The Effects of Phragmites Removal on Nutrient Pools in a Freshwater Tidal Marsh Ecosystem

Selected nitrogen and phosphorus pools in two freshwater tidal marsh ecosystems on the lower Connecticut River were measured relative to Phragmites, Typha and mixed native wetland plant cover types. For both the Chapman Pond Preserve and Chester Creek Marsh, significant differences were found between plant cover types in porewater ammonium and phosphate for some months during the 1998 growing season; porewater nitrate was always below the detection limit. At Chapman Pond, no significant differences were detected between Phragmites and Typha for plant tissue N concentrations. The standing stock of nitrogen was higher in Phragmites stands, however, owing to its greater aboveground biomass. No significant difference was found between plant cover types for total soil N at Chapman Pond, but KCl extractable ammonium was higher in the mixed cover type than Phragmites or Typha. The results of this study suggest that Phragmites is affecting nutrient pools in freshwater tidal marshes, a result that should be considered in future management design.     

A comparison of Phragmites australisin freshwater and brackish marsh environments in North America

This paper compares the available North Americanliterature and data concerning several ecologicalfactors affecting Phragmites australisin inlandfreshwater, tidal fresh, and tidal brackish marshsystems. We compare aboveground productivity, plantspecies diversity, and sediment biogeochemistry; andwe summarize Phragmiteseffects on faunalpopulations in these habitats. These data suggest thatPhragmitesaboveground biomass is higher thanthat of other plant species occurring in the samemarsh system. Available data do not indicate anysignificant difference in the aboveground Phragmitesbiomass between marsh types, nor doesthere appear to be an effect of salinity on height.However, Phragmitesstem density wassignificantly lower in inland non-tidal freshwatermarshes than in tidal marshes, whether fresh orbrackish. Studies of the effects of Phragmiteson plant species richness suggest that Phragmitesdominated sites have lower diversity.Furthermore, Phragmiteseradication infreshwater sites increased plant diversity in allcases. Phragmitesdominated communities appearto have different patterns of nitrogen cyclingcompared to adjacent plant communities. Abovegroundstanding stocks of nitrogen (N) were found to behigher in Phragmitessites compared to thosewithout Phragmites. Porewater ammonium(NH₄ ⁺) did not differ among plant covertypes in the freshwater tidal wetlands, but inbrackish marshes NH₄ ⁺was much higher inSpartinaspp. than in neighboring Phragmitesstands. Faunal uses of Phragmitesdominated sites in North America were found to vary bytaxa and in some cases equaled or exceeded use ofother robust emergent plant communities. In light ofthese findings, we make recommendations for futureresearch.     

O-acetylserine (thiol) lyase activity in Phragmites and Typha plants under cadmium and NaCl stress conditions and the involvement of ABA in the stress response

The roles of O-acetylserine (thiol) lyase (OASTL, EC 4.2.99.8) and abscisic (ABA) acid in stress responses to NaCl and cadmium treatments were investigated in Typha latifolia L. and Phragmites australis (Cav.) Trin. ex Steudel plants. OASTL activity increased under stress (25-300 microM Cd, 100mM NaCl, 1 microM ABA) in both Typha and Phragmites mainly in roots, contributing substantially to satisfy the higher demand of cysteine for adaptation and protection. The earliest significant responses in intact roots were recorded after 12-24 h of Cd treatments, but different levels of stimulation were also observed after 3 and 7 days of exposure. The OASTL activity responses of Phragmites to salinity (100mM NaCl) were higher than those of Typha. Cysteine synthesis in Typha is much higher than in Phragmites, which supports the efficiency of the thiol-metabolism-based protection shown in Typha. Exogenous ABA increased OASTL activity in both species. Cd treatments led to increased ABA levels in roots. Phragmites showed higher ABA levels compared to Typha. The increase of ABA content indicates the involvement of this phytohormone in early stress responses, while the stimulation of OASTL following the ABA application suggests that ABA has a role in an OASTL activation pathway.     

Managing Non-Native Plant Populations Through Intensive Community Restoration in Cades Cove, Great Smoky Mountains National Park, U.S.A.

Abstract Cades Cove, Great Smoky Mountains National Park, U.S.A. was historically cleared largely for pastoral purposes; it is now comprised of recently abandoned pastures dominated by non‐native pasture species. To investigate the potential for reducing non‐native species relative to native species, park managers initiated an experiment in 1995 that included mowing, herbicide application, planting of seed, and burning of replicate 20 × 50–m plots at each of two sites within Cades Cove. Between 1995 and 2001 we evaluated the response of the plant community (i.e., species‐specific cover and frequency, biomass, diversity) to this suite of treatments and compared it with unmanipulated control plots at each site. Four years after treatment initiation abundance measures of Plantago lanceolata, Setaria geniculata, and Trifolium spp. averaged one‐third lower in treated than control plots. Frequency of Festuca pratensis was lower in treated than in control plots for 2 years, but after 4 years its frequency, cover, and biomass did not differ between treated and control plots. By 2000 the cover of Sorghastrum nutans in treated plots increased to 23–47%, depending on the site. Total biomass and diversity increased in treated plots. The dominance of Lespedeza cuneata at one site apparently reduced planting success, biomass production, and diversity and evenness. Post‐treatment lags in response for several species, coupled with interannual variation in response to environmental conditions, suggest that evaluations of treatment success would differ greatly depending on when the evaluation was conducted.     

Species Composition and Inter-annual Dynamics of a Freshwater Tidal Plant Community Following Removal of the Invasive Grass, Phragmites australis

We document the regeneration of native freshwater wetland plant assemblages following removal of the common reed, Phragmites australis (Cav.) Trin. ex Steudel from two sites at Chapman Pond, East Haddam, Connecticut, USA. We gathered field data on composition of the vegetation 1 year before and for each of the 3 years after the removal in fall 1995/spring 1996 of Phragmites by two slightly different methods (hand-removal and herbiciding in one area, mowing/mulching and herbiciding in another). An area where Phragmites was left intact was similarly monitored. Our goals for this monitoring were: (1) to document plant species composition and richness before and after Phragmites removal and (2) to examine temporal and spatial variability in patterns of plant recruitment. Phragmites declined in both density and extent in both plots where removal treatments were applied. Richness, evenness, and density of non-Phragmites species increased steadily from 1996 to 1997 in all removal and intact plots. However, the species composition of the removal plots was richer than that of the intact plot, and more closely resembled that of comparable, uninvaded freshwater tidal wetlands. Rates of recovery of species richness in the removal plots declined from 1997 to 1998, potentially reflecting saturation of available colonization space, or the return of Phragmites. Phragmites has expanded its range in both of the removal plots since 1997. A model of its colonization indicates that Phragmites occupies space through localized proliferation of dense rhizomes rather than diffusely foraging with long tillers. Vigilance in monitoring is needed to document the spread of invasives, to evaluate the multi-faceted ecological effects of eradication efforts on both the invader and the regenerating community, and develop strategies for preventing re-invasion.     

A Paleoecological Assessment of Phragmites australis in New England Tidal Marshes: Changes in Plant Community Structure During the Last Few Millennia

Although Phragmites has been an upper border tidal marsh species for thousands of years, it is only recently (within the last century or so) that the distribution of this plant within the coastal marsh community has become prominent. Prior to approximately 100 years ago, Phragmites was an upper border/brackish marsh co-dominant in many marsh systems. Occurrence of this species varied between associations of sedges, Typha, forbs and a variety of woody shrubs. Paleoreconstructions rarely show the presence of a Phragmites monoculture or early associations with salt marsh species. However, since the turn of this century (and perhaps as early as the middle of the last century) the distribution of Phragmites has changed substantially. Today, this plant often forms dense monocultures and is commonly found in association with Spartina grasses. The results of this paleoecological investigation show that the changes that have been observed in Phragmites communities during the last 100 years are not part of the long-term cycle of development in these systems and are new to the landscape.     

A phylogeographic study of the cosmopolitan genus Phragmites (Poaceae) based on AFLPs

Within the genus Phragmites (Poaceae), the species P. australis (the common reed) is virtually cosmopolitan, and shows considerable variation in ploidy level and morphology. Genetic variation in Phragmites was studied using AFLPs, and analysed with parsimony and distance methods. Groups of P. australis strongly supported in the analyses include one that comprises all South American clones, a distinct group from the US Gulf Coast, and a group of E. Asian and Australian octoploids. Among the other species, the paleotropical P. vallatoria is supported as monophyletic and most closely related to the paraphyletic P. mauritianus and to the Gulf Coast and S. American groups. The E. Asian species P. japonicus is closely related to a group of P. australis clones mostly from central North America. Tetraploidy predominates in the genus, and optimisation of chromosome numbers onto the phylogeny shows that higher ploidy levels have evolved many times.     

Patterns of vegetation surrounding springs in Goshen Bay,Utah County,Utah U.S.A.

Saline meadows in Goshen Bay, Utah County, Utah, USA, occur interspersed among large areas of salt playa. Springs irrigate these meadows which show concentric vegetational zones surrounding each spring. Each vegetational zone demonstrates its own unique dominant vascular plant species. The central zone is dominated primarily by Scirpus americanus, the middle zone by Eleocharis palustris and the outer zone by Juncus balticus, Distichlis spicata and Muhlenbergia asperifolia. As distance increases from the springs, pH and soluble salt concentration increase, while percent organic matter, percent moisture and phosphorus decrease. With the increase in salt levels and decrease in water levels, halophytic plant species generally increase with distance from the springs.     

Effects of the emerald ash borer invasion on the community composition of arthropods associated with ash tree boles in Maryland,U.S.A.

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高寒草甸种间性状差异和物种均匀度对物种多样性与功能多样性关系的影响

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Macroinvertebrate communities in Phragmites australis (Cav.) Trin. ex Steud. reed beds and open bank habitats in central victorian streams in Australia

Reed invasion is a common phenomenon of open streams with disturbed riparian vegetation in river catchments. Knowledge of the effects of such vegetation change on aquatic communities is fundamental to river management. Macroinvertebrate fauna in Phragmites australis (Cav.) Trin. ex Steud. and open bank habitats were examined in three rivers in central Victoria in order to understand the effect of such littoral habitat on macroinvertebrates. Data were analysed using Partially Nested Factorial ANOVA with season, river and habitats as main effects. Habitat structure had a significant effect (p<0.05) on macroinvertebrate species richness, however this was not seasonally consistent across the three rivers. There was a significant increase (p<0.05) in macroinvertebrate taxa richness in Phragmites habitats during winter and spring seasons. Total abundance of taxa showed no consistent significant differences in the two habitats. Results of Canonical Analysis of Principle Coordinates indicated significant differences (p<0.05) in macroinvertebrate assemblages between Phragmites and bare bank habitats in all seasons. Habitat selection by taxa could be related to the microphysical environment of the habitats. This study suggests that reed beds create important littoral habitat structures which support diverse macroinvertebrate assemblages.     

南京市加拿大一枝黄花入侵地群落的物种组成与多样性特征研究(附表)

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Plant regeneration from the protoplasts of Solanum tuberosum, S. nigrum and S. bulbocastanum

The mesophyll protoplasts were isolated from the Solanum tuberosum (S. tbr) clones of different ploidy level (4x Bzura cv., 2x H-8105, and 2x ZEL-1136) as well as from the wild species: S. bulbocastanum (S. blb, 2x) and two accessions of S. nigrum (S. ngr, 6x). Additionally, the protoplasts were isolated from the cell suspensions of Bzura cv. and H-8105 clone. The conditions of protoplast isolation as well as the media for their culturing and regeneration, were selected and optimized for the studied genotypes. For mesophyll protoplasts, the shooting calli were produced by all the cultured protoclones except that of S. bulbocastanum. The shoots excised from the protoplast-derived calli developed into whole plants in all the studied potato clones but only in one accession of S. nigrum, i.e. S. ngr var. gigantea. As for suspension-cell-derived protoplasts, only H-8105 clone produced the regenerative type of calli, though normal shoots could not be obtained. The regenerative capacity of the protoplasts isolated from leaves and cell suspensions is compared and discussed. We regret to report the death of M. Sc. Maria Borkowska after the completion of this work.     

Seasonal changes in respiration of halophytes in salt playas in the Great Basin,U.S.A.

Many desert playas are covered with water in the early spring. As theweather becomes warmer and drier, water evaporates, increasing saltcontent of the soil from 7,000 to almost 16,000 mmol NaCl Kg^-1. Changes in respiratory metabolism during the growing season of fourhalophytes characteristic of cold desert playas was followed usingcalorimetry. In order of decreasing salt tolerance, the species examinedwere: the forbs Salicornia rubra, S. utahensis; the grass Distichlisspicata; and the shrub Allenrolfea occidentalis. Tissue collected in thefield from sites of low and high salinity in a single playa during May, June,and August of 1997 was put in isothermal calorimeters and the metabolicheat rate (q) and respiration rate (R_CO2) measured. Efficiency ofsubstrate carbon conversion (q/R_CO2) and predicted specific growthrate (H_BR_SG) were calculated. These species are allwell-adapted to the environment in which they are found. Highestmetabolism, respiration, efficiency and growth are found during May andJune and are lowest during the hot, dry month of August. Differencesbetween the species are also noted.     

Three new green coccoid zoospore-producing algae from the Great Smoky Mountains National Park,Tennessee, U.S.A.

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Damage by episodic flooding to Phragmites reeds in a prealpine lake: proposal of a model

Summary The development of lakeside fringes of Phragmites reeds can be affected by high water levels, leading in extreme cases to die-back. A model is presented that allows estimation of the proportions of the damage. The model-formulated for 1 year and one Phragmites stalk—is based on the growth curve of the stalk, the altitude of the growth site, and the water level curve for the year. Applied to a reed stand over a series of years, the model is based upon the frequency distribution of the critical stalk length and the chance that the water level will be below a given value, each parameter being time dependent. Three case studies from Lake Constance-Untersee provide an example of the significance of episodic high water levels. Hence, aestival high water levels are expected to be one of the main factors controlling the lakeside frontline of the reedbelt. The model can be used in waterworks engineering, where reed plantations are to be established on the shores of lakes and reservoirs with strongly fluctuating water levels.     

Activities and properties of cellulase and xylanase associated with Phragmites leaf litter in a seawater lake

The activities and properties of cellulases and xylanases associated with Phragmites communis leaves were followed during the course of their decomposition from autumn to summer in a seawater lake. Cellulases and xylanases of low optimum pH (4 or less) were detected on aerial dead leaves before submergence. These enzymes remained on the leaves immediately after submergence, but were replaced by enzymes with a higher optimum pH (about 5.5 to 6.5), the activity of which increased rapidly during the initial two weeks. The enzyme activities then declined with water temperature until about day 100, but gradually increased again thereafter. This successive change in enzyme activities closely correlated with that of the decomposition rates of cellulose and xylan. The molecular weight distribution of the cellulases and xylanases changed markedly in the latter half of the experimental period, which suggested a change in the flora of active decomposer microorganisms.     

Disturbance events affecting phytoplankton biomass,composition and species diversity in a shallow,eutrophic, temperate lake

The seasonal changes in phytoplankton biomass and species diversity in a shallow, eutrophic Danish lake are described and related to different disturbance events acting on the phytoplankton community.Both the spring diatom maximum and the summer bloom of the filamentous blue-green alga, Aphanizomenon flos-aquae (L.) Ralfs, coincided with low values of phytoplankton species diversity and equitability. Diatom collapse was mainly due to internal modifications as nutrient depletion (Si, P) caused by rapid growth of phytoplankton, and increased grazing activity from zooplankton. A large population of Daphnia longispina O.F. Müller in June effectively removed smaller algal competitors, thus favouring the development of a huge summer bloom (140 mm³ l^–1) of Aphanizomenon flos-aquae. Heavy rainfall and storms in late July increased the loss of Apahnizomenon by out-flow and disturbed the stratification of the lake. These events caused a marked decline in phytoplankton biomass but had no effect on species diversity. A second storm period in late August circulated the lake completely and was followed by a rapid increase in phytoplankton diversity, and a change in the phytoplankton community structure from dominance of large, slow-growing K-selected species (Aphanizomenon) to small, fast-growing r-selected species (cryptomonads).     

井冈山鹿角杜鹃群落灌木层功能多样性及其随海拔梯度的变化

研究植物群落功能多样性沿环境梯度的变化可以揭示功能多样性与生态系统功能间的关系及维持机制。以井冈山地区鹿角杜鹃（Rhododendron latoucheae）群落为研究对象,通过调查不同海拔梯度群落灌木层植物的物种组成与结构特征,研究了该群落类型灌木层植物的物种多样性、功能多样性、环境因子的特征及其相互之间的关系。结果表明：1）群落类型灌木层植物物种多样性和功能多样性沿海拔梯度呈现不同的变化趋势。物种多样性指数均随着海拔的升高呈减小趋势,而功能多样性指数的变化却较为复杂。其中FRic、FEve和FDis随着海拔的升高显著减小,FDiv和Rao却随海拔的升高而增加;2）群落中物种多样性和功能多样性呈现复杂的相关性。FRic、FEve与丰富度指数呈显著正相关,而Rao、FDis、FDiv与Simpson优势度指数呈线性相关关系,且具有显著相关性;3）群落所分布的坡位及土壤氮与磷含量等环境因子对灌木植物的功能多样性有着重要的影响。鹿角杜鹃群落灌木层植物的物种多样性和功能多样性的相互关系及其对环境变化的响应共同决定了群落的生态系统功能。     

Growth,survival, and metal content of marsh invertebrates fed diets of detritus from Spartina alterniflora Loisel. and Phragmites australis Cav. Trin. ex Steud. from metal-contaminated and clean sites

Marsh vegetation plays an important role in trophic ecology of estuaries. Once broken down to detritus, it is an important food source for manyorganisms. In Atlantic Coast marshes, the reed Phragmites australis hasbeen invading many areas once dominated by smooth cordgrass, Spartina alterniflora. In this study we evaluated the growth of and trophictransfer of metals to estuarine invertebrates when fed diets of detritus fromthese different plant species. Decaying leaves from populations of Phragmites, natural Spartina, and restored Spartina from boththe Hackensack Meadowlands, New Jersey, and the more pristineAccabonac Harbor of East Hampton, New York, were collected from themarsh surface in the spring. Decaying leaves were pureed and fed to thefiddler crabs Uca pugnax and U. pugilator, and to the grassshrimp Palaemonetes pugio. In fiddler crabs we monitored limbregeneration, molting and weight. U. pugilator regenerated limbs andmolted equally well on all six diets. Most of the U. pugnax arrestedgrowth midway through regeneration on all 6 diets. A repeat experimentwith smaller crabs, which did complete the process, found no consistentdifferences among the six diets and control food, although control food andPhragmites detritus had higher N concentrations than the Spartinadetritus. Grass shrimp fed all six diets did not survive beyond 3 weeks. Inanother experiment using HM sediments from each vegetation type(containing detritus, meiofauna, and microflora), survival was equally highamong treatments and the shrimp fed sediments from the restored Spartina site or control food grew better than those fed sediments fromthe Phragmites or natural Spartina sites. Although metalconcentrations in detritus varied between sites and plant species, the crabsof each group did not differ in metal concentrations after the feedingexperiment. Our data do not support the general assumption that Phragmites leaf detritus is of poorer nutritional quality than Spartinaalterniflora leaf detritus to estuarine consumers.