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.     

Vegetation Monitoring of Created Dune Swale Wetlands, Vandenberg Air Force Base, California

A monitoring program was established on San Antonio Terrace at Vandenberg Air Force Base to compare vegetation development at two created wetland sites and six nearby natural wetlands. The reference wetlands were chosen to represent a range of habitats in dune swale wetlands on the Terrace. Vegetation in the reference wetland plant communities varies from low-growing herbaceous marsh species with open canopies to closed canopies dominated by shrub or tree species. Transects and plots for long-term vegetation monitoring were established in all the wetlands, stratified by plant communities in the reference wetlands and by geomorphic location in the newly created wetlands. Quantitative vegetation and environmental data were collected at all the sites; measures included species distributions, species cover, and topographical elevations. Over the first three years of monitoring, variations in groundwater depth at different geomorphic locations in the created wetlands resulted in a variety of physical conditions for plant growth. In the first year, more than 100 plant species were observed, the majority being natives. During the next two years, species richness at the created wetland sites remained relatively stable and was higher than at the reference sites. Statistical comparisons of vegetation parameters by analysis of variance and hierarchical clustering exhibited patterns of increasing similarity between the created and reference wetlands. Long-term monitoring will be continued to track the progress of vegetation at the created sites, and to assess their development relative to the reference wetlands.     

Terrestrial Arthropods as Indicators of Ecological Restoration Success in Coastal Sage Scrub (California, U.S.A.)

Abstract Ecological restoration enjoys widespread use as a technique to mitigate for environmental damage. Success of a restoration project often is evaluated on the basis of plant cover only. Recovery of a native arthropod fauna is also important to achieve conservation goals. I sampled arthropod communities by pitfall trapping in undisturbed, disturbed, and restored coastal sage scrub habitats in southern California. I evaluated arthropod community composition, diversity, and abundance using summary statistics, cluster analysis, and detrended correspondence analysis (DCA) and investigated influence of vegetation on arthropod communities with multiple regression analysis. Arthropod diversity at undisturbed and disturbed sites was greater than at sites that were 5 and 15 years following restoration ( p < 0.05). Number of arthropod species was not significantly different among undisturbed, disturbed, and restored sites, and two restoration sites had significantly more individuals than other sites. Vegetation at disturbed and undisturbed sites differed significantly; older restorations did not differ significantly from undisturbed sites in diversity, percent cover, or structural complexity. In multiple regression models, arthropod species richness and diversity was negatively related to vegetation height but positively related to structural complexity at intermediate heights. Exotic arthropod species were negatively associated with overall arthropod diversity, with abundance of the earwig Forficula auricularia best predicting diversity at comparison (not restored) sites (r² = 0.29), and abundance of the spider Dysdera crocata and the ant Linepithema humile predicting diversity at all sites combined (r² = 0.48). Native scavengers were less abundant at restored sites than all other sites and, with a notable exception, native predators were less abundant as well. DCA of all species separated restored sites from all other sites on the first axis, which was highly correlated with arthropod diversity and exotic arthropod species abundance. Lower taxonomic levels showed similar but weaker patterns, with example families not discriminating between site histories. Vegetation characteristics did not differ significantly between the newly restored site and disturbed sites, or between mature restoration sites and undisturbed sites. In contrast, arthropod communities at all restored sites were, as a group, significantly different from both disturbed and undisturbed sites. As found in other studies of other restoration sites, arthropod communities are less diverse and have altered guild structure. If restoration is to be successful as compensatory mitigation, restoration success standards must be expanded to include arthropods.     

Seasonal wetlands on the Lake Wales Ridge, Florida: does a relict seed bank persist despite long term disturbance?

Wetlands maintain biodiversity and provide numerous ecosystem services, so the pressure to perform successful restoration consequently is high. However, restoration projects rarely include an in-depth assessment of wetland potential for recovery, and restoration techniques may not be tailored to site-specific concerns. This study examined the seed bank of disturbed wetlands slotted for hydrologic, but not vegetation, restoration to determine if a seed bank comparable to that of nearby undisturbed wetlands persisted despite long-term anthropogenic disturbance. We compared the aboveground vegetation and seed bank compositions under drained, drawdown, and flooded conditions between undisturbed and historically ditched (“disturbed”) wetlands. Disturbed and undisturbed wetlands shared fewer than 30 % of total aboveground species. While undisturbed wetlands were dominated by graminoids, disturbed wetlands had greater cover of forbs. The seed banks of disturbed wetlands had high species diversity, but their composition was dissimilar to that of nearby undisturbed wetlands. In total, the seed banks of both disturbance histories germinated 56 species; drained conditions had the fewest germinants while flooded conditions had the most. Germinant richness was significantly affected by disturbance, moisture, and their interaction; evenness was significantly affected by moisture, and Shannon diversity by disturbance. Because the seed bank of disturbed wetlands included many fast-growing wetland plants, passive vegetation restoration and active hydrologic restoration may result in wetlands overgrown with weedy species and with fewer conservative wetland plants. An understanding of the capacity for seed banks to re-vegetate wetlands post-restoration and approximate undisturbed wetlands is crucial to the overall success of restoration projects.     

Wetland Vegetation Response to the Restoration of Sheet Flow at Cheyenne Bottoms, Kansas

The restoration of inland salt‐affected plant communities, including saltflat mixed prairie and playa lakes wetlands, has received little attention despite the importance of these communities for critical wildlife habitat. The salt‐affected communities of Cheyenne Bottoms, located in central Kansas, are a crucial stopover site for migratory waterfowl and shorebirds. In 1998, The Nature Conservancy attempted to restore native plant communities to grazed and former cropland at Cheyenne Bottoms by reestablishing sheet flow across these disturbed areas. We collected vegetation cover data along permanent transects established in rangeland, former cropland, and in a shallow basin 3 years (1996–1998) before the hydrological changes and continued to collect vegetation data for 3 years (1999–2001) after the hydrological changes. Vegetation composition changes in response to the restored hydrology were subtle, but the average wetland index along the transects in the basin and the rangeland significantly declined. Significant decreases occurred in the cover of perennials and graminoids in both spring and fall species assemblages of the rangeland area. Changes in the former cropped areas were mixed, indicating the difficulty of restoring these disturbed plant communities to native plant assemblages within a few years.     

青藏高原多年冻土区不同草地生态系统恢复能力评价

草地生态系统恢复能力是评价人类工程活动对青藏高原多年冻土生态系统影响的重要组分.分析了不同草地生态系统干扰带和非干扰带群落特征、植物多样性、草地初级生产力和经济类群,综合评价了青藏高原多年冻土区地上植被在受工程活动干扰后的综合恢复能力.结果表明:经过近20多年的自然恢复,青藏苔草草原、紫花针茅草原、扇穗茅草原、高山嵩草草甸、矮蒿草草甸和藏蒿草沼泽化草甸6种草地的盖度和物种组成均有一定程度的恢复,且草原群落的恢复程度好于草甸群落,但干扰群落仍低于未干扰群落;紫花针茅草原分布区物种多样性恢复好于其他草地类型分布区;干扰带由最初的地上植物生物量全部为0恢复到148.8～489.6 g·m^-2,其中藏嵩草沼泽化草甸干扰带恢复最好,生物量达489.6 g·m^-2;除藏嵩草恢复群落的饲用植物类群组成相对稳定外,干扰后的其他5种草地类型饲用价值降低.高寒草原生态系统的植被综合恢复能力显著高于草甸生态系统.     

The Impact of Hydrological Restoration on Benthic Aquatic Invertebrate Communities in a New Zealand Wetland

Drainage is a major disturbance affecting wetlands, as drains lower water tables and convert lentic habitats to lotic ones. Consequently, invertebrate communities in drained wetlands are likely to differ from those in unimpacted wetlands. This study investigated the effect of hydrological restoration on invertebrate communities in small drains in a New Zealand fen. Invertebrates were collected over 4 summers from 10 drains within the wetland, one of which was blocked as part of a restoration program. The sampling protocol thus represented a Before‐After Control‐Impact experiment. Invertebrate community composition varied over the 4 years, but variability was greatest in the manipulated drain before and after it was blocked. Relative abundance of the amphipod Paraleptamphopus decreased after blockage, whereas those of the midges Chironomus zelandicus and Tanypodinae increased. Relative abundances of these taxa in control sites were unchanged. Hydraulic restoration thus had a demonstrable impact on the invertebrate communities. The invertebrate community of the blocked drain was compared to that of natural wetlands in undisturbed catchments. Similarity was very low prior to drain blockage, but increased following drain blockage. Invertebrate communities in the restored drain were more similar to those of low pH wetlands than high pH wetlands. Given the goal of restoring the communities to those similar to natural conditions, this was a beneficial result. These results, coupled with studies that showed a decline in the cover of alien pasture grasses around the blocked drain, suggest that drain blockage represents a cost‐effective way of restoring wetland plant and aquatic invertebrate communities, especially where connectivity allows for the natural recruitment of these organisms into restored areas.     

茂县土地岭植被恢复过程中物种多样性动态特征

植被恢复是退化生态系统重建的重要途径,植被恢复过程物种多样性的变化反映了植被的恢复程度.通过群落调查和多样性分析,研究了岷江上游土地岭植被恢复过程中群落物种多样性特征.结果表明： 恢复过程中6类不同类型群落分别表现其对于不同环境特征、干扰及更新方式等的响应;森林是较灌丛更适合当地环境状况的植被类型;人工恢复无干扰和轻度干扰群落的多样性相对较高,是较好的恢复模式.重度干扰使得1年生植物与地下芽植物比例增加,其它口食性较好的多年生草本减少.较强的干扰是群落无法更新、长期处于灌丛阶段且多样性较低的重要原因.本地区人工恢复群落在更新进程和多样性维持上优于自然更新群落,种植华山松加速了本地区植被演替进程.建议以适合恢复区域的多种恢复配置方式进行造林,并避免较强干扰,可以加速群落演替进程并保持恢复群落较高的物种丰富度与多样性.     

Carbon storage dynamics of temperate freshwater wetlands in Pennsylvania

Healthy wetlands play a significant role in climate change mitigation by storing carbon that would otherwise contribute to global warming, leading to the reduction of water and food resources as well as more extreme weather phenomena. Investigating the magnitude of carbon storage potential of different freshwater wetland systems using multiple ecological indicators at varying spatial scales provides insight and justification for selective wetland restoration and conservation initiatives. We provide a holistic accounting of total carbon values for 193 wetland sites, integrating existing carbon algorithms to rapidly assess each of the following carbon pools: above-ground, below-ground, soil, woody debris, shrub cover, and herbaceous cover. Aspects of soil, vegetation, and ecosystem characteristics and stressors were measured to obtain an overall understanding of the ecosystems ability to store carbon (long-term) along a gradient of human disturbance. Based on a review of the literature, methods were prioritized based on the initial data available from field measurements as well as their practicality and ease in replicating the process in the future. Lacustrine human impounded (88.7?±?18.0 tC/ha), riverine beaver impounded (116.2?±?29.4 tC/ha), riverine upper perennial (163.3?±?11.8 tC/ha), riverine lower perennial (199.2?±?24.7 tC/ha), riverine headwater complex (159.5?±?22.2 tC/ha), perennial/seasonal depression (269.6?±?42.4 tC/ha), and slope (162.2?±?14.6 tC/ha) wetland types were compared. Overall results showed moderate variability (9.33–835.95 tC/ha) for total carbon storage values across the wetland types, with an average total carbon storage of 174.6?±?8.8 tC/ha for all wetlands. Results show that carbon storage was significantly higher (p?=?0.002) in least disturbed wetland sites. Apart from perennial/seasonal depression wetlands, all reference standard wetlands had greater carbon storage, less disturbance impact, and a greater extent of forest cover than non-reference wetlands. Carbon storage values calculated were comparable to published literature.     

Structural and functional loss in restored wetland ecosystems

Wetlands are among the most productive and economically valuable ecosystems in the world. However, because of human activities, over half of the wetland ecosystems existing in North America, Europe, Australia, and China in the early 20th century have been lost. Ecological restoration to recover critical ecosystem services has been widely attempted, but the degree of actual recovery of ecosystem functioning and structure from these efforts remains uncertain. Our results from a meta-analysis of 621 wetland sites from throughout the world show that even a century after restoration efforts, biological structure (driven mostly by plant assemblages), and biogeochemical functioning (driven primarily by the storage of carbon in wetland soils), remained on average 26% and 23% lower, respectively, than in reference sites. Either recovery has been very slow, or postdisturbance systems have moved towards alternative states that differ from reference conditions. We also found significant effects of environmental settings on the rate and degree of recovery. Large wetland areas (>100 ha) and wetlands restored in warm (temperate and tropical) climates recovered more rapidly than smaller wetlands and wetlands restored in cold climates. Also, wetlands experiencing more (riverine and tidal) hydrologic exchange recovered more rapidly than depressional wetlands. Restoration performance is limited: current restoration practice fails to recover original levels of wetland ecosystem functions, even after many decades. If restoration as currently practiced is used to justify further degradation, global loss of wetland ecosystem function and structure will spread.     

Detecting soil and plant community changes in restored wetlands using a chronosequence approach

Wetland restoration aims to recreate or enhance valuable ecosystem services lost during wetland destruction. Regaining wetland ecosystem services depends on restarting basic wetland functions, like carbon (C) storage, which are unmeasured in many Wetlands Reserve Program (WRP) restoration sites. We collected soil and plant data from 17 WRP sites in western New York that were used for tillage or non-tillage agriculture and then actively restored as isolated depressional wetlands by excavating basins and disabling drainage systems. Sites had been restored for 0–15 years when sampled in August-October 2010. We analyzed data as chronosequences and tested whether soil and vegetation parameters in restored wetlands, over time, (1) departed from pre-restoration baselines, estimated using active agricultural fields paired to each WRP site, and (2) converged towards “natural” benchmarks, estimated from four naturally-occurring wetlands. Restored WRP soils remained similar to agricultural soils in organic matter, density, moisture, and belowground plant biomass across chronosequences, indicating negligible C storage and belowground development for 15 years following restoration. Soil changes were limited in sites restored after both tillage and non-tillage agriculture and throughout the upland meadow, emergent shoreline, and open-water habitat zones that characterize these sites. Many plant metrics like aboveground biomass matched natural wetlands within 15 years, but recovered inconsistently among tilled and untilled sites and across all habitat zones, suggesting land-use history impacts and/or zonation effects. Disparities in recovery times exists between vegetation, which can respond quickly to wetland restoration, and underlying soils, which show limited signs of recovery 15 years after being restored.     

Testing a Passive Revegetation Approach for Restoring Coastal Plain Depression Wetlands

Restoration of coastal plain depressions, a biologically significant and threatened wetland type of the southeastern United States, has received little systematic research. Within the context of an experimental project designed to evaluate several restoration approaches, we tested whether successful revegetation can be achieved by passive methods (recruitment from seed banks or seed dispersal) that allow for wetland "self-design" in response to hydrologic recovery. For 16 forested depressions that historically had been drained and altered, drainage ditches were plugged to reestablish natural ponding regimes, and the successional forest was harvested to open the sites and promote establishment of emergent wetland vegetation. We sampled seed bank and vegetation composition 1 year before restoration and monitored vegetation response for 3 years after. Following forest removal and ditch plugging, the restored wetlands quickly developed a dense cover of herbaceous plant species, of which roughly half were wetland species. Seed banks were a major source of wetland species for early revegetation. However, hydrologic recovery was slowed by a prolonged drought, which allowed nonwetland plant species to establish from seed banks and dispersal or to regrow after site harvest. Some nonwetland species were later suppressed by ponded conditions in the third year, but resprouting woody plants persisted and could alter the future trajectory of revegetation. Some characteristic wetland species were largely absent in the restored sites, indicating that passive methods may not fully replicate the composition of reference systems. Passive revegetation was partially successful, but regional droughts present inherent challenges to restoring depressional wetlands whose hydrologic regimes are strongly controlled by rainfall variability.     

Waterbird Response to Wetlands Restored Through the Conservation Reserve Enhancement Program

Abstract: Conservation programs that facilitate restoration of natural areas on private land are one of the best strategies for recovery of valuable wetland acreage in critical ecoregions of the United States. Wetlands enrolled in the Conservation Reserve Enhancement Program (CREP) provide many ecological functions but may be particularly important as habitat for migrant and resident waterbirds; however, use of, and factors associated with use of, CREP wetlands as stopover and breeding sites have not been evaluated. We surveyed a random sample of CREP wetlands in the Illinois River watershed in 2004 and 2005 to quantify use of restored wetlands by spring migrating and breeding waterbirds. Waterbirds used 75% of wetlands during spring migration. Total use-day abundance for the entire spring migration ranged from 0 to 49,633 per wetland and averaged 6,437 ± 1,887 (SE). Semipermanent wetlands supported the greatest total number of use-days and the greatest number of use-days relative to wetland area. Species richness ranged from 0 to 42 (x̄ = 10.0 ± 1.5 [SE]), and 5 of these species were classified as endangered in Illinois. Density of waterfowl breeding pairs ranged from 0.0 pairs/ha to 16.6 pairs/ha (x̄ = 1.9 ± 0.5 [SE] pairs/ha), and 16 species of wetland birds were identified as local breeders. Density of waterfowl broods ranged from 0.0 broods/ha to 3.6 broods/ha and averaged 0.5 ± 0.1 (SE) broods/ha. We also modeled spring stopover use, waterbird species richness, and waterfowl reproduction in relation to spatial, physical, and floristic characteristics of CREP wetlands. The best approximating models to explain variation in all 3 dependent variables included only the covariate accounting for level of hydrologic management (i.e., none, passive, or active). Active management was associated with 858% greater use-days during spring than sites with only passive water management. Sites where hydrology was passively managed also averaged 402% greater species richness than sites where no hydrologic management was possible. Density of waterfowl broods was 120% greater on passively managed sites than on sites without water management but was 29% less on sites with active compared to passive hydrologic management. Densities of waterfowl broods also were greatest when ratios of open water to cover were 70:30. Models that accounted for vegetation quality and landscape variables ranked lower than models based solely on hydrologic management or vegetation cover in all candidate sets. Although placement and clustering of sites may be critical for maintaining populations of some wetland bird species, these factors appeared to be less important for attracting migrant waterbirds in our study area. In the context of restored CREP wetlands, we suggest the greatest gains in waterbird use and reproduction may be accomplished by emphasizing site-specific restoration efforts related to hydrology and floristic structure. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):654–664; 2008)     

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.     

A Comparison of Remote Sensing and Ground-Based Methods for Monitoring Wetland Restoration Success

Abstract Efficient and accurate vegetation sampling techniques are essential for the assessment of wetland restoration success. Remotely acquired data, used extensively in many locations, have not been widely used to monitor restored wetlands. We compared three different vegetation sampling techniques to determine the accuracy associated with each method when used to determine species composition and cover in restored Pacific coast wetlands dominated by Salicornia virginica (perennial pickleweed). Two ground‐based techniques, using quadrat and line intercept sampling, and a remote sensing technique, using low altitude, high resolution, color and color infrared photographs, were applied to estimate cover in three small restoration sites. The remote technique provided an accurate and efficient means of sampling vegetation cover, but individual species could not be identified, precluding estimates of species density and distribution. Aerial photography was determined to be an effective tool for vegetation monitoring of simple (i.e., single‐species) habitat types or when species identities are not important (e.g., when vegetation is developing on a new restoration site). The efficiency associated with these vegetation sampling techniques was dependent on the scale of the assessment, with aerial photography more efficient than ground‐based sampling methods for assessing large areas. However, the inability of aerial photography to identify individual species, especially mixed‐species stands common in southern California salt marshes, limits its usefulness for monitoring restoration success. A combination of aerial photography and ground‐based methods may be the most effective means of monitoring the success of large wetland restoration projects.     

基于地表土壤动物与植物完整性指数评估若尔盖沼泽湿地受扰现状

利用地表土壤动物与植物群落生物完整性指数评价若尔盖沼泽湿地受扰现状,为若尔盖沼泽湿地恢复提供依据。2018年7月与2019年7月对若尔盖10处典型湿地(参照区4个,受扰区6个)地表土壤动物与湿地植被群落进行调查。通过对74个候选指标的分布范围、判别能力及相关分析,确定中生性植物、一年生植物、龙胆科植物、一年生植物/多年生植物比4个植物核心指标,地表土壤动物总个体数量、中小型动物类群数量、蜘蛛目物种数量、菌食性土壤动物与腐食性土壤动物5个核心指标,构建若尔盖沼泽湿地地表土壤动物与植物完整性指数。以所有采样点95%分位数为最佳期望值,四分位法确定研究区域未受干扰、轻度干扰程度、中度干扰与重度干扰4个等级,作为判断若尔盖沼泽湿地受扰状况。结果显示,若尔盖沼泽湿地相对原始沼泽、花湖沼泽化草甸2、长期低强度排水疏干区、短期高强度排水疏干区分别处于未受干扰、轻度干扰、中度干扰与重度干扰状态。所调查的若尔盖典型湿地中,20%的湿地未受到干扰,30%的湿地受到轻度干扰,30%的湿地受到中度干扰,20%的湿地受到重度干扰。Pearson相关系数分析显示,地表土壤动物完整性指数与植物完整性指数存在显著正相...     

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.     

Plant traits in response to raising groundwater levels in wetland restoration: evidence from three case studies

Question: Is raising groundwater tables successful as a wetland restoration strategy? Location: Kennemer dunes, The Netherlands; Moksloot dunes, The Netherlands and Bullock Creek fen, New Zealand. Methods: Generalizations were made by analysing soil dynamics and the responsiveness of integrative plant traits on moisture, nutrient regime and seed dispersal in three case studies of re wetted vs. control wetlands with the same actual groundwater levels. Soil conditions included mineral (calcareous and non‐calcareous) soils with no initial vegetation, mineral soils with established vegetation and organic soils with vegetation. Results: The responsiveness of traits to raised groundwater tables was related to soil type and vegetation presence and depended on actual groundwater levels. In the moist‐wet zone, oligotrophic species, ‘drier’ species with higher seed longevity occupied gaps created by vegetation dieback on rewetting. The other rewetted zones still reflected trait values of the vegetation prevalent prior to rewetting with fewer adaptations to wet conditions, increased nutrient richness and higher seed longevity. Moreover, ‘eutrophic’ and ‘drier’ species increased at rewetted sites, so that these restored sites became dissimilar to control wetlands. Conclusions: The prevalent traits of the restored wetlands do not coincide with traits belonging to generally targeted plant species of wetland restoration. Long‐term observations in restored and control wetlands with different groundwater regimes are needed to determine whether target plant species eventually re vegetate restored wetlands.     

基于植物多样性特征的武汉市城市湖泊湿地植被分类保护和恢复

湿地植被多样性特征及其影响因素的调查分析是湿地植被保护与恢复策略制定的基础。借鉴生物多样性热点分析原理,在武汉市城市湖泊湿地植物多样性调查的基础上,研究了湖泊湿地的植被多样性特征,探讨了城市湖泊湿地植被分类保护与恢复对策。结果表明,武汉市湿地维管束植物的物种丰富度、植物多样性、优势度和均匀度指数在各湖泊间的变化趋势较为一致,但在空间变化幅度上存在一定差异。按照物种丰富度、多样性、优势度、均匀度、湿地植被群丛数目,以及典型湿地植物的物种所占比例、丰富度和优势度的差异,可将调查涉及的26个典型湖泊湿地分为原生植被湖泊、次生植被湖泊、人工植被湖泊和退化植被湖泊4类。原生植被湖泊应建立相对严格的湿地保护区,优先保护原有湿地植被。次生植被湖泊最多,城市发展区内的次生植被湖泊应建立30-100m的植被缓冲带,促进植被自然恢复和发育;而农业区的次生植被湖泊应引导和规范湖泊周围的农业生产模式,以减少人类活动干扰。人工植被湖泊应通过建立城市湿地公园,人工促进植被的近自然恢复。而退化植被湖泊则应尽快采用生态工程法促进湿地植被生境改善,并积极开展近自然湿地植被重建与恢复。     

A comparison of created and natural wetlands in Pennsylvania,USA

Recent research suggests that created wetlands do not look, or function, like the natural systems they are intended to replace. Proper planning, construction, and the introduction of appropriate biotic material should initiate natural processes which continue indefinitely in a successful wetland creation project, with minimal human input. To determine if differences existed between created and natural wetlands, we compared soil matrix chroma, organic matter content, rock fragment content, bulk density, particle size distribution, vegetation species richness, total plant cover, and average wetland indicator status in created (n = 12) and natural (n = 14)wetlands in Pennsylvania (USA). Created wetlands ranged in age from two to 18 years. Soils in created wetlands had less organic matter content, greater bulk densities, higher matrix chroma, and more rock fragments than reference wetlands. Soils in reference wetlands had clay loam textures with high silt content, while sandy clay loam textures predominated in the created sites. Vegetation species richness and total cover were both greater in natural reference wetlands. Vegetation in created wetlands included a greater proportion of upland species than found in the reference wetlands. There were significant differences in soils and vegetation characteristics between younger and older created wetlands, though we could not say older created sites were trending towards the reference wetland condition. Updated site selection practices, more careful consideration of monitoring period lengths, and, especially, a stronger effort to recreate wetland types native to the region should result in increased similarity between created and natural wetlands.