Native Wetland Plant Species Research Articles

Traits for transport: Alien wetland plants gain an advantage during endozoochorous seed dispersal by waterfowl

Abstract The expansion of alien plant species is of global concern, yet our understanding of their dispersal mechanisms is limited. Here we address the potential of alien plant seeds to disperse via ingestion, transport and egestion in waterfowl (endozoochory). Based on their general rapid expansions, we expected alien plant species to have several advantages for endozoochory compared to native plant species. We hypothesised that seeds of alien species would have higher passage rate, longer gut retention times, higher germinability after gut passage and shorter time‐to‐germination after egestion by waterfowl. In order to test our hypotheses, we compared the endozoochorous dispersal ability of six pairs of congeneric alien and native wetland plant species in a feeding experiment with mallards (Anas platyrhynchos). We focused on differences in seed survival, gut retention time, germinability and time‐to‐germination. In the analyses we corrected for seed shape and volume as these seed traits are known to have important effects. With gut passage, alien species had higher passage rates and germinated slower, whereas native species had shorter retention times and greater germinability. Controlling for seed traits did not alter these conclusions, but seed traits affected all aspects of the endozoochory process. This suggests that alien species may have particular traits correlated with a higher endozoochory potential. Among control seeds, alien seeds germinated faster and their germinability was higher than natives. Seed traits explained differences in germinability and time‐to‐germination in control seeds. Seeds of alien plant species have traits that correlate with successful endozoochory. This may provide alien species with a competitive advantage over native plant species by ensuring higher endozoochory rates in new environments, potentially enabling their rapid expansions. Our study underlines the important role of seed traits in the endozoochory potential of alien and native plant species, notably through their influence on retention time and germination.

The Paradox of Culturally Useful Invasive Species: Southern Cattail (Typha domingensis) Crafts of Lake Pátzcuaro, Mexico

This study explores the cultural, economic, and ecosystem impacts of an invasive plant species, southern cattail (Typha domingensis), on the indigenous Purépecha community of Lake Pátzcuaro, Mexico. Locally known as chuspatel, the species inhabits the same lacustrine space as the native southern bulrush (Schoenoplectus californicus), known locally as tule. In order to control the species, southern cattail is routinely mechanically harvested in parts of the lake. Southern bulrush, on the other hand, is native to the lake, has similar ecological characteristics as southern cattail, and has long been used by indigenous crafts persons. Our initial goal was to explore the distribution and possible negative effects of an invasive plant on a culturally important native wetland plant species. Data collection included open ended interviews, participant observation, and GIS-based vegetation mapping of the two species. Contrary to expectations, our results revealed several cultural, economic, and possibly ecosystem service benefits associated with the arrival and spread of this invasive organism. Cartographic data show that the two species overlap in distribution in the lake. Observations suggest that the invasive species may provide an additional ecosystem service of enhanced habitat for an endemic snake subspecies (Thamnophis eques patzcuaroensis). Moreover, rather than displacing a culturally useful native species, the invasive southern cattail has been incorporated into the repertoire of local crafts and now represents an important addition to the income and culture of the Purépecha. Our study suggests that greater management emphasis should be placed on local and cultural values when considering the overall impacts of invasive organisms.

Exposure of Juncus effusus to seven perfluoroalkyl acids: Uptake, accumulation and phytotoxicity

The extensive use of poly- and perfluoroalkyl substances (PFAS) has led to perfluoroalkyl acids (PFAAs) contamination in various environmental matrices. To remove PFAAs from contaminated water, this study investigated plant uptake of PFAAs by a native wetland plant species in the US, Juncus effusus. The results showed that J. effusus translocated selected PFAAs, including perfluoropentanoic acid (PFPA), perfluorobutanesulfonic acid (PFBS), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS). During the 21-day experimental period, the uptake of PFAAs increased with increasing PFAAs exposure concentration and time. PFOS was largely accumulated in the roots with limited upward translocation. PFAAs with shorter carbon chain length were taken up by J. effusus roots and tended to accumulate in plant shoots. The highest removal efficiency (11.4%) of spiked PFAAs by J. effusus was achieved when it was exposed to PFAAs at around 4.6 mg/L for 21 days. The exposure to PFAAs stimulated the antioxidative defense system in J. effusus shoots but inhibited the superoxide dismutase (SOD) and catalase (CAT) activities and damaged the antioxidative defense system in J. effusus roots. These results warrant further studies to evaluate J. effusus's long-term performance in a PFAAs contaminated environment.

Carbon storage potential by four macrophytes as affected by planting diversity in a created wetland

Wetland creation has become a commonplace method for mitigating the loss of natural wetlands. Often mitigation projects fail to restore ecosystem services of the impacted natural wetlands. One of the key ecosystem services of newly created wetlands is carbon accumulation/sequestration, but little is known about how planting diversity (PD) affects the ability of herbaceous wetland plants to store carbon in newly created wetlands. Most mitigation projects involve a planting regime, but PD, which may be critical in establishing biologically diverse and ecologically functioning wetlands, is seldom required. Using a set of 34 mesocosms (∼1 m2 each), we investigated the effects of planting diversity on carbon storage potential of four native wetland plant species that are commonly planted in created mitigation wetlands in Virginia – Carex vulpinoidea, Eleocharis obtusa, Juncus effusus, and Mimulus ringens. The plants were grown under the four distinctive PD treatments [i.e., monoculture (PD 1) through four different species mixture (PD 4)]. Plant biomass was harvested after two growing seasons and analyzed for tissue carbon content. Competition values (CV) were calculated to understand how the PD treatment affected the competitive ability of plants relative to their biomass production and thus carbon storage potentials. Aboveground biomass ranged from 988 g/m2 – 1515 g/m2, being greatest in monocultures, but only when compared to the most diverse mixture (p = 0.021). However, carbon storage potential estimates per mesocosm ranged between 344 g C/m2 in the most diverse mesocosms (PD 4) to 610 g C/m2 in monoculture ones with no significant difference (p = 0.089). CV of E. obtusa and C. vulpinoidea showed a declining trend when grown in the most diverse mixtures but J. effusus and M. ringens displayed no difference across the PD gradient (p = 0.910). In monocultures, both M. ringens, and J. effusus appeared to store carbon as biomass more effectively than the other species, suggesting that the choice of plant species may play an important role in facilitating the development of carbon accumulation/storage in created wetlands. Plant community diversity provides many ecosystem services (e.g., habitat and floristic quality) other than carbon storage function. Thus, a further study is needed that will focus on investigating how other design elements such as microtopography and hydrologic connectivity may interact with PD in terms of enhancing the carbon storage potential of newly created wetlands.

Plant-Pollinator Interactions in a Northwest Arum Related to Plant Traits but not Riparian Forest Management

Abstract Studies in Pacific Northwest riparian forests highlight the role of forest management in conserving target species, but rarely consider impacts on interspecies relationships such as pollination. We investigated plant-pollinator interactions among a native species of rove beetle, Pelecomalius testaceum, and a widespread native wetland plant species in the Pacific Northwest, Lysichiton americanus (western skunk cabbage), in an experimental framework comparing three riparian forest management regimes. Our study addressed the central question: what factors best predict pollinating beetle abundance on L. americanus in a managed Northwest landscape? We measured P. testaceum abundance on skunk cabbages in three riparian treatments in a managed forest: (1) an unlogged riparian zone, (2) a logged riparian zone with a limited buffer corridor, and (3) a clear-cut riparian zone with no remaining corridor. Across this diversity of forest treatments, we also measured inflorescence temperature, foliar damage, a...

Object-based classification of Worldview-2 imagery for mapping invasive common reed, Phragmites australis

Wetlands provide many environmental and societal benefits. Unfortunately, the importance of wetlands has only recently been acknowledged after centuries of drainage and conversion to other land uses. An emerging threat to North American wetlands is the introduction of invasive plant species such as Phragmites australis, a reed introduced from Europe. Previous high spatial resolution satellite imagery used for mapping Phragmites was limited spectrally to four bands (blue, green, red, and near-infrared). A recently launched satellite, Worldview-2, has four additional spectral bands that may allow for more accurate mapping of Phragmites. In this study, a single-date Worldview-2 image was used to map wetland vegetation at Walpole Island, Canada. Object-based and per-pixel maximum likelihood classifications were performed on a four-band subset simulating traditional multispectral imagery and the full eight-band set of Worldview-2. The overall classification accuracy of 94.0% achieved for the eight-band object-based method was the highest of the four classifications methods used. The accuracy achieved by the eight-band object-based classification shows that single-date Worldview-2 image is promising for distinguishing Phragmites from native wetland plant species late in the growing season in coastal Great Lakes wetlands.

Effects of tillage and irrigation on the occurrence and establishment of native wetland plant species in fallow paddy fields

Traditional weed management, such as tillage and irrigation, has led to an enhanced maintenance of wetland plant species in fallow paddy fields. Recent herbicide usage and improvements in irrigation and drainage systems however have caused habitat loss of these species, especially in fields on open lowlands. We conducted experiments in three fallow paddy fields situated on the alluvial Echigo Plain in central Japan with an aim to restore the habitat of native wetland plant species. The three experimental fields were managed under different irrigation regimes, (1) perennially flooded with water, (2) intermittent irrigation, and (3) temporary irrigation. Half the area of each experimental field was tilled before irrigation. Detrended correspondence analysis revealed obvious floristic differences between experimental and control fields with no irrigation. The proportion of wetland plant species in the experimental fields increased corresponding to the irrigation period, ranging 60–86%, and was relatively greater than that in control fields. In the experimental fields, differences in both tillage and irrigation affected the occurrence of plant species. Tillage restricted the occurrence of many non-wetland plant species, and had a positive effect on the establishment of several annual wetland plant species. In addition, a longer duration of irrigation is not necessarily suitable for the occurrence of all wetland plant species. We concluded that fallow paddy fields provide a possible habitat for the restoration of native wetland plant species through appropriate tillage and irrigation.

Effects of Light Regime, Temperature, and Plant Age on Uptake of Arsenic by Spartina Pectinata and Carex Stricta

We report here on efforts to show that a combination of native wetland plant species might perform better than a monoculture in wetlands designed for arsenic remediation by supplementing weaknesses. Carex stricta and Spartina pectinata were used in hydroponic experiments. (i) Arsenic uptake was first assessed at two ages via exposure to control or arsenic-laden solutions (0 or 1.5 mg As L−1 as Na2HAsO4) for two weeks. Age had no significant effect on arsenic concentrations in roots, but translocation factors were greater in older plants of C. stricta and S. pectinata (0.45 and 0.07, respectively) than in younger plants (0.10 and 0.01, respectively). (ii) Seasonal effects were assessed by determining uptake kinetics for both species in conditions representative of spring temperatures (15/5°C) and light regimes (1050 μmol m−2 s−1, 13 h day−1) and summer temperatures (28/17°C) and light regimes (1300 μmol m−2 s−1, 15 h day−1). Both species had comparable rates of arsenic uptake into roots in summer conditions (44.0 and 46.5 mg As kg−1 dry wt. h−1 in C. stricta and S. pectinata, respectively), but C. stricta had a higher maximum net influx rate in spring conditions (24.5 versus 10.4 mg As kg−1 dry wt. h−1).

Do riparian plant community characteristics differ between Tamarix (L.) invaded and non-invaded sites on the upper Verde River, Arizona?

Invasion by Tamarix (L.) can severely alter riparian areas of the western U.S., which are globally rare ecosystems. The upper Verde River, Arizona, is a relatively free-flowing river and has abundant native riparian vegetation. Tamarix is present on the upper Verde but is a minor component of the vegetation (8% of stems). This study sought to determine whether riparian vegetation characteristics differed between sites where Tamarix was present and sites where Tamarix was absent during the invasion of the upper Verde. We hypothesized that herbaceous understory and woody plant communities would differ between Tamarix present and absent sites. Our hypothesis was generally confirmed, the two types of sites were different. Tamarix present sites had greater abundance of all vegetation, native understory species, graminoids, and native trees, and a positive association with perennial native wetland plant species. Tamarix absent sites had greater abundance of exotic plants and upland adapted plants and an association with greater abiotic cover and litter. These results are contrary to other reports of Tamarix association with depauperate riparian plant communities, and suggest that Tamarix invasion of a watershed with a relatively natural flow regime and a robust native plant community follows similar establishment patterns as the native riparian plant community.

Recent Land Cover History and Nutrient Retention in Riparian Wetlands

Wetland ecosystems are profoundly affected by altered nutrient and sediment loads received from anthropogenic activity in their surrounding watersheds. Our objective was to compare a gradient of agricultural and urban land cover history during the period from 1949 to 1997, with plant and soil nutrient concentrations in, and sediment deposition to, riparian wetlands in a rapidly urbanizing landscape. We observed that recent agricultural land cover was associated with increases in Nitrogen (N) and Phosphorus (P) concentrations in a native wetland plant species. Conversely, recent urban land cover appeared to alter receiving wetland environmental conditions by increasing the relative availability of P versus N, as reflected in an invasive, but not a native, plant species. In addition, increases in surface soil Fe content suggests recent inputs of terrestrial sediments associated specifically with increasing urban land cover. The observed correlation between urban land cover and riparian wetland plant tissue and surface soil nutrient concentrations and sediment deposition, suggest that urbanization specifically enhances the suitability of riparian wetland habitats for the invasive species Japanese stiltgrass [Microstegium vimenium (Trinius) A. Camus].

Ecological Assessment of Plant Succession and Water Quality in Abandoned Rice Fields

The increasing area of abandoned rice fields could provide new opportunities for wetland restoration in Asia. However, it is unknown how quickly or completely abandoned rice fields will recover from agricultural disturbances. We assessed water quality and plant community succession in abandoned rice fields with different hydrology in a mountain valley to understand the effects of hydrological regime on recovery. Water level, soil redox potential, water quality, plant composition, and primary production were measured. The sites, coded as D6, N13, and N16, had been recovering for 6, 13, and 16 years by 2006. N13 and N16 have been recovering naturally whereas D6 has been drained with a nearby dike and was tilled in 2001. The typical hydroperiods of D6, N13, and N16 were no surface water, permanently flooded, and seasonally flooded, respectively. The major change in vegetation structure of both D6 and N13 was the replacement of herbaceous species by woody species. Drawdown accelerated this change because Salix koreensis grew better in damp conditions than in flooded conditions. Phragmites japonica reduced plot-level plant species richness. The removal efficiency of <TEX>$NH_4-N$</TEX>, <TEX>$NO_3-N$</TEX>, and <TEX>$PO_4-P$</TEX> from water varied seasonally, ranging between -78.8 to 44.3%, 0 to 97.5%, and -26.0 to 44.4%, respectively. In summary, abandoned rice fields quickly became suitable habitat for native wetland plant species and improved regional water quality. Variation among our sites indicates that it is likely possible to manage abandoned rice fields, mostly through controlling hydrology, to achieve site-specific restoration goals.

Vegetative Nutrient Pools in a Constructed Wetland in Southeastern Idaho

ABSTRACT We examined the vegetative pools of carbon (C), nitrogen (N), and phosphorus (P) in constructed wetlands receiving irrigation return flows in southeastern Idaho. Seven native wetland plant species were introduced into the wetlands in 1999. Carex nebrascensis, Eleocharis palustris, Juncus balticus, and Scheonoplectus maritimus were planted in replicate wetland meadows (primary filters), and Scheonoplectus acutus, Scheonoplectus pungens, and Typha latifolia were planted in replicate experimental marshes (shallow wetlands). The elemental percentages of C, N, and P for aboveground biomass and litter varied among species, and the pattern of temporal change for each element in plant tissues was unique. At the end of the 2003 growing season, J. balitcus had more C and S. maritimus had less N and P than other species in the primary filter cells. No differences were detected in shoot N and P content among shallow wetland species, but litter from shallow wetlands had greater percentages of N and P than did standing biomass. C. nebrascensis aboveground biomass represented the largest pool of N and P (7.65 g/m2 and 0.45 g/m2). Litter nutrient pools contributed considerably to the total aboveground nutrient pool, and this was especially true for J. balticus patches where the pool for litter N (17.2 g/m2) was four times larger than the pool for biomass N (4.3 g/m2). This work suggests that larger nutrient pools were associated with areas of higher production rather than areas containing species with higher concentrations of nutrients.

Invasive Plant and Experimental Venue Affect Tadpole Performance

Introductions of non-native predators and competitors appear to contribute to worldwide amphibian declines; however, potential negative impacts of invasive plants on habitat quality and amphibian populations have not been examined. Loss of diversity and alterations in ecosystem function associated with plant invasions may disrupt food webs, potentially leading to further declines of already threatened amphibian populations. We used a combination of small bins, mesocosms, and field experiments to examine the impacts of Eurasian purple loosestrife (Lythrum salicaria) replacing native cattails (Typha latifolia) in North American freshwater wetlands on survival, developmental rate, and diet (freshwater algae) of American toad (Bufo americanus) tadpoles. Tadpoles developed slower in L. salicaria compared to tadpoles developing in T. latifolia. This effect was consistent across experimental venues, although mesocosms showed this effect only in the second year of our study. Survival and development rates were always more variable in purple loosestrife than in cattail. In bins, tadpoles showed significantly reduced survival when raised in purple loosestrife extract and addition of leaf litter exacerbated this negative effect. Tadpole survival rates in mesocosms and field cages were not significantly different between plant species, most likely an effect of high variability among replicates. We suspect a combination of direct toxicity of high tannin concentrations in L. salicaria leaves and their indirect negative impacts on aquatic food webs are responsible for these results. Tadpole gut analyses revealed differences in algal communities among venues and between L. salicaria and T. latifolia suggesting that alterations in tadpole food quality and quantity contribute to the observed reduced tadpole performance. The replacement of native wetland plant species by L. salicaria does not represent a simple exchange of ecological equivalents and the function of invaded habitats for native species has clearly changed. While we were investigating only a single amphibian species, our results suggest that the impact of L. salicaria on ecosystem processes and aquatic food webs may be more general and likely to negatively affect other wetland species. The threats non-indigenous plants represent for amphibian populations and food webs may be underestimated, and warrant further investigation.

Competitive effect versus competitive response of invasive and native wetland plant species.

Non-native plants can have adverse effects on ecosystem structure and processes by invading and out-competing native plants. I examined the hypothesis that mature plants of non-native and native species exert differential effects on the growth of conspecific and heterospecific seedlings by testing predictions that (1) invasive vegetation has a stronger suppressive effect on seedlings than does native vegetation, (2) seedlings of invasive species are better able to grow in established vegetation than are native seedlings, and (3) invasive species facilitate conspecific and inhibit heterospecific seedling growth. I measured growth rates and interaction intensities for seedlings of four species that were transplanted into five wetland monoculture types: invasive Lythrum salicaria; native L. alatum, Typha angustifolia, T. latifolia; unvegetated control. Invasive L. salicaria had the strongest suppressive effect on actual and per-individual bases, but not on a per-gram basis. Seedlings of T. latifolia were better able to grow in established vegetation than were those of L. salicaria and T. angustifolia. These results suggest that L. salicaria is not a good invader of established vegetation, but once established, it is fairly resistant to invasion. Thus, it is likely that disturbance of established vegetation facilitates invasion by L. salicaria, allowing it to compete with other species in even-aged stands where its high growth rate and consequent production of aboveground biomass confer a competitive advantage.

Constructed Wetlands for River Water Quality Improvement

The Des Plaines River Wetlands Demonstration Project has reconstructed four wetlands in Wadsworth, Illinois, USA. The river drains an agricultural and urban watershed, and carries a non-point source contaminant load of sediment, nutrients and agricultural chemicals. Up to 40% of the average stream flow is pumped to the wetlands, and allowed to return from the wetlands to the river through control structures followed by vegetated channels. Native wetland plant species have been established, ranging from cattail, bulrushes, water lilies, and arrowhead to duckweed and algae. Pumping began in the summer of 1989, and has continued during the ensuing spring, summer and fall periods. The experimental design provides for different hydraulic loading rates, ranging from 5 to 60 cm/week. Intensive wetland research began in late summer 1989, and continues to present. Detailed hydrology is measured for each wetland. Sediment removal efficiencies ranged from 86–100% for the four cells during summer, and from 38–95% during winter. Phosphorus removal efficiencies ranged from 60–100% in summer and 27–100% in winter. The river contains both old, persistent and modem, degradable agricultural chemicals. The principal modem pollutant is atrazine, of which the wetlands remove approximately half. The project is successfully illustrating the potential of constructed wetlands for controlling non-point source pollution at an intermediate position in the watershed.

Freshwater wetland vegetation of Viti Levu, Fiji

Abstract The wetlands of Viti Levu, Fiji occur on Recent alluvium in the high rainfall regions of the island. Most of the wetlands formed after the sea reached its present level, and they have probably been affected by man through most of this time. It is suggested that the peat bogs developed as a result of forest clearance in areas of impeded drainage. The wetlands are classified into peat, colluvium- peat, gley soils, and brackish soils, ~nd the vegetation is described for each of the major wetlands and substrate types. Most of the native wetland plant species also occur in dryland habitats. The majority of the plant species are recent introductions. The dispersal of Sphagnum cuspidatum. Metroxylon vitiense, and Eleocharis dulcis is discussed.