Carex Species Research Articles

Plant species selection by sheep in semi-natural dry grasslands extensively grazed in the south-western Italian Alps

Sheep can have an important role in the conservation of abandoned and shrub- and tree-encroached, semi-natural dry grasslands because their feeding behaviour is known to affect plant diversity and structure. Nevertheless, little information is available about feeding preferences of sheep at the sward-patch scale and about the effects of stocking density on their selectivity. Consequently, we investigated plant-species selection by sheep managed with a low-intensity grazing, examining the influence of stocking density and plant species abundance by means of vegetation surveys and animal GPS tracking. Sheep grazed a graminoid-dominated, semi-natural dry grassland (Festuco–Brometea) in Piedmont Region, north-west Italy. Plant species, classified into graminoids, suffruticose forbs, and herbaceous forbs, were selected with a different intensity by sheep, which preferred graminoids over suffruticose and herbaceous forbs. Plant species showing a high consumption ratio (CR), i.e. the level of selection of plant species (CR >10%), were mostly graminoids (e.g. Bromus erectus, Koeleria vallesiana and Stipa pennata). Furthermore, Carex species were also noticeably selected, in particular C. humilis, whereas spiny species and those with a rosette or prostrate forms were rarely grazed. The heterogeneity of stocking density over the pasture allowed testing of the relationships between stocking density and CR. For many species, the higher the stocking density, the higher was the CR, regardless of the abundance of dominant neighbouring species. Results suggest that sheep under low-intensity grazing conditions exert a specific plant-species selection in abandoned dry grasslands. By regulating the stocking density through the management of grazing sheep, it may be possible to condition the consumption of certain plant species, with medium–long-term effects on the botanical composition.

Evaluation of cold resistance of four wild Carex speices

Four wild Carex speices (C. rigescens, C. lancifolia, C. leucochlora and C. humilis) collected from Mount Taishan were used as experimental materials. The adaption across the winter and physiological characteristics resistant to cold stress were investigated, semi-lethal temperature (LT50) was calculated and fuzzy subordination method was used to generally evaluate the Carex resistant to cold stress. The results showed that 4 Carex species all survived in the winter safely and restored well to grow in the following spring. The green period of the species was between 260 d and 310 d, and percentage of the withered leaves was between 12% and 95%, the range of LT50 was from -18.65 ℃ to -11.74 ℃. With intensifying cold stress, the contents of MDA, proline (Pro) and soluble protein increased at first and then decreased, while the soluble sugar content increased with the treatment time. C. rigescens with poor cold tolerance showed the early accumulation of MDA, Pro and soluble sugar. The value of soluble protein peaked at the late stage of low tempe-rature stress, and the Carex with stronger cold-resistance showed the smaller value. The SOD activity in the leaves of C. lancifolia was higher than that of the other three species in the beginning of treatments. The cold resistance of four Carex species was in order of C. lancifolia>C. leucochlora>C. humilis>C. rigescens.

Regulation of dauciform root formation and root phosphatase activities of sedges (Carex) by nitrogen and phosphorus

Dauciform roots (DR) are formed by some Cyperaceae under phosphorus (P) deficiency. To advance our understanding of their physiological function, I ask: Is DR formation regulated by shoot P status or external P supply? How does it respond to nitrogen (N)? Do DR enhance root monoesterase, diesterase or phytase activities and ability to utilize organic P? Greenhouse experiments were carried out with two Carex species grown in sand with (1) different combinations of N and P supply, (2) local supply of N or P to root halves, and (3) different organic P forms. Carex flava produced DR in all treatments. The density of DR and phosphatase activities increased with N supply; they were regulated by shoot P status and external N (but not P) supply. All phosphatase activities increased with DR density. Carex muricata produced no DR and had lower diesterase activity than C. flava but both species grew equally well with diester-P. DR and phosphatase activities are regulated by both N and P supply. Similar growth responses to nutrients in both species suggest small costs and benefits of DR under experimental conditions but confirmation is needed for plants grown on natural soils.

Eutrophication alters Si cycling and litter decomposition in wetlands

Anthropogenic eutrophication of wetlands may have a significant impact on the global biogeochemical silicon (Si) cycle, as Si filtering by wetland vegetation codetermines fluxes of Si towards the oceans. We experimentally investigated how macronutrient (NPK) enrichment alters total Si storage and Si stoichiometry in litter from six wetland species of Carex, which we related to other parameters of litter quality and litter decomposition rates. Nutrient enrichment stimulated primary biomass production, which resulted in an increased total Si storage in plants. However, this eutrophication-induced stimulatory effect on Si fixation in plant biomass was counterbalanced by consistently lower (up to 50 % reduction) litter Si concentrations in all species, suggesting a plant-physiological response following the relief of nutrient stress. Moreover, competitive species (typical for eutrophic conditions) tended to accumulate less Si (per g DM) than slow-growing species (typical for nutrient-poor conditions). Finally, a negative correlation between litter Si concentrations and litter decomposition rates in nutrient-poor environments suggested an inhibiting effect of Si on decomposition. However, negative correlations between litter Si concentrations and litter macronutrient concentrations as well as positive correlations between litter Si concentrations and C:N and lignin:N ratios indicated a strong interdependence of Si with other litter quality parameters that determine decomposition. We conclude that stimulatory effects of eutrophication on total Si storage in wetland vegetation (following an increase in biomass production) need to be balanced with the plant-physiological response of lower tissue Si concentrations. We argue that rates of Si cycling are likely to be altered through shifts in litter quality and decomposition rates.

Ecological and Evolutionary Diversification Within the Genus <I>Carex</I> (Cyperaceae): Consequences for Community Assembly in Subarctic Fens

The concept of limiting similarity predicts that closely related taxa are less likely to co-occur than expected by chance. The degree to which the phylogenetic relatedness in plant communities is in accord with limiting similarity has been little tested at the scale where the consequences of adaptive differentiation during speciation should be most evident: the scale of neighboring, congeneric plants within a community. To quantify species co-occurrence patterns in relation to environment, we sampled sedge species, their rooting level relative to the water table, and the water pH in 2,124 0.25 m2 quadrats distributed across 29 subarctic fens in the central Labrador Peninsula. We estimated phylogenetic relationships using four DNA regions (ETS, ITS, matK, trnL-trnF) for all species of Carex (42), Eriophorum (6), and Trichophorum (2) in the region, of which 21, four, and two, respectively, occurred in the sampled fens. We demonstrate that closely related species of Carex are less likely to co-occur than expected by chance using 1) a probabilistic method to test the significance of pairwise co-occurrence patterns of species, and 2) linear mixed modeling to relate these patterns to phylogenetic relationships and ecological tolerances along gradients of substrate pH and rooting level in relation to the water table. The results also indicate that suites of species with significant mutual pairwise co-occurrence belong to distant lineages within the Cariceae-Dulichieae-Scirpeae clade of Cyperaceae and have stabilizing niche differences. We suggest that niche differentiation during the evolution and diversification of a clade of wetland Carex species over the past few million years, especially during the dynamic glacial cycles of the Pleistocene, has resulted in diverse sedge communities that share space and resources in harsh northern peatland habitats.

Clarification of the Use of the Terms Perigynium and Utricle in <I>Carex</I> L. (Cyperaceae)

Abstract Despite previous efforts to unify the terminology for Cyperaceae, two different terms, perigynium and utricle, are in common use for the prophyllar bract enclosing the female flower of Carex. Use of these terms is divided largely on geographic lines (mainly North American versus European and other authors, respectively). The recent merging of Kobresia with Carex requires a single term to refer to both the open prophyll of Kobresia and the laterally closed one of Carex. However, even when authors use utricle for Carex species, these same authors do not refer to the open prophyll of Kobresia as a utricle. We show that perigynium was apparently coined earlier than utricle, at the end of the 18th century, but the term utricle became more widespread than perigynium by the 20th century. Neither of the two terms is unambiguous, as both have also been used for other structures in other plant groups. Given this background, we propose revised definitions of both terms based on two facts: 1) the greater sem...

Root respiratory costs of ion uptake, root growth, and root maintenance in wetland plants: efficiency and strategy of O2 use for adaptation to hypoxia.

Oxygen use in roots is an important aspect of wetland plant ecophysiology, and it depends on the respiratory costs of three major processes: ion uptake, root growth, and root maintenance. However, O2 allocation in wetland plants has received little attention. This study aimed to determine the O2 allocation and specific respiratory cost of each process under hypoxic conditions, to better understand the strategy and efficiency of O2 use in wetland plants. The root respiration rate, nitrogen uptake, and root growth in three Carex species with different growth rates were examined under hypoxic conditions using different N sources, and the respiratory costs of ion uptake, root growth, and root maintenance were statistically estimated. All species exhibited low specific costs and low ratios of O2 allocation for root growth (2.0±0.4mmol O2g(-1) and 15.2±2.7%, respectively). The specific cost of ion uptake was 20-30% lower in fast-growing species than in slow-growing species. As plant growth rate increased, the O2 allocation ratio for ion uptake increased, and that for root maintenance decreased. The cost was higher when NO3 (-) was fed, than when NH4 (+) was fed, although the pattern of O2 allocation ratios for three processes was similar for NO3 (-) and NH4 (+). Our results indicate that wetland plants primarily employ an O2 use strategy of minimising the respiratory costs of root growth, and fast-growing plants specifically use O2 to maximise ion uptake. These findings provide new insights into ecophysiological behaviours of roots in adaptation to hypoxia.

Two new species of Carex (Cyperaceae) from northern South America

We describe and illustrate two new species of Carex from northern South America. Carex via-incaica from Ecuador belongs to section Aciculares. Carex haematopus from Colombia belongs to section Carex. Both species are so far known only from their type localities.

Carex nilagirica(Cyperaceae), a new sedge species from the Nilgiri Biosphere Reserve, India

Carex nilagirica (Cyperaceae) is described as a new species from Nilgiri Biosphere Reserve, Western Ghats, India. The new species belonging to sect. Graciles distinctly differs from related species Carex longipes D. Don. ex Tilloch & Taylor by its smaller size, shorter leaf blades, nature of inflorescence form and number of spikes. A detailed description, phenology, colour plates, distribution and taxonomic notes are provided.

Soil seed banks and their implications for wetland restoration along the Nongjiang River, Northeastern China

Soil seed banks provide seeds for the redevelopment of plant communities in wetlands. They can be important components of the ecological restoration of farmed wetlands, particularly if the seeds can survive periods of cultivation. We assessed if key structural dominant wetland plant species were present as seeds in farmed sedge meadows in northeastern China. We conducted a germination experiment in a greenhouse to compare the seed banks of four natural sedge meadows and four adjacent farmed fields along the Nongjiang River under drained and flooded conditions. We further conducted vegetation surveys in four natural sedge meadows. Sedges (Carex species) and the grass Calamagrostis angustifolia dominated plant communities in the natural sedge meadows. Many important sedge meadow species (>30 species, e.g., Calamogrostis angustifolia and Potamogeton crispus) survived cultivation as seeds. Farmed fields converted from sedge meadows are nearly devoid of dominant Carex species, including two keystone tussock-forming species, Carex appendiculata and Carex meyeriana. Species of various life history types require either drawdown (emergent, e.g., Carex lasiocarpa and Calamogrostis angustifolia) or flooding (submerged, e.g., Potamogeton crispus and Ceratophyllum demersum) for successful germination. The structure of the seed bank was related to experimental water regime, and the field environments of latitude, number of years farmed, and field water depth based on Nonmetric Multidimensional Scaling (NMDS) analysis. Our study indicated that, although certain critical components of the vegetation are not retained in seed banks, which made it difficult to replicate historic habitat via natural recolonization, the seed banks of farmed sedge meadows could still contribute toward the restoration of novel wetland vegetation assemblages under suitable environmental conditions. Carex reestablishment could rely upon artificial introduction if necessary.

Notes on South American Carex section Schiedeanae and description of the new species Carex roalsoniana

The new species Carex roalsoniana (Cyperaceae) from Ecuador and Peru (northern South America) is here described and illustrated. It is related to C. subandrogyna, a species that has been placed in section Schiedeanae. An additional incertae sedis species, Carex lepida from Ecuador, may also be related to them. Section Schiedanae is a morphologically well-defined group previously known from southern North America (southern USA and Mexico), and southern South America (northern Argentina and southern Bolivia). The new species presents very clear-cut characters that distinguish it from all the other members of the section. Specifically, C. roalsoniana and C. subandrogyna differ in utricle morphology (3.6–4.1 mm long, with a beak 0.5–1.2 mm in C. roalsoniana vs. 2.4–2.9 mm long, with a beak up to 0.3 mm long or beakless in C. subandrogyna) and leaves (up to 3–4 mm wide, stiff, in C. roalsoniana vs. up to 5.6–7.5 mm wide, very soft in C. subandrogyna). Carex lepida is easily distinguished from C. roalsoniana and C. subandrogyna because its habit (rhizomes elongated vs. rhizomes densely caespitose) and number of stigmas (two vs. three). The glabrous nerveless utricles of the three South American species distinguish them from the North American species of the section, which have scabrid to hispidulous, conspicuously nerved utricles. The formal ascription of C. lepida among the South American members of section Schiedeanae is also discussed. A brief key to distinguish C. lepida and C. roalsoniana from the other species of the section and the co-occurring species is provided.

Utilizing RADseq data for phylogenetic analysis of challenging taxonomic groups: A case study in Carex sect. Racemosae.

Relationships among closely related and recently diverged taxa can be especially difficult to resolve. Here we use both Sanger sequencing and next-generation RADseq data sets to estimate phylogenetic relationships among species of Carex section Racemosae (Cyperaceae), a clade largely restricted to high latitudes and elevations. Interest in relationships among these taxa derives from questions about the species' biogeographic histories and possible links between diversification and Pleistocene glaciations. A combination of approaches and molecular markers were used to estimate relationships among Carex species within sect. Racemosae and taxa from closely related sections. Nuclear and chloroplast loci generated by Sanger sequencing were analyzed with *BEAST, and SNP data from RADseq loci were analyzed as a concatenated data set using maximum likelihood and as independent loci using SVDquartets. Sanger sequencing data sets resolved relationships among taxa at intermediate phylogenetic depths (albeit with low levels of support). Only the RADseq data resolved relationships with strong support at all phylogenetic depths. Moreover, different methods and data partitions of the RADseq data resulted in nearly identical topologies. Carex sect. Racemosae is a strongly supported clade, although a handful of species were found to group with closely related sections. Herbarium specimens up to 35 yr old successfully produced informative RADseq data. Despite the short read lengths of RADseq data, they nevertheless resolved relationships that Sanger sequencing data did not. Resolution of the phylogenetic relationships among recently and rapidly diversifying taxa within sect. Racemosae clades suggest a role for the Pleistocene glaciations in clade diversification.

Community and species‐specific responses to simulated global change in two subarctic‐alpine plant communities

Long‐term observational studies have detected greening and shrub encroachment in the subarctic attributed to current climate change, while global change simulations have showed that community composition and productivity may shift drastically in arctic, subarctic, and alpine tundra plant communities in the future. However, responses to global change can be highly species‐ and context‐dependent. We examined community‐level and species‐specific responses to a six‐year factorial temperature and nutrient (nitrogen and phosphorus) amendment experiment in two alpine plant communities in northern Sweden: a species‐poor dwarf shrub heath, and a more species‐rich meadow. We hypothesized that abundance responses to global change would be variable within commonly defined vascular plant functional groups (e.g., forbs, evergreen shrubs, deciduous shrubs) and that new species would appear in experimental plots over time due to the ameliorated growing conditions. We found that within most functional groups, species were highly individualistic with respect to the global change simulation, particularly within the forbs, whereas within the shrubs, responses were neutral to negative and widely variable in magnitude. In the heath community the response of the graminoid functional group was driven almost entirely by the grass Calamagrostis lapponica, which increased in abundance by an order of magnitude in the combined temperature and nutrient treatment. Furthermore, community context was important for species' responses to the simulations. Abundance of the pan‐arctic species Carex bigelowii and Vaccinium vitis‐idaea responded primarily to the temperature treatment in the meadow community whereas the nutrient treatment had stronger effects in the heath community. Over six growing seasons, more new species appeared in the experimental plots than in control plots in the meadow community, whereas in the heath community only one new species appeared. Our results from two closely situated but different plant communities show that functional groups do not predict individual species responses to simulated global change, and that these responses depend to a large extent on pre‐existing physical conditions as well as biotic interactions such as competition and facilitation. It may be difficult to apply general trends of global change responses to specific local communities.

Molecular and morphological perspectives on the circumscription of Carex section Heleoglochin (Cyperaceae)

Vignea is the only monophyletic subgenus in the genus Carex (Cyperaceae), comprising nearly 300 members grouped into 19–28 sections. Molecular studies have demonstrated that most of these sections are polyphyletic. Here, we seek to clarify the relationships among species in section Heleoglochin based on phylogenetic and morphological analyses. We analyzed sequence data using nuclear ribosomal DNA internal and external transcriber spacer regions of 60 representative specimens of sect. Heleoglochin, representing the full geographic range of the section and of species that are themselves geographically widespread. We used maximum likelihood and Bayesian inference to estimate phylogeny and divergence times based on molecular data. We scored 17 vegetative and inflorescence characters on 303 specimens and 23 perigynium characters on 56 specimens to characterize morphological variation within and among species and clades. We undertook a comparative analysis of morphological, molecular, and biogeographic patterns to evaluate sectional limits and relationships. Our findings confirm that section Heleoglochin is polyphyletic, with three main lineages—Eurasiatic, North American, and Oceanic clades—supported by molecular, morphological, and biogeographic data. Morphological and molecular analyses support two disjunctures: the European species Carex appropinquata appears sister to the Oceanic lineage, and all the specimens of C. diandra distributed worldwide are grouped together in the North American clade. Concordance among morphological, molecular, and biogeographic data supports each of the lineages and highlights the potential of integrative studies to illuminate the causes of mismatches between phylogeny and traditional classifications. Such integrative studies are needed to make headway on the systematics of this thorny genus, in which non-monophyly of traditional sections is the rule rather than the exception.

Winter diets of reintroduced bison (Bison bison) in northwestern Canada

I examined the winter diets of a reintroduced population of bison (Bison bison) in a mountainous region of northwestern Canada. The impetus of this study was to examine the winter diets of bison in this ecological region and to test for sexual and seasonal variation in the winter diet. Microhistological analyses of fecal samples from animals of known sex- and age-classes were examined to determine winter diets. I evaluated the hypothesis that sexual segregation in bison may be due to differences in diet. In addition, diet composition between early and late winter was examined to test for seasonal differences. Overall, bison winter diets were diverse, including at least 31 genera of vascular plants, but dominated by sedges (Carex). Nine species of Carex were identified in the winter diet. Diets of adult males in early winter differed in percentages of 7 forage classes used from those in late winter. The proportion of shrubs increased in late-winter diets, while that of sedges decreased. No evidence was found to support hypotheses of sexual segregation in bison based on differences in diet, at least for this population during late winter. This study shows that bison diets in winter are more diverse than previously thought based on studies in lowland boreal environments, where dietary niche breadth was comparatively narrow. Dietary flexibility is important within the context of choosing new sites for reintroducing bison, or predicting colonization of vacant habitats as existing populations grow.

Phylogenetic congruence of parasitic smut fungi (Anthracoidea, Anthracoideaceae) and their host plants (Carex, Cyperaceae): Cospeciation or host-shift speciation?

• Fahrenholz's rule states that common ancestors of extant parasites were parasites of the common ancestors of extant hosts. Consequently, parasite phylogeny should mirror host phylogeny. The smut fungi genus Anthracoidea (Anthracoideaceae) is mainly hosted by species of the genus Carex (Cyperaceae). Whether smut fungi phylogeny mirrors sedge phylogeny is still under debate.• The nuclear large subunit DNA region (LSU; 57 accessions) from 31 Anthracoidea species and the ITS, ETS, and trnL-F spacer-trnL intron complex from 41 Carex species were used to infer the phylogenetic history of parasites and their hosts using a maximum likelihood approach. Event-based and distance-based cophylogenetic methods were used to test the hypothesis of whether the phylogeny of smut fungi from the genus Anthracoidea matches the phylogeny of the sedge Carex species they host.• Cophylogenetic reconstructions taking into account phylogenetic uncertainties based on event-based analyses demonstrated that the Anthracoidea phylogeny has significant topological congruence with the phylogeny of their Carex hosts. A distance-based test was also significant; therefore, the phylogenies of Anthracoide and Carex are partially congruent.• The phylogenetic congruence of Anthracoidea and Carex is partially based on smut fungi species being preferentially hosted by closely related sedges (host conservatism). In addition, many different events rather than only codivergence events are inferred. All of this evidence suggests that host-shift speciation rather than cospeciation seems to explain the cophylogenetic patterns of Anthracoidea and Carex.

Facilitation of Pinus albicaulis seedling regeneration by Vaccinium scoparium

Plants often facilitate each other in harsh environments, and facilitation appears to be important for conifer recruitment in subalpine forests and the formation of treelines. This study investigated the potential role of facilitation for the establishment of Pinus albicaulis (whitebark pine), a dominant Rocky Mountain tree species that is in decline due to an exotic blister rust disease (Cronartium ribicola), bark beetle outbreaks, and fire suppression. Surveys were conducted at five subalpine sites for spatial associations between naturally regenerating P. albicaulis seedlings and other plant species, and found that the cover of Vaccinium scoparium was higher in proximity to P. albicaulis seedlings. In transplant experiments, survival of P. albicaulis seedlings was higher when planted with V. scoparium and in shade cloth treatments, but neither survival nor growth rates were altered by clipping or rhizome severing of V. scoparium, suggesting a below-ground rather than above-ground facilitation mechanism. In contrast, Carex species reduced the survival and growth rates of P. albicaulis. In a fertilization experiment, no effect of nitrogen and/or phosphorous fertilization was found on Pinus albicaulis seedling growth, but seedlings growing with V. scoparium had higher growth rates and increased leaf phosphorus concentrations relative to seedlings growing in bare ground. In a microcosm experiment, P. albicaulis seedlings growing with V. scoparium had higher growth rates and leaf phosphorus concentrations than when grown alone, but only if P. albicaulis needles were added on the soil surface. My results suggest success of restoration plantings of greenhouse grown P. albicaulis seedlings may be improved by planting in areas where V. scoparium occurs, and avoiding areas dominated by Carex species. Removal of adjacent vegetation prior to planting seedlings may be ineffective in significantly altering either positive or negative effects of the neighboring plants. Selection of sites with adjacent shading elements, such as rocks, logs, stumps, or snags, may also improve seedling survival.

Direct long‐distance dispersal best explains the bipolar distribution of Carex arctogena (Carex sect. Capituligerae, Cyperaceae)

AbstractAimThe bipolar disjunction, a biogeographical pattern defined by taxa with a distribution at very high latitudes in both hemispheres (> 55° N; > 52° S), is only known to occur in about 30 vascular plant species. Our aim was to use the bipolar species Carex arctogena to test the four classic hypotheses proposed to explain this exceptional disjunction: convergent evolution, vicariance, mountain‐hopping and direct long‐distance dispersal.LocationArctic/boreal and temperate latitudes of both hemispheres.MethodsA combination of molecular and bioclimatic data was used to test phylogeographical hypotheses in C. arctogena. Three chloroplast markers (atpF–atpH, matK and rps16) and the nuclear ITS region were sequenced for all species in Carex sections Capituligerae and Longespicatae; Carex rupestris, C. obtusata and Uncinia triquetra were used as outrgroups. Phylogenetic relationships, divergence‐time estimates and biogeographical patterns were inferred using maximum likelihood, statistical parsimony and Bayesian inference.ResultsCarex sections Capituligerae and Longespicatae formed a monophyletic group that diverged during the late Miocene. Two main lineages of C. arctogena were inferred. Southern Hemisphere populations of C. arctogena shared the same haplotype as a widespread circumboreal lineage. Bioclimatic data show that Southern and Northern Hemisphere populations currently differ in their ecological regimes.Main conclusionsTwo of the four hypotheses accounting for bipolar disjunctions may be rejected. Our results suggest that direct long‐distance dispersal, probably southwards and mediated by birds, best explains the bipolar distribution of C. arctogena.

Plant zonation patterns reflected by the differences in plant growth, biomass partitioning and root traits along a water level gradient among four common vascular plants in freshwater marshes of the Sanjiang Plain, Northeast China

Water level is important in determining plant zonation distribution patterns in freshwater wetlands. However, the role of whole-plants’ morphological traits in response to water level gradients in accounting for the distribution of marsh species is far from clear. Four typical dominant vascular plants with different distribution patterns (high-elevation species Deyeuxia angustifolia, mid-elevation species Carex lasiocarpa and Glyceria spiculosa, and low-elevation species Carex pseudocuraica) in freshwater marshes in the Sanjiang Plain of Northeast China were treated with four static water level conditions (−5, 0, +5, and +15cm relative to the soil surface), and each plant’s growth characteristics, biomass allocation and root traits were investigated. With the rising water level, the growth of D. angustifolia performed worse than other species, whereas the total biomass, plant height and relative growth rate (RGR) of C. pseudocuraica increased steadily. Compared with the other three species, C. pseudocuraica showed a distinct pattern with increasing water levels in the biomass allocation to photosynthetic and non-photosynthetic organs, as well as for coarse and fine roots. Flooding stress significantly reduced root diameter and C/N ratio but simultaneously increased the specific root length (SRL), specific root area (SRA) and root nitrogen concentration (RNC) for both coarse roots (1st order, >0.2mm) and fine roots (2nd and 3rd orders, <0.2mm). However, these root parameters of C. pseudocuraica exhibited an opposite response with the increase in the water level between such two different branching orders. Our results indicate that wetland plants could acclimate to flooding stress through resource trade-off among different tissues and trait-coordinated variation within the root system. Furthermore, species-specific shifts in above- and below-ground traits could help to better understand and predict the vegetation zonation patterns in temperate freshwater wetlands.

Group-based modeling of ecological trajectories in restored wetlands.

Repeated measures taken at the same restoration sites over time are used to describe restoration trajectories and identify sites that are trending toward unexpected outcomes. Analogously, social scientists use repeated measures of individuals to describe developmental trajectories of behaviors or other outcomes. Group-based trajectory modeling (GBTM) is one statistical method used in behavioral and health sciences for this purpose. I introduce the use of GBTM to identify clusters of similar restoration trajectories within a sample of sites. Data collected at 54 restored wetlands in Illinois for up to 15 years post-restoration were used to describe trajectories of six indicators: plant species richness, number of Carex (sedge) species, mean coefficient of conservatism (mean C), native plant cover, perennial plant cover, and planted species cover. For each indicator, I used GBTM to classify wetlands into three to four groups with distinct trajectories. In general, cover by native and planted species declined, while species richness and mean C increased over time or peaked then declined. Site context and management may explain trajectory group membership. Specifically, wetlands restored more recently and those restored within forested contexts were more likely to follow increasing trajectories. I show GBTM to be useful for identifying typical restoration trajectory patterns, developing hypotheses regarding factors driving those patterns and pinpointing critical times for intervention. Furthermore, GBTM might be applied more broadly in ecological research to identify common patterns of community assembly in large numbers of plots or sites.