Ericaceous Heath Research Articles

Post-Fire Habitat Heterogeneity Leads to Black Spruce–Kalmia L. Shrub Savannah Alternate State

Many nutrient-poor coarse-textured Kalmia L.–black spruce forest sites in eastern Canada turn to ericaceous heath dominated by Kalmia angustifolia L. after clearcutting and fire. While the mechanisms of post-fire forest and heath formation have been well documented, the origin of shrub savanna vegetation has received limited attention. This study demonstrates the significance of post-fire island regeneration of black spruce in Kalmia heath to the origin of shrub savannah alternate state. The study was conducted in Three Brooks, 10 km west of Grand Falls-Windsor, Newfoundland (48°51′ N; 55°37′ E). Black spruce forest in the site was clearcut, then a wildfire burned the area, and the site was subsequently planted with black spruce. Plant species cover, black spruce growth (stem density, stem height, basal diameter, and yearly volume increment), and foliar nutrients of planted spruce and soil properties (pH, humus and Ae horizon depth, and nutrients) in tree islands were compared with adjacent Kalmia heath. Black spruce islands had significantly lower cover of Kalmia and higher stem density of black spruce compared to Kalmia heath (7100 stems/ha in islands vs. 1920 stems/ha in heath). Height, basal diameter, and yearly volume increment of black spruce were more than three times higher in spruce islands than in Kalmia heath. Foliar nutrients of black spruce growing in Kalmia heath had significantly lower N and Mg (33 and 38%, respectively) but had significantly higher Mn and Zn (46 and 33%, respectively) than in black spruce islands. Black spruce growth inhibition in Kalmia heath is attributed to soil nutrient imbalance due to Kalmia evidenced by reduced concentrations of N and Mg and increased concentrations of Al, Fe, and other inorganic ions in the foliage. These results suggest that post-fire black spruce islands in severely burned patches provide “safe sites” for spruce regeneration, whereas Kalmia heath developing in non-severe burn area inhibits spruce regeneration and creates shrub savannah community as an alternate vegetation state.

Soil chemistry drives below ground traits in an alternate successional pathway from forest to heath.

To understand impacts of post-disturbance assembly mechanisms on the functional diversity (FD) of plant communities, it is necessary to determine how the environment drives their functional trait composition. In the boreal forest, post-fire abiotic filters may control community assembly by selecting plants with specific traits. Ericaceous heaths are characterized by low FD and are thought to be subject to such filters. We hypothesized that soil parameters select for a specific suite of traits and act as a secondary abiotic filter in post-fire ericaceous heath and contribute to the observed reduction of FD. We measured six soil parameters, five functional traits, and plant species abundances in eight post-fire heath and four regenerating forest sites in Eastern Canada. We conducted a combined analysis of RLQ (R-table Linked to Q-table) and fourth-corner methods to examine the links between plant traits and plot-level soil parameters, mediated by species abundances. Only below ground traits were significantly linked to soil variables. Specific root length and ericoid mycorrhizal associations were negatively linked to total soil nitrogen, available ammonium, and pH. Post-fire heath soils favour a specific suite of species traits. Only a portion of the regional species pool possesses the above-mentioned traits, and when they are favoured by habitat conditions, they assemble into a community with low FD. The novelty of our study is here we show how the relationship between traits and soil chemistry can act as a secondary filter and exert community-level trait changes responsible for the low functional diversity observed in heaths.

Plant carbon allocation drives turnover of old soil organic matter in permafrost tundra soils

AbstractCarbon cycle feedbacks from permafrost ecosystems are expected to accelerate global climate change. Shifts in vegetation productivity and composition in permafrost regions could influence soil organic carbon (SOC) turnover rates via rhizosphere (root zone) priming effects (RPEs), but these processes are not currently accounted for in model predictions. We use a radiocarbon (bomb‐14C) approach to test for RPEs in two Arctic tall shrubs, alder (Alnus viridis (Chaix) DC.) and birch (Betula glandulosa Michx.), and in ericaceous heath tundra vegetation. We compare surface CO2 efflux rates and 14C content between intact vegetation and plots in which below‐ground allocation of recent photosynthate was prevented by trenching and removal of above‐ground biomass. We show, for the first time, that recent photosynthate drives mineralization of older (>50 years old) SOC under birch shrubs and ericaceous heath tundra. By contrast, we find no evidence of RPEs in soils under alder. This is the first direct evidence from permafrost systems that vegetation influences SOC turnover through below‐ground C allocation. The vulnerability of SOC to decomposition in permafrost systems may therefore be directly linked to vegetation change, such that expansion of birch shrubs across the Arctic could increase decomposition of older SOC. Our results suggest that carbon cycle models that do not include RPEs risk underestimating the carbon cycle feedbacks associated with changing conditions in tundra regions.

Lichen matted seedbeds inhibit while moss dominated seedbeds facilitate black spruce (Picea mariana) seedling regeneration in post-fire boreal forest

The subject of conifer regeneration failure after canopy removing disturbance leading to expansion of ericaceous heaths in boreal forests received considerable attention. However, despite seedbed quality being a key factor in tree regeneration, our understanding of the role of lichen and moss dominated seedbeds on tree seedling regeneration after forest fires remains unclear. Objective of this study was to investigate the effect of time since fire and post-fire cryptogamic (lichen and moss) seedbeds with variable organic matter thickness on black spruce regeneration. We conducted black spruce seeding experiment in black spruce – Kalmia forests burned 11, 17 and 37 years ago. In each site we applied three seedbed manipulation treatments (mat-intact, mat-mixed and mat-removed) to test if seedbed manipulation improves spruce regeneration. This experiment was extended to three moss-dominated seedbeds to compare seedbed moisture and temperature effects on spruce regeneration. We also tested potential allelopathic effect of two common lichen and moss species in laboratory bioassay. Seed regeneration was low in all seedbeds. Black spruce germination and seedling growth was lowest in presence of Cladonia cristatella followed by C. stellaris, Polytrichum juniperinnum and Pleurozium schriberi. HPLC analysis of C. cristatella indicated the presence of usnic acid, a common germination inhibiting allelochemical. Moss seedbeds were relatively favourable for spruce regeneration. We conclude that (i) lichen seedbeds inhibit seedling regeneration due to adverse biophysical and chemical (allelopathic) effects, (ii) moss seedbeds facilitate black spruce regeneration by maintaining favourable moisture and temperature, and (iii) seedbed manipulation treatments produce mixed results depending on the dominant cryptogam, organic matter thickness and seedbed moisture and temperature.

Description of Mesocriconema ericaceum n. sp. (Nematoda: Criconematidae) and notes on other nematode species discovered in an ericaceous heath bald community in Great Smoky Mountains National Park, USA

A new species of Mesocriconema and a unique assemblage of plant-parasitic nematodes was discovered in a heath bald atop Brushy Mountain in Great Smoky Mountains National Park. Mesocriconema ericaceum n. sp., a species with males, superficially resembles M. xenoplax. DNA barcoding with the mitochondrial COI gene provided evidence of the new species as a distinct lineage. SEM revealed significant variability in arrangement of labial submedian lobes, plates, and anterior and posterior annuli. Three other nematodes in the family Criconematidae were characterised from the heath bald. Ogma seymouri, when analysed by statistical parsimony, established connections with isolates from north-eastern Atlantic coastal and north-western Pacific coastal wet forests. Criconema loofi has a southern Gulf Coast distribution associated with boggy soils. Criconema cf. acriculum is known from northern coastal forests of California. Understanding linkages between these species and their distribution may lead to the broader development of a terrestrial soil nematode biogeography.

Black spruce (Picea mariana) restoration in Kalmia heath by scarification and microsite mulching

Canopy removing disturbance such as clearcutting and fire in nutrient-poor boreal and temperate forests often create shrub-dominated vegetation causing significant delay in forest succession. Lack of favourable microsites for black spruce seedling establishment and growth has been identified as the primary cause for conifer regeneration failure in post-fire Kalmia heath in eastern Canada. The aim of this study was to compare the growth performance of black spruce planted in scarified plots and in microsites developed by a novel technique called micro-site mulching (MSM) in Kalmia heaths. We hypothesized that because of vegetation removal and exposure of mineral soil in scarified and MSM treatments, planted black spruce would suffer from frost heaving and animal browsing, but these treatments may offer better seedling growth by ameliorating the inhibitory effects of Kalmia organic matter and providing with favourable soil moisture, soil temperature, soil respiration and nutrient availability. We conducted this study in a 13year-old post-fire Kalmia heath in Triton Brook, Newfoundland, Canada (48°30′N, 50°00′W). We measured black spruce seedling survival and growth annually for three complete growing seasons and soil nutrient availability one year post-planting. In all three treatments black spruce seedling survival was >90%. About 20% of the seedlings in scarified and MSM treatments suffered herbivore damage and frost heaving with little damage in control plots. Black spruce in scarified and MSM plots were associated with significantly higher growth than control, with differences amplified each consecutive year since planting. Higher seedling growth in scarified and MSM plots was associated with higher soil moisture, lower organic matter content, and lower soil temperature. Soil nutrient differences in treatments had little effect on seedling growth. Since MSM treatment produced substantially less soil disturbance with similar or better seedling growth than scarification, we suggest MSM as a preferred site preparation technique in Kalmia heath in contexts where large-scale soil disturbance by standard mechanized scarification is undesirable. The novelty of his paper is the development of MSM as a potential alternative to scarification in creating suitable microsites for planted black spruce to restore forest cover in ericaceous heaths. However, an operationally suitable MSM tool must be developed and a longer-term (10years) monitoring is necessary before the method can be applied as a restoration tool.

Biomass, Productivity, and Nutrient Allocation in Subalpine Shrublands and Meadows of the Emerald Lake Basin, Sequoia National Park, California

The Emerald Lake Basin provides a long-term site for research on hydrology, ecology, and biogeochemistry, as well as baseline data for a representative subalpine watershed in the Sierra Nevada of California. Field studies provided quantitative data on the biomass, net primary production, and nutrient allocation of major subalpine shrub and meadow communities. Measurements carried out over two growing seasons found aboveground biomass per unit canopy area was 3857 g m-2 in Chrysolepis sempervirens, 3360 g m-2 in Salix orestera, and 1614 g m-2 in Phyllodoce breweri. The biomass for Chrysolepis and Salix canopies were high compared to other published data for subalpine and alpine shrublands, but the Phyllodoce biomass was comparable to values for ericaceous heath in the Rocky Mountains and European Alps. Wet and dry meadows had 377 and 98 g m-2, respectively, in aboveground living tissues, comparable to values from the Rocky Mountains and European Alps. Belowground biomass for shrub communities was the highest for Phyllodoce (3670 g m-2), followed by Chrysolepis (2400 g m-2) and Salix (2070 g m-2). The wet meadow community had a surprisingly high belowground biomass of 2897 g m-2, reflecting the dominance of large perennial herb species. This resulted from a root:shoot ratio of 8.21 compared to 5.72 in the dry meadow community. Canopies of Chrysolepis and Salix had root:shoot ratios of 0.62 and 0.61, respectively, and Phyllodoce a ratio of 2.27.

Mycorrhizal fungal communities in coastal sand dunes and heaths investigated by pyrosequencing analyses.

Maritime sand dunes and coastal ericaceous heaths are unstable and dynamic habitats for mycorrhizal fungi. Creeping willow (Salix repens) is an important host plant in these habitats in parts of Europe. In this study, we wanted to assess which mycorrhizal fungi are associated with S. repens in four different coastal vegetation types in Southern Norway, three types from sand dunes and one from heaths. Moreover, we investigated which ecological factors are important for the fungal community structure in these vegetation types. Mycorrhizal fungi on S. repens root samples were identified by 454 pyrosequencing of tag-encoded internal transcribed spacer 1 (ITS1) amplicons. Significantly higher fungal richness was observed in hummock dunes and dune slacks compared to eroded dune vegetation. The compositional variation was mainly accounted for by location (plot) and vegetation type and was significantly correlated to content of carbon, nitrogen and phosphorus in soil. The investigated maritime sand dunes and coastal ericaceous heaths hosted mycorrhizal taxa mainly associated with Helotiales, Sebacinales, Thelephorales and Agaricales.

Managing Understory Vegetation for Maintaining Productivity in Black Spruce Forests: A Synthesis within a Multi-Scale Research Model

Sustainable management of boreal ecosystems involves the establishment of vigorous tree regeneration after harvest. However, two groups of understory plants influence regeneration success in eastern boreal Canada. Ericaceous shrubs are recognized to rapidly dominate susceptible boreal sites after harvest. Such dominance reduces recruitment and causes stagnant conifer growth, lasting decades on some sites. Additionally, peat accumulation due to Sphagnum growth after harvest forces the roots of regenerating conifers out of the relatively nutrient rich and warm mineral soil into the relatively nutrient poor and cool organic layer, with drastic effects on growth. Shifts from once productive black spruce forests to ericaceous heaths or paludified forests affect forest productivity and biodiversity. Under natural disturbance dynamics, fires severe enough to substantially reduce the organic layer thickness and affect ground cover species are required to establish a productive regeneration layer on such sites. We succinctly review how understory vegetation influences black spruce ecosystem dynamics in eastern boreal Canada, and present a multi-scale research model to understand, limit the loss and restore productive and diverse ecosystems in this region. Our model integrates knowledge of plant-level mechanisms in the development of silvicultural tools to sustain productivity. Fundamental knowledge is integrated at stand, landscape, regional and provincial levels to understand the distribution and dynamics of ericaceous shrubs and paludification processes and to support tactical and strategic forest management. The model can be adapted and applied to other natural resource management problems, in other biomes.

Influence of the spatial variability of soil type and tree colonization on the dynamics of Molinia caerulea (L.) Moench in managed heathland

European heathland communities on acid, nutrient-poor soils have a high ecological value due to their special environmental conditions. Natural succession (tree colonization and the emergence of grasses) poses a threat to this type of habitat and different types of management strategy must be considered if it is to be maintained. A previous study on a dry heathland area located in the Fontainebleau forest (France) showed a gradual shift from a pure ericaceous stand to a mosaic of grasses and Ericaceae, despite the application of measures such as removal of woodland species to sustain the habitat. Habitat change was due to local expansion of a grass, Molinia caerulea (L.) Moench. The present paper aimed to identify factors responsible for the expansion of M. caerulea and the subsequent decrease in ericaceous heath. We focused our study on spatial variability of soil properties (soil horizons, pH, water content) and reforestation (density of birch individuals and proximity to woodland) as a suite of possible factors promoting the expansion of M. caerulea. We show that the development of grasses was correlated with thin soil E horizon and spatial distribution of old shoots of birch, Betula pendula Roth, which are regularly cut and then resprout. These results suggest that new methods to avoid tree colonization must be introduced if typical heathland is to be maintained.

The Biology of Canadian Weeds. 146. Rhododendron groenlandicum (Oeder) Kron and Judd

Hebert, F. and Thiffault, N. 2011. The Biology of Canadian Weeds. 146. Rhododendron groenlandicum (Oeder) Kron and Judd. Can. J. Plant Sci. 91: 725-738. Rhododendron groenlandicum (Oeder) Kron and Judd, bog Labrador tea, is an evergreen shrub from the Ericacae family native to North America. Bog Labrador tea is associated with the later stages of forest successions in black spruce forest stands of the boreal ecosystems with cool climates, but responds aggressively to forest openings where it is already present. In general, bog Labrador tea is associated with nutrient-poor, acidic soils, with drainage ranging from moist to wet. Layering is the main regeneration strategy of the species; evidence suggests that this could be especially true following disturbances that open the forest canopy. Sexual reproduction maintains viability in undisturbed communities through wind or water dispersal. Rhododendron groenlandicum acclimates more rapidly relative to black spruce after perturbations through a higher rate of resource utilization when resources are available. The species is a highly competitive shrub for soil nutrients; it competes with regenerating conifers for soil nitrogen and phosphorus. It can also assimilate organic nitrogen from the soil through its mycorhizae. These characteristics may lead to the formation of ericaceous heaths that can stay unforested indefinitely. However, this species can be eradicated by herbicides (glyphosate) and heavy site scarification can limit its propagation.

The Biology of Canadian Weeds. 146.Rhododendron groenlandicum(Oeder) Kron and Judd

Hébert, F. and Thiffault, N. 2011. The Biology of Canadian Weeds. 146. Rhododendron groenlandicum (Oeder) Kron and Judd. Can. J. Plant Sci. 91: 725–738. Rhododendron groenlandicum (Oeder) Kron and Judd, bog Labrador tea, is an evergreen shrub from the Ericacae family native to North America. Bog Labrador tea is associated with the later stages of forest successions in black spruce forest stands of the boreal ecosystems with cool climates, but responds aggressively to forest openings where it is already present. In general, bog Labrador tea is associated with nutrient-poor, acidic soils, with drainage ranging from moist to wet. Layering is the main regeneration strategy of the species; evidence suggests that this could be especially true following disturbances that open the forest canopy. Sexual reproduction maintains viability in undisturbed communities through wind or water dispersal. Rhododendron groenlandicum acclimates more rapidly relative to black spruce after perturbations through a higher rate of resource utilization when resources are available. The species is a highly competitive shrub for soil nutrients; it competes with regenerating conifers for soil nitrogen and phosphorus. It can also assimilate organic nitrogen from the soil through its mycorhizae. These characteristics may lead to the formation of ericaceous heaths that can stay unforested indefinitely. However, this species can be eradicated by herbicides (glyphosate) and heavy site scarification can limit its propagation.

Effect of Human Disturbance on Bee Communities in a Forested Ecosystem

It is important for conservation biologists to understand how well species persist in human-dominated ecosystems because protected areas constitute a small fraction of the Earth's surface and because anthropogenic habitats may offer more opportunities for conservation than has been previously thought. We investigated how an important functional group, pollinators (bees; Hymenoptera: Apiformes), are affected by human land use at the landscape and local scales in southern New Jersey (U.S.A.). We established 40 sites that differed in surrounding landscape cover or local habitat type and collected 2551 bees of 130 species. The natural habitat in this ecosystem is a forested, ericaceous heath. Bee abundance and species richness within forest habitat decreased, not increased, with increasing forest cover in the surrounding landscape. Similarly, bee abundance was greater in agricultural fields and suburban and urban developments than in extensive forests, and the same trend was found for species richness. Particular species groups that might be expected to show greater sensitivity to habitat loss, such as floral specialists and bees of small or large body size, did not show strong positive associations with forest habitat. Nevertheless, 18 of the 130 bee species studied were positively associated with extensive forest. One of these species is a narrow endemic that was last seen in 1939. Our results suggest that at least in this system, moderate anthropogenic land use may be compatible with the conservation of many, but not all, bee species.

Postglacial formation and dynamics of North Patagonian Rainforest in the Chonos Archipelago, Southern Chile

Pollen analysis of continuous sediment cores from two lakes in the northern Chonos Archipelago (44°S) in southern Chile shows a complete postglacial record of vegetation change. The fossil records indicate that deglaciation was complete in the northern Chonos by at least 13,600 14C yr BP. Ericaceous heath and grassland persisted for more than 600 years after deglaciation under the influence of dry/cold climates and frequent burning. Nothofagus- Pilgerodendron- Podocarpus forest, with modern analogues in the southern Chonos Archipelago, was established across the northern islands by 12,400 14C yr BP under increasingly warm and wet climates. There is no evidence for a return to cooler climates during the Younger Dryas chronozone. The rise of Tepualia stipularis and Weinmannia trichosperma as important forest components between 10,600 and 6000 14C yr BP may be associated with climates that were warmer than present. The collapse of Pilgerodendron communities during this time may have been triggered by a combination of factors related to disturbance frequency including tephra deposition events, fire and climate change. After 6000 14C yr BP Pilgerodendron recovers and Nothofagus-Pilgerodendron-Tepualia forest persists until the present. European logging and burning activity may have increased the susceptibility of North Patagonian Rainforest to invasion by introduced species and to future collapse of the long-lived Pilgerodendron communities.

Conifer Regeneration Problems in Boreal and Temperate Forests with Ericaceous Understory: Role of Disturbance, Seedbed Limitation, and Keytsone Species Change

Conifer regeneration failure in the presence of dense ericaceous cover resulting from the removal of canopy trees by forest harvesting observed in boreal and temperate forest has been attributed to allelopathy, competition, and soil nutrient imbalance. Ecosystem-level alleopathic effect has been argued as a cause for conifer regeneration failure by citing examples from a species-poor boreal forest in northern Sweden with ground vegetation dominated by crowberry (Empetrum hermaphroditum, Ericales) and New Zealand dairy pastures invaded by nodding or musk thistle (Carduus nutans). This article aims to explain the phenomenon of vegetation shift from conifer forest to ericaceous heath by extending the argument of ecosystem-level impact of ericaceous plants and linking the disturbance-mediated regeneration strategies of the dominant conifer species and the understory ericaceous species with the quality of seedbed substrate that influence the direction of secondary succession. It has been argued that fire severity plays a pivotal role in controlling seedbed quality and the regeneration mechanisms of conifers, which in turn determines the direction of post-disturbance succession. The post-fire-dominated ericaceous plants and their habitat-modifying effects have been explained from the point of view of keystone species concept and their role as ecosystem engineers. In the absence of high severity natural fires the canopy keystone species (conifer) fails to regenerate successfully mainly due to limitation of favorable seedbed. On the other hand, the understory ericaceous plants regenerate vigorously by vegetative methods from the belowground components that survived the fire. Forest harvesting by clearcutting or selective cutting also create similar vigorous vegetative regrowth of ericaceous plants, but conifer regeneration suffers from the lack of a suitable seedbed. Thus in the absence of successful conifer regeneration, the vigorously growing understory ericaceous plants become the new keystone species. The new keystone ericaceous species bring about a significant long-term habitat change by rapid accumulation of plyphenol-rich humus. Ericaceous phenolic compounds have been found to inhibit seed germination and seedling growth of conifers. By forming protein-phenol complexes they cause a further reduction of available nitrogen of the already nutrient-stressed habitat. A low pH condition in the presence of phenolic compounds causes the leaching of metallic ions and forms hard iron pans that impair soil water movement. The phenolic allelochemicals of ericaceous humus are also inhibitory to many conifer ectomycorrhizae.On the other hand, ericaceous plants perpetuate in the community by their stress-tolerating strategies as well as their ability to acquire nutrients through ericoid mycorrhizae. Three mechanisms working at the ecosystem level can be suggested as the cause of vegetation shift from forest to ericaceous heath. These are (1) the absence of high severity natural fire and the limitation of suitable conifer seedbed in the presence of thick humus, (2) increased competition resulting from the rapid vegetative regeneration of understory ericaceous plants after forest canopy opening by harvesting or nonsevere fire, and (3) habitat degradation by phenolic allelochemicals of ericaceous plants causing a soil nutrient imbalance and iron pan formation. Thus, a shift in keystone species from conifer to ericaceous plant in the post-disturbance habitat may induce a retrogressive succession due to ecosystem-level engineering effects of the new keystone species.Vegetation management in conifer-ericaceous communities depends on land management objectives. If the objective is to produce timber and other forest products then the control of ericaceous plants and site preparation is necessary after forest harvesting. Ploughing and liming followed by conifer planting and repeated N fertilization has been applied successfully to promote afforestation of Calluna heathlands in Britain. However, such practice has not been proven successful in the reforestation of Kalmia-dominated sites in eastern Canada. If, on the other hand, the land management objective is to maintain heathlands for herbivore production or conservation of cultural landscape, as in the case of certain Calluna-dominated heathland in Western Europe, then moderately hot prescribed burning is useful as a management tool.

Biodiversity and vegetation dynamics in the coastal heathlands of western Norway

The heaths of Lygra, western Norway, were investigated, and 19 communities at the association level were distinguished. Distinct ecotypes of Ranunculus acris and Poa humilis and microspecies of Euphrasia were restricted to the grass heaths. No distinct ecotypes were found in the Calluna‐dominated vegetation. It is suggested that the regular burning, which has been part of the management of the area, has activated the seed bank of the ericaceous heath, and thus maintained genetic diversity and slowed down ecotype differentiation. The grass heaths, with no combustible material, have been unaffected in this way. Permanent plots in the two dominant heath types, dry heath (Vaccinio‐Callunetum) and wet heath (Ericetum tetralicis) were followed over six years and the data analysed using a modification of Jaccard's index, allowing for species abundances.

Micro‐scale patterns of modern pollen deposition within three alpine plant communities*

summaryFew studies have examined patterns of pollen deposition or the relationship between vegetation and pollen assemblages at the small scale. This paper examines the representation of both individual taxa and whole plant communities in modern pollen spectra. Micro‐scale variations in modern pollen deposition were studied in three alpine plant communities on Storbreen glacier foreland, southern Norway: a pioneer community; a Salix‐shrub community; and an ericaceous heath community. The relationships between vegetation and modern pollen deposition and the variability of these relationships at the local scale were investigated within 16 × 1 m2‐quadrats. The data were classified using two‐way indicator‐species analysis (TWINSPAN) and ordinated using detrended‐correspondence analysis (DCA). In addition, the pollen and vegetation data were ordinated simultaneously, using canonical correspondence analysis (CCA). The effect of removing arboreal pollen from the pollen sum was examined. The three plant communities were distinguished successfully by multivariate statistical techniques, using; both pollen data and vegetation data. However, within the communities there was high variability in pollen deposition, which was most pronounced in the Salix‐shrub community. The abundance of individual taxa in the vegetation was compared with their representation in the pollen spectra. The strongest relationships were shown by Salix Ericales, Empetrum and Lycopodium. Certain taxa showed consistent, reproducible patterns of behaviour. These patterns provided valuable evidence for separating contrasting plant communities. Comparison of modern pollen‐vegetation relationships of this kind with pollen data from Holocene and Pleistocene sites is important to improve the reconstruction of past plant communities. Statistical analyses showed that for the majority of taxa a moss polster consisting of 20 subsamples was necessary to reduce the effect of microscale variability in this environment to acceptable levels.

Sphagnum skyense sp. nov

Abstract Spagnum skyense (Sect. Acutifolia) sp. nov. can be recognized in the field by its robust appearance, its convex and predominantly reddish capitula, its pale red stem and its large and broadly triangular to triangular-lingulate stem leaves. Microscopically, it is recognized by the common occurrence of fibrils in the stem leaves, the occasional occurrence of pores in the stem cortex, and the large and broad cells of the divergent branch leaves.The new species show similarities to S. quinquefarium (Braithw.) Warnst. and S. subnitens Russ. & Warnst. ssp. subnitens. It is recorded from ericaceous heath on the Isle of Skye, north-west Scotland.

Studies on the peat deposits of the island of Foula, Shetland

Summary The results of macroscopic and pollen analytical studies on the island of Foula, Shetland, are described and discussed. The tree pollen count never exceeds 11% of the total pollen count in the pollen diagrams. The dominant vegetation of the island during the period which is represented by the peat deposits is shown to have been Ericaceous heath. Macroscopic studies show that although several species of tree did once occur on the island they were never a dominant part of the island's vegetation. It was found impossible to date the peat deposits on the basis of pollen diagrams in view of the extremely low values of the tree pollen curves.