Differential Response of Aquatic Oligochaete Species to Increased Nutrient Availability – a Comparative Study between Estonian and Dutch Raised Bogs

To assess the effects of increased nutrient availability on aquatic oligochaetes in raised bogs, species assemblages were compared within and between fairly pristine raised bogs in Estonia and raised bog remnants in The Netherlands. Within the pristine bog landscape a distinct pattern in the species assemblage is present. In the most nutrient-poor water bodies, in the ombrotrophic raised bog, only the fragmenting, almost never mature, acid-tolerant species Cognettia sphagnetorum is present. In pristine Estonian raised bogs Nais variabilis, Lumbriculus variegatus and sexually reproducing species are limited to more minerotrophic water bodies, which have a higher decomposition rate of dead organic matter and, consequently, higher nutrient availability. With ten species the lagg zone is the most species-rich part of a pristine raised bog landscape. Most of these lagg zone species are not present in Dutch bog remnants as this part of the bog landscape has long been cultivated. Nais variabilis occurs in the Dutch bog remnants much more frequently than in Estonian bogs, whereas the frequency of C. sphagnetorum and L. variegatus is similar between both countries. These three species respond differently to the increased nutrient availability in The Netherlands, which could be linked to differences in their diets. In contrast to pristine bog pools, N. variabilis in Dutch raised bog remnants is present in water bodies not influenced by minerotrophic water. In Dutch raised bog remnants the occurrence of oligochaetes is not limited anymore by nutrient availability, due to the higher atmospheric nitrogen and sulphur loads in The Netherlands. Overall, it can be concluded that the degradation of Dutch raised bogs has resulted in the loss of both the nutrient-poor parts of the landscape and the special lagg conditions.     

Laggs can develop and be restored inside a raised bog

The lagg is an integral part of the hydrological system of a raised bog and can add significantly to the biological diversity of the ecosystem. Conservation and restoration of raised bogs should therefore involve this transition zone. The ideal situation for conservation is to protect or restore the natural lagg at the outside margin of the bog. However, it is not always possible to restore the lagg where it was historically situated. An analysis of historic maps of a raised bog in British Columbia, Canada, shows that in areas where the outflow of water from the bog has been impeded, lagg plant communities have naturally colonized parts of the bog that were historically open bog. This suggests that it is possible to create the ecohydrological conditions of a lagg in areas that are currently occupied by bog species. Based on this knowledge and the hydrochemical, hydrological, and vegetative characteristics of a regionally-specific lagg reference ecosystem, we describe several lagg restoration options for locations where it is not possible to restore the lagg at the outside margin of the bog.     

Moorland pools as refugia for endangered species characteristic of raised bog gradients

In intact raised bog landscapes transitions from ombrotrophic into minerotrophic conditions occur. These gradients are lost from many bogs due to peat harvesting and drainage, and are difficult to restore. To determine which endangered species are characteristic of pristine raised bog gradients and their current status in degraded bogs, plants and macroinvertebrates were surveyed in Estonian intact raised bogs and Dutch degraded bog remnants. Dutch national distribution data were used to determine whether communities with these species occurred outside bog habitats. Water chemistry data were used to describe associated environmental conditions. Intact bog gradients were the preferred habitat for six plant species and fifteen macroinvertebrate species, all of which are endangered. In degraded bogs these species were scarce or not recorded. In intact bogs these species lived at sites where runoff from the bog massif came into contact with regional ground water resulting in a gradient in pH, alkalinity, Ca, Fe and ionic ratio. Analysis of Dutch national distribution data revealed aggregations of these endangered species in moorland pools. These pools contained water chemistry gradients similar to those found in pristine bogs, which occurred at sites were groundwater seepage and stream water came in contact. In the past, stream water has been used to increase pH and trophic status of moorland pools facilitating fisheries. Today, this practice offers a conservation strategy for the protection of endangered species for which no short-term alternatives are available.     

Restoration of a Terrestrialized Soak Lake of an Irish Raised Bog: Results of Field Experiments

Soaks (areas of mesotrophic/minerotrophic vegetation within acid bog) add to the overall heterogeneity and biodiversity of raised bog landscapes due to the presence of flora and fauna communities not typically associated with acid bog systems. A field experiment was set up to investigate the potential to restore the minerotrophic and aquatic communities that previously occurred within a soak of an oceanic raised bog in Ireland, which has recently undergone acidification with the expansion of acid bog type vegetation. Three different treatments, control (intact sphagnaceous raft), permeable (sphagnaceous raft removed), and enclosed (sphagnaceous raft removed and plots isolated from surrounding surface water influence) were applied to a total of six plots (each measuring 4 × 4 m), each treatment consisting of two replicates. Within 3 years a sphagnaceous raft with similar vegetation to the surroundings had developed in both permeable plots, while aquatic communities similar to those that occurred at the site in the past had established within the enclosed pots. Our results show that with manipulation of local hydrology it is possible to recreate conditions suitable for aquatic plant communities that once characterized the site. The results also give an insight into the likely processes responsible for the initial terrestrialization of the entire soak over the past century. Application of the results in relation to the site and the widespread practice of restoring bog vegetation on degraded peatlands are discussed.     

Environmental controls of raised-bog vegetation in the Baltic boreo-nemoral zone

Raised peat bogs harbor unique vegetation types in specific hydrological conditions. Environmental controls of peat bog vegetation are relatively well known for the boreal zone, while in the European boreo-nemoral zone healthy raised bogs are nowadays very rare. By contrast, Latvia, located in the transition zone between the nemoral and the boreal biomes, still has a large number of active raised bogs. The aim of the present study was to characterize the environmental controls on raised bog vegetation structure, species composition and ecology in Latvia. The study includes 17 raised bogs, where vascular plants, bryophytes and lichens were recorded in 480 sample plots and related to environmental variables (microtopography, litter cover, electric conductivity, pH, and macroelements Na, K, Ca, Mg and P in bog surface waters). The factor best explaining total species richness and composition was microtopography, which also affected most other explanatory factors. Thereby total species richness and cover were highest on hummocks. However, the importance and direction of the effects of microtopography and the other factors differed between vegetation groups. When disregarding microtopography, species composition was most strongly correlated with alkaline ions and litter cover and for bryophytes also with vascular plant cover. The present study is the first wide-scale study in Latvia relating raised bog vegetation to environmental conditions.     

Effects of a hydrological protection zone on the restoration of a raised bog: a case study from Northeast-Germany 1997–2008

We investigated the changes of water level and vegetation in a restored cut-over raised bog in response to a hydrological protection zone established around the bog. The restoration began 1997 and techniques involved ditch blocking within and around the bog to stimulate a return to conditions of intact bog ecosystems. In order to monitor the rehabilitation of the raised bog, water levels and vegetation have been recorded since before restoration measures began. The monitoring is ongoing, but an assessment of 15 year’s data (1994–2008) is presented. A hydrological protection zone with continuous high water levels could be established around the raised bog which minimizes the runoff of precipitation. Shortly after the first measures, the water levels increased significantly at all dipwells. Parallel to the increasing water levels a vascular plant species assemblage and a diverse Sphagnum community developed. In particular Sphagnum fimbriatum, S. palustre, S. recurvum and S. squarrosum spread efficiently. The cover of trees decreased significantly because of high water levels and ongoing acidification by Sphagnum spp. The high water levels have stimulated the re-vegetation and the hydrology self-regulation of the acrotelm. The successful regeneration of the acrotelm particularly became apparent in years with below-average precipitations (e.g. 2008), when the water levels in the central parts of the raised bog did not fall back to the low level reached in previous years, which had also remarkably water deficits (e.g. 2003).     

Mid‐Holocene pine woodland phases and mire development – significance of dendroecological data from subfossil trees from northwest Germany

Question: Can investigations of subfossil bog‐pine woodlands contribute to the understanding of mire development, especially the influence of climate fluctuations on the fen–bog transition? Location: Lowlands of northwest Germany. Methods: We investigated pine (Pinus sylvestris L.) tree remains (stumps and trunks) buried in peat deposits. Dendrochronology was used to date each sampled tree to calendar years and to reconstruct population dynamics of the pine woodlands. Ecological changes, especially changes in site hydrology during the pine woodland phases were inferred from peat stratigraphic analyses and investigations of stem and root morphology of the tree remains. Results: The subfossil pine woodlands occurred mostly during the transition from fen to raised bog conditions within the mire development. The population dynamics are strikingly wave‐like whereas woodland phases of 100 to 250 years duration are separated by much shorter (10–50 years) phases of high germination and dying‐off rates (GDO phases). Such GDO phases are often synchronous at different sites and are also linked to growth depressions of the independent regional oak master chronology (LSBOC), indicating a climate trigger. Conclusions: The development of raised bogs started about 7000 BC and had a main phase between 5100 and 3600 BC in northwest Germany. The subfossil bog‐pine woodlands document the transitional phase towards the onset of raised bog formation, as characterized by initial dry conditions that were followed by increasing wetness of the sites, whereas this development is at least partly the result of climate variations.     

Types and Succession of Forest Bogs in Hingganling and Changbaishan

Climate and geomorphy arc the main factors of the formation of forest bogs in Hingganling and changbaishan. The bogs are both multiple in types and widespread in distribution. There exist not only the type of lower bog, but also that of middle bog and raised bog. They are chiefly distributed in the alluvial flat or valley and in the watershed. The succession process of forest bog is generalized into two kinds: (1) The formation of forest bogs as a result of the natural succession of forest vegetation under the influence of natural conditions. (2) The formation of forest bogs as a result of the bogginess in the vicinity of forestland.     

Effects of Rewetting Measures in Dutch Raised Bog Remnants on Assemblages of Aquatic Rotifera and Microcrustaceans

Species differ in their life cycle, habitat demands and dispersal capacity. Consequently different species or species groups may respond differently to restoration measures. To evaluate effects of restoration measures in raised bog remnants on aquatic microinvertebrates, species assemblages of Rotifera and microcrustaceans were sampled in 10 rewetted and 10 non-rewetted sites, situated in 7 Dutch raised bog remnants. A total of 129 species (Rotifera 108, Cladocera 15, Copepoda 6 species) were found. The species assemblages, total numbers of species and numbers of characteristic raised bog species did not differ between the 10 rewetted and 10 non-rewetted sites. The dominant pattern in the variation in microinvertebrate assemblages could be explained by the presence or absence of open water and variation in physico-chemical variables of surface water and organic matter. Furthermore, the species assemblages of water bodies situated in the same area were on average more similar to each other than to assemblages from other areas. These differences between areas may be due to differences in environmental conditions of water bodies, and possibly also to differences in the local species pool and the subsequent immigration sequence of species. We conclude that, in contrast to earlier findings on aquatic macroinvertebrates, populations of microinvertebrate species, including characteristic species, can either persist in the raised bog remnants during the process of rewetting or (re-)establish within a relatively short period of time (less than about 5 years).     

Do restoration measures rehabilitate fauna diversity in raised bogs? A comparative study on aquatic macroinvertebrates

To assess whether raised bog restorationmeasures contribute to the conservation andrestoration of the fauna diversity,macroinvertebrate species assemblages werecompared between water bodies created byrewetting measures and water bodies whichhave not been subject to restorationmeasures, but are remnants offormer peat cuttings and trenches used forbuckwheat culture in the past.The restoration sites were inhabited bycharacteristic raised bog species and rarespecies, but their numbers were higher atthe remnant sites not affected byrestoration management. A considerablenumber of characteristic and rare faunaspecies were only found at the remnantsites. The remnant sites includedconsiderably more variation inmacroinvertebrate species assemblages andhad a higher cumulative species richness.The number of characteristicmacroinvertebrate species was not clearlyrelated to the presence of a characteristicraised bog vegetation. In restoration sitesnumbers of rare and characteristic speciesper site tended to increase with the timeelapsed after rewetting. However,restoration measures will not automaticallyresult in restoration of a more or lesscomplete macroinvertebrate speciesspectrum, as restoration measures have sofar resulted in habitats for only a limitednumber of the characteristic species.When planning restoration measures, it isrecommended to protect the populations ofrare and characteristic species present inthe area, as these populations may becomethe sources for colonization of rewettedsites. Safeguarding habitat diversityduring the restoration process andrestoration of different elements of thehabitat diversity of complete raised bogsystems will result in the characteristicfauna diversity being conserved andrestored more successfully.     

Contrasting responses to environmental changes by pine (Pinus sylvestris L.) growing on peat and mineral soil: An example from a Polish Baltic bog

A comparison of the tree-ring width of pines growing in areas adjacent to a peat bog and on a Baltic raised bog dome suggests that cambium activity in each tree group is affected by different factors. The study was aimed at pinpointing effects of meteorological factors on two pine populations growing under different hydrological conditions. The study further sought to identify periods during which anthropogenic pressure affected the two populations. The pines growing on mineral soil were characterised by ring-width growth–climate responses typical of this part of Europe, whereas the tree-ring growth of the pines growing on the peat bog showed no unequivocal relationship with meteorological conditions. The tree-ring width growth dynamics of that population responded primarily to changes in the level of the groundwater table. These changes were associated with human activities over the last two centuries. The development of the tree stands on the peat bog and in its immediate vicinity was reconstructed using this assumption and available historical evidence. A banding drainage ditch dug around 1880 resulted in the drying of the peat bog, the introduction of pines, and the forestation of the bog. Digging of central ditches (in the 1960s) resulted in periodic desiccation of the bog surface and reduction of the tree-ring widths; similar responses were observed in the 1980s as a consequence of the deepening and opening of the drainage ditches. The recent years are characterised by decreasing ring-width growth as a result of the damming of drainage ditches. Damming resulted in an increase of the groundwater table level in the bog and in a partial inundation of tree roots. This partial inundation interfered with gas exchange and adversely affected the health status of the pines studied. Our results allow conclusions to be drawn regarding peat bog palaeohydrology and facilitate absolute dating of changes associated with anthropogenic transformations. In active nature protection, such data are of key importance for understanding the functioning of a peatland and for planning active conservation measures.     

Impact of climatic change on bog ecosystems,with special reference to sub-oceanic raised bogs

The relation between climatic conditions and type of peatland ecosystem in the different climate zones in Europe is discussed. Special attention is given to the hydrology of raised bogs in the sub-oceanic region. Possible effects of climatic change on such raised bog systems are discussed in terms of changes in water discharge, ground-water table, rate of peat accumulation, and flora and vegetation. It is concluded that future changes, as suggested by the more widely accepted scenarios for climatic change, will seriously disrupt the ecological functioning of these peatland ecosystems, and it is doubtful whether at least the most southerly examples of sub-oceanic raised bogs will at all survive. Finally, suggestions are given for future research on the impact of climatic change on peatland ecosystems.     

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.     

Raised peat bog development and possible responses to environmental changes during the mid- to late-Holocene. Can the palaeoecological record be used to predict the nature and response of raised peat bogs to future climate change?

Palaeoecological analyses of raised peat bog deposits in northwest Europe show the naturalness, antiquity and robust response of these ecosystems to environmental changes from c. 7800 years ago to the present. A review of the techniques used to identify these long-term features is presented and the role of climate change, autogenic change processes and human disturbance is discussed. Millennial records of vegetation changes recorded in peat deposits demonstrate the response (often rapid) of raised peat bog vegetation to climatic changes during the mid-Holocene, Bronze Age/Iron Age transition and the Little Ice Age. Greenhouse warming scenarios exceed the reconstructed Holocene record of climatic changes (c. the last 11, 500 years), and bog-water tables may fall considerably. A combination of centennial palaeoecological analyses of bogs affected by human disturbance and experimental manipulations have been used as analogues for the potential response of raised peat bog vegetation to these changes. These show that possible greenhouse gas climate forcing scenarios may exceed the ability of Sphagnum- dominated raised peat bogs to respond to projected increases in summer temperature and decreases in summer precipitation. In combination with increasing N deposition, a loss of their Sphagnum-rich vegetation and increases in the abundance of vascular plants could occur on decadal timescales.     

Late Holocene climate change and human impact recorded in a south Swedish ombrotrophic peat bog

A peat core from a raised bog in southern Sweden was examined (plant macrofossils, pollen/non-pollen microfossils, colorimetric humification, carbon/nitrogen ratios, bulk densities, loss on ignition) to investigate the effects of climate change and human impact on the plant species composition and carbon accumulation of the peat forming vegetation. ¹⁴C wiggle-match dating was applied for fine-resolution dating. Cooling at the start of the Little Ice Age was reflected by a decline of thermophilous trees from the pollen record between ca. cal AD 1275–1590, coinciding with increases in atmospheric Δ¹⁴C pointing to decreases of solar activity (Wolf and Spörer minimum). Human impact also decreased. Later, the effect of human impact was clearly visible in the form of a black brown, decomposed peat layer, the top of which marks a gap of more than 300 years. Artificial drainage probably caused secondary decomposition and oxidation of the peat. From ca. cal AD 1960 the water table of the peat bog was restored following construction of a road and raised bog vegetation regenerated.     

POLLEN SUCCESSION,ABSOLUTE POLLEN FREQUENCY,AND RECURRENCE SURFACES IN CENTRAL JAPAN

A generalized pollen diagram, associated with three simplified pollen diagrams from Tsubogakure (1,500 m), Nakatashiro (1,400 m) and Yashima-ga-hara (1,650 m) bogs in central Japan, represents five pollen zones for the last 12,000 years, i.e., L (before 10,500 B.P., pine-boreal); R I (10,500–9,500 B.P., boreal-oak); R II (9,500–4,500 B.P., temperate); R IIIa (4,500–1,500 B.P., temperate-boreal); and R IIIb (after 1,500 B.P., pino-nonarboreal). Absolute pollen frequency is high in well-humified peat, in gyttja (deposited immediately below the first peat formation), and in peat in the part of the R IIIa cooling stage, and it is low in less-humified peat, since the former sediments have slow and the latter rapid rates of accumulation, respectively. Changes of plant communities should affect the absolute pollen frequency, but changes of sedimentation rates are more critical. After a re-examination of Nakatashiro bog, it is hardly possible to recognize a recurrence surface in the European sense, nor can the accumulation of thin tephra on the bog surface be responsible for a temporary halt in peat growth. Nakatashiro bog (like Tsubogakure bog) is a low-moor bog, and true recurrence surfaces would not be expected in it. In a raised Yashima-ga-hara bog, however, there are seven recurrence surfaces without a volcanic ash band; the well-humified horizons correspond to low values of Sphagnum spores and Cyperaceae pollen, and the less-humified horizons to high values of Sphagnum spores and Cyperaceae pollen. Peaks of these species in the upper core correspond to those Cryptomeria pollen, an indicator of the high precipitation (generally >1,800 mm/yr). Regularly interrelated fluctuations among these species, absolute pollen frequency, and peat horizons suggest that the precipitation was low in well-humified peat and was high in less-humified peat.     

A

A valley mire was sampled on the flanks of Swampy Hill, east Otago, New Zealand. It formed in a narrow valley, apparently originally comprising two basins. The end of the mire nearest the outlet contained species typical of fens (i.e., rheotrophic mires). At the head of the valley there was a section of the mire with mixed vegetation cover comprising the tussock grass Chionochloa rubra, Sphagnum species, and cushion/herb/shrub cover. Ombrotrophic status of this section was indicated by a slightly raised profile, greater acidity, lower exchangeable Na and K, and lower substrate cation exchange capacity, identifying it as a bog. Total Ca:Mg molar ratios were generally above 1.0, but this rule-of-thumb for ombrotrophic status may be inapplicable here. It is not known whether New Zealand Sphagnum species are as efficient at lowering the pH as those investigated elsewhere. Macrofosssil evidence indicates that some components of the bog, such as Sphagnum and epacridaceous subshrubs, have remained constant, almost since the inception of the bog. However, Empodisma minus, currently absent from the bog and rare in the region, was present at one stage. The change from cover with Empodisma and Dracophyllum as significant components, to the present Chionochloa/Sphagnum/cushion composition, occurred a few hundred years ago, probably initiated by fire. Comparison with preliminary information for other bogs suggests that those in the eastern part of the South Island vary considerably in species composition, with individualistic assemblages of species. The site is seen as having high conservation values. To protect these values the bog needs protection from invasive exotic weeds, and from damage by wild pigs.     

Development of ombrotrophic raised bogs in North-east Germany 17?years after the adoption of a protective program

The present study reports on the development of ombrotrophic raised bogs in NE Germany after the adoption of a protective program with a focus on the hydrological and floristic changes in two simultaneously restored cut-over bogs as a reference for all other bogs. At the moment, four fifths of the bogs area is dominated by woody vegetation forms and <5?% is characterized by typical raised bog vegetation. The trend of increasing areas with woody vegetation forms and decreasing areas with vegetation typical for ombrotrophic raised bogs could not be prevented despite increasing the portion of revitalized areas. The reason for the negative developments is founded in the different types of raised bogs in NE Germany, which differ in regard to the historical lagg area and the original grown up raised peat body. This as well as the kind and intensity of anthropogenic use have significant implications for the possibilities of revitalization and protection. Except for those bogs where no peat remnants remain, the revitalization of cut-over raised bogs in NE Germany can succeed if an almost closed hydrological protection zone (HPZ which is equal to the historical lagg area) is established so that the gradient of entire lateral water flow between the higher lying peat remnant and the lower lying surrounding area is reduced. The attainment of a lateral water flow gradient comparable to the original state and of a water-saturated peat body succeeds in turn in the precondition for growing Sphagnum species, which readjust the system??s self regulation. The comparison of two bogs with similar preconditions concerning location, climate, and anthropogenic transformation has shown that an incompletely closed HPZ is one important reason for the decreasing portion of intact raised bogs with their typical vegetation. The influence of climate change on current hydrological and floristic changes in NE German ombrotrophic raised bogs has less influence on the success of revitalization than the historic grown type of bog and the intensity of anthropogenic use.     

Palynological study of a holocene peat and a miocene coal deposit from NW Borneo

The development of a Holocene peat near Marudi (Sarawak) and a Miocene coal near Berakas (Brunei) is studied pollen-analytically and stratigraphically by comparison with present-day swamp vegetation along the NW Bornean coast. A number of 76 pollen and spore types were recognized and are briefly diagnosed.The Marudi profile starts on mangrove sediment and shows a succession which is closely comparable to the present-day zonation of the large raised bog of which it forms part.The Berakas profile starts on fluviatile sediments and remains in the mixed swamp forest stage. This small deposit has remained close to the coast and peat growth is terminated by marine transgression.The floristic composition of the mixed swamp forest stage in both bogs, separated in age by approximately seven million years is closely comparable. Minor differences which exist can be attributed to differences in size, ecologic conditions and accessibility from mainland reservoirs.Only on spore type, Stenochlaena areolaris has become extinct in Borneo.     

Persistent versus transient tree encroachment of temperate peat bogs: effects of climate warming and drought events

Peatlands store approximately 30% of global soil carbon, most in moss‐dominated bogs. Future climatic changes, such as changes in precipitation patterns and warming, are expected to affect peat bog vegetation composition and thereby its long‐term carbon sequestration capacity. Theoretical work suggests that an episode of rapid environmental change is more likely to trigger transitions to alternative ecosystem states than a gradual, but equally large, change in conditions. We used a dynamic vegetation model to explore the impacts of drought events and increased temperature on vegetation composition of temperate peat bogs. We analyzed the consequences of six patterns of summer drought events combined with five temperature scenarios to test whether an open peat bog dominated by moss (Sphagnum) could shift to a tree‐dominated state. Unexpectedly, neither a gradual decrease in the amount of summer precipitation nor the occurrence of a number of extremely dry summers in a row could shift the moss‐dominated peat bog permanently into a tree‐dominated peat bog. The increase in tree biomass during drought events was unable to trigger positive feedbacks that keep the ecosystem in a tree‐dominated state after a return to previous ‘normal’ rainfall conditions. In contrast, temperature increases from 1 °C onward already shifted peat bogs into tree‐dominated ecosystems. In our simulations, drought events facilitated tree establishment, but temperature determined how much tree biomass could develop. Our results suggest that under current climatic conditions, peat bog vegetation is rather resilient to drought events, but very sensitive to temperature increases, indicating that future warming is likely to trigger persistent vegetation shifts.