Secretive marsh bird habitat relationships at mid-continent spring migration stopover sites

Despite several secretive marsh bird (SMB) species being listed as critically imperiled throughout the mid-continent of North America, limited information on SMB distribution and habitat use within primary migratory corridors results in uncertainty on contributions of wetlands in mid-latitude states toward their annual cycle needs. Our objectives were to quantify temporal patterns of SMB wetland occupancy during spring migration at a mid-latitude state and evaluate the relationships between SMB colonization probability and water-level management practices, and the resulting habitat conditions during spring migration. We conducted a 2-year, dynamic occupancy study (2013–2014) that included 6 rounds of repeated call-back surveys to detect the presence of 5 SMB species (i.e., Virginia rail [Rallus limicola], sora [Porzana carolina], king rail [R. elegans], least bittern [Ixobrychus exilis], and American bittern [Botaurus lentiginosus]) during spring (Apr–Jun) on 107 wetlands across 8 conservation areas and 4 national wildlife refuges throughout Missouri, USA. We detected sora most frequently, followed by least bittern, American bittern, Virginia rail, and king rail. Coefficient estimates indicated colonization probability for all species was positively associated with emergent vegetation cover and negatively associated with amount of open water. Open water was the only variable in the best supported model explaining American bittern site colonization, to which they were negatively associated. Virginia rail colonization had a strong positive association with vegetation height, whereas least bittern and sora site colonization were influenced positively by water depth and agriculture, respectively. Based on the habitat associations within and among SMB species identified in this study, wetland managers can tailor management strategies to optimize spring migration habitat for single- or multi-species objectives.     

Distribution and Habitat Use of King Rails in the Illinois and Upper Mississippi River Valleys

ABSTRACT The migratory population of the king rail (Rallus elegans) has declined dramatically during the past 40 years, emphasizing the need to identify habitat requirements of this species to help guide conservation efforts. To assess distribution and habitat use of king rails along the Illinois and Upper Mississippi valleys, USA, we conducted repeated call-broadcast surveys at 83 locations in 2006 and 114 locations in 2007 distributed among 21 study sites. We detected king rails at 12 survey locations in 2006 and 14 locations in 2007, illustrating the limited distribution of king rails in this region. We found king rails concentrated at Clarence Cannon National Wildlife Refuge, an adjacent private Wetlands Reserve program site, and B. K. Leach Conservation Area, which were located in the Mississippi River floodplain in northeast Missouri. Using Program PRESENCE, we estimated detection probabilities and built models to identify habitat covariates that were important in king rail site occupancy. Habitat covariates included percentage of cover by tall (>1 m) and short (>1 m) emergent vegetation, percentage of cover of woody vegetation, and interspersion of water and vegetation (2007 only) within 50 m of the survey location. Detection probability was 0.43 (SE = 0.12) in 2006 and 0.35 (SE = 0.03) in 2007 and was influenced by observer identity and percentage of cover by tall herbaceous vegetation. Site occupancy was 0.11 (SE = 0.04) in 2006 and 0.14 (SE = 0.04) in 2007 and was negatively influenced most by percentage of cover by woody vegetation. In addition, we found that interspersion of vegetation and water was positively related to occupancy in 2007. Thus, nesting king rails used wetlands that were characterized by high water-vegetation interspersion and little or no cover by woody vegetation. Our results suggest that biologists can improve king rail habitat by implementing management techniques that reduce woody cover and increase vegetation-water interspersion in wetlands.     

Coastal wetland restoration improves habitat for juvenile sportfish in Tampa Bay,Florida, U.S.A.

Increasing human populations and urban development have led to losses of estuarine habitats for fish and wildlife. Where resource managers are restoring coastal wetlands, in addition to meeting goals related to hydrologic connectivity, biodiversity, and recreational opportunities, efforts are being made to provide habitat that is suitable for juvenile sportfish. An 18‐month study was conducted to compare juvenile sportfish use of natural, restored, and impacted sites along Tampa Bay, Florida, shorelines. Juvenile sportfish densities at restored sites were broadly comparable to natural sites and greater than at impacted sites. However, site‐specific differences in sportfish use did occur within site types. For example, one restored site had significantly higher densities of red drum Sciaenops ocellatus than any other site, while black drum Pogonias cromis were found exclusively at another restored site. To evaluate whether the restored sites are providing suitable habitat for juvenile fish, we assessed growth (estimated from counts of daily rings on otoliths) and condition (determined by lipid analyses) of juvenile common snook Centropomus undecimalis, an archetypal coastal wetland‐dependent species. Growth (0.43–0.56 mm SL/day) and condition (4.6–6.1% lipid of dry weight) exhibited only site‐specific differences and did not vary among natural, restored, and impacted site types. Although mortality rates of juvenile sportfish were not determined, use of a 40‐m seine found that densities of potential piscine predators in these coastal wetlands were relatively low compared to published studies of open estuarine shorelines. The restoration and creation of coastal wetlands in Tampa Bay provides improved habitat for juvenile sportfish.     

Restoration of Wetlands from Abandoned Rice Fields for Nutrient Removal, and Biological Community and Landscape Diversity

A number of experimental freshwater wetlands (150 m long × 75 m wide) with different ages since they were abandoned as rice fields, were used to analyze the prospects of multipurpose wetland restoration for such degraded areas. Nitrogen and phosphorus removal rate of the wetlands were determined monthly during the flooding season to estimate their efficiency as filters to remove nutrients from agricultural sewage. The number of wetland birds was recorded regularly to identify their habitat preferences. Both the temporal dynamics and changes in the spatial pattern of land use cover during the last 20 years were determined from aerial photographs and field analysis. All the wetlands appeared to be very efficient in the removal of nitrogen and phosphorus exported from rice fields. Usually 50–98% of the nitrogen and less than 50% of the soluble phosphorus were removed by the wetlands at any stage of restoration. Wetland birds preferred wetlands with intermediate plant cover for resting and sleeping activities better than rice fields and either very open wetlands or very dense ones with tall vegetation. Apart from the improvement in water quality and the restoration of natural habitats, restoration of wetland belts around lagoons will increase spatial heterogeneity and diversity of the landscape.     

Wintering Shorebird Assemblages and Behavior in Restored Tidal Wetlands in Southern California

Habitat restoration can partially compensate for the extensive loss of coastal wetlands, but creation of functional habitat and assessment of restoration success remain challenging tasks. To evaluate wintering shorebird use of restored coastal wetlands, we quantified shorebird assemblages and behavior of selected focal species at five restored sites and paired reference sites in Mugu Lagoon, southern California, United States. The Shannon–Wiener index of species diversity (for all birds in order Charadriiformes) was higher in the restored than in the reference portion of three of the five sites, higher in the reference portion of a fourth site, and similar between reference and restored areas of the fifth site. Species diversity was lower in sites closer to man‐made structures. The four most abundant species groups across the five sites were selected for detailed analysis of site use and behavior: Willets (Catoptrophorus semipalmatus), Marbled Godwits (Limosa fedoa), Dowitchers (Limnodromus spp.), and Sandpipers (Calidris spp.) (Western, Least, and Dunlin). Each focal species group exhibited distinct site preferences, and densities in restored sites were often as high or higher than in reference sites. Willets and Dowitchers preferred habitats with more extensive tidal flats, a characteristic of restored sites. Godwits and Sandpipers preferred heterogeneous habitats with a mix of water and tidal flats. Most birds were engaged in feeding activities during the ebb tides surveyed, and there were no apparent differences in behavior between reference and restored sites. Though not all restored sites were used equally by all species, the creation of multiple restored sites with varied habitat characteristics attracted a diverse assemblage of shorebirds and may have contributed to the integrity of the regional wetland landscape.     

Incomplete recovery of plant diversity in restored prairie wetlands on agricultural landscapes

Restoration efforts are being implemented globally to mitigate the degradation and loss of wetland habitat; however, the rate and success of wetland vegetation recovery post‐restoration is highly variable across wetland classes and geographies. Here, we measured the recovery of plant diversity along a chronosequence of restored temporary and seasonal prairie wetlands ranging from 0 to 23 years since restoration, including drained and natural wetlands embedded in agricultural and natural reserve landscapes in central Alberta, Canada. We assessed plant diversity using the following structural indicators: percent cover of hydrophytes, native and non‐native species, species richness, and community composition. Our findings indicate that plant diversity recovered to resemble reference wetlands in agricultural landscapes within 3–5 years of restoration; however, restored wetlands maintained significantly lower species richness and a distinct community composition compared to reference wetlands located within natural reserves. Early establishment of non‐native species during recovery, dispersal limitation, and depauperated native seed bank were probable barriers to complete recovery. Determining the success of vegetation recovery provides important knowledge that can be used to improve restoration strategies, especially considering projected future changes in land use and climate.     

Effects of Local and Landscape Variables on Wetland Bird Habitat Use During Migration Through the Rainwater Basin

ABSTRACT Staging areas and migratory stopovers of wetland birds can function as geographic bottlenecks; common dependence among migratory wetland bird species on these sites has major implications for wetland conservation. Although 90% of playa wetlands in the Rainwater Basin (RWB) region of Nebraska, USA, have been destroyed, the area still provides essential stopover habitat for up to 10 million waterfowl each spring. Our objectives were to determine local (within wetland and immediate watershed) and landscape-scale factors influencing wetland bird abundance and species richness during spring migration at RWB playas. We surveyed 36–40 playas twice weekly in the RWB and observed approximately 1.6 million individual migratory wetland birds representing 72 species during spring migrations 2002–2004. We tested a priori hypotheses about whether local and landscape variables influenced overall species richness and abundance of geese, dabbling ducks, diving ducks, and shorebirds. Wetland area had a positive influence on goose abundance in all years, whereas percent emergent vegetation and hunting pressure had negative influences. Models predicting dabbling duck abundance differed among years; however, individual wetland area and area of semipermanent wetlands within 10 km of the study wetland consistently had a positive influence on dabbling duck abundance. Percent emergent vegetation also was a positive predictor of dabbling duck abundance in all years, indicating that wetlands with intermediate (50%) vegetation coverage have the greatest dabbling duck abundance. Shorebird abundance was positively influenced by wetland area and number of wetlands within 10 km and negatively influenced by water depth. Wetland area, water depth, and area of wetlands within 10 km were all equally important in models predicting overall species richness. Total species richness was positively influenced by wetland area and negatively influenced by water depth and area of semipermanent wetlands within 10 km. Avian species richness also was greatest in wetlands with intermediate vegetation coverage. Restoring playa hydrology should promote intermediate percent cover of emergent vegetation, which will increase use by dabbling ducks and shorebirds, and decrease snow goose (Chen caerulescens) use of these wetlands. We observed a reduction in dabbling duck abundance on wetlands open to spring snow goose hunting and recommend further investigation of the effects of this conservation order on nontarget species. Our results indicate that wildlife managers at migration stopover areas should conserve wetlands in complexes to meet the continuing and future habitat requirements of migratory birds, especially dabbling ducks, during spring migration.     

Use of aerial imagery to assess habitat suitability and predict site occupancy for a declining wetland-dependent bird

Remote sensing is a valuable tool for wetland habitat quantification, monitoring and assessment. Here we show that habitat assessment via aerial image inspection is useful in predicting wetland site occupancy by black terns (Chlidonias niger), an imperiled and declining species throughout much of North America. We used Google Earth^® images and National Wetlands Inventory maps to rank 390 candidate wetlands throughout Wisconsin (USA) according to their apparent suitability as nesting habitat for black terns and quantified habitat features associated with the suitability rankings. We then conducted ground-based suitability assessments and point counts of terns at most wetlands from May to July 2010. Pre-survey assessment resulted in 123 wetlands classified as suitable, 81 as marginal, and 186 as unsuitable. Wetlands ranked as suitable were more likely to be in the hemi-marsh stage, part of a wetland complex and relatively undisturbed. Black terns were present at 47 % of the wetlands considered suitable but only 11 % of the sites considered marginal or unsuitable. Of the 42 sites where nesting was confirmed, 79 % were at wetlands classified as suitable; no nesting was recorded in any wetlands deemed unsuitable. We found strong concordance in wetland suitability rankings between the two assessment methods (remote sensing, site surveys). We propose that remote sensing is an efficient and inexpensive way to predict site occupancy by wetland birds, such as black terns, that prefer a specific kind of habitat discernible from aerial imagery. This method may be particularly useful in areas, such as the Prairie Pothole region of North America, where ground surveys of all wetlands are not feasible.     

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.     

A method to prioritize and monitor wetland restoration for water-quality improvement

Wetland restoration can improve water quality by reducing concentrations of sediment, total phosphorus, and nitrate in runoff. Managers need a simple method to choose among many possible restoration sites, particularly in large agricultural basins covering thousands of square kilometers. The purpose of this paper is to outline a method for prioritizing and monitoring wetland restoration sites in light of the factors that affect water-quality improvement by wetlands. These factors are categorized as loading factors, path factors, and process factors. The method for prioritizing wetland restoration sites depends primarily on assessing the potential effectiveness of the wetland for improving water quality. Three types of effectiveness are considered: problem effectiveness (is the site in an area with known water-quality problems?), function effectiveness (is the site likely to improve water quality more or less than other sites?), and information effectiveness (does the site fit within an overall research plan to gain information on how wetlands improve water quality?). The variables of hydraulic residence time, hydraulic flux, and wetland area, volume, and average depth are combined into a single variable termed and used as a proxy for estimating the relative function effectiveness of potential restoration sites. Monitoring restoration sites is targeted at establishing a minimum data set that can be collected consistently at different sites over time, and that can be used for inter-site comparison with simple statistical techniques. The Minnesota River Basin is used as an example throughout to demonstrate the types of data that are available to plan wetland restoration. While this paper focuses on the water-quality benefits, wetland restoration should be a multi-disciplinary effort to integrate other benefits of restoration, such as improvement of wildlife habitat and flood abatement.     

Influence of area,habitat and water chemistry on richness and composition of macrophyte assemblages in southern Brazilian wetlands

Questions: Two hypotheses were tested: (1) physical features, such as wetland surface area and habitat diversity, together with water chemistry, are important determinants of species richness and composition of macrophyte assemblages and (2) species richness and composition of macrophyte assemblages differ between wetlands of different types (i.e., palustrine versus lacustrine) and between wetlands of different hydrologies (i.e. permanent versus intermittent). Location: A subtropical coastal plain segment (2500 km²) of southern Brazil. Methods: Quarterly collections were carried out in 15 wetlands (2004–2005) in southern Brazil. Differences in richness over time were tested using repeated measures ANOVA. Stepwise multiple regression was performed to investigate relationships between total richness and environmental variables. Significance of differences between wetland types and hydroperiods on species composition was verified by MRPP (Multi‐Response Permutation Procedure). The influence of the environmental variables on species composition was assessed using CCA (Canonical Correspondence Analysis). Results: Macrophyte species richness changed with time, was not significantly different between wetland types, but was higher in permanent wetlands than in intermittent ones. Area, habitat diversity and soluble reactive phosphorus concentration explained 76% of the variation in species richness. Species composition was different between permanent and intermittent wetlands, although it was not significantly different between wetland types. Area, habitat diversity and water chemistry explained 50.1% of species composition. Conclusions: Species richness and composition of wetland macrophytes were mainly determined by area, habitat diversity and hydroperiod. These results can be used for the development of conservation and management programs in southern Brazil.     

Hydrologic similarity to reference wetlands does not lead to similar plant communities in restored wetlands

Few wetland restoration projects include long‐term hydrologic and floristic data collection, limiting our understanding of community assembly over restored hydrologic gradients. Although reference sites are commonly used to evaluate outcomes, it remains unclear whether restoring similar water levels to reference sites also leads to similar plant communities. We evaluated long‐term datasets from reference and restored wetlands 15 years after restoration to test whether similar water levels in reference and restored sites led to vegetation similarity. We compared the hydrologic regimes for three different wetland types, tested whether restored wetland water levels were different from reference water levels, and whether hydrologic similarity between reference and restored wetlands led to similarity in plant species composition. We found restored wetlands had similar water levels to references 15 years after restoration, and that species richness was higher in reference than restored wetlands. Vegetation composition was similar across all wetland types and was weakly correlated to wetland water levels overall. Contrary to our hypothesis, water table depth similarity between restored and reference wetlands did not lead to similar plant species composition. Our results highlight the importance of the initial planting following restoration and the importance of hydrologic monitoring. When the restoration goal is to create a specific wetland type, plant community composition may not be a suitable indicator of restoration progress in all wetland types.     

崇明东滩鸟类栖息地优化区越冬水鸟的栖息地利用及影响因子

阐明水鸟栖息地利用与环境因子的关系有助于制定针对性的水鸟保护对策。本研究在2012~2013年冬季对崇明东滩鸟类栖息地优化区内越冬水鸟的种类、数量以及6种环境因子(植被面积比例、裸地面积比例、水深、地形变异、栖息地结构多样性和干扰)进行调查,以了解水鸟对人工湿地的栖息地利用及其影响因子。野外调查共记录到水鸟24种9 018只,其中优势种为斑嘴鸭(Anas poecilorhyncha)和绿头鸭(A.platyrhynchos);栖息地优化区内水鸟休息的个体数量占总数量的79.2%,这表明优化区是大多数水鸟的休息地,而小(Tachybaptus ruficollis)、白骨顶(Fulica atra)、黑水鸡(Gallinula chloropus)、白琵鹭(Platalea leucorodia)和黑脸琵鹭(P.minor)的觅食个体数量超过60%,说明优化区也为这些鸟类提供了觅食地。逐步回归分析表明,裸地面积比例是影响越冬水鸟种类分布的最主要因子;尽管游禽在地形变异较大、植被面积比例较低的区域数量较多,但在休息时游禽更偏好于裸地面积比例较高的区域,而涉禽休息时偏好于地形变异较大的区域。为增加栖息地优化区内的水鸟多样性,建议在优化区内种植水鸟可食的沉水植物以增加水鸟的食物资源,同时增加裸地面积比例和地形变异程度,更好地为水鸟提供栖息地。     

三江平原恢复湿地土壤种子库特征及其与植被的关系

通过幼苗萌发法和样方调查相结合的方法对三江平原不同演替恢复阶段的种子库特征及其与植被的关系进行了研究。将开垦湿地、不同演替恢复阶段湿地以及天然湿地不同土壤层次(0-5、5-10 cm和根茎)的种子库在两种水分条件下(湿润、淹水10 cm)进行萌发处理。结果表明: 随着演替恢复阶段的进行, 种子库的结构和规模逐渐扩大, 地表群落表现出由旱生物种占优势的群落逐渐演变成以小叶章(Calamagrostis angustifolia)占优势的湿生群落的演替趋势。恢复7年湿地、恢复14年湿地、天然湿地土壤种子库萌发物种数分别为24种、29种、39种, 植被物种数为21种、25种、14种。湿地类型、水分条件和土壤层次均显著影响种子库萌发的物种数及幼苗数(p < 0.01)。种子库具有明显的分层现象, 天然湿地0-5 cm土层种子库种子萌发密度是5-10 cm土层的4倍左右, 而恢复湿地仅1.3倍左右, 且土层间萌发物种相似性系数较低。湿润条件下的萌发物种数显著高于淹水条件, 且两种水分条件下萌发物种的生活型不同。由于恢复时间较短, 不同演替恢复阶段的种子库与植被相似性维持在30%以下。湿地中根茎分蘖出大量的湿地物种, 对于小叶章等优势物种的繁殖具有重要作用。研究表明, 在开垦湿地退耕后的次生演替阶段, 种子库能够保持大量的湿地物种, 通过对湿地种子库与植被的关系研究, 能够为三江平原湿地群落演替与湿地恢复提供策略指导。     

Simulated Effects of Stream Restoration on the Distribution of Wet‐Meadow Vegetation

Meadow restoration efforts typically involve the modification of stream channels to re‐establish hydrologic conditions necessary for the maintenance of native vegetation. To predict change in the distribution of common meadow plant species in response to meadow restoration, a hydrologic model was loosely coupled to a suite of individual plant species distribution models. The approach was tested on a well‐documented meadow/stream restoration project on Bear Creek, a tributary to the Fall River in northeastern California, U.S.A. We developed a surface‐water and groundwater hydrologic model for the meadow. Vegetation presence and absence data from 170 plots were combined with simulated water‐table depth time series to develop habitat‐suitability models for 11 herbaceous plant species. In each model, the habitat suitability is predicted as a function of growing‐season, water‐table depth, and range. The hydrologic model was used to simulate water‐table depth time series for the pre‐ and post‐restoration conditions. These results were used to predict the spatial distribution of habitat suitability for the 11 herbaceous plant species. Model results indicate that restoration changed water levels throughout the study area, extending well beyond the near‐stream region. Model results also indicate an increase in the spatial distribution of suitable habitat for mesic vegetation and a concomitant decrease in the spatial distribution of suitable habitat for xeric vegetation. The methods utilized in this study could be used to improve setting of objective and performance measures in restoration projects in similar environments, in addition to providing a quantitative, science‐based approach to guide riparian restoration and active revegetation efforts.     

上海大莲湖湖滨带湿地的生态修复

采用改变土地利用模式、水系改造和植被配置等技术开展了上海青浦大莲湖湿地修复示范工程。本文从2008年8月到2010年3月跟踪调查了土地利用方式、鸟类群落、两栖爬行类、水质等多类指标来对示范工程进行评估。结果表明,实验区生态系统的生境结构和生物多样性组成都发生了明显的变化。实验区内土地利用由主要以人工养殖鱼塘和林地为主的人工湿地(人工鱼塘占50%,林地占25%),转变为以开放性水域和乔灌草相结合的半自然状态下的自然湿地(明水面面积占30%,各类植被群落占50%,人工鱼塘完全消失),植被从只有片段化林地转变为乔木、灌木丛、草本植物及各类水生植物相结合的格局;工程后鸟类种类和数量均高于工程前(新纪录到11种鸟类),鸟类多样性指数和均匀性指数也有明显增加,其中目标鸟类——雁鸭类新增6种,种类和数量都呈显著增加;两栖爬行类种类变化不大,共记录到6科12种,但整体数量比工程前增长了59.1%;水质指标的变化也很突出,与工程前人工鱼塘相比,实验区内水体中总氮(TN)、硝态氮(NO3-N)、总磷(TP)、叶绿素a(Chla)、高锰酸钾指数(CODMn)等主要指标均有显著下降(P<0.05),水质改善显著。由此说明,修复工程改善了大莲湖湖滨带湿地的生态环境,生物多样性得到较好的恢复,呈现出良好的湿地修复效果。     

基于二元水循环效率提升的城市湿地修复策略

城市湿地对人地系统的水循环调节起着关键作用。随着城市的发展,水资源短缺问题日益突出,探讨湿地在缓解城市水资源危机中的作用具有重要意义。基于“自然-社会”二元水循环理论,综合分析了我国城市用水量在全国总用水量占比急剧增加的现状,以及城市水循环效率低下的重点问题;基于城市水循环途径的取水、输水、用水、排水和回水五个阶段,系统提出湿地的保护恢复有助于改善城市水资源利用状况,增强城市湿地空间优化配置和水资源可持续利用的协同效应;充分考虑城市生态空间整体优化及湿地布局,全面阐释在城市国土空间规划指导下,通过增加城市水循环中社会水回归容量和缩短社会水回归距离,提升城市水循环效率,充分发挥湿地生态工程对城市水循环优化的调控作用;最后,兼顾城市中长期规划发展的协调性、适应性,探讨了湿地保护修复以提升水循环效率的策略,包括多功能水源地建设、缩短汇水距离、多级净水、营建小微湿地以及构建自循环理念的再生系统等具体措施,为城市湿地资源空间规划的整体布局提供重要依据,对促进城市水资源可持续利用和建设人与自然和谐共生的韧性城市具有重要意义。     

Relationships among Amphibian Assemblage Structure,Wetland pH,and Forest Cover

A common mesofilter approach to conservation of biological diversity and ecosystem function used in agricultural and urban landscapes is maintenance of wetlands and an undisturbed terrestrial buffer surrounding wetlands. Although it is generally accepted that forest buffers protect wetland-associated biological diversity and ecosystem function, the effectiveness and optimal spatial extent of buffers is still an area of debate. During 2007 and 2008 we surveyed amphibians and environmental conditions associated with 54 depression wetlands on the Delmarva Peninsula of Maryland, USA, to examine the role of forest buffers and wetland characteristics in structuring amphibian communities. Forest cover within a 50-m buffer surrounding wetlands was correlated (r = −0.81) with wetland pH but no other wetland characteristics. Wetland pH, canopy cover, hydroperiod, and adjacent forest cover were important predictors of wetland use by individual amphibian species, with many species more likely to occur at wetlands that dried late in the hydrological year and with open canopies. At least one common species preferred circumneutral pH and several restricted-distribution species preferred lower pH (<5). Contrary to expectations, relationships between species occurrence and adjacent forest cover were negative. Our results suggest that current regulations that provide buffers of 30 m or less do not provide adequate protection of wetland water chemistry but that forest encroachment into wetlands may be a threat to the integrity of amphibian communities and should be the target of monitoring, future research, and management efforts. © 2021 The Wildlife Society.     

Vegetation Similarity and Avifaunal Food Value of Restored and Natural Marshes in Northern New York

Measuring the success of wetland restoration efforts requires an assessment of the wetland plant community as it changes following restoration. But analyses of restored wetlands often include plant community data from only one time period. We studied the development of plant communities at 13 restored marshes in northern New York for 4 years, including 1 year prior to restoration and 3 years afterwards. Restored wetlands ranged in size from 0.23 to 1.70 ha. Four reference wetlands of similar basin morphology, soil type, and size (0.29–0.48 ha) that occurred naturally in the same area were studied as comparisons. Dike construction to restore hydrology disturbed the existing vegetation in some parts of the restored sites, and vegetation was monitored in both disturbed and undisturbed areas. Undisturbed areas within the restored sites, which were dominated by upland field grasses before restoration, developed wetland plant communities with lower wetland index values but comparable numbers of wetland plant species than the reference wetlands, and they lagged behind the reference sites in terms of total wetland plant cover. There were significantly more plant species valuable as food sources for wetland birds, and a significantly higher percent cover of these species, at the undisturbed areas of the restored sites than at the reference wetlands. Areas of the restored sites that were disturbed by dike construction, however, often developed dense, monospecific cattail stands. In general, the plant communities at restored sites became increasingly similar to those at the reference wetlands over time, but higher numbers of herbaceous plants developed at the restored sites, including food plants for waterfowl, rails, and songbirds. Differences in shrub cover will probably lessen as natural recolonization increases shrub cover at the restored sites. Natural recolonization appears to be an effective technique for restoring wetlands on abandoned agricultural fields with established plant cover, but it is less successful in areas where soil has been exposed by construction activity.     

Avian Use of Wetlands in Reclaimed Minelands in Southwestern Indiana

We studied the use of mineland wetlands by birds and the relationship between avian communities and wetland characteristics. Data were collected from 20 wetlands in Pike County, Indiana, and included wetland size, depth, water conductivity and salinity, aquatic macroinvertebrate abundance, vegetation, and bird use. Principal component analysis showed that physical variables could be explained by two principal component scores and that wetlands could be grouped on the basis of size and conductivity. Principal component analysis could not reduce vegetation variables to fewer principal component scores, meaning that wetland vegetation characteristics were independent of one another and did not show any trend. Most wetlands had low invertebrate density, and wetlands with higher invertebrate density had low invertebrate diversity. Wetlands with similar habitat characteristics (physical, vegetative, and invertebrate) did not necessarily show similarities in bird assemblages. Bird similarity index values ranged from 0 to 59%, implying that each wetland has its own bird community. Stepwise multiple regression analysis (α= 0.05) relating bird use and habitat characteristics showed that bird species richness increased with the species richness of submergent vegetation and was correlated negatively with the species richness of emergent vegetation. There was no significant relationship between bird species richness or bird species diversity and wetland size. The number of species within different avian guilds correlated with different habitat characteristics. The species richness of submergent plants was a factor that correlated positively with the number of species of several guilds (dabblers, wading birds, and plunge divers). Wetland age was not a factor that determined bird use.