Scotlands threatened mires and mosses: Policies to protect the peatlands of caithness and sutherland

Summary

Scottish peatlands have suffered loss and damage for centuries through cutting for fuel and agricultural and forestry practices. The ombrogenous blanket mires of Caithness and Sutherland (the ‘Flow Country’) are of international importance for the range and quality of their peatland types and vegetation, and their breeding bird populations. Loss of this habitat in the last decade, due to rapid expansion of forestry, caused great concern which was expressed by voluntary and statutory nature conservation organizations and the national media. Government at both national and local levels responded with changes in forestry policies, protection of large areas of peatland and by a land-use strategy which divides the area into four forestry policy zones.     

Breeding bird populations of Irish peatlands

Capsule Peatlands are very important habitats for birds despite low species diversity.

Aims To describe the variation in breeding bird populations that occur on different types of Irish peatlands and their associated habitat characteristics.

Methods Bird abundance and diversity were compared between four peatland habitat types (fens, raised bogs, Atlantic blanket bogs and montane blanket bogs) at 12 study sites using transects. Various measures of habitat quality were also taken at each location.

Results Only 21 species were recorded during the study, with Meadow Pipit Anthus pratensis and Sky Lark Alauda arvensis accounting for over 80% of all birds recorded. Fens had greater bird species diversity and densities than the other three peatland types. Raised bogs, Atlantic blanket bogs and montane blanket bogs were very similar in terms of their avian diversity. Each of the recorded bird species was associated with different aspects of the peatland habitat.

Conclusion This study shows that despite the relatively low avian species diversity of Irish peatlands, they are of enormous conservation value due to the presence of species of high conservation concern such as Willow Ptarmigan (Red Grouse) Lagopus lagopus and Eurasian Curlew Numenius arquata.     

Response of blanket bog vegetation to drain‐blocking

Question: Does blocking of moorland drains increase bog vegetation on blanket peat? Location: Two sites with blocked drains and two with unblocked drains on Forsinard Flows National Nature Reserve, Sutherland, UK. Methods: Vegetation cover was recorded from 70 locations, with 12 sampling points at different distances (0.5‐14.5 m) from moorland drains in each location. Gradients in the cover of species indicative of wet and dry conditions, as well as bog recovery and degradation in relation to distance from drain, were compared from a sample of drains at two sites with blocked drains and two with unblocked drains. Results: There was evidence for drain‐blocking having a negative effect on vegetation indicative of drier conditions and bog degradation. One of the blocked sites had the lowest values of these indices near to the drain and increasing at greater distances perpendicular from the drain. The two unblocked sites, and the other blocked site, had a contrasting pattern of highest values of these indices close to the drain declining with distance. Cover of species indicative of bog recovery was greater where the drains had been blocked for the longest time. Conclusions: In some cases drain‐blocking can improve the ecological functioning of blanket bogs by increasing cover of healthy bog vegetation. Further studies into the causes of such variability in restoring vegetation through drain‐blocking are needed to aid targeting of peatland restoration projects to areas or methods most likely to be effective.     

Effects on water chemistry after drainage of a bog for forestry

Drainage for forestry has received increasing interest during recent decades. Generally, drainage concerns wet mineral soils while the utilization of peatlands is a matter of controversy. The peatlands mainly involved are fens, while forestry on bogs is an insignificant activity. Consequently, hydrology of bogs and effects of drainage on their hydrochemistry are little known.The investigation performed aimed at elucidating the parent conditions and the drainage impact on the hydrology and hydrochemistry of an ombrotrophic bog. Two bogs were first compared during a calibration period of two years and then, after drainage of one of them, during a period of three years. The second bog was kept virgin as a control.Considerable influences on runoff and stream water quality were found from the surrounding mineral soil uplands of the bog. Significant differences occurred between the chemical composition of the groundwater in the mineral soil and in the bog peat.Effects on runoff water from drainage of the bog deviate from drainage of minerotrophic peatlands with respect to decreased concentrations and losses of organic carbon and nitrogen. From two small bog catchments within the drained bog, there generally were greater losses of nutrients than from the catchment as a whole. Furthermore, the runoff from the drained bog decreased in comparison with the undrained condition. However, there were also similarities to drainage of other peatlands as regards increased pH, alkalinity and concentrations of sulphate. Also, concentrations of total-phosphorus increased in spite of a decreased phosphate (MRP) concentration.     

Methane flux dynamics in an Irish lowland blanket bog

Pristine peatlands are a significant source of atmospheric methane (CH₄). Large spatio–temporal variation has been observed in flux rates within and between peatlands. Variation is commonly associated with water level, vegetation structure, soil chemistry and climatic variability. We measured spatial and temporal variation in CH₄ fluxes in a blanket bog during the period 2003–2005. The surface of the bog was composed of different vegetation communities (hummocks, lawns and hollows) along a water level gradient. CH₄ fluxes were measured in each community using a chamber method. Regression modelling was used to relate the fluxes with environmental variables and to integrate fluxes over the study period. Water level was the strongest controller of spatial variation; the average flux rate was lowest in hummocks and highest in hollows, ranging from 3 to 53 mg CH₄ m⁻² day⁻¹. In vegetation communities with a permanently high water level, the amount and species composition of vegetation was also a good indicator of flux rate. We observed a clear seasonal variation in flux that was chiefly controlled by temperature. The annual average flux (6.2 g CH₄ m⁻² year⁻¹) was similar to previous estimates from blanket bogs and continental raised bogs. No interannual variation was observed.     

Some critical questions concerning the restorability of damaged raised bogs

Abstract. In principle, the restoration of damaged raised bogs has rather few requirements: (1) a sufficient supply, and retention, of precipitation water of appropriate quality; and (2) the availability of a suitable range of recolonist species. However, to meet these requirements it may be necessary to engineer the topography of the peatland and drainage systems and to adopt a policy of species introduction. This paper provides a critical summary review of: (1) existing knowledge about the environmental conditions necessary for the effective regeneration of damaged ombrogenous peatlands; (2) approaches adopted for generating conditions appropriate for the re-establishment of plant species typical of raised bogs; (3) possible external constraints (especially atmospheric contaminants) upon the feasibility of restoration; and (4) the prospects and possibilities for effective species recolonization. Particular attention is given to the identification of uncertainties and critical gaps in existing knowledge about raised bog restoration and of some of the natural processes that help regulate the development of raised bogs.     

Assessing butterfly diversity and their response to habitat condition in pristine peat bogs in Belarus

Peat bogs are valuable ecosystems because they support regional and local hydrological conditions, and store carbon and other greenhouse gases. Nevertheless, their area in Europe is extremely reduced due to human activities. As a result, the number of studies on biodiversity and the environmental factors affecting the distribution of insects, including butterflies, in large intact peatlands is limited. Such studies provide an important baseline for the subsequent analysis of changes during climate warming and for the assessment of succession in degraded peatlands. The results of such research have shown how butterfly assemblages react to local peat bog habitat conditions and contribute new information on the relations of consumers and the very specific environment of peat bogs. The presented research targets the relationship between characteristics of butterfly assemblages and key environmental variables in intact peat bog habitats. A total of 1427 individuals belonging to 23 butterfly species were recorded. In this study, I found that butterfly abundance, diversity and species composition varied significantly among three main habitat types, namely lagg zones, pine bogs and open bogs, although these habitats did not differ in species richness. The highest abundance was in the pine bogs which are characterized by higher plant community structural complexity and, as a result, higher butterfly food resources. The results confirmed positive responses of species richness and abundance of butterflies to nectariferous flower cover. On the other hand, open, sunny, but windy sites on the peat bogs contribute to a decrease of abundance.     

Gradients of continentality and moisture in South Patagonian ombrotrophic peatland vegetation

This study presents the analysis of 381 phytosociological relevés describing predominantly ombrotrophic South Patagonian lowland peatland vegetation along a gradient of increasing continentality. Numerical methods such as cluster analysis and detrended correspondence analysis (DCA) were carried out to explore the data set. Cluster analysis resulted in nine vegetation types that were also distinctly separated in DCA ordination. The major floristic coenocline along the first DCA axis reflected a gradient of continentality ranging from pacific blanket bogs dominated by cushion plants toSphagnum-dominated continental raised bogs. Increasing continentality along the first axis was parallel with decreasing peat decomposition and increasing peat depth and acidity. In contrast, floristic variation along the second DCA axis represented a water level gradient. The typical sequence of vegetation types along the hollow-hummock moisture gradient that is well established for north hemispherical peatlands could also be observed inSphagnum-dominated South Patagonian raised bogs with a surprising similarity in floristic and structural features. Concerning the gradient of continentality significant differences in comparison with the northern hemisphere could be established. Most obvious was the dominance of cushion building plants (e.g.Astelia pumila, Donatia fascicularis) in South Patagonian oceanic peatlands, whereas this life form is totally absent from the northern hemisphere. Similar to the continentalSphagnum bogs the cushion plant vegetation of hyperoceanic peatlands exhibited a clear separation along the moisture gradient.     

Abundance, biomass, structure, and activity of the microbial complexes of minerotrophic and ombrotrophic peatlands

Very large microbial biomass was revealed in peat bogs by means of fluorescence microscopy. In ombrotrophic peatlands, the pool of the dry-weight microbial biomass in the 1.5-m layer constituted 3-4 t/ha and was twice as high as in the minerotrophic peat bogs. Fungal biomass was predominant (55-99%) in ombrotrophic peatlands, while bacterial biomass predominated in minerotrophic peatlands (55-86%). In ombrotrophic peatlands, the microbial biomass was concentrated in the upper layers, while in minerotrophic peatlands, it was uniformly distributed in the bulk. After drainage, the microbial pool in the ombrotrophic peatlands increased twofold; that in the minerotrophic peatlands remained at the same level. The potential activity of nitrogen fixation and denitrification was revealed across the whole profile of the peatlands. The average values of these potential activities were five times higher in the minerotrophic peatlands, where bacterial biomass predominated.     

Patterns and gradients of diversity in South Patagonian ombrotrophic peat bogs

Many north‐hemispherical mires seemingly untouched by drainage and cultivation are influenced by a diffuse sum of man‐made environmental changes, such as atmospherical nitrogen deposition that mask general patterns in species richness and functional group responses along resource gradients. To obtain insights into natural diversity‐environment relationships, we studied the vegetation and the peat chemistry of pristine bog ecosystems in southern Patagonia along a west–east transect across the Andes. The studied bog ecosystems covered a floristic gradient from hyperoceanic blanket bogs dominated by cushion building vascular plants via a transitional mixed type to Sphagnum‐dominated raised bogs east of the mountain range. To test the influence of resource availability on diversity patterns, species richness and functional groups were related to environmental variables by calculating general regression models and generalized additive models. Species richness showed strong linear correlations to peat chemical features and the general regression model resulted in three major environmental variables (water level, total nitrogen, NH₄Cl soluble calcium), altogether explaining 76% of variance. Functional group response illustrated a clear separation along environmental gradients. Mosses dominated at the low end of a nitrogen gradient, whereas cushion plants had their optimum at intermediate levels, and graminoids dominated at high nitrogen contents. Further shifts were related to NH₄Cl soluble calcium and water level. The models documented partly non‐linear relationships between functional group response and trophical peat properties. Within the three bog types, the calculated models differed remarkably illustrating the scale‐dependency of the explanatory factors. Our findings confirmed several general patterns of species richness and functional shifts along resource gradients in a surprisingly clear way and underpin the significance of undisturbed peatlands as reference systems for testing of ecological theory and for conservation and ecological restoration in landscapes with strong human impact.     

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.     

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.     

Abundance,biomass, structure,and activity of the microbial complexes of minerotrophic and ombrotrophic peatlands

A very large microbial biomass was revealed in peat bogs by means of fluorescence microscopy. In ombrotrophic peatlands, the pool of the dry-weight microbial biomass in the 1.5-m layer constituted 3–4 t/ha and was twice as high as in the minerotrophic peat bogs. Fungal biomass was predominant (55–99%) in ombrotrophic peatlands, while bacterial biomass predominated (55–86%) in minerotrophic peatlands. In ombrotrophic peatlands, the microbial biomass was concentrated in the upper layers, while in minerotrophic peatlands, it was uniformly distributed in the bulk. After drainage, the microbial pool in the ombrotrophic peatlands increased twofold; that in the minerotrophic peatlands remained at the same level. The potential activity of nitrogen fixation and denitrification was revealed across the whole profile of the peatlands. The average values of these potential activities were five times higher in the minerotrophic peatlands, where bacterial biomass predominated.     

Water mites as potential long-term bioindicators in formerly drained and rewetted raised bogs

Many environmental studies of restored peatlands focus on biogeochemical cycles, productivity and decomposition. However, changes in the composition and structure of invertebrate assemblages in restored bogs have received little attention. In the present study we describe effects of rewetting on the water mite faunas (Acari: Hydrachnidia) of four raised bogs located in northwestern Germany. All examined peatlands had been drained in the past, and two of them had been subjected to peat extraction. The examined sites had been rewetted 2, 12, 14 and 25 years prior to our surveys, and currently represent different stages of plant succession. With increasing age after rewetting, the vegetation developed more complex structure as defined by Sphagnum status, and water mite fauna became somewhat similar to the fauna in an undisturbed raised reference bog. Water mites were found almost exclusively in bogs 25 years after wetting, and in these bogs they occurred in sites with more complex vegetation structure. Because water mites have high demands on abiotic and biotic factors due to their complex life cycle (i.e., the larvae are parasites, and the nymphs and adults are predators), we can infer that their mere presence irrespective of species abundance and richness reflects positive effects of the rewetting measures conducted in peat bogs.     

Initiation of microtopography in revegetated cutover peatlands

Question: How many years are required for a gradient of microtopography to be initiated in revegetated cutover peatlands and become similar to natural bogs? Location: Newly formed Sphagnum carpets on cutover peatlands that revegetated spontaneously after site abandonment (in Estonia), or following active restoration (in Canada) and on undisturbed natural bogs nearby. Methods: Moss surface height was measured along linear transects above a local reference level (the lowest point for a given transect). Heights of at least 20 cm were associated with hummocks. Frequency distributions of surface height and principal component analyses (separately for Canada and Estonia) were conducted to follow the evolution of microtopography in revegetated sites and their similarity with those of natural peatlands. In Canada, regressions were also performed to estimate the time required for the microtopography in revegetated cutover peatlands to become similar to that found in natural bogs. Results: Only 10–30 yr were needed for microstructures comparable to those in natural bogs to develop on restored peatlands where Sphagnum diaspores have been reintroduced. However, this process may take more than a century in cutover peatlands left to revegetate spontaneously. Conclusions: In cutover peatlands with spontaneous revegetation, hummock–hollow formation starts on bare peat which lacks both plant propagules and viable seed banks, and the initiation of microstructures is probably more akin to the process that occurs naturally. Nonetheless, hummock–hollow microtopography resembling that found in natural bogs without pools appeared, in all of the examined cutover peatlands, over periods that are short in terms of peatland development time‐scales. Active peatland restoration could effectively reduce the time required for initiation of microtopography by about 70 yr.     

Organic matter losses from temperate ombrotrophic peatlands: an evaluation of the ash residue method

Peatlands act as CO₂ sinks that store more soil carbon per unit area than any other ecosystem. Increased aeration and subsequent oxidation following drainage causes peatlands to lose carbon and leads to a relative increase in the concentration of inorganic compounds. To infer carbon losses as a result of drainage, we studied four sites in Central Europe with different drainage states and land-use histories. We used differences in ash content of both catotelm peat and near-surface layers as well as the results of soil carbon inventories. The method yielded reasonable results, at least for two drained sites, where the mean loss rates varied between 0.14 and 0.49 kg?C m^?2 a^?1. Comparison with a pristine bog showed that a relative increase of ash content is not unique to drained sites and that previous land management also affected natural peatlands with concomitant losses similar in magnitude to their drained counterparts. Rehabilitation of a previously drained site dissipated the original ash peak profile. In conclusion, the method is suitable for predicting carbon losses from ombrotrophic bogs under certain conditions but in countries with a long-lasting tradition of anthropogenic interference it is impossible to attribute drainage as the only factor governing relative increases in ash content in ombrotrophic peatlands.     

For peat's sake: conservation or exploitation?

Peatlands form a unique and irreplaceable part of our natural and cultural heritage and require effective conservation. Despite there being so few fragments of lowland bog remaining in Britain, internationally important peatlands are still being destroyed. The Peatland Consortium of ten voluntary conservation organizations has mounted a successful campaign to safeguard remaining lowland bogs. This initiative will continue until successful achievement of its objectives.     

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.     

The Effects of Permafrost Thaw on Soil Hydrologic, Thermal, and Carbon Dynamics in an Alaskan Peatland

Recent warming at high-latitudes has accelerated permafrost thaw in northern peatlands, and thaw can have profound effects on local hydrology and ecosystem carbon balance. To assess the impact of permafrost thaw on soil organic carbon (OC) dynamics, we measured soil hydrologic and thermal dynamics and soil OC stocks across a collapse-scar bog chronosequence in interior Alaska. We observed dramatic changes in the distribution of soil water associated with thawing of ice-rich frozen peat. The impoundment of warm water in collapse-scar bogs initiated talik formation and the lateral expansion of bogs over time. On average, Permafrost Plateaus stored 137 ± 37 kg C m⁻², whereas OC storage in Young Bogs and Old Bogs averaged 84 ± 13 kg C m⁻². Based on our reconstructions, the accumulation of OC in near-surface bog peat continued for nearly 1,000 years following permafrost thaw, at which point accumulation rates slowed. Rapid decomposition of thawed forest peat reduced deep OC stocks by nearly half during the first 100 years following thaw. Using a simple mass-balance model, we show that accumulation rates at the bog surface were not sufficient to balance deep OC losses, resulting in a net loss of OC from the entire peat column. An uncertainty analysis also revealed that the magnitude and timing of soil OC loss from thawed forest peat depends substantially on variation in OC input rates to bog peat and variation in decay constants for shallow and deep OC stocks. These findings suggest that permafrost thaw and the subsequent release of OC from thawed peat will likely reduce the strength of northern permafrost-affected peatlands as a carbon dioxide sink, and consequently, will likely accelerate rates of atmospheric warming.     

Interspecific and geographical differences of plant tissue nutrient concentrations along an environmental gradient in Southern Patagonia, Chile

Foliar nutrient concentrations of South Patagonian ombrotrophic peatland species were analyzed along a gradient of increasing continentality. We paid particular attention to nutrient demands of Sphagnum magellanicum, the dominant constituent of continental raised bogs, and to those of cushion-forming vascular plants such as Astelia pumila, dominating in western hyperoceanic blanket bogs. With exception of one graminoid species, nutrient concentrations in leaf tissues were generally low, but showed considerable variation. Extremely low concentrations were measured in S. magellanicum reflecting the unpolluted, pristine character of the investigated bog ecosystems. Nutrient concentrations in cushion plants showed remarkable variation. While nutrient concentrations in Donatia fascicularis were almost as low as in S. magellanicum, they were significantly higher in A. pumila. Variation in foliar nutrient concentrations was predominantly due to differences between species. Nevertheless, there was a significant shift within species along the considered west-to-east continental gradient. The stronger minerotrophic character of the western cushion bogs was reflected by higher Ca contents. N concentrations increased and P concentrations decreased westward in most species. Consequently, the most noticeable shift was an increasing N:P ratio indicating a higher degree of P limitation towards western cushion dominated blanket bogs.