Persistence and recolonisation determine success of bog restoration for aquatic invertebrates: a comment on Mazerolle et al. (2006)

1. Mazerolle et al. (2006) concluded that some aquatic invertebrate species, including bog‐associated species, readily colonise man‐made bog pools. In contrast, in Dutch bog remnants Van Duinen et al. (2003) found that a considerable number of bog‐associated species do not colonise newly created bog pools. 2. The conclusion of Mazerolle et al. (2006) is based on vagile aquatic invertebrates. Here, we question whether their conclusion can be extended to more sedentary species, which were not captured in the Canadian study, but made up an important part of the invertebrate assemblage in the Dutch study. This discrepancy could be caused by sampling artefacts, low colonisation rates of these species or an incomplete restoration of site conditions. 3. In Canada, chances of recolonisation may be higher than in the Netherlands, as natural and near‐natural bogs are more extensive. In the Netherlands, with low chances of recolonisation, persistence of species may be more important. To disentangle the relative importance of persistence and recolonisation, evaluations of the success of restoration projects need to cover the entire invertebrate assemblage, including both vagile and more sedentary species.     

Animal and vegetation patterns in natural and man-made bog pools: implications for restoration

1. Peatlands have suffered great losses following drainage for agriculture, forestry, urbanisation, or peat mining, near inhabited areas. We evaluated the faunal and vegetation patterns after restoration of a peatland formerly mined for peat. We assessed whether bog pools created during restoration are similar to natural bog pools in terms of water chemistry, vegetation structure and composition, as well as amphibian and arthropod occurrence patterns. 2. Both avian species richness and peatland vegetation cover at the site increased following restoration. Within bog pools, however, the vegetation composition differed between natural and man‐made pools. The cover of low shrubs, Sphagnum moss, submerged, emergent and floating vegetation in man‐made pools was lower than in natural pools, whereas pH was higher than in typical bog pools. Dominant plant species also differed between man‐made and natural pools. 3. Amphibian tadpoles, juveniles and adults occurred more often in man‐made pools than natural bog pools. Although some arthropods, including Coleoptera bog specialists, readily colonised the pools, their abundance was two to 26 times lower than in natural bog pools. Plant introduction in bog pools, at the stocking densities we applied, had no effect on the occurrence of most groups. 4. We conclude that our restoration efforts were partially successful. Peatland‐wide vegetation patterns following restoration mimicked those of natural peatlands, but 4 years were not sufficient for man‐made pools to fully emulate the characteristics of natural bog pools.     

Ecological restoration success: a policy analysis understanding

This article discusses how ecological restoration success can be understood and evaluated using a policy analysis lens. First, this article details a conceptual tool that helps to develop a more encompassing set of criteria to assess restoration activities that provide socioeconomic benefits. Second, by broadening the understanding of restoration success and how it can be evaluated, it allows a more critical view of evaluation itself and its uses as a policy tool. A table is presented that can help practitioners reveal preferences and clarify the aims and objectives of particular initiatives. The table also sensitizes practitioners to the complexity of the links between restoration rationales and evaluation criteria, which in turn may open up much needed discussion and dialogue between restoration participants about the underlying values an actor may wish to promote. It heightens awareness of the fact that evaluation methods need to recognize that restoration is driven by multiple rationales often in the same project, both process driven and output oriented, which in turn can change over time. Adding process and output criteria together may also raise issues of priority. Evaluation criteria thus need to be assigned in ways that reflect these multiplicities, while at the same time recognizing that some restoration values might be conflictual and that there may be winners and losers. Furthermore, judgement about “failure” of a project can change as new goals emerge in delivery and implementation. Ecological restoration evaluation should therefore be ongoing, contextual, and not a one‐off event.     

Hydrological differences between bogs and bog-relicts and consequences for bog restoration

The hydrology of bog relicts differs from that in undisturbed bogs. The surface layers of these relicts mostly consist of moderately to strongly humified, secondary weathered peat as a result of drainage and peat cutting. The hydrophysical properties of these layers cause relatively high groundwater level fluctuations. Deep drainage systems, both in the bog relicts and in their surroundings, may have increased the downward seepage. Reduction of these downward water losses may be crucial for the restoration of the required hydrological conditions in certain bog relicts (hydrological bufferzone as external water management option). The potential of internal hydrological modifications, where the increase in storage capacity near the surface is essential, should be emphasized in many bog relicts. Considerable reductions in water level fluctuations can be achieved e.g. when the open water within the area is enlarged and when this water is equally distributed over the area with small peat ridges in between. In general, attention should be given to both the internal and external options in studies on water management.     

Diatom flora of a kettle-hole bog in relation to hydrarch succession zones

Diatom assemblages were compared to the vegetational seres and to physical and chemical parameters of a kettle-hole bog which had distinct hydrarch successional zones and was in turn surrounded by a cattail marsh and a willow swamp. Multivariate analysis of variance showed the water parameters (temperature, pH, conductivity, color, free calcium) among the zones were significantly different (p < 0.0001). Diatoms were enumerated using the first 500 valves counting method and results showed each zone had a distinct flora. Cluster analysis of the diatom data by both species and zones grouped the bog successional zones into one major group and the marsh/swamp zones into the second major group. The occurrence of well defined seral stages of vegetation and diatoms suggests microorganisms are undergoing ecological succession in kettle-hole bogs.     

Improving sampling designs for measuring restoration in aquatic habitats

Restoration of degraded habitat is an increasingly important toll for management. Unfortunately, much of the emphasis has been on restoring large structural elements of habitat (e.g. planting vegetation,removing weeds), with little consideration about how well these activities restore ecologically functioning habitat. There has been considerable research in recent years into improving sampling designs and analytical techniques to measure the effects of environmental impacts taking into account the large spatial and temporal variability that occurs naturally in undisturbed habitats. In a similar manner to detection of impacts, restoration needs to be measured as an interaction between spatial and temporal components of variation against a variable background. Very few studies of restoration have explicitly addressed how best to do this. Neither have they attempted to assess the usefulness of some of these new techniques for measuring restoration. This review discusses some of the problems that need to be considered when measuring restoration and the potential value of some of these new methodologies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Vegetation and environment of a New Zealand raised bog

Abstract. The vegetation of a mire in a medium‐high rainfall area of South Island, New Zealand is described. The central part of the bog is raised 6 m above the surroundings, suggesting that it is ombrotrophic, and the species present are those of apparently ombrotrophic bogs elsewhere in New Zealand. pH of < 4.0 and Ca/Mg molar quotient of < 1.0 also indicates ombrotrophic conditions. Within the mire, these criteria provide effective discrimination between the fen (rheotrophic) and bog (ombrotrophic) communities. A bimodal distribution of ordination scores suggests that the change in pH and in Ca/Mg quotients cause a switch to operate.     

CH4 emission from a hollow-ridge complex in a raised bog: The role of CH4 production and oxidation

The aim of this study was to correlate magnitude andcontrols of CH₄ fluxes with the microtopographyand the vegetation in a hollow-ridge complex of araised bog. High CH₄ emission rates were measuredfrom hollows and mud-bottom hollows, while hummocksconsumed atmospheric CH₄ at a low rate. Thehighest emissions were measured from plots with Eriophorum vaginatum and Scheuchzeriapalustris. CH₄ emission ceased after Scheuchzeria had been clipped below the water table,indicating the importance of this aerenchymatic plantas a conduit for CH₄.Peat in the upper catotelm of hollows was younger andless decomposed than in hummocks. Potential CH₄production in vitro was higher and themethanogenic association was better adapted to highertemperatures in hollow than in hummock peat. Highertemperatures in hollows resulted in a strongerCH₄ source in hollows than in hummocks. Negativefluxes from hummocks indicated that even in wetlandsmethanotrophic bacteria exist that are able to oxidizeCH₄ at atmospheric mixing ratios, and thatoxidation controls CH₄ emission completely. TheCH₄ mixing ratio was low in the acrotelm, but itincreased within the catotelm. Comparing fluxesmeasured in static chambers with fluxes calculatedfrom the porewater CH₄ profiles it was deducedthat the zone of methane oxidation was located closeto the water table.In hollows, CH₄ production at in situtemperature was far higher than emission into theatmosphere, corresponding to an oxidation rate ofnearly 99%. The CH₄ flux between the catotelmand the acrotelm of hollows was also higher than theemission, indicating the importance of CH₄oxidation in the aerobic acrotelm, too. CH₄microprofiles showed that CH₄ oxidation inmud-bottom hollows was confined to the topmost 2 mm,and that in Sphagnum-covered hollows CH₄oxidation occurred at the lower edge of green Sphagnum-parts.     

DNA metabarcoding uncovers dispersal-constrained arthropods in a highly fragmented restoration setting

Degraded areas are often restored through active revegetation; however, recolonization by animals is rarely engineered. Recolonization may be rapid for species with strong dispersal abilities. However, poor dispersers, such as many flightless arthropods, may struggle to recolonize newly restored sites. Actively reintroducing or “rewilding” arthropods may therefore be necessary to facilitate recolonization and restoration of arthropod communities and the ecological functions they perform. However, active interventions are rare. The purpose of this study was twofold. First, we asked whether potential source remnant arthropod communities were dispersal-constrained and struggling to recolonize restoration sites. Second, we tested whether reintroducing entire arthropod communities from remnant populations would help dispersal-constrained species establish during farmland ecological restoration in southern Australia. Rewilding was conducted in summer 2018 by transplanting leaf litter, soil, and entire communities contained within it from remnant source populations into geographically isolated restoration sites, which were paired with untreated controls (n = 6 remnant, rewilding transplant, and control sites). We collected leaf litter and extracted arthropod communities 19 months after the initial rewilding event, then sequenced mite, springtail, and insect communities using a metabarcoding approach. Within all groups, community similarity decreased with spatial distance between sites, suggesting significant dispersal barriers. However, only mite communities showed a strong response to rewilding, which was expressed as increased compositional similarity toward remnant sites and greater species richness relative to controls. Our results demonstrate that many arthropod species may struggle to recolonize geographically isolated restoration sites and that full community restoration requires active interventions via rewilding.     

A review of methodologies and success indicators for coastal wetland restoration

Coastal wetlands are considered to be amongst the most productive ecosystems and can provide invaluable ecological services. However, coastal wetlands are listed amongst the most threatened ecosystems suffering from anthropogenic activities. The loss or degradation of coastal wetlands has drawn a high level of attention to wetland restoration. Improvement of the structure and function of degraded, damaged and destroyed wetlands may be achieved through ecological restoration. Large numbers of restoration projects have been conducted worldwide based on different restoration goals and different methods. It is undoubtedly important to evaluate whether coastal wetland restoration is successful. However, coastal wetland restoration assessment has become challenging because of current disagreement on definitions and concepts of restoration evaluation. We reviewed the methodology of coastal wetland restoration and criteria for success evaluation, and then summarized the issues for current wetland restoration and success evaluation based on literature review. Moreover, we used an estuarine wetland affected by urbanization as a sample to demonstrate how to establish a success indicator system for guiding wetland restoration and evaluating the success of wetland restoration.     

A practical technique for non-destructive monitoring of soil surface invertebrates for ecological restoration programmes

Summary This study investigates the suitability of using wooden discs as facsimiles for natural fallen logs to non‐destructively monitor invertebrates. Wooden discs cut from tree trunks were placed on the ground at five sites and monitored. A diverse range of species was found under the discs including large numbers of some species. On Quail Island, Pine, Macrocarpa, Oak and Beech discs were compared. Beech discs had significantly fewer invertebrates and recognizable taxonomic units than other disc types. Pine discs had significantly more flatworms than the other three disc types. A comparison of invertebrate numbers when discs were placed directly on soil or grass indicated that larger numbers of individuals and recognizable taxonomic units were found under discs placed on bare soil compared with those on grass. Discs with a soil cavity beneath had significantly fewer individuals and recognizable taxonomic units than discs without cavities. Carabids showed considerable seasonal variation, with highest numbers in spring and lowest in winter, and larger numbers were found under discs at moist sites. Skinks over‐wintered under discs in drier open sites at Lincoln and Quail Island. Disc condition was assessed after 28 months and showed Macrocarpa had deteriorated the most of the four disc types. Wooden discs are a useful tool for the ecological management of terrestrial invertebrate fauna in restoration programmes for monitoring and considerable potential exists for discs to provide habitat for restoration of terrestrial invertebrate taxa.     

Ecological restoration of aquatic and semi-aquatic ecosystems in the Netherlands: an introduction*

Hydrobiologia - In 1989, a symposium was held under the title `Netherlands-Wetlands', aiming at the presentation of the state of the art of the existing knowledge of structure and functioning...     

武汉东湖水生植被及其恢复途径探讨

１９９２～１９９３年对武汉东湖三个主要湖区（郭郑湖、汤林湖和牛巢湖）水生植被的调查表明,该湖区共有水生植物３２种,优势种为大茨藻、狐尾藻、苦草和菱。金鱼藻呈不断扩大的趋势。植被类型可分为１１个群丛,植被面积约为０．６５ｋｍ￣２,总生物量为１２３６．３９ｔ（湿重）,植被带状分布仅见于汤林湖北部和其他部分湖汊。汤林湖和牛巢湖水生植被正处于自然恢复演替阶段。     

The acceptable range of variation within the desirable stable state as a measure of restoration success

It is standard practice to compare the status of performance indicators between restoration and reference sites to monitor restoration progress and demonstrate restoration success. However, standard methods for defining the reference ecosystem, selecting reference sites, and measuring success are surprisingly lacking. Our study develops these methods based on the acceptable range of variation (ARV) within the desirable stable (reference) state as a measure of restoration success. The method (1) constrains application to the contemporary landscape to avoid the problematic historical range of variation concept and idealized restoration targets; (2) acknowledges the theory of alternative stable states and ecosystem dynamics and posits that the reference ecosystem should be clearly defined as a desirable stable (reference) state; and (3) shows that identifying an acceptable thematic (classification) scale and an acceptable management timeframe is essential to defining the desirable stable (reference) state. We present two approaches to calculating an ARV and a simulation method to explore reference site replication sufficiency. We apply the methods to two contrasting Australian restoration case studies and recommend that routine adoption of these methods would make a significant contribution to the science and practice of restoration ecology and to the assessment of restoration success.     

Polytrichum Strictum as a Solution to Frost Heaving in Disturbed Ecosystems: A Case Study with Milled Peatlands

Substrate instability is a common problem in many disturbed ecosystems. In the case of milled harvested peatlands, the pioneer moss Polytrichum strictum is commonly found; it is well adapted to tolerate the harsh microclimatic conditions and peat instability of these sites. A field experiment was used to determine the effectiveness of P. strictum against frost heaving, a major type of disturbance on bare peat. Wooden dowels and fir trees (Abies balsamea) placed in a P. strictum carpet experienced almost no frost heaving, whereas heaving was severe on bare peat. Reintroduced P. strictum fragments thinly spread on bare peat reduced but did not eliminate frost heaving. Straw mulch (a protective cover often required in peatland restoration) effectively reduced heaving in the fall, but was less effective in the spring because it had partially decomposed. The P. strictum carpet, P. strictum fragments, and straw mulch reduced frost heaving by reducing the number of freeze–thaw cycles, by slowing the rate of ground thaw in the spring, and by reducing the unfrozen water content of the peat during the spring thaw. Different species of Polytrichum mosses should be considered for the restoration or regeneration of disturbed ecosystems where soil stability is problematic.     

Rehabilitation of industrial cutaway Atlantic blanket bog in County Mayo,North-West Ireland

Bord na Móna (the Irish PeatDevelopment Corporation) began peatextraction at Bellacorick, in County Mayo,in the north-west of Ireland in 1961. Thepeat production area comprised 8000 ha ofAtlantic blanket bog. To date, about 25%of the area has been taken out ofproduction as the peat resources wereexhausted. The cutaway landscape isheterogeneous, with some intact bogremnants among gravel hills bared throughpeat erosion, shallow acid highly-humifiedpeat deposits overlying relatively levelglacial till, and occasional pockets ofmineral-enriched peat in depressions. Theaims of the work described here are (a) toprovide a baseline vegetation survey of thecutaway, (b) to test potential managementtools for accelerating re-vegetation, and(c) to promote the re-establishment ofpeatland characteristics where possible.Thirteen plant communities were recorded onthe cutaway bog at Bellacorick. Extensiveareas of cutaway are colonised by Juncus effusus. Peatland communities havedeveloped where the drainage of cutaway hasbeen impeded and the water-table remains ator above the surface. Remnants of intactAtlantic blanket bog within the productionarea provide a local source of propagulesfor colonisation of adjacent bare cutaway.They also constitute locations for plantswith restricted distributions within theproduction area.Experimental plots were used to show thepositive impacts of (a) re-wetting ofcutaway surfaces in promoting thecolonisation and spread of Sphagnum,and (b) ridging of exposed gravel till thatprovides waterlogged and sheltered furrowsin which accelerated plant colonisationtakes place.A management plan is currently beingdevised for the rehabilitation of theBellacorick cutaway. Bog remnants should bemaintained as an essential part ofrehabilitation management. Rehabilitationwill include restoration of peat-formingconditions facilitated by waterlogging,which has been shown in experimental trialsto be enhanced by dam construction,infilling of drains and surface ridging. AtBellacorick, it is evident that, with time,peat-forming conditions can be restoredwith minimal management and economic cost.     

Diurnal and seasonal variation of carbon dioxide exchange from a former true raised bog

Carbon dioxide exchange was measured, using the eddy covariance technique, during a one and a half year period in 1994 and 1995. The measurements took place over a former true raised bog, characterized by a shallow peat layer and a vegetation dominated by Molinia caerulea. The growing season extended from May until late October, with a maximum LAI in August of 1.7. The carbon balance shows a net release of 97 g C m^–2 y^–1 (265 kg C ha^–1 y^–1) from the peat bog ecosystem to the atmosphere. During June, July and August there is net consumption of CO₂, while during the rest of the year there is net production of CO₂. The average daytime assimilation rates ranged between – 0.2 and – 0.5 mg CO₂ m^–2 s^–1 (– 45 and –11.3 μmol CO₂ m^–2 s^–1), in a period where the LAI ranged between 1 and 1.7. A high vapour pressure deficit (> 15 hPa) corresponding with high temperatures was found to reduce the assimilation rate by on average 50%. Apart from these factors, LAI and the soil temperature codetermine the net exchange of CO₂. The total nocturnal respiration during the growing season lies within the same order as the average daytime net assimilation rate. Temperature was found to be the main factor controlling soil respiration, with a Q₁₀ of 4.8.     

Impedance conversion as a method of research for assessing behavioural responses of aquatic invertebrates

The concept of non-invasive, remote monitoring of the behaviour of aquatic organisms has been a long-sought research goal. In an effort to overcome the induction of artefacts and the generation of unnatural behaviour, a system of quantification of organism activity was developed based upon the theory of impedance conversion. The system is described in detail, and application was made to assess the respiratory behaviour of three aquatic invertebrates,Daphnia magna, Chironomus sp., andTanytarsus sp. in response to declining oxygen tensions. The system shows broad applicability for quantifying organism behaviour over four orders of magnitude in size range.