Carex Stricta Research Articles

Alleviation of Plant Stress Precedes Termination of Rich Fen Stages in Peat Profiles of Lowland Mires

Mesotrophic rich fens, that is, groundwater-fed mires, may be long-lasting, as well as transient ecosystems, displaced in time by poor fens, bogs, forests or eutrophic reeds. We hypothesized that fen stability is controlled by plant stress caused by waterlogging with calcium-rich and nutrient-poor groundwater, which limits expansion of hummock mosses, tussock sedges and trees. We analysed 32 European Holocene macrofossil profiles of rich fens using plant functional traits (PFTs) which indicate the level of plant stress in the environment: canopy height, clonal spread, diaspore mass, specific leaf area, leaf dry matter content, Ellenberg moisture value, hummock-forming ability, mycorrhizal status and plant functional groups. Six PFTs, which formed long-term significant trends during mire development, were compiled as rich fen stress indicator (RFSI). We found that RFSI values at the start of fen development were correlated with the thickness of subsequently accumulated rich fen peat. RFSI declined in fens approaching change into another mire type, regardless whether it was shifting into bog, forest or eutrophic reeds. RFSI remained comparatively high and stable in three rich fens, which have not terminated naturally until present times. By applying PFT analysis to macrofossil data, we demonstrated that fens may undergo a gradual autogenic process, which lowers the ecosystem’s resistance and enhances shifts to other mire types. Long-lasting rich fens, documented by deep peat deposits, are rare. Because autogenic processes tend to alleviate stress in fens, high levels of stress are needed at initial stages of rich fen development to enable its long persistence and continuous peat accumulation.

Assessing nitrogen and phosphorus removal potential of five plant species in floating treatment wetlands receiving simulated nursery runoff.

The feasibility of using floating treatment wetlands (FTWs) to treat runoff typical of commercial nurseries was investigated using two 8-week trials with replicated mesocosms. Plants were supported by Beemat rafts. Five monoculture treatments of Agrostis alba (red top), Canna × generalis 'Firebird' (canna lily), Carex stricta (tussock sedge), Iris ensata 'Rising Sun' (Japanese water iris), Panicum virgatum (switchgrass), two mixed species treatments, and an unplanted control were assessed. These plant species are used for ornamental, wetland, and biofuel purposes. Nitrogen (N) and phosphorus (P) removals were evaluated after a 7-day hydraulic retention time (HRT). N removal (sum of ammonium-N, nitrate-N, and nitrite-N) from FTW treatments ranged from 0.255 to 0.738g·m-2·d-1 (38.9 to 82.4% removal) and 0.147 to 0.656g·m-2·d-1 (12.9 to 59.6% removal) for trials 1 and 2, respectively. P removal (phosphate-P) ranged from 0.052 to 0.128g·m-2·d-1 (26.1 to 64.7% removal) for trial 1, and 0.074 to 0.194g·m-2·d-1 (26.8 to 63.2% removal) for trial 2. Panicum virgatum removed more N and P than any other FTW treatment and the control in both trials. Results show that species selection and timing of FTW harvest impact the rate and mass of nutrient remediation. FTWs can effectively remove N and P from runoff from commercial nurseries.

Фитоценотическое разнообразие и динамика сообществ ассоциации Caricetum gracilis Savich 1926 в условиях ксерофитизации поймы реки Десны

The paper presents the results of a comparative analysis of the floristic and phytocoenotic diversity within widespread association of acute sedge meadows Caricetum gracilis Savich 1926 in the floodplain of the Desna River (Bryansk and Smolensk regions, Russia). Available geobotanical data on Desna floodplain, collected in the last 40 years, allowed identifying the main dynamic trends in the syntaxonomical space. Based on 36 relevés made by the authors in 1975–1990 previously (Bulokhov, 2001) 3 subassociations, which communities were prevalent in the Desna valley, were established: Caricetum gracilis typicum, С. g. oenanthetosum aquaticae, С. g. beckmannietosum eruciformis. As a survey of the Desna floodplain in 2015–2018 showed, both flow decrease and drop in the level of spring flood and groundwater in the XXI century have led to a change in the appearance, floristic composition, and structure of acute sedge meadows. Xerophytization of the floodplain resulted in the disappearance of the С. g. oenanthetosum aquaticae and С. g. beckmannietosum eruciformis communities. Drying of typical habitats of moist acute sedge meadows became the background of the formation of diverse communities of other types in their place. In the coenoflors of these communities changes occurred at the class level from Phragmito-Magnocaricetea Klika in Klika et Novák 1941 to Molinio-Arrhenatheretea Tx. 1937. Two groups of communities have been formed. The first group is represented by syntaxa of the alliance Magnocaricion gracilis (class Phragmito-Magnocaricetea): Caricetum gracilis typicum with variant Achillea salicifolia as well as by the communities Lythrum salicaria, Calystegia sepium, Calamagrostis canescens. The share of the alliance characteristic species in their coenofloras is 54–64%, and Carex acuta, as a rule, dominates. The second group represents the communities of wet meadows (order Molinietalia caeruleae) of the class Molinio-Arrhenatheretea. The alliance Deschampsion cespitosae is established with subass. Poo palustris–Alopecuretum pratensis typicum (with three variants: Veronica longifolia, Hierochloё odorata, Galium physocarpum) and three communities (Cirsium arvense, Lysimachia vulgaris, Stachys palustris) The share of characteristic species of the order in their coenofloras is 58–95%. All communities and variants form series along the moisture gradient in habitats of acute sedge meadows. Communities Lythrum salicaria, Calystegia sepium, Calamagrostis canescens are distributed in the wettest and richest in mineral nitrogen habitats in the Middle Desna area, in the former long-flooded low-level floodplain. The other ones occur, first of all, in the Upper and Middle Desna areas on a short- and long-flooded floodplain of an average level. These communities are forming on moist and fresh soils. The variants and communities on the gradients of moisture and the richness of mineral nitrogen of the soil were ordinated using the ecological scales of H. Ellenberg et al. (1992). Serial communities form an ecological-dynamic sere on a humidity gradient, showing the direction of their dynamics. The same localization of studies carried out both in 1975–1990 and in 2015–2018 identified changes in vascular plant coenoflora of the ass. Caricetum gracilis for this period: from 62 species in 1975–1990 to 143 species in 2015–2018. There are three groups of species, which reflects these changes. Besides species affine to the class Phragmito-Magnocaricetea, numerous meadow herbs of the class Molinio-Arrhenatheretea appeared: Agrimonia eupatoria, Agrostis tenuis, Bromopsis inermis, Carex praecox, Dactilys glomerata, Dianthus deltoides, Elytrigia repens, Equisetum arvense, Festuca pratensis, Galium mollugo, Geranium pratense, Galium physocarpum, Hieracium umbellatum, Hierochloё odorata, Lathyrus pratensis, Odontites vulgaris, Poa pratensis, Potentilla argentea, Potentilla erecta, Phleum pratense, Vicia cracca. A complex of ruderal explerent and nitrophilous species with numerous alien ones has been formed: Bidens frondosa, Chamaenerion angustifolium, Cirsium arvense, Echinocystis lobata, Epilobium adenocaulon, E. collinum, E. pseudorubescens, E. tetragonum, Erigeron annuus, E. canadensis, Lactuca serriola, Linaria vulgaris, Senecio jacobaea, Sonchus arvensis. Most of these species are anemoсhores, and their presence in the sedge communities is associated with open site formation due to the soil drying between hummocks, as well as the destruction of sedge tussocks under drying and fire. Over the past decade invasive species Bidens frondosa, Erigeron annuus subsp. septentrionalis, E. canadensis,and Lactuca serriola have become an ordinary component of the Desna’s river valley flora. Trees and shrubs (Acer negundo, Betula pendula, Frangula alnus, Quercus robur, Rosa majalis, Salix cinerea, S. pentandra, Swida alba) enter into meadow communities because the lack of haymowing. The following changes in the life form spectrum took place due to the floodplain xerophytization and acute sedge meadow transformation: the proportion of long-rhizome species decreased, while that of rod-root, short-rhizome, and annuals increased; trees and shrubs appeared. Obvious also are changes in the ecobiomorphspectrum: the proportion of mesomorphic species increased, that of hygromophic and mesogygromorphic ones decreased; xero-mesomorphic plants appeared.

Assessing Dynamic Soil Properties in Southern New England Forests within an Ecological Site Framework

Core Ideas Coniferous and deciduous forests are two common states within a glaciofluvial upland ecological site. Upland soils with contrasting particle size showed similar ecological potential. Poorly drained and very poorly drained riparian ecosystems should be considered separate ecological sites. Ecological sites are a framework for documenting ecosystem conditions within a region but few have been developed for forested ecosystems. We developed ecological site concepts for southern New England glaciated forested upland and riparian benchmark soils with contrasting inherent properties. Within upland and riparian soils, we quantified the resistance or resilience of dynamic soil properties following specific management or disturbance. Although the upland soils had contrasting particle size classes, the vegetation composition, tree productivity, and soil organic C (SOC) pools were similar, suggesting that these soils have similar ecological potential. Coniferous and deciduous upland sites showed minimal differences. Selective harvest of 50% of overstory trees in the uplands decreased C addition from litter by 28% (p = 0.036) but did not significantly impact O horizon thickness or SOC contents, suggesting that C pools in these soils are resilient to selective harvesting. Although poorly and very poorly drained riparian soils had similar stands of Acer rubrum L., very poorly drained soils had larger SOC pools and thicker O horizons, and Carex stricta Lam. and Symplocarpus foetidus (L.) Salisb. ex W.P.C.Barton dominated the understory. These differences suggest these riparian soils should be considered separate ecological sites. Simulated N enrichment of riparian soils significantly (p = 0.006) increased root biomass but not CO2 respiration. Over time, N additions may increase C pools in riparian soils. Our studies suggest that ecological site concepts can be applied in southern New England forest ecosystems to establish a framework for understanding plant and soil responses to disturbance or management.

Microgeographic Variation in Bog Turtle Nesting Ecology

Abstract Bog Turtles (Glyptemys muhlenbergii) are cryptic habitat specialists, requiring spring-fed bogs, fens, and wet meadows, and are among the most imperiled turtles in North America. Despite the sensitive conservation status of this species, data on nesting ecology remain scant. We used radiotelemetry to collect information on the nesting ecology and nest success of Bog Turtles at two sites in Maryland. We had three main objectives: 1) to determine elements of reproductive biology critical to population viability, 2) to investigate rates of nest and egg success, and 3) to compare these variables between two proximate geographic localities. We documented a total of 41 nests across both sites and study years, all between 8 and 22 June of each year. In some cases, turtles used the same nest sites between years, and nests were in moist soil, moss, sedge tussocks, and mats of vegetation. Nesting turtles were typically observed in the late afternoon and evening, between 1557 and 2222 h. Clutch sizes averag...

Environmental and individual correlates of common pochard (Aythya ferina) nesting success

Common pochard (Aythya ferina) is a harvested diving duck that has experienced a decline in population size over the past 20 years in Europe. This decline has been hypothesized to result from reduced breeding success in strongholds of Central Europe. Thus, assessing factors underlying breeding success is a priority. To evaluate determinants of nesting success, we modelled daily survival probabilities of nests on Grand-Lieu Lake, France. Nest survival rates varied with female age and annually (range, 5% for the worst year in yearling females to 74% for the best year in adult females). The effect of year was entirely absorbed by the onset of laying, computed separately by age, with higher survival rates observed in both adults and in years of early onset of nesting. Nest survival was also positively correlated with clutch size and female body condition. Nest survival was related negatively to numbers of neighbouring nests destroyed. Area of open water, wet meadows and sedge tussocks had a positive influence on nest survival; in contrast, that of willows had a negative influence. Spring temperatures on one hand and cumulative rainfall and water levels on the other were positively and negatively correlated to the annual start of nesting, respectively, although these factors were not retained in the best-approximating models for daily survival probabilities. Nest survival seemed to depend most on female quality, including timing of nesting, and to variables affecting predation risk. Management actions targeting these variables could therefore be the best way to improve nesting success in this species.

High growth temperatures and high soil nitrogen do not alter differences in CO2 assimilation between invasive Phalaris arundinacea (reed canarygrass) and Carex stricta (tussock sedge).

Global change in temperature and soil nitrogen availability could affect plant community composition, potentially giving an advantage to invasive species compared to native species. We addressed how high temperatures affected CO2 assimilation parameters for invasive Phalaris arundinacea and a sedge, Carex stricta, it displaces, in natural and controlled environments. Photosynthetic parameters were measured in a wetland in Indiana, USA during the abnormally warm year of 2012. In a growth chamber, photosynthetic parameters were measured on the plants grown under three levels of nitrogen and exposed to optimum temperatures followed by 2012-like summer conditions and then hot temperatures with an autumn-like photoperiod. In the wetland, C. stricta exhibited signs of midsummer leaf senescence, whereas P. arundinacea maintained CO2 assimilation at ambient pCO2 (Aamb ) through mid-October. In the chamber, 2012-like conditions reduced Aamb for both species through reductions in maximum carboxylation (Vcmax ) and electron transport (Jmax ) without further change during subsequent hot, autumn-like conditions, whereas the quantum efficiency of carbon assimilation (qe) declined throughout the experiment. However, P. arundinacea had higher values of Aamb , Jmax , and qe than C. stricta. A general, the positive effect of increasing nitrogen availability occurred for photosynthetic processes for both species in hot conditions. Our data suggest that C. stricta is more susceptible to excessive light stress than P. arundinacea during hot, sunny periods, leading to leaf senescence. Field confirmation of this idea is needed, but frequent heat waves should favor P. arundinacea over C. stricta with or without eutrophication.

A Non-Soil Seed Bank Dependent on the Size of Clonal Plants: The Case ofCarex cespitosa, a Guerrilla Species in an Unmown Meadow

ABSTRACT Long-lived clonal plants provide an optimal place for the natural storage of seeds as a ‘non-soil seed bank’. We tested the hypothesis that the size and species diversity of a non-soil seed bank deposited within the clonal plant Carex cespitosa depends mainly on the plant's size. To verify this hypothesis, an experiment was conducted on an unmown meadow in the Bialowieza National Park. The emerging seedlings of different species originating from C. cespitosa tussocks of different size (large and small) were observed under greenhouse conditions for four years. The size of a non-soil seed bank was evaluated based on the number of seedlings. Significant differences in the seedling number were found between large and small sedge tussocks (Mann-Whitney test Z = 3.96, P < 0.001). However, the number of recorded species was independent of tussock size. Both types of tussocks were dominated by meadow, forest and swamp species (in decreasing order). Some of these species are no longer present in the studi...

Hibernation Ecology of an Isolated Population of Bog Turtles,Glyptemys muhlenbergii

Information on the hibernation ecology of Bog Turtles (Glyptemys muhlenbergii) throughout their range is limited. Few studies have identified suitable hibernacula or documented behavior during hibernation including site fidelity, communal hibernation, and entrance and emergence times. Our study presents long-term documentation of hibernation in a relatively understudied portion of the species' range. From fall 2005 to spring 2014, we observed the hibernation of 13 marked turtles in an isolated population located in the southern Appalachian Mountains of North Carolina. During the course of our study, nine turtles were radio-tracked for 1–5 y. Turtles spent about six months in hibernation, usually entering the hibernaculum in late September into October and emerging in mid-April. Using radiotelemetry, we identified 11 hibernacula of three types: root masses of trees/shrubs, root masses of cinnamon ferns (Osmundastrum cinnamomeum), and sedge (Carex stricta) clumps. Site fidelity and communal use were common in our study. Ten turtles located in multiple winters repeated their use of a hibernaculum in at least two of those winters. Twelve turtles hibernated communally in at least one year. No mortality was observed at the hibernacula. Our study demonstrates the importance of root masses with soft deep substrate for survival in long, harsh winter conditions. Bog Turtles spend about half of every year, and therefore half of their lives, in hibernation, making the identification and protection of suitable habitat for hibernation imperative for successful management to ensure the long-term viability of the species.

Vegetation Type Dominates the Spatial Variability in CH4 Emissions Across Multiple Arctic Tundra Landscapes

Methane (CH4) emissions from Arctic tundra are an important feedback to global climate. Currently, modelling and predicting CH4 fluxes at broader scales are limited by the challenge of upscaling plot-scale measurements in spatially heterogeneous landscapes, and by uncertainties regarding key controls of CH4 emissions. In this study, CH4 and CO2 fluxes were measured together with a range of environmental variables and detailed vegetation analysis at four sites spanning 300 km latitude from Barrow to Ivotuk (Alaska). We used multiple regression modelling to identify drivers of CH4 flux, and to examine relationships between gross primary productivity (GPP), dissolved organic carbon (DOC) and CH4 fluxes. We found that a highly simplified vegetation classification consisting of just three vegetation types (wet sedge, tussock sedge and other) explained 54% of the variation in CH4 fluxes across the entire transect, performing almost as well as a more complex model including water table, sedge height and soil moisture (explaining 58% of the variation in CH4 fluxes). Substantial CH4 emissions were recorded from tussock sedges in locations even when the water table was lower than 40 cm below the surface, demonstrating the importance of plant-mediated transport. We also found no relationship between instantaneous GPP and CH4 fluxes, suggesting that models should be cautious in assuming a direct relationship between primary production and CH4 emissions. Our findings demonstrate the importance of vegetation as an integrator of processes controlling CH4 emissions in Arctic ecosystems, and provide a simplified framework for upscaling plot scale CH4 flux measurements from Arctic ecosystems.

Sedge/Grass Meadow Restoration on Former Agricultural Lands along a Lake Ontario Drowned-River-Mouth Tributary

Restoration of sedge/grass meadow habitat was implemented on former agricultural lands adjacent to a Lake Ontario drowned-river-mouth tributary at an elevation that historically supports this community type. Four hectares of land were disked in spring and seeded with diverse wetland mixes containing sedges, grasses, and forbs, with additional Calamagrostis canadensis (bluejoint) and Carex stricta (upright sedge) seeds added. Seedling plugs of C. canadensis and C. stricta were also planted. Mowing at a height of 45 cm to control tall, invasive annual weeds prior to seed-set was conducted as an adaptive management practice. Three years after implementation, C. canadensis and C. stricta were not found, but seeded Carex vulpinoidea (fox sedge) was dominant, and seeded Carex lupulina (hop sedge) and Carex lurida (shallow sedge) were also present. Most invasive annuals were rare, but canopies created by larger perennials may pose future problems. Although a greenhouse seed-bank emergence study was conducted, field sampling suggested that plants growing on adjacent lands were a better predictor of future plant communities, with select seeded species serving as a secondary predictor. Failure of some sedges to survive after seeding likely was not related to stratification or diurnal temperature range. However, inadequate soil moisture related to soil type and a second-year drought likely played a role, as might loss of viability of seeds during storage. Future efforts on similar lands might use fresh Carex seeds broadcast in autumn for over-winter stratification, and specially developed seed mixes could focus on species that established at the site and native species found nearby, while avoiding some potential problem species.

Assessing floodplain porosity for accurate quantification of water retention capacity of near-natural riparian ecosystems—A case study of the Lower Biebrza Basin, Poland

Near-natural lowland floodplains, which nearly disappeared in temperate climates due to the vast anthropopression, play a critically important role in shaping biodiversity in regional scales. The other important aspects of floodplains such as their role in flood mitigation for downstream reaches of rivers, catchment-scale ecosystem services, and agriculture emphasize the need for research of these ecosystems, with special focus on the flood-vegetation interactions. In our study we performed an experiment oriented at the accurate quantification of water retention capacity of the densely vegetated floodplain located in NE Poland, referring to the floodplain porosity (ε). We conducted measurements of the geometry of selected types of the floodplain vegetation, with a special focus on the communities dominated by the common reed (Phragmites australis (Cav.) Trin. ex Steud.), the reed-manna grass (Glyceria maxima (Hartm.) Holumb.) and dominant representatives of loosely structured sedges (Carex acuta L.) and of tussock sedges (Carex appropinquata Schumach.)., which allowed us to derive the volume of these species and eventually the floodplain porosity coefficients in a function of various flood depths. Estimated values of ε equalled from 0.882 to 0.993. Average value of ε for all vegetation communities analysed for all flood depths considered equalled 0.968. Consideration of the derived ε values in the case study on the floodplain water retention capacity estimation in hypothetical conditions of a standard flood (2-year recurrence interval) resulted in the reduction of the total water storage volume of the floodplain by 0.75mnm3 of water. Results of our research indicated that the studies oriented at quantification of water storage within the floodplain as an asset for ecosystem services should consider floodplain porosity due to its significance in the accurate estimation of floodplain capacity.

Phenology of Carex stricta: It pays to be tall!

Southern Wisconsin tussock meadows are greatly diminished in area relative to pre-settlement times (Zedler and Potter 2008; Figure 1), and restoration is warranted. The geographically-widespread sedge, Carex stricta, is considered a “superplant” for restoring southern Wisconsin’s wet meadows because it is readily grown from both ramets (vegetative propagules) and seeds (Leaflet 22; see arboretum.wisc.edu/leaflets). Young plants can be tailored to different restoration sites by manipulating water and nitrogen (Gallagher 2009). Also, the species is easy to outplant in restoration sites, and canopies rapidly expand to create dense cover.

Environmental predictors of woody plant encroachment in calcareous fens are modified by biotic and abiotic land‐use legacies

Summary Woody plant encroachment in grasslands is a world‐wide concern. Assertions that abiotic stress reduction facilitates encroachment are not universally supported. To devise restoration and management strategies, the ability of stress reduction, in the context of co‐occurring biotic land‐use legacies, needs to be assessed to predict shrub cover. We determined whether legacy‐induced reduction in Carex stricta (a potential facilitator of shrub encroachment and attractor of animal dispersers) and an increase in herbaceous invaders (potential competitors) altered the ability of stress reduction to predict woody plant cover in ploughed and never‐ploughed plots within 11 Wisconsin (USA) calcareous fens. We hypothesized that drier conditions (low saturation stress) and higher nutrient availability associated with ploughing would be associated with high woody plant cover; that higher cover of herbaceous invaders associated with ploughing would predict low woody plant cover, and C. stricta cover predicts high woody plant cover in saturated, never‐ploughed plots. Restricted maximum‐likelihood (REML) multiple regression was used to determine the importance of interactions among ploughing, saturation, nutrients and the two biotic legacies in predicting woody richness and cover, as well as cover by dispersal syndromes and individual species. Unexpectedly, encroachment by animal‐dispersed species was higher in never‐ploughed plots, while wind‐dispersed species had no relationship with ploughing. Animal‐dispersed species cover decreased with saturation stress in never‐ploughed plots, only. Carex cover was associated with increased encroachment by animal‐dispersed species, mainly in never‐ploughed highly saturated plots. Herbaceous‐invasive cover was associated with decreased encroachment. Wind‐dispersed species cover declined with increasing saturation stress, with responses varying among species. Synthesis and applications. The results suggest that the impacts of stress reduction on encroachment are not uniform and are modified by biotic legacies. We suggest that impacts of restoring stressful abiotic conditions on encroachment may not be known until the impacts on competitors and facilitators are understood.

Reproductive Performance of a Declining Forest Passerine in Relation to Environmental and Social Factors: Implications for Species Conservation.

Identifying factors influencing a species' ecological niche and demography is a prerequisite for species conservation. However, our understanding of the interplay between demographic rates and biotic/abiotic factors is still poor for most species of conservation concern. We evaluated relevance of eight hypotheses relating to timing of breeding, temporal nest exposure, nest concealment, topography, tree structure, predation risk and disturbance, density dependence and weather for explaining variation in reproductive performance of the declining wood warbler Phylloscopus sibilatrix in northern Switzerland. Reproductive performance was monitored with cameras at 136 nests from 2010 to 2012 and was associated to temporal exposure, timing of breeding and concealment of nests. Daily nest survival was positively related to the number of grass and sedge tussocks, nest concealment and nest age. Clutch size and number of fledglings decreased, the later in the season a nest was initiated. Nest survival over an average nesting period of 31 days was 46.9 ± 0.07% (mean ± SE), daily nest survival rate was 0.976 ± 0.002. As for many ground-breeding birds, nest predation was the principal cause of nest failure, accounting for 79% of all nest losses. Conservation measures should aim at increasing the area of relatively homogenous forest stands featuring suitable habitats characterized by abundant and accessible grass and sedge tussocks. In managed forests, such conditions can be found in stands of middle age (i.e. pole wood) with little to no shrub layer.

Effects of farming on the soil seed banks and wetland restoration potential in Sanjiang Plain, Northeastern China

Seed bank is an important source of regenerative material in wetlands, and can be of value in the restoration of farmed wetlands if the seeds can survive periods of cultivation. A seed bank assay of soils from sedge meadows was conducted to determine the extent to which seeds are maintained during farming for various lengths of time. Soils from natural sedge meadows, soybean fields and paddy fields farmed for 1–30 years were collected in Sanjiang Plain, northeastern China. Soils were placed in a glasshouse setting in freely drained condition. We found that species richness and seed density in sedge meadows were higher than in soybean and paddy fields. There were significantly negative effects of the length of time of farming on the seed bank in soybean fields. Important wetland species survived cultivation as seeds within 10 years (e.g., Calamagrostis angustifolia and Polygonum amphibium), but most sedge meadow species disappeared when farmed for more than 10 years in soybean fields. Species richness and seed densities of species kept in a very low level in paddy fields farmed for various periods. Key structural dominants Carex species maintained with low seeds in natural wetlands and soybean fields farmed for 1–5 years, and tussock-forming Carex (e.g., Carex appendiculata and Carex meyeriana) were all absent in farmed fields. The structure of the seed bank was related to environmental factors including latitude, number of years farmed and field water depth as based on Non-metric Multidimensional Scaling analysis. Critical components of the vegetation are not maintained in seed banks, which may make these floodplain wetlands difficult to restore via natural recolonization. To re-establish the structure imposed by tussock sedges, specific technologies (e.g., planting, hydrochory) might be developed to encourage the development of tussocks.

An invasive exotic grass reduced sedge meadow species richness by half

A debate over the impacts of invasive plants is fueled by varied terminology, ecosystem types, response metrics, and conflicting evidence across scales. We quantify the effects of invading Phalaris arundinacea (Pa) on species richness and abundance in Wisconsin sedge meadows dominated by Carex stricta (Cs). Among species area curves from four nested plots (0.25, 1, 4, and 16 m2) in seven sites, Pa stands averaged 48 % fewer species than the adjacent Cs. Species richness was reduced by about half regardless of plot size. Total richness for Pa stands was 50 species compared to 83 for Cs, and Pa stands had consistently lower additive percent cover of subordinate species at all scales. However, resident species responded differentially to Pa invasion. Only one species, Calamagrostis canadensis (a tall clonal grass), had similar importance values (using cover and frequency) in Cs and Pa stands at 0.25 and 16-m2 scales. Other species declined with Pa invasion, mostly in frequency. Despite losing half of their resident species, sites did not differ significantly in their native exotic richness relationship (NERR). NERR confounds the effects of invasiveness with species’ origins, and it under-represents impacts of dominant invaders in wetlands. Debates should be fewer if studies specify if the invader is exotic or native, type of invaded ecosystem, the metric used to assess responses, and the spatial scale.

Plasticity of nitrogen allocation in the leaves of the invasive wetland grass, Phalaris arundinacea and co-occurring Carex species determines the photosynthetic sensitivity to nitrogen availability

Phalaris arundinacea displaces the slower-growing, native sedge, Carex stricta, where nitrogen availability is high. Our aim was to address whether morphological and physiological traits associated with carbon gain for P. arundinacea and C. stricta responded to nitrogen supply differently and if the species exhibited different degrees of plasticity in these traits. The plants were grown in gravel and provided modified Hoagland's solution containing four nitrogen concentrations from 0.15 to 15mM for 6 to 7 weeks. Supplied nitrogen affected the leaf nitrogen content to the same degree for both species. Increasing supplied nitrogen strongly increased CO2 assimilation (A), photosynthetic nitrogen use efficiency (PNUE), and respiration for P. arundinacea but had only a small effect on these parameters for C. stricta. Relative to growth at 15mM nitrogen, growth at 0.15mM for young leaves decreased carboxylation capacity and efficiency and the capacity for electron transport for P. arundinacea and a larger, stouter Carex species, Carex lacustris, by 53 to 70% but only 20 to 24% for C. stricta. Leaf nitrogen decreased approximately 50% for all species, but vacuolar nitrate did not decrease for P. arundinacea and C. stricta, suggesting that it does not serve as a nitrogen reserve for use during nitrogen deprivation in these species. After 4 months of nitrogen deprivation, P. arundinacea doubled A in 12 days after being supplied 15mM nitrogen, whereas A for C. stricta increased only 22%. We propose that one factor linking P. arundinacea abundance to nitrogen availability involves this species’ plastic response of carbon gain to nitrogen supply. C. stricta appears to be adapted to tolerate low nitrogen availability but cannot respond as rapidly and extensively as P. arundinacea when nitrogen supply is high.

Increasing substrate heterogeneity as a bet‐hedging strategy for restoring wetland vegetation

AbstractMimicking the natural heterogeneity of wetland substrates, e.g. by roughening surface soil or constructing hummocks, has been shown to facilitate wetland plant establishment. We asked if incorporating substrate heterogeneity could also help plants withstand variation in moisture levels. In a wetland with Carex stricta (tussock sedge) as the main restoration target, we manipulated substrates to create different soil moisture environments for planted C. stricta plugs. Our artificial mounds mimicked tussocks formed by C. stricta in natural meadows (circa 10–40 cm in height); we also varied mound compositions and created shallow depressions. Monitoring demonstrated variation in soil moisture among our treatments and natural differences in soil moisture between experimental blocks. Additionally, rainfall varied from severe drought in year 1 to extreme rainfall in year 2. Plug survival, flowering, cover, biomass, leaf length, and growth rate all varied with treatment, block, and/or year. Interactions among those factors were common. Planting plugs in shallow depressions exacerbated stress in a wet block during a wet year, causing low survival. Planting plugs in moisture‐retaining peat pots allowed them to survive and sustain growth even in a dry block during a dry year. We conclude that heterogeneous substrates can be used to hedge against environmental variability by widening the range of microsites available within a restoration site and thereby moderating stressful conditions in some areas.

Nest survival in the Reed Bunting Emberiza schoeniclus in fragmented wetland habitats: the effect of nest-site selection

Nest survival in fragmented wetlands is usually affected by micro-habitat variables. The main aim of the study was to investigate the factors affecting Reed Bunting Emberiza schoeniclus nest survival in wetland habitats within a mosaic Central European land-scape. In total, we monitored 95 nests on five separate fishponds in South Bohemia, Czech Republic during a six-year study between 2002 and 2007. In order to determine the effects on nest survival of nest site characteristic, the first egg laying date and nest age, we estimated daily survival rate (DSR) and built models using program MARK. DSR was significantly higher in nests located in Reed Canary Grass Phalaris arundinacea and tall vegetation Cattail Typha latifolia and Common Reed Phragmites australis than in sedges Carex spp. Surprisingly, expanding Reed Canary Grass was occupied later in the breeding season and likely less preferred vegetation type than sedges. Structure of sedge tussocks changed due to eutrophication and likely lost its suitability as quality microhabitat of the nest site. Furthermore, we found mild support that DSR increased with the distance from the nearest tree and that the lowest DSR was between 19th and 20th day of the nesting cycle, close after the hatching of the nestlings which can attract potential predators. These findings could indicate the importance of birds as predators on Reed Bunting nests. Nest site selection appears to be a display of anti-predator strategy in the Reed Bunting.