Fire history and vegetation recovery in two raised bogs at the Baltic Sea

Questions: What were the bog fire patterns and frequencies in two boreal peatlands during the last 5000 years? What is the nature and time‐scale of post‐fire vegetation successions? Were fire events related to climate? Location: Männikjärve bog, central east Estonia; Kontolanrahka bog, southwest Finland. Methods: Macroscopic charcoal, plant macrofossils and radiocarbon dating were examined. Redundancy analysis was used in the assessments. Results: During the last 5000 years, both of the above peatlands have experienced several fire events. A typical pre‐fire vegetation community consisted of dry hummock Sphagnum spp., often accompanied by Calluna vulgaris. Only the most severe occasional fires resulted in a dramatic change in the vegetation composition. In these cases, a wet shift occurred, where the pre‐fire hummock community was replaced by a wet hollow community. Calluna vulgaris was found to be a key species in both pre‐ and post‐fire vegetation dynamics. The recovery time of dry microtopes following severe combustion and the subsequent hydrological change could take up to 350 years. Even after a long‐lasting wet phase, the post‐fire disturbance succession led towards a dry hummock community. Conclusions: Fire succession appeared to be cyclic, starting as and developing towards a dry hummock community. Fires have been a regular phenomenon in boreal bogs, even in regions with rather low human impact. The fire history records did not indicate any direct link to the regional long‐term climate.     

Impact of rewetting on the vegetation of a cut‐away peatland

Abstract. We tested whether rewetting improved environmental conditions during peatland restoration and promoted colonization and development of mire vegetation. Vegetation change was monitored in a cut‐away peatland one year before, and four years after, rewetting. Colonizers before rewetting were perennials, mostly typical of hummocks or bare peat surfaces. The main variation in vegetation was related to variation in the amounts of major nutrients and water table level. The wettest site with the highest nutrient level had the highest total vegetation cover and diversity, as well as some species typical of wet minerotrophic mires. Raising the water table level above, or close to, the soil surface promoted development of wet minerotrophic vegetation. Diversity initially decreased because of the disappearance of hummock vegetation but started to recover in the third year. Eriophorum vaginatum and Carex rostrata were both favoured, and bryophytes typical of wet habitats colonized the site. Moderate rewetting promoted the development of Eriophorum vaginatum seedlings and an increase in the cover of tussocks. Bryophytes typical of disturbed peat surfaces spread. In the control site development continued slowly towards closed hummock vegetation. The study showed that raising the water level to, or above, soil surface promotes conditions wet enough for a rapid succession towards closed mire vegetation.     

South Patagonian ombrotrophic bog vegetation reflects biogeochemical gradients at the landscape level

Question: Which environmental variables affect the floristic composition of south Patagonian bog vegetation along a gradient of climate and biogeochemical changes with increasing distance from the Pacific ocean? Location: Trans‐Andean transect (53° S), southern Patagonia Material and Methods: Floristic composition, peat characteristics (water level, decomposition, pH, total nitrogen, total carbon, ash content and plant available P, K, Na, Ca, Mg, Fe, Mn, Zn, and Al) and climatic constraints of ombrotrophic peat‐lands were measured at 82 plots along a gradient of increasing distance from the Pacific Ocean. Results: Climatic constraints and biogeochemical peat characteristics significantly change with increasing distance from the Pacific. Peatland vegetation shifted from hyperoceanic blanket bogs dominated by cushion forming vascular plants to the west to Sphagnum bogs to the east. Climatic and biogeochemical variables explained a large proportion of the floristic variation along the first DCA axis. The second axis represented a water level gradient. When ‘distance to the Pacific’ was defined as a covariable in partial CCA, the proportion of variance explained declined for most other variables, especially in the case of annual precipitation and exchangeable base cations and related traits. The differences in biogeochemical characteristics related to peat were mainly attributed to the input of sea‐borne cations. Conclusions: While variation in vegetation composition along a longitudinal gradient crossing the southern Andes was attributed to climatic constraints as expected, vegetation composition was also strongly affected by the biogeochemical characteristics of peat. Sea spray was of high ecological importance to peat chemistry and, consequently, to floristic composition. Presumably, south Patagonian peat bogs represent a glimpse of pre‐industrial environments, so that these peat bogs may act as reference systems with respect to atmospheric inputs in mire ecology research.     

Secondary succession in a Swiss mire after a bog burst

Severe natural disturbances can lead to the recovery of the original vegetation or the shift to new vegetation types. While post-disturbance succession is well documented for regularly disturbed ecosystems, little is known about the pathways and rapidity of vegetation dynamics after rare events such as peat mass movements in bogs. We monitored the floristic changes in a mire subject to a bog burst in 1987 for two decades through the repeated sampling of permanent plots. The mean species number per plot increased continuously, while the evenness increased only in the first decade and then slightly decreased. Declining species were mostly mire species, while colonist species were mostly wet meadow species. Species turnover was higher in the first decade after the disturbance, and was also higher in the area of peat erosion than in the area of peat accumulation. Changes in plant species composition indicate a succession towards tall-forb vegetation (Filipendulion), acidic fen vegetation (Caricion fuscae) and swamp willow forest (Salicion). We conclude that the effects of the disturbance are still ongoing, and that the mire’s potential for recovery is therefore difficult to predict.     

Seasonal variation in rates of methane production from peat of various botanical origins: effects of temperature and substrate quality

The methane produced in peat soils can vary over the growing season due to variations in the supply of available substrate, the activity of the microbial community or changes in temperature. Our aim was to study how these factors regulate the methane production over the season from five different peat types of different botanical origin. Peat samples were collected on seven occasions between June and September. After each sampling, the peat soils were incubated at five different temperatures (7, 10, 15, 20 and 25 degrees C) without added substrate, or at 20 degrees C with added substrate (glucose, or H(2)/CO(2), or starch). Rates of methane production averaged over the season differed significantly (P<0.05, R(2)=0.76) among the five peat types, the minerotrophic lawn producing the highest rates, and the hummock peat producing the lowest. The seasonal average Q(10) values for each plant community varied between 4.6 and 9.2, the highest value being associated with the ombrotrophic lawn and the lowest value with the mud-bottom plant community. For the unamended peat samples, the rates of methane production from each plant community varied significantly (P<0.05) over the season. This implies that the quality of organic matter, in combination with changes in temperature, explains the seasonal variation in methane production. However, addition of saturating amounts of glucose, H(2)/CO(2) or starch at 20 degrees C significantly reduced the seasonal variation (P<0.05) in methane production in peat from the minerotrophic lawn, wet carpet and mud-bottom plant communities. This suggests that substrate supply (e.g. root exudates) for the micro-organisms also varied over the season at these sites. Seasonal variation in methane production rates was apparent in peat from the hummock and ombrotrophic lawn plant communities even after addition of substrates, suggesting that the active biomass of the anaerobic microbial populations at these sites was regulated by other factors than the ones studied.     

Multiple gradients in mire vegetation: a comparison of a Swedish and an Italian bog

The major environmental gradients underlying plant species distribution were outlined in two climatically and bio-geographically contrasting mires: a Swedish bog in the boreo-nemoral zone, and an Italian bog in the south-eastern Alps. Data on mire morphology, surface hydrology, floristic composition, peat chemistry and pore-water chemistry were collected along transects from the mire margin (i.e., the outer portion of the mire in contact with the surrounding mineral soil) towards the mire expanse (i.e., the inner portion of the mire). The delimitation and the extent of the minerotrophic mire margin were related to the steepness of the lateral mire slope which, in turns, controls the direction of surface water flow. The mineral soil water limit was mirrored in geochemical variables such as pH, alkalinity, Ca²⁺, Mg²⁺, Al³⁺, Mn²⁺, and SiO₂ concentrations in pore-water, as well as Ca, Al, Fe, N and P contents in surface peat. Depending on regional requirements of plant species, different species were useful as fen limit indicators at the two sites. The main environmental factors affecting distribution of habitat types and plant species in the two mires were the acidity-alkalinity gradient, and the gradient in depth to the water table. The mire margin – mire expanse gradient corresponds to a complex gradient mainly reflected in a differentiation of vegetation structure in relation to the aeration of the peat substrate.     

Differences in CO2 dynamics between successional mire plant communities during wet and dry summers

Questions: What impact do a wet and a dry growing season have on CO₂ dynamics of mire plant communities along a primary succession gradient from the initiation stage to the bog stage? Location: Mires on a land uplift coast, Finland. Methods: We measured CO₂ dynamics and vascular plant green area development on five mires that form a sequence of mire succession. TWINSPAN was used to define successional mire plant communities and regression analyses were used to explore the temporal variation in CO₂ dynamics of the communities. Results: CO₂ dynamics of successional plant communities reacted differently to a wet and a dry growing season. The net CO₂ uptake rate of the earlier successional communities decreased in the dry growing season due to a decrease in photosynthesizing leaf area. Concurrently, CO₂ uptake of the later successional communities moderately increased or did not change. Generally, the difference in net ecosystem exchange (NEE) between a dry and a wet year resulted from the altered rate of gross photosynthesis (P_G) rather than ecosystem respiration (R_E). Conclusions: Critical factors for the more stable carbon (C) gas dynamics in the later stages of mire succession were (1) higher autogenic control of the physical environment and (2) an increase in the number of factors regulating the P_G rate. These factors may buffer mire ecosystems (in terms of the C sink function) from extreme and unfavourable variations in environmental conditions.     

Fine-scale patterns of vegetation and environmental factors on an ombrotrophic mire expanse: a numerical approach

The vegetation within an ombrotrophic mire expanse in SE Norway is studied in detail. Percentage cover of 45 species in 436 sample plots (16 ×16 cm), dispersed on 26 transects, are recorded. In addition, species abundance in 6976 subplots (4×4 cm) are recorded. 14 variables are recorded for each of the sample plots, while only distance to the water-table is estimated for the subplots. Spatial co-ordinates are supplied for all sample- and subplots. DCA ordination of a data-set consisting of 412 sample plots reveals two ecologically interpretable vegetational gradients: the hummock-hollow gradient (DCA 1), and a gradient associated with the peat-production of the bottom layer (DCA 2). Passive DCA of subplots is used to get an impression of within sample plot heterogeneity, and shows that the fine-scale compositional turnover may be considerable. Partitioning of the variation in species abundance data is done by use of (partial) CCA. The fraction of unexplained variation is rather large for all the tested data-sets, but within the total variation explained, both distance to the water-table and spatial structure explain large parts.     

The effect of light conditions on herbs, bryophytes and seedlings of temperate mixed forests in ?rség, Western Hungary

A vegetation survey was carried out in a relatively intact Atlantic blanket bog in Southwest Ireland to study the vegetation patterns in relation to environmental variation, and to quantify the effect of artificial and natural borders on compositional variation. The data were analysed using canonical correspondence analysis. In terms of both vegetation and water chemistry, the study site can be categorized as typical of Atlantic blanket bogs in the maritime regions of North-western Europe. The distribution of plant species was explained mainly by depth of the water table. The distribution of bryophytes was secondarily explained by the pH of the bog water, while the distribution of vascular plants was secondarily explained by concentrations of ammonia. The vegetation distribution exhibited little variation between the central sector of the peatland and its disturbed edges (hill-grazing and restoration areas), but a substantial variation was observed between the area along a natural edge (stream) and the areas close to the other peatland borders or centre. Similarly, the internal variation within each sector (centre, hill-grazing edge and restoration area edge) was small, but substantial vegetation variation was observed within the area located along the stream. The area along the stream was associated with relatively deep water table, shallow peat depth, high water colour, pH and NH₄ ⁺ concentrations, and low Cl⁻ concentrations in the bog water. Our results suggest the existence of strong centre-natural margin gradients, as in raised bogs, and indicate that human or animal disturbance do not give rise to the marked transition zones that often characterize natural margins of mire systems. This indicates that even small areas and remnants of Atlantic blanket bogs are worthy of conservation and that their conservation value would benefit from the inclusion of sectors close to the natural peatland borders, which would increase the plant biodiversity of the conserved area.     

The age of Calluna stands moderates post‐fire regeneration rate and trends in northern Calluna heathlands

Questions: Does stand age influence the direction and rate of post‐fire successional dynamics in coastal Calluna heaths and can old degraded heath vegetation be restored through reintroduction of fire? Location: Coastal heaths in the Tarva archipelago, central Norway. Methods: We investigated revegetation dynamics after experimental fires set in young (8 years since last fire) and old (>50 years since last fire) grazed heath stands. A repeated measures design was used, with floristic data recorded in permanent plots in the post‐fire successions (n=12) over a 7‐year period. The data were analysed using multivariate ordination techniques (PCA, RDA and PRC) and mixed effects models. Results: The age of Calluna stands strongly influenced post‐fire succession, different trends due to age explained 10.4% of variation in floristic data. Young heath showed faster succession towards pre‐fire community composition than old heath, and this could partially be explained by succession‐related factors: young heath had lower cover of mosses and lichens in the pre‐burned vegetation, and lower cover of litter early in succession. Young heath had a less pronounced overall community response to fire than old heath. Vegetative regeneration of C. vulgaris was absent in both old and young heath, but Calluna still re‐established as the dominant species within 5–7 years in both young and old stands. Regeneration dynamics were also affected by habitat conditions, different trends due to habitat explained 6% of variation. Conclusions: Our study demonstrates that old stands do develop characteristic heathland vegetation and structure after fire, and while potential invasives into the system such as trees and rhizomatous species are present, they do not impair Calluna regeneration or vegetation development towards the target heathland community composition and structure. Further, as our young stands are only in their second fire rotation after restoration, we suggest that characteristic dynamics of managed heathlands can re‐establish relatively rapidly, even in severely degenerated sites (>50 years since last fire). Site‐specific factors also need to be considered. We conclude that there is restoration potential in old heaths, despite slow dynamics in the first rotation.     

Decadal change in wetland–woodland boundaries during the late 20th century reflects climatic trends

Wetlands are important and restricted habitats for dependent biota and play vital roles in landscape function, hydrology and carbon sequestration. They are also likely to be one of the most sensitive components of the terrestrial biosphere to global climate change. An understanding of relationships between wetland persistence and climate is imperative for predicting, mitigating and adapting to the impacts of future climate change on wetland extent and function. We investigated whether mire wetlands had contracted, expanded or remained stable during 1960–2000. We chose a study area encompassing a regional climatic gradient in southeastern Australia, specifically to avoid confounding effects of water extraction on wetland hydrology and extent. We first characterized trends in climate by examining data from local weather stations, which showed a slight increase in precipitation and marked decline in pan evaporation over the relevant period. Remote sensing of vegetation boundaries showed a marked lateral expansion of mires during 1961–1998, and a corresponding contraction of woodland. The spatial patterns in vegetation change were consistent with the regional climatic gradient and showed a weaker co‐relationship to fire history. Resource exploitation, wildland fires and autogenic mire development failed to explain the observed expansion of mire vegetation in the absence of climate change. We therefore conclude that the extent of mire wetlands is likely to be sensitive to variation in climatic moisture over decadal time scales. Late 20th‐century trends in climatic moisture may be related primarily to reduced irradiance and/or reduced wind speeds. In the 21st century, however, net climatic moisture in this region is projected to decline. As mires are apparently sensitive to hydrological change, we anticipate lateral contraction of mire boundaries in coming decades as projected climatic drying eventuates. This raises concerns about the future hydrological functions, carbon storage capacity and unique biodiversity of these important ecosystems.     

Fifty‐seven years of composition change in the eastern boreal forest of Canada

Question: In the boreal forest of eastern Canada, how does forest vegetation change in the sustained absence of fire? Location: Eastern boreal forest in Quebec's North Shore region, Canada (49°30′–50°00′N; 67°30′–68°35′W). Methods: Aerial photos from three different periods (1930, 1965 and 1987) were used to characterize changes in vegetation composition in 23 scenes of 200 ha. Time since fire, presence of secondary disturbances and data on soil and topographic variables were obtained. Ordination and clustering techniques were used to define compositional trajectories of change over the 57‐yr period. These trajectories were further grouped into pathways based on compositional changes, time since fire and preferential deposit‐drainage types. Results: Among the 26 compositional trajectories, three successional pathways were distinguished. Two start post‐fire succession with a dominance of intolerant hardwood. In one of these, this is followed by an increase in Abies balsamea, while in the second the importance of Picea mariana increases with time. In the third pathway P. mariana is an important component from the outset. In this pathway, we observed modest fluctuation in the relative dominance of P. mariana and A. balsamea and variation in stand structure. Conclusion: The boreal forest vegetation of Eastern Canada is diverse and dynamic even in the absence of fire, notably under the influence of partial disturbances. Such disturbances can be associated with changes in composition or stand structure. The development of management strategies aimed at maintaining stand diversity by emulating a broader variety of partial and secondary disturbances should be encouraged.     

Multiproxy study of anthropogenic and climatic changes in the last two millennia from a small mire in central Poland

The Żabieniec kettle hole is the first peatland in central Poland analyzed quantitatively with four biotic proxies (plant macrofossils, pollen, testate amoebae and chironomids) to reconstruct the past environmental change. Palaeoecological data were supported by historical and archaeological records. We focused on autogenic vegetation change and human impact in relation to climatic effects. The aims of our study were (a) to describe the development history of the mire during the last 2,000 years, (b) to date and reconstruct the anthropogenic land-use changes and (c) to discuss a possible climatic signal in the peat archive. The combination of proxies revealed dramatic shifts that took place in the peatland since the Roman Period. Żabieniec was a very wet telmatic habitat until ca. AD 600. Then, the water table declined, and the site transformed into a Sphagnum-dominated mire. This dry shift took place mainly during the Early Medieval Period. Human impact was gradually increasing, and it was particularly emphasized by deforestation since AD 1250 (beginning of the Late Medieval Period). Consequently, surface run-off and aeolian transport from the exposed soils caused the eutrophication of the mire. Furthermore, chironomids and testate amoebae reveal the beginning of a wet shift ca. AD 1350. Openness considerably increased in the Late Medieval and the Modern Periods. The highest water table during the last 1,000 years was recorded between AD 1500 and 1800. This wet event is connected with deforestation, but it could be also associated with the Little Ice Age. Our study shows plant succession in the Żabieniec peatland, which can be explained with the recent landscape transformation. However, such changes are also possibly linked with the major climatic episodes during the last two millennia, such as the Medieval Warm Period and the Little Ice Age. Guest editors: K. Buczkó, J. Korponai, J. Padisák & S. W. Starratt Palaeolimnological Proxies as Tools of Environmental Reconstruction in Fresh Water     

Classification and ordination of the mire vegetation of Stormyra near Tynset, S Norway

The vegetation of Stormyra, a flat fen at Tynset, in Hedmark province, Southern Norway is classified by cluster analyses into seven different plant communities, all of a nonfixed hierarchical, low rank as follows:
(1) Scorpidium scorpioides comm., (2) Campylium stellatum - Drepanocladus revolvers comm., (3) Carex rostrata - Calliergon giganteum comm., (4) Sphagnum papillosum - S. subfulvum comm., (5) Homalothecium nitens - Sphagnum warnstorfii comm., (6) Pinus sylvestris - Sphagnum angustifolium comm. and (7) Empetrum hermaphroditum - Sphagnum fuscum comm.
A DCA-ordination showed that the samples were distributed mainly along a hummock - mud-bottom vegetational gradient, reflecting the local groundwater level. The range of the plant communities in terms of the traditional poor - rich and mire expanse - mire margin vegetational gradients is also dealt with. The vegetation and its relationship to such environmental factors as the ground-water level, and its seasonal fluctuations, the supply or absence of running surface water, the pH and electrical conductivity, are also discussed.     

Beryllium-7 as a natural tracer for short-term downwash in peat

Several factors can affect the integrity of natural archives such as peat records, e.g., decomposition and nutrient cycling, and it has also been hypothesized that some rapid downward transport of atmospherically derived elements may occur. We test this hypothesis by analyzing the short-lived, natural tracer beryllium-7 (t½ = 53.4 days) in five cores from two peatlands. In triplicate hummock cores from a raised bog in southern Sweden, ⁷Be could be measured to 20, 18 and 8 cm depth, and in a nutrient-poor mire in northern Sweden to a depth of 16 cm in a Sphagnum lawn core, but only 4 cm in the dominant, more-decomposed fen peat, indicating some spatial variability both within and between sites. Total ⁷Be inventories were 320–450 Bq m^?2 in the bog, and 150 Bq m^?2 (lawn) and 240 Bq m^?2 (fen peat) in the mire. 25–79 % of the total inventory of ⁷Be was located in the upper 2-cm layer. To further test downwashing, in the laboratory we applied a CuBr-solution to two cores and a Cu-solution to one core taken from the mire Sphagnum lawn, all with low water table conditions. About 50 % of the added Cu and ~35 % of the added Br were retained in the surface (2 cm) layer; 1–3 % of the Cu was found at 8–12 cm depth and ~1 % of the Br was measured in the lowest level (20–22 cm). Based on our novel approach using ⁷Be and experimental work we show that short-term downwashing can occur in peatlands and we suggest the depth of this will depend on the properties of the peat, e.g., bulk density and decomposition, as well as hydrology.     

Vascular plant compositional gradients within and between Iowa fens

Question: What is the nature and relative importance of compositional gradients within‐ and between fens? Location: Iowa, USA. Methods: 506 0.5 m × 0.5 m quadrats were sampled from 31 fens across a 550 km extent. Presence/absence of all vascular plant taxa, plus the non‐vascular genera Sphagnum and Chara, and values for 24 environmental variables were noted. Global Non‐Metric Multidimensional Scaling and Monte Carlo tests were used to describe compositional variation and identify significant environmental co‐variables. Model‐based cluster analysis was used to identify the optimal number of groups supported by the data, while k‐means clustering was used to assign each quadrat to a group. The number of occurrences (and frequency) of each species within each group was calculated. Two‐dimensional 95% Gaussian confidence intervals, ANOVA, correlation coefficient homogeneity tests, log‐linear modelling, and Fisher's exact tests were used to document patterns of compositional change. Results: Two stable axes of variation were identified: the first being most closely correlated with soil pH, Mg, Ca, P, S, vegetation height, surface and ?10 cm soil temperature, site area, perimeter, perimeter/area ratio, growing season, and air temperature, with the second being most correlated to soil moisture, N, disturbance level, % organic matter, hummock height, N‐S coordinate, and precipitation. Individual sites harboured between 20–47% of total compositional variation, with 28% of Axis 1 and 55% of Axis 2 scores being contained within‐sites. Five compositional regions were identified that differed in the proportion of calciphile and hydrophile species. Compositional groups differed significantly between geologic types. Conclusions: While the principal axis of variation (corresponding to the rich‐poor fen gradient) is present largely between sites, the second axis (corresponding to water level) is largely repeated within sites. Documentation and protection of vegetation patterns and species diversity within Iowa fens will thus require consideration of multiple sites across the landscape.     

Recognition of peat-forming plant communities from their peat deposits in two south Swedish bog complexes

Peat samples, 3 015 from 103 boring points, on two mires (Åkhult mire, Store Mosse mire) south Sweden, have been subjected to macrofossil analysis. Based on plant remains, 9 peat groups were distinguished in the field. A further classification using phytosociological methods revealed 29 peat types. The affinities between the peat types were determined from TABORD classification and a Reciprocal Averaging ordination. The primary floristic differentiation is correlated with a gradient from treeless-to wooded stands, which coincides largely with the mire expanse-mire margin gradient. The poor-rich gradient seems to parallel the treeless-wooded gradient as well and may reflect the natural conditions in this mire before it was affected by man. The hummock-mud-bottom gradient is easy to distinguish in peat, formed by bog communities, but is not distinct in peat formed by fen communities and impossible to detect in peat dominated by wood remains. The amount of identifiable remains depends on the decomposition, which is determined by (1) the period of time the plant litter stays in the acrotelm, and (2) the nutrient status. The decomposition is greatest in fen-peat with abundant wood remains. This probably depends on a good supply of oxygen caused by greater horizontal water movements and better nutrient status.     

Ecology of Racomitrium lanuginosum in British blanket mire - evidence from the palaeoecological record

Abstract

The moss Racomitrium lanuginosum (Hedw.) Brid. is widely distributed in the cool-oceanic north and west of the British Isles, where it is an important element in the vegetation of blanket mire. It has been described as occurring on the present-day surface of British blanket mire in two situations (i.e. where the local mire water table may be lowered, despite high atmospheric humidity), on the tops of tall hummocks and adjacent to areas of peat erosion, where it may be dominant in the vegetation. Accordingly, the occurrence of R. lanuginosum is widely perceived as indicative of drier mire conditions and/or mire degradation. In contrast, recent palaeoecological studies have documented the recurrence of R. lanuginosum in the absence of either hummock upgrowth or peat erosion. Such studies suggest that R. lanuginosum may also occur on blanket mire as a component of climatically-mediated mire development. This paper presents critical new data to document the decomposition of R. lanuginosum and describes the results of recent palaeoecological studies that have negated the exclusive role of R. lanuginosum in mire drying/degradation. We present evidence for the active role of R. lanuginosum in persistent blanket mire development, suggesting the moss may occur during periods of climate change towards increased wetness, after a sustained period of drier conditions. The results are of wider relevance in evidencing the sensitivity of oceanic blanket mire to past climate change.     

Microtopography and the Properties of Residual Peat Are Convenient Indicators for Restoration Planning of Abandoned Extracted Peatlands

The natural recovery of vegetation on abandoned peat extraction areas lasts for decades and the result of restoration succession can be unpredictable. The aim of the study was to specify environmental factors that affect the formation of the pioneer stages of mire communities and, therefore, be helpful in the prediction of the resulting ecosystem properties. We used the national inventory data from 64 milled peatlands in Estonia, distributed over the region of 300 × 200 km. This is the first national‐scale statistical evaluation of abandoned extracted peatlands. During surveys, vascular plants, bryophytes, and residual peat properties were recorded on three microtopographic forms: flats, ditch margins, and ditches. The microtopography was the main factor distinguishing the composition of plant communities on flats and ditches, while ditch margins resembled flats. The extracted indicator species suggested two successional pathways, toward fen or raised bog community. A single indicator trait—the depth of residual peat, which combines the information about peat properties (e.g. pH, ash content, and trophicity status), predicted the plant community succession in microtopographic habitats. We suggest that peatland management plans about the cost‐efficient restoration of abandoned peat mining areas should consider properties of residual peat layer as the baseline indicator: milled peatfields with thin (<2.3 m) and well‐decomposed residual peat should be restored toward fen vegetation types, whereas sites with thick (>2.3 m) and less decomposed residual peat layer should be restored toward transitional mires or raised bogs. Specific methodological suggestions are provided .     

Vegetation, climatic changes and net carbon sequestration in a North-Scandinavian subarctic mire over 30 years

This study deals with changes in the plant cover and its net carbon sequestration over 30 years on a subarctic Sphagnum-mire with permafrost near Abisko, northernmost Sweden, in relation to climatic variations during the same period. Aerial colour infrared images from 1970 and 2000 were compared to reveal changes in surface structure and vegetation over the whole mire, while the plant populations were studied within a smaller, mainly ombrotrophic part. The results demonstrated two processes, namely (1) that wet sites dominated by graminoids expanded while hummock sites dominated by dwarf shrubs receded, and (2) that on the hummocks lichens expanded while evergreen dwarf shrubs and mosses decreased, both processes creating an instability in the surface structure. A successive degradation of the permafrost is the likely reason for the increase in wet areas, while the changes in the hummock vegetation might have resulted from higher spring temperatures giving rise to an intensified snow melt, exposing the vegetation to frost drought. Because of the vegetation changes, the annual litter input of carbon to the mire has increased slightly, by 4 g m⁻² a⁻¹ (7.3%), over these years while an increased erosion has resulted in a loss of 40–80 Mg carbon or 7–17 g m⁻² a⁻¹ for the entire mire over the same period. As the recalcitrant proportion of the litter has decreased, the decay rate in the acrotelm might be expected to increase in the future.