD concentration versus time measured in batch-loaded wetland microcosms. The time series sets were divided into four replicates of four plant species treatments; Carex utriculata (sedge), Schoenoplectus acutus (bulrush), Typha latifolia (cattail) and unplanted controls housed in a controlled-environment greenhouse in which temperature was cycled in 4 °C increments from 24 to 4 °C and back to 24 °C over a yearlong period. One 20-day batch incubation was conducted at each temperature setting during which seven chemical oxygen demand (COD) samples were drawn from each of 16 wetland columns. Non-linear mixed effects regression was used to fit parameters of the model. Best-fit values of the rate parameter k and the background concentration C* varied significantly by plant species and greenhouse temperature setting. An Arrhenius relationship was used to assess the effect of temperature on these parameters. Species greatly influenced the value of volumetric rate parameter at 20 °C (k20) and ranked Carex > Schoenoplectus > Typha > unplanted control (0.925, 0.743, 0.612 and 0.366 day−1, respectively). All displayed decreasing values for increasing temperature but species variation was much less (θk = 0.945, 0.957, 0.953 and 0.936, respectively). Background COD concentration values at 20 °C (C20*) ranked Carex

Although clonal growth is a dominant mode of plant growth in wetlands, the importance of clonal integration, resource sharing among ramets, to individual ramet generations (mother and daughter) and entire clones of coexisting species has not been well investigated. This study evaluated the significance of clonal integration in four sedge species of varying ramet aggregations, from clump-forming species (Clumpers –Carex sterilis, Eleocharis rostellata), with tightly aggregated ramets (rhizomes

A 9.9-ha constructed wetland designed to reduce nitrogen in municipal wastewater following conventional secondary treatment began operating in southern California's San Jacinto Valley in September 1994. The wetland incorporated zones of bulrush (Schoenoplectus acutus and S. californicus) for effluent treatment, plus areas of 1.8-m deep open water and other features to benefit wintering waterfowl. A one-year long program to monitor bird use and evaluate their contribution to loadings of nitrogen and phosphorus was initiated seven months later and a second, four-month long period of monitoring was initiated after a 20-month hiatus. Daily bird use peaked at nearly 12,000 individuals during the second period. Estimates of maximum daily nitrogen and phosphorus input by birds were 139 g N ha−1 day−1 and 56 g P ha−1 day−1. Following a reconfiguration of the wetland that increased the area of open water, a third year-long period of monitoring was initiated in September 2000. Estimated maximum daily loadi...

Total nitrogen (TN) removal in treatment wetlands (TWs) is challenging due to nitrogen cycle complexity and the variation of influent nitrogen species. Plant species, season, temperature and hydraulic loading most likely influence root zone oxygenation and appurtenant nitrogen removal, especially for ammonium-rich wastewater. Nitrogen data were collected from two experiments utilizing batch-loaded (3-, 6-, 9- and 20-day residence times), sub-surface TWs monitored for at least one year during which temperature was varied between 4 and 24 °C. Synthetic wastewater containing 17 mg/l N as NH 4 and 27 mg/l amino-N, 450 mg/l chemical oxygen demand (COD), and 13 mg/l SO 4 -S was applied to four replicates of Carex utriculata , Schoenoplectus acutus and Typha latifolia and unplanted controls. Plant presence and species had a greater effect on TN removal than temperature or residence time. Planted columns achieved approximately twice the nitrogen removal of unplanted controls (40–95% versus 20–50% removal) regardless of season and temperature. TWs planted with Carex outperformed both Typha and Schoenoplectus and demonstrated less temperature dependency. TN removal with Carex was excellent at all temperatures and residence times; Schoenoplectus and Typha TN removal improved at longer residence times. Reductions in TN were not accompanied by increases in NO 3 , which was consistently below 1 mg/l N.

Coastal marshes depend on belowground biomass of roots and rhizomes to contribute to peat and soil organic carbon, accrete soil and alleviate flooding as sea level rises. For nutrient-limited plants, eutrophication has either reduced or stimulated belowground biomass depending on plant biomass allocation response to fertilization. Within a freshwater wetland impoundment receiving minimal sediments, we used experimental plots to explore growth models for a common freshwater macrophyte, Schoenoplectus acutus. We used N-addition and control plots (4 each) to test whether remotely sensed vegetation indices could predict leaf N concentration, root:shoot ratios and belowground biomass of S. acutus. Following 5 months of summer growth, we harvested whole plants, measured leaf N and total plant biomass of all above and belowground vegetation. Prior to harvest, we simulated measurement of plant spectral reflectance over 164 hyperspectral Hyperion satellite bands (350-2500 nm) with a portable spectroradiometer. N-addition did not alter whole plant, but reduced belowground biomass 36% and increased aboveground biomass 71%. We correlated leaf N concentration with known N-related spectral regions using all possible normalized difference (ND), simple band ratio (SR) and first order derivative ND (FDN) and SR (FDS) vegetation indices. FDN(1235, 549) was most strongly correlated with leaf N concentration and also was related to belowground biomass, the first demonstration of spectral indices and belowground biomass relationships. While S. acutus exhibited balanced growth (reduced root:shoot ratio with respect to nutrient addition), our methods also might relate N-enrichment to biomass point estimates for plants with isometric root growth. For isometric growth, foliar N indices will scale equivalently with above and belowground biomass. Leaf N vegetation indices should aid in scaling-up field estimates of biomass and assist regional monitoring.

A field study on the removal of Se from agricultural subsurface drainage was conducted from May 1997 to February 2001 in the Tulare Lake Drainage District (TLDD) of San Joaquin Valley, California. A flow-through wetland system was constructed consisting of ten 15- x 76-m unlined cells that were continuously flooded and planted with either a monotype or combination of plants, including sturdy bulrush [Schoenoplectus robustus (Pursh) M.T. Strong], baltic rush (Juncus balticus Willd.), smooth cordgrass (Spartina alterniflora Loisel.), rabbitsfoot grass [Polypogon monspeliensis (L.) Desf.], salt-grass lDistichlis spicata (L.) Greene], cattail (Typha latifolia L.), tule [Schoenoplectus acutus (Muhl. ex Bigelow) A. Love & D. Love], and widgeon grass (Ruppia maritima L.). One cell had no vegetation planted. The objectives of this research were to evaluate Se removal efficiency of each wetland cell and to carry out a mass balance on Se. The inflow drainage water to the cells had average annual Se concentrations of 19 to 22 microg L(-1) dominated by selenate [Se(VI), 95%]. Average weekly water residence time varied from about 3 to 15 d for Cells 1 through 7 (target 7 d), 19 to 33 d for Cells 8 and 9 (target 21 d), and 13 to 18 d for Cell 10 (target 14 d). Average weekly Se concentration ratios of outflow to inflow ranged from 0.45 to 0.79 and mass ratio (concentration x water volume) from 0.24 to 0.52 for year 2000, that is, 21 to 55% reduction in Se concentration and 48 to 76% Se removal in mass by the wetland, respectively. The nonvegetated cell showed the least Se removal both in concentration and in mass. The global mass balance showed that on the average about 59% of the total inflow Se was retained within the cells and Se outputs were outflow (35%), seepage (4%), and volatilization (2%). Independent measurements of the Se retained in the cells totaled 53% of the total Se inflow: 33% in the surface (0-20 cm) sediment, 18% in the organic detrital layer above the sediment, 2% in the fallen litter, < 1% in the standing plants, and < 1% in the surface water. Thus, about 6% of the total Se inflow was unaccounted for in the internal compartments.

Constructed wetlands are widely used for wastewater treatment, but there is little information on processes affecting their performance in cold climates, effects of plants on seasonal performance, or plant selection for cold regions. We evaluated the effects of three plant species on seasonal removal of dissolved organic matter (OM) (measured by chemical oxygen demand and dissolved organic carbon) and root zone oxidation status (measured by redox potential [Eh] and sulfate [SO4(2-)]) in subsurface-flow wetland (SSW) microcosms. A series of 20-d incubations of simulated wastewater was conducted during a 28-mo greenhouse study at temperatures from 4 to 24 degrees C. Presence and species of plants strongly affected seasonal differences in OM removal and root zone oxidation. All plants enhanced OM removal compared with unplanted controls, but plant effects and differences among species were much greater at 4 degrees C, during dormancy, than at 24 degrees C, during the growing season. Low temperatures were associated with decreased OM removal in unplanted controls and broadleaf cattail (Typha latifolia L.) microcosms and with increased removal in beaked sedge (Carex rostrata Stokes) and hardstem bulrush [Schoenoplectus acutus (Muhl. ex Bigelow) A. & D. Love var. acutus] microcosms. Differences in OM removal corresponded to species' apparent abilities to increase root zone oxygen supply. Sedge and bulrush significantly raised Eh values and SO4(2-) concentrations, particularly at 4 degrees C. These results add to evidence that SSWs can be effective in cold climates and suggest that plant species selection may be especially important to optimizing SSW performance in cold climates.

La productivite des macrophytes du lac Saint-Pierre, Quebec, a ete evaluee selon trois zones: la zone terrestre, la zone semi-aquatique et la zone aquatique. Les resultats permettent de definir six unites vegetales. La productivite de ces unites (grammes par metre carre) se repartit ainsi: Calamagrostis canadensis, 528; Phalaris arundinacea, 1096; Sparganium eurycarpum, 508; Scirpus fluviatilis, 436; Scirpus acutus, 284; Vallisneria americana, 138. Les auteurs decrivent la distribution de la vegetation en fonction de I'elevation et de la distance a la ligne de rivage. Les resultats sont compares aux donnees disponibles dans la Iitterature. The productivity of macrophytes has been studied in three different zones of Lake Saint-Pierre, Quebec: terrestrial, semiaquatic, and aquatic. From the data collected, six vegetation units can be defined. The productivity (grams per square metre) of each unit is as follows: alamagrostis canadensis, 528; Phalaris arundinacea, 1096; Sparganium eurycarpum, 508; Scirpus fluviatilis, 436; Scirpus acutus, 284; Vallisneria americana, 138. The vegetation distribution is described as a function of elevation and distance from the shore. The results are compared with available data in the literature.