Effects of Moisture, Temperature, and Time on Seed Germination of Five Wetland Carices: Implications for Restoration

Successful restoration of sedge meadow wetlands is limited by lack of information regarding reintroduction of sedge (Carex) propagules. While restoration from seed is common for prairie restorations, little is known about the germination characteristics of many wetland plants, including sedges. We present the results of a 2.5-year study on seed germination and viability for five species of Carex common to sedge meadow and prairie pothole wetlands in temperate North America. Seed storage and germination conditions were investigated to determine the optimum combination for maintaining seed viability and stimulating germination rates over time. Seeds were germinated under seven different temperature and three moisture regimes after storage for 4, 10, and 14 months under one of four different storage regimes (dry-warm, dry-cold, moist-cold, and wet-cold). The efficacy of short-term wet-cold stratification to stimulate germination of 2.5-year-old seed after long-term dry storage was also investigated. Carex stricta, Carex comosa, and Carex lacustris showed the greatest germination response after wet-cold or moist-cold storage, while Carex lasiocarpa and Carex rostrata showed similar rates of germination after either wet-cold or dry-warm storage. Wet-cold long-term storage was associated with a high level of viability in all five species after 2.5 years. Viability and germination rates were reduced in Carex stricta, Carex comosa, and Carex lasiocarpa after long-term dry-cold storage. Germination rates of seeds stored dry for 2.5 years are not improved by short-term wet-cold treatment in any species tested. Carex seeds should be stored under wet-cold conditions to maintain seed viability over time, thus increasing the likelihood of seeding success for sedge meadow restoration.     

Restoring prairie pothole wetlands: does the species pool concept offer decision‐making guidance for re‐vegetation?

Question: Do regional species pools, landscape isolation or on‐site constraints cause plants from different guilds to vary in their ability to colonize restored wetlands? Location: Iowa, Minnesota, and South Dakota, USA. Methods: Floristic surveys of 41 restored wetlands were made three and 12 years after reflooding to determine changes in local species pools for eight plant guilds. The effect of landscape isolation on colonization efficiency was evaluated for each guild by plotting local species pools against distance to nearby natural wetlands, and the relative importance of dispersal vs. on‐site constraints in limiting colonization was explored by comparing the local species pools of restored and natural wetlands within the region. Results: Of the 517 wetland plant taxa occurring in the region, 50% have established within 12 years. The proportion of the regional species pool represented in local species pools differed among guilds, with sedge‐meadow perennials, emergent perennials and floating/submersed aquatics least represented (33‐36%) and annual guilds most represented (74‐94%). Colonization‐to‐extinction ratios suggest that floating/submersed aquatics have already reached a species equilibrium while sedge‐meadow and emergent perennials are still accumulating species. Increasing distance to nearest wetlands decreased the proportion of the regional species pool present in local pools for all guilds except native annuals and woody plants. The maximum proportion predicted, assuming no distance constraint, was comparable to the lowest‐diversity natural wetlands for most perennial guilds, and also lower than what was achieved in a planted, weeded restoration. Conclusions: A biotic constraints seem to limit the colonization of floating/submersed aquatics into natural or restored wetlands, whereas all other guilds are potentially constrained by dispersal or biotic factors (i.e. competition from invasive species). Using species pools to evaluate restoration progress revealed that immigration potential varies considerably among guilds, that local species richness does not necessarily correspond to immigration limitations, and that some guilds (e.g. sedge‐meadow perennials) will likely benefit more than others from being planted at restoration sites.     

A Test of Two Annual Cover Crops for Controlling Phalaris arundinacea Invasion in Restored Sedge Meadow Wetlands

Abstract Rapid establishment by aggressive plants such as Phalaris arundinacea (reed canarygrass) often interferes with sedge meadow establishment in restored prairie pothole wetlands in the mid‐continental United States. Introducing a cover crop during community establishment might suppress P. arundinacea invasion in restored prairie potholes by reducing resource availability. We evaluated two potential cover crops, Echinochloa crusgalli (barnyardgrass) and Polygonum lapathifolium (nodding smartweed), for suppressing P. arundinacea invasion in an experimental wetland using replacement series competition experiments. Further, we assessed the effects of E. crusgalli and P. lapathifolium on sedge meadow establishment by sowing Carex hystericina, a common wetland sedge, as a third species at a constant density in the replacement experiments. Echinochloa crusgalli, compared with no cover crop, reduced P. arundinacea biomass by more than 1,000 g/m² (65%) after two growing seasons. Polygonum lapathifolium did not affect P. arundinacea biomass. Dense E. crusgalli canopies in the first year and thick E. crusgalli thatch in the second year substantially reduced light availability for P. arundinacea establishment. Echinochloa crusgalli also reduced C. hystericina biomass by more than 1,800 g/m² (99%) after two growing seasons. Carex hystericina biomass was similar in plots sown with E. crusgalli to P. arundinacea monocultures. Neither E. crusgalli nor P. lapathifolium is likely to improve sedge meadow restoration success. These trends were not sensitive to initial sowing density or elevation above water level. Without methods to suppress P. arundinacea invasions, sedge meadow restorations may often fail. Thorough site preparation to remove P. arundinacea propagule sources before restoration is essential.     

Evaluating the realized niche and plant–water relations of wetland species using experimental transplants

Wet meadows are a common focus of wetland restoration efforts, and the species within them often exist within a restricted range of water levels. Unfortunately, many restored wetlands have higher water levels and more open water than naturally occurring reference wetlands, and many are invaded and dominated by species of Typha. Most studies evaluating the optimal water level for plant species use observational methods, yet experimental methods are required to understand the breadth of a species’ niche. We used experimental transplants of Carex pellita, a common wet meadow sedge used in restoration in the interior of the USA, and Typha latifolia, a species of cattail which invades many restored wetlands, to test whether higher water levels in a restored wetland were prohibitive to the target sedge species. Physiological and growth measurements were collected on both species. We found that C. pellita grew as well or better when transplanted into the ponded water levels, while T. latifolia had reduced growth when transplanted into the relatively drier meadow conditions. Interestingly, C. pellita was able to adjust its Turgor Loss Point in response to changing water levels. Only recently the assumption of a constant Turgor Loss Point for each species has been questioned. Our results provide evidence that wet meadow species have a broader hydrologic niche than previously thought, and their ability to make physiological adjustments in response to changing water levels may allow them to thrive in areas with widely varying water levels.

     

Vegetation trajectories of restored agricultural wetlands following sediment removal

Recognition of wetland ecosystem services has led to substantial investment in wetland restoration in recent decades. Wetland restorations can be designed to meet numerous goals, among which reestablishing a diverse native wetland plant community is a common aim. In agricultural areas, where previously drained wetland basins can fill with eroded sediment from the surrounding landscape, restoration often includes excavation to expose buried seed banks. The extent to which excavation improves the diversity of wetland plant communities is unclear, particularly in terms of longer‐term outcomes. We examined plant species diversity and community composition in 24 restored agricultural wetlands across west‐central Minnesota, U.S.A. In all study wetlands, hydrology was restored by removing subsurface drainage and plugging drainage ditches, thus reestablishing groundwater connectivity and hydroperiod (“business as usual” treatment). In half of the wetlands, accumulated sediment was removed from the basin and redeposited on the surrounding landscape (“excavated” treatment). Initially, sediment removal significantly decreased invasive species cover, particularly of hybrid cattail (Typha × glauca) and reed canary grass (Phalaris arundinacea), and increased community diversity and evenness. Over time, the effects of sediment removal diminished, and eventually disappeared by approximately 6 years after restoration. While our results demonstrate that sediment removal improves initial restoration outcomes for plant communities, longer‐term benefits require sustained management, such as invasive species control or resetting of basins through additional excavation.     

Nonequilibrium dynamics of sedge meadows grazed by cattle in southern Wisconsin

Equilibrium theory predicts that after disturbance, ecosystemseventually regain the structural and functional properties characteristic oftheir predisturbance condition. This study tested this idea by examining theeffects of cattle grazing and exclusion on the long-term structuralcharacteristics of sedge meadows in southern Wisconsin. To compare structuralchanges in mean percentage cover and height, repeated measures analysis wasconducted on two sedge meadows over a twenty year period from 1977 to 1997. Onesedge meadow was recovering from cattle grazing (cattle excluded in 1973) andthe other was a reference area (nearly undisturbed). Both of these study siteschanged structurally from 1977 to 1997, supporting non-equilibrium theory.Additional observations were made in a heavily and lightly grazed sedge meadowthat were surveyed in 1977. As based on the positions of subunits in anordination graph produced using Non-Metric Multidimensional Scaling (NMS), therecovery sedge meadow became less structurally similar to the grazed and moresimilar to the reference site over the 20 year study. However, from theperspective of mean maximum height in another NMS analysis, the recovery sedgemeadow became less similar to the reference site over time likely because by1997, a shrub carr of Cornus sericea had developed in therecovery sedge meadow that had been dominated by graminoids and forbs in 1977(mean maximum height: 1977 vs. 1997; 0 vs. 47 cm). Seedlings ofCornus sericea were invading the grazed sedge meadows andin the recovery sedge meadow (cattle excluded 4 years earlier) in 1977. A shrubcarr did not develop in the reference sedge meadow. Changes in the referencesite were relatively minor over this time interval; certain species eitherincreased or decreased in dominance, e.g., Carex strictaincreased in cover (1977 vs. 1997, 20 and 28 mean percentage (%) cover,respectively). A few short-term species of the recovery sedge meadow followedthe tenets of equilibrium theory. These became less common or disappeared4–9 years after cattle exclusion including Asterlanceolatus, Calamagrostis canadensis,Poa compressa, Solidago altissima andVerbena hastata. Some of these species were eaten andlikely spread by the cattle. This study suggests that the progression of sedgemeadow to shrub carr may not be an inevitable outcome of succession but insteadcan be a consequence of past cattle grazing history. Also, because the recoveryand the reference sedge both changed structurally over time, the tenets ofnon-equilibrium theory were supported by this study.     

Establishment of Carex stricta Lam. seedlings in experimental wetlands with implications for restoration

The loss of Carex dominated meadows due to agricultural drainage in the previously glaciated midcontinent of North America has been extensive. The lack of natural Carex recruitment in wetland restorations and the failures of revegetation attempts underscore the need for information on the establishment requirements of wetland sedges. In this study, seedlings of Carex stricta Lam. were planted in three experimental wetlands in east-central Minnesota, USA to investigate the biotic and abiotic environmental limitations to establishment. Seedlings were planted along an elevational water depth gradient to assess the effects of water depth and water level fluctuation on seedling survival and growth. A different water level fluctuation regime was assigned to each of the experimental wetlands to assess seedling tolerance for seasonal water level changes. The effects of seedling planting density and the presence or absence of non-sedge colonizers on seedling survival and growth were also studied. The experiment was followed for three growing seasons. The results of this study indicate that C. stricta seedlings were sensitive to the timing and duration of inundation during the first growing season. Once established, plants tolerated a broad range of seasonal drying and flooding conditions. Seedling and juvenile growth was slowed by non-sedge colonizers during the first two growing seasons, but by the third growing season, C. stricta was able to out-grow all annual and perennial weeds, except the aggressive perennial, Phalaris arundinacea L. The rapid growth of C. stricta plants, once established, indicates that the use of seedlings is a successful method for (re) introducing this tussock sedge into wetland restorations under a variety of environmental conditions. Comparison with other studies performed under similar conditions suggests that planting of seedlings is a more appropriate method of establishing this species than the use of transplanted rhizomes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Fathead Minnow Colonization and Removal on a Prairie Wetland Ecosystem

Fish communities in prairie wetlands are extremely dynamic. Due to complete winterkills and periodic colonization, individual basins alternate between supporting a fish population and being fishless. Here we assess the ecological consequences of colonization and subsequent extinction of a fathead minnow population in a prairie wetland. We used a BACI-type approach (before-after control impact) in which data from the colonized wetland were paired with data from a similar fishless site first when both wetlands were fishless (1996), then when the minnow population reached moderate densities in the colonized site (1998), and then again when the colonized site became fishless after treatment with rotenone (1999). Fish colonization resulted in significant increases in turbidity, total phosphorus, and chlorophyll a in the water column; it also caused significant decreases in the abundance of aquatic insects and large cladocerans. Elimination of the minnow population largely reversed the effects of minnow colonization. Our results indicate that characteristics of prairie wetlands can vary as they alternate between supporting fathead minnow populations and being fishless and that ecological characteristics may change rapidly in response to minnow colonization or elimination. Received 18 July 2000; Accepted 17 January 2001.     

水陆生境和氮沉降对香菇草(Hydrocotyle vulgaris)入侵湿地植物群落的影响

大气氮沉降对湿地外来植物入侵的影响已成为生态学研究的热点之一。选用梭鱼草(Pontederia cordata)、水菖蒲(Acorus calamus)、黄花鸢尾(Iris wilsonii)和粉绿狐尾藻(Myriophyllum aquaticum)模拟湿地植物群落,设置有无香菇草入侵、水生和陆生生境(水位分别为15 cm和0 cm)及有无氮沉降处理(15 g N m~(-2)a(-1)和0)交叉组成的8种处理组合,进行为期70d的温室控制实验,以分析水陆生境及氮沉降对香菇草入侵湿地植物群落的影响。结果表明:(1)水生生境下,香菇草的总生物量、叶生物量、叶片数和节点数与陆生生境相比显著降低;水生生境下氮沉降处理对香菇草各指标无显著影响,陆生生境下氮沉降处理的香菇草叶片数、节点数显著多于无氮沉降处理。(2)实验周期内氮沉降和香菇草入侵没有对群落的多样性指数及群落内4种湿地植物的生物量产生显著影响;水生生境下植物群落的总生物量及梭鱼草和粉绿狐尾藻的生物量与陆生生境相比显著提高。(3)水生生境下香菇草的相对优势度相比陆生生境下显著下降;氮沉降只在陆生生境下显著提高了香菇草的相对优势度。因此,香菇草向水生生境扩散和入侵的能力不强,其入侵在短时间内对湿地植物群落影响较小。研究结果可以为入侵植物生态学研究提供案例借鉴。     

Winter Burning and the Reduction of Cornus sericea in Sedge Meadows in Southern Wisconsin

To control shrubs, which are increasing in dominance in wetlands worldwide, winter burning may be an important tool, especially from the perspective of minimizing urban hazards. The goal of this project was to determine if winter burning was successful in reducing the dominance (mean percentage cover and maximum height) of Cornus sericea in sedge meadows in southern Wisconsin, where shrubs proliferated after cattle were excluded. Experimental burn and control plots were set up within sedge meadows, including an ungrazed “reference” site that had been little, if ever, grazed and a “historically grazed” site, a recovery site that had not been grazed by cattle since 1973. None of the dominant species including C. sericea was significantly affected by burning for either mean percentage cover or maximum height (analysis of variance: no burning × species interaction). Both mean percentage cover and maximum height were only weakly related to burning (28.1 and 14.3% of the variability contributed to the cumulative percentage of the coefficient of determination, respectively) at both sites based on non‐metric multidimensional scaling analysis. Although species richness increased in burned plots in 1999 and 2000, no differences were apparent between pre‐burned and unburned plots in 1997 and unburned plots in 1999 and 2000 (analysis of variance: year × burning interaction). After burning in the ungrazed site, herbaceous species appeared that had not been detected for decades, including Chelone glabra and Lathyrus palustris. Exotic species were present in both the ungrazed reference and recovery site. Although winter burning treatments did not reduce the dominance of woody shrub species in the site recovering from cattle grazing, burning was useful in stimulating the maintenance of species richness in the ungrazed sedge meadow.     

Altering Light and Soil N to Limit Phalaris arundinacea Reinvasion in Sedge Meadow Restorations

Efforts to eradicate invasive plants in restorations can unintentionally create conditions that favor reinvasion over the establishment of desired species, especially when remnant invasive propagules persist. Reducing resources needed by the invader for seedling establishment, however, may be an effective strategy to prevent reinvasion. Propagules of Phalaris arundinacea persist after removal from sedge meadow wetlands and reestablish quickly in posteradication conditions, hindering community restoration. A study was conducted in two experimental wetlands with controlled hydrologic regimes to determine if reducing light by sowing short‐lived, nonpersistent native cover crops or immobilizing soil N by incorporating soil–sawdust amendments can prevent Phalaris reinvasion, allowing native communities to recover. A 10‐species perennial target community and Phalaris were sown with high‐diversity, low‐diversity, or no cover crops in soils with or without sawdust, and seedling emergence, establishment, and growth were measured. High‐diversity cover crops reduced light, decreasing Phalaris and target community seedling establishment by 89 and 57%, respectively. Short‐term nitrogen reduction in sawdust‐amended soils delayed Phalaris seedling emergence and decreased Phalaris seedling establishment by 59% but did not affect total target community seedling establishment. The target community reduced Phalaris seedling establishment as effectively as cover crops did. In plots where the target community was grown, amending soils with sawdust further reduced Phalaris seedling growth but not establishment. Results show that use of cover crops can reduce seedling establishment of desired species and is counterproductive to restoration goals. Further, establishing target species is more important and practical for limiting Phalaris reinvasion than is immobilizing nitrogen.     

Wetland hydrologic class change from prior to European settlement to present on the Des Moines Lobe, Iowa

It has been hypothesized that wetland restoration policies have favored the restoration of the wettest classes of wetlands on the Des Moines Lobe of the prairie pothole region. To test this hypothesis we compared pre-drainage wetland distributions based on soils data and National Wetland Inventory (NWI) estimates of contemporary wetland distributions on the Des Moines Lobe. Based on the NWI data, the Des Moines Lobe today has only 3–4% of the wetland area that it had prior to the onset of drainage. On the basis of their soils, pre-drainage wetlands were predominantly temporarily flooded to saturated wetlands (84%), with only about 6% of the wetlands with water regimes classified as semi-permanently to permanently flooded. Depending on the interpretation of wetland modifiers on NWI maps, wetlands classified by the NWI as semi-permanent to permanently flooded make up more than 41% of the wetland area while wetlands with temporarily flooded to saturated water regimes account for 45–58% of the Lobe’s wetland area. The water regimes of contemporary wetlands when compared to their historic regimes suggest that many of today’s wetlands have different water regimes than they did prior to the onset of drainage. Because of the regional lowering of the groundwater table, many of today’s wetlands have drier water regimes, but some have wetter water regimes because they receive drainage tile inputs. Our results indicate that restoration has favored the wettest classes of wetlands and that temporarily to saturated wetland classes have not been restored in proportion to their relative abundance in the pre-drainage landscape.     

Set‐backs in Replacing Phalaris arundinacea Monotypes with Sedge Meadow Vegetation

Reed canary grass (Phalaris arundinacea) invades wetlands, forms monotypes, and resists control efforts, suggesting that strong feedbacks sustain its dominance, as in the alternative states model. In nine field experiments, we tested the hypothesis that applying a graminicide (sethoxydim) for three years would progressively reduce Phalaris abundance, and that seeding sedge meadow species (except grasses) would reestablish native plant dominance. The graminicide prevented Phalaris from flowering, reduced its height by 50% and reduced its cover, often to less than 40%. However, only two of the nine sites showed progressive declines over the three‐year experiment. The first setback was that Phalaris recovered annually in nearly all treatment plots. A second setback was that seeding did not reestablish sedge meadow. In five sites, unseeded plots had similar numbers of native species as those seeded with either forbs, forbs and graminoids, or graminoids. In four formerly agricultural sites, however, non‐native weeds increased in species richness and cover (a third setback). In only one site did the graminicide's effect on Phalaris allow native species to increase in number and cover. But short‐term gains were not long‐lasting. In year four, three sites that developed high native‐species cover were again strongly dominated by Phalaris (a fourth setback). The feedbacks that sustain this invader include resistance to the graminicide aboveground and rapid and robust regrowth from rhizomes and seeds belowground. The weak effect of this graminicide was a surprise; hence, we recommend stronger management actions to control Phalaris.     

Grazing effects of Black Swans <Emphasis Type="Italic">Cygnus atratus</Emphasis> (Latham) on a seasonally flooded coastal wetland of eastern Australia

Little is known about the effects of grazing by birds on seasonally flooded Australian wetlands. Grazing by Black Swans Cygnus atratus (Latham) has an obvious visual impact in Little Broadwater, an ecologically important wetland on the Clarence River floodplain on the east coast of Australia. We measured the impact of grazing by swans in this wetland from March to September 2007 by comparing the structure and biomass of marsh vegetation (emergent and submerged macrophytes) in sites from which swans had been excluded and sites to which they had access. In grazed sites, after 135 days, the mean above-sediment biomass of the dominant sedge Eleocharis equisetina C. Presl was 52% less than in ungrazed sites. This difference was mostly because of the loss of leaf biomass above the waterline in grazed sites where biomass had been reduced by 99% compared with ungrazed sites. This created more habitat for other birds such as wading birds (e.g., Royal Spoonbills Platalea regia Gould) and dabbling ducks (e.g., Grey Teal Anas gracilis Buller). Where water levels can be artificially manipulated, local wetland managers could attempt to restore the flood pulse to wetlands that are large enough to sustain Black Swan populations to retain a variety of other waterbirds that require open water.     

Hyperspectral Analysis of Columbia Spotted Frog Habitat

Abstract: Wildlife managers increasingly are using remotely sensed imagery to improve habitat delineations and sampling strategies. Advances in remote sensing technology, such as hyperspectral imagery, provide more information than previously was available with multispectral sensors. We evaluated accuracy of high-resolution hyperspectral image classifications to identify wetlands and wetland habitat features important for Columbia spotted frogs (Rana luteiventris) and compared the results to multispectral image classification and United States Geological Survey topographic maps. The study area spanned 3 lake basins in the Salmon River Mountains, Idaho, USA. Hyperspectral data were collected with an airborne sensor on 30 June 2002 and on 8 July 2006. A 12-year comprehensive ground survey of the study area for Columbia spotted frog reproduction served as validation for image classifications. Hyperspectral image classification accuracy of wetlands was high, with a producer's accuracy of 96% (44 wetlands) correctly classified with the 2002 data and 89% (41 wetlands) correctly classified with the 2006 data. We applied habitat-based rules to delineate breeding habitat from other wetlands, and successfully predicted 74% (14 wetlands) of known breeding wetlands for the Columbia spotted frog. Emergent sedge microhabitat classification showed promise for directly predicting Columbia spotted frog egg mass locations within a wetland by correctly identifying 72% (23 of 32) of known locations. Our study indicates hyperspectral imagery can be an effective tool for mapping spotted frog breeding habitat in the selected mountain basins. We conclude that this technique has potential for improving site selection for inventory and monitoring programs conducted across similar wetland habitat and can be a useful tool for delineating wildlife habitats.     

Is hydrological manipulation an effective management tool for rehabilitating chronically flooded,brackish‐water wetlands?

1. Reinstating more natural water regimes is often a priority intervention to rehabilitate wetlands that have been degraded through anthropogenic changes to their natural wetting and drying cycles. Hydrological interventions are often made in chronically desiccated wetlands but less commonly in wetlands that have been permanently inundated and that require a drawdown phase for rehabilitation. Reports on the effectiveness of reinstating a drawdown phase in chronically inundated wetlands are particularly rare. 2. We undertook a landscape‐scale, experimental drawdown of water levels at Dowd Morass, a large, Ramsar‐listed, brackish‐water wetland in south‐eastern Australia that had been artificially flooded for 30+ years. During the hydrological manipulation, c. 500 ha of the wetland was drawn down and re‐flooded, and the remaining c. 1000 ha was used as a control site. Fringing areas with a fluctuating water regime were used as a reference site. Results were analysed in terms of gradient analysis, by classifying the different water regimes created by the hydrological interventions. The response of wetland vegetation was measured along replicated transects over a 4‐year period, before, during and after drawdown. Wetland plants were assigned to plant functional groups for analysis. Assembly theory and knowledge of life‐history traits were used to predict that drawdown would promote recruitment of plant species that required exposed sediment for germination and seedling establishment. 3. Within‐wetland microtopography interacted with the hydrological interventions to generate three distinct water regimes, which were differentiated by the spatial extent of exposed sediment and duration of the dry period. Drawdown promoted limited recruitment of some plant species, and the survival of cohorts then depended strongly on the extent and duration of the dry period. Species richness and vegetation cover (understorey and overstorey) continued to decline in constantly flooded areas of the wetland. Increased salinisation of sediments and surface waters reduced the effectiveness of the drawdown and dramatically affected species richness and cover of aquatic vegetation, which did not recover fully when fresher conditions returned. 4. The capacity of vegetation to respond to the reinstatement of a drawdown cycle following chronic inundation was constrained by abiotic (e.g. salinity) and biotic (e.g. depauperate seedbanks) factors. Reinstating a dry phase in chronically inundated, brackish‐water wetlands is complex and risky and may not effectively improve vegetation condition in the short term. In the case of Dowd Morass, rehabilitation was most successful in sites that had been shallowly flooded prior to drawdown and that remained dry for longest.     

Conserving a wetland butterfly: quantifying early lifestage survival through seasonal flooding, adult nectar, and habitat preference

Conservation of once thought extinct populations of Lycaena xanthoides in western Oregon will require specific information of how the butterfly interacts with its now rare wetland habitat. Three experiments were conducted to yield information directly applicable to wetland restoration work: (1) to quantify the survival of L. xanthoides eggs laid on inundated plants, (2) to quantify adult nectar preferences, (3) to investigate the role of adult resources and how butterflies assess habitat quality. Survival of eggs laid on inundated plants was nearly seven times lower than the survival of eggs laid on uninundated plants, indicating that eggs laid on plants that are seasonally flooded are a population sink. Adult L. xanthoides preferred an endemic native nectar plant, Grindelia integrifolia × nana, as an adult resource and used it approximately 88% of the time while other butterfly species preferred to nectar on the non-native Mentha pulegium. Adult L. xanthoides had a significantly greater short-term recapture rate in two restored study sites that had a high relative amount of Grindelia integrifolia × nana compared to a degraded site that lacked the preferred nectar source. Based on the results from the three small experiments, restoration of wetlands for L. xanthoides should concentrate plantings of host plant in non-flooded areas and propagate conspicuous patches of the preferred nectar plant.     

Holcus lanatus invasion slows decomposition through its interaction with a macroinvertebrate detritivore, Porcellio scaber

Detritus based food webs may mediate the impacts of invasive species on ecosystem processes. Holcus lanatus (L.) is an invasive perennial grass that is rapidly spreading in the coastal prairie of California. We used litterbags to determine if H. lanatus altered the rate of litter decomposition through its interaction with the dominant macroinvertebrate detritivore at our study site, the isopod Porcellio scaber (Latreille). Over the course of a year, H. lanatus litter loss was 15% less than annual grasses, a difference that was directly attributable to P. scaber. Although there was no effect of isopods on litter loss during the winter, when most decomposition occurred, isopods had substantial effects on litter loss of annual grasses during the summer. P. scaber had no effect on litter loss of H. lanatus litter. Our findings suggest that H. lanatus invasion slows decomposition in the coastal prairie because it is unusually refractory to an important detritivore. The decreased decomposition of H. lanatus litter, along with increased production during the growing season, lead to a doubling of the end-of-season litter biomass where H. lanatus had invaded.     

Factors Affecting Revegetation of Carex lacustris and Carex stricta from Rhizomes

The revegetation of sedge meadows has been problematic because natural recolonization does not occur under many circumstances and because planted propagules often fail to reestablish successfully. In this study, detached rhizomes of Carex lacustris Willd. and Carex stricta Lam. were transplanted in both fall (September) and spring (May) into three experimental wetlands to determine the effects of both planting season and hydrology on survival and establishment. Each experimental wetland had the same mean water depth across 5% slopes, but one had a constant water depth (0.5 m) throughout the growing season, another fell from a mean depth of 0.75 m to 0.25 m, and a third rose from a mean depth of 0.25 m to 0.75 m. Initial rhizome survival, shoot growth, and soil characteristics were recorded over 2 years. Neither planting proved successful (6.9% versus 0.5%) for C. stricta, a tussock-forming sedge. For C. lacustris, a sedge with spreading rhizomes, spring planting had greater rhizome survival (53.2% survival) than fall planting (0.7%). Since both species initiate new shoots in the fall, they are susceptible to transplant failure during this season. The highest survival rates (71–100%) and plant production (736.0 and 494.5 g/m²) for C. lacustris occurred near the water’s edge in both the constant and falling basins. In the rising basin, establishment and growth of this species was high at all water depths (71–96%; 399 g/m²). C. lacustris grew optimally at the same elevations where rhizome survival was greatest, suggesting that shoots are more sensitive to early-season than late-season water levels.     

Comparison of created and natural freshwater emergent wetlands in Connecticut (USA)

Five three- to four-year old created palustrine/emergent wetland sites were compared with five nearby natural wetlands of comparable size and type. Hydrologic, soil and vegetation data were compiled over a nearly two-year period (1988-90). Created sites, which were located along major highways, exhibited more open water, greater water depth, and greater fluctuation in water depth than natural wetlands. Typical wetland soils exhibiting mottling and organic accumulation were wanting in created sites as compared with natural sites. Typha latifolia (common cattail) was the characteristic emergent vegetation at created sites, whereas a more diverse mosaic of emergent wetland species was often associated with Typha at the natural sites. Species richness was slightly higher in created (22–45) vs. natural (20–39) wetlands, but the mean difference (33 vs. 30) was not significant. Nearly half (44%) of the 54 wetland taxa found at the various study sites were more frequently recorded at created than natural wetlands. The presence of mycorrhizae in roots of Typha angustifolia (narrow-leaved cattail) and Phragmites australis (common reed) was greater at created than natural wetlands, which may be related to differential nutrient availability. Wildlife use at all sites ranged from occasional to rare, with more sightings of different species in the natural (39) than created (29) wetlands. The presence of P. australis and introduced Lythrum salicaria (purple loosestrife) may pose a threat to future species richness at the created sites. One created site has permanent flow-through hydrology, and its vegetation and wildlife somewhat mimic a natural wetland; however, the presence of P. australis and its potential spread pose an uncertain future for this site. This study suggests the possibility of creating small palustrine/emergent wetlands having certain functions associated with natural wetlands, such as flood water storage, sediment accretion and wildlife habitat. It is premature to evaluate fully the outcome of these wetland creation efforts. A decade or more is needed, emphasizing the importance of long term monitoring and the need to establish demonstration areas.