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AIMS: To apply the Landscape Reconstruction Algorithm (LRA) to pollen count data from multiple sites to estimate local vegetation abundance and compare with charcoal‐derived records of burning. LOCATION: Exmoor, southwest England, UK. METHODS: Pollen count data from 16 sites were transformed to estimates of distance‐weighted vegetation abundance using the LRA (REVEALS and LOVE models), correcting for bias in pollen production and dispersal. Charcoal concentration data from six sites were normalized using Box‐Cox transformation to produce z‐scores. Moving‐window correlation was undertaken to compare pollen percentage values for key taxa (Calluna, Poaceae) and localized burning. Estimates of distance‐vegetation abundance (LRA output) and time‐averaged charcoal z‐scores were compared to assess the role of burning as a driver for upland vegetation cover. RESULTS: Comparison of pollen percentage and normalized charcoal z‐scores show little correlation between vegetation cover and burning. Estimates of distance‐weighted vegetation abundance and normalized charcoal data show relationships between vegetation change and burning at four of the six sites. The relationships are site‐specific: three sites suggest burning promoted grass‐dominated vegetation, at one site burning promoted heather‐dominated vegetation, and in two sites there is no apparent relationship. CONCLUSIONS: The patterning of vegetation within uplands is a crucial part of ecosystem service delivery, and contemporary and future management benefits from understanding of ‘long‐term’ development, i.e. patterns over millennia. The correction of biases within pollen production and dispersal to produce local vegetation estimates has demonstrated spatial heterogeneity in vegetation cover on Exmoor that is not otherwise evident in the pollen percentage data (which retain a strong influence of the regional vegetation cover). The relationship between LRA‐derived vegetation cover and burning is not apparent in comparisons between pollen percentage data and charcoal records. This implies that studies that use pollen proportional data alone can misrepresent the relationship between vegetation cover and fire. This study demonstrates that fire has been an important part of the development of this cultural landscape.

Question Studying the effects of alterations in precipitation regime on plant communities, including drought and heavy rain spells, is gaining increased importance under climate change. Numerous studies focus on shifts in above-ground production, analysing, climate response of vegetative plant traits, but few consider plant fitness and reproduction. We investigated the response to climate manipulation of generative plant traits and the role of community composition for target species performance. Location An experimental heathlands in Central Europe. Methods We investigated the effects of extreme events such as drought and heavy rainfall, as well as homogeneous precipitation supply, i.e. continuous water availability, on experimental heath communities differing in species numbers (two, four) and functional groups (one, two). We investigated generative traits (number of flowers, number of seeds, seed rain, seed mass, germination rate and reproductive success) and vegetative traits (above-ground biomass, ratio of abundance in 2010 to abundance in 2005, cover) of the two common heath species Vaccinium myrtillus L. and Calluna vulgaris (L.) Hull. Results First, the species composition of the community had a larger influence on target species traits than precipitation manipulations. Second, our four-species community had higher production of flowers, seeds and increased reproductive success of target individuals than the two-species C. vulgaris–V. myrtillus community. Third, homogeneous water supply (weekly irrigation) increased the reproductive success of C. vulgaris. Conclusions Our results provide evidence that community composition and richness might be crucial for heath performance, with the facilitative effects of species interactions gaining increased importance under climatic instability.

Questions How does heathland vegetation composition change during ca. 100 yr of succession in the absence of management? Is succession divergent or mono-directional? Do soil conditions and land-use history explain the variation in vegetation dynamics? Is there evidence for alternative stable states? Location Norholm hede, a 350-ha heathland in southwest Denmark that was abandoned in 1895 and left to develop naturally via succession. Methods Permanent vegetation inventory plots were established and have been revisited 11 times between 1921 and 2012. Soil conditions were recorded in 2012. We used clustering, linear mixed models, linear models, ANOVA and multivariate techniques (redundancy analysis and principal response curves) to investigate changes in the plant community and how differences in plant community composition related to soil conditions and disturbance history. Results Ericaceous dwarf shrubs dominated most of the heathland initially. A dominance shift from dwarf shrubs to grasses occurred on about half of the plots. The other half of the plots remained dominated by dwarf shrubs, although Empetrum nigrum expanded at the expense of Calluna vulgaris. Lichen cover decreased dramatically across all plots. The divergent successional pattern was not explained by nutrient concentrations. Grasses mainly expanded in areas where they already had a substantial presence, and this initial presence was largely correlated with historical soil disturbance. Plots where dwarf shrubs remained dominant had a relatively thick O-horizon. Conclusions Vegetation dynamics during heathland succession were not deterministically determined by soil conditions. Grass and tree expansion occurred slowly and dwarf shrub dominance was stable for more than 100 yr on large parts of the heath, even in the absence of management. Management actions that disturb stable dwarf shrub vegetation may enhance grass and tree colonization.

Questions The coastal heathlands of northwest Europe are classified as highly endangered and a habitat of high conservation importance throughout their geographic range. Previous research into heathland vegetation dynamics has typically been carried out within single sites or regions, and hence little is known about the variability of land-use effects and successional dynamics along biogeographic gradients. We test the hypothesis that the bioclimatic gradient is a key factor shaping post-fire regeneration dynamics in Calluna heathlands, with progressively slower regrowth and lower post-fire pioneer species richness towards colder climates. Location Wet and dry Calluna heath vegetation in five sites spanning a 340-km latitudinal gradient along the west coast of Norway (60.70°–63.79° N). Methods A repeated measures design was used, with floristic data recorded from permanent plots in a number of experimental post-fire successions over a 3-yr period (n = 344). The data were analysed using multivariate ordination techniques: detrended correspondence analysis, partial redundancy analysis and principal response curves, and mixed effects models. Results Regeneration rates decrease from south to north and the wet heath stands regenerate faster towards the pre-fire community composition than the dry stands. Calluna decreases immediately after fire in all sites, but increases from the second year onwards, with the southernmost site having the fastest return. Regeneration of grasses, herbs, mosses and lichens is also faster in the south. Across all sites, species richness decreased the first year after fire, followed by an increase that exceeds pre-fire levels by the second year. The number of pioneer species entering the heathlands after fire decreases northwards. Conclusions We found considerable geographic variation, not only in species composition, but also in post-fire successional trends and dynamics. This is probably linked to higher productivity and larger pools of pioneer species in southern sites, and higher growth rates of shrubs and mosses in the wet heath habitat. This calls for conservation of a geographically diverse set of heathland sites, as well as development of regional- and site-specific management plans.

Questions What are the effects of conifer invasion on plant species composition and richness of coastal heathlands; do effects differ between heathlands invaded by introduced or native coniferous tree species? Location Threatened coastal Calluna heathlands, western Norway. Methods We compared the effects of invasion by introduced Sitka spruce (Picea sitchensis (Bong.) Carr.) and native Scots pine (Pinus sylvestris L.) on heathland plant communities by focusing on the local impacts of single coniferous tree canopies. For each of 58 target coniferous trees (2–4-m tall), 2-m transects were laid out in a north and south orientation from the tree stem to beyond the tree canopy, and control transects were laid out in open heathland adjacent to the target trees. Vascular plants and bryophytes were recorded within 0.0625 m2 contiguous quadrats along the transects. Principal response curves (PRC) and generalized linear mixed models (GLMMs) were used to investigate tree canopy effects on species composition and richness. Results Invasion by coniferous trees induced considerable changes in the coastal heathland vegetation: distinct microcommunitites developed beneath the canopies of relatively young, single coniferous trees in the heathlands. There was a marked difference in subcanopy species composition under the introduced Sitka spruce relative to the native Scots pine; forest floor species had colonized to a greater extent under Sitka spruce, replacing the light-demanding species characteristic of the coastal heathland vegetation. Conclusion Our study showed that conifer invasion induces considerable and rapid changes in heathland vegetation, and that the effects were stronger under the introduced conifer. This suggests that Sitka spruce invasion may pose a more immediate threat to the characteristic coastal heathland vegetation and flora than succession based on native conifers. The open coastal heathlands along the Atlantic coast of Western Europe are a threatened landscape of high conservation value, and our results suggest that the spread of Sitka spruce into these landscapes should be controlled, especially in heathlands that are targeted for conservation.

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: Mannikjarve 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.

The design of a cell-based spatial simulation model of heathland vegetation dynamics including the impacts of rainfall, nitrogen deposition and management is described. The model includes aspects of life history, colonization and seed dispersal for Calluna vulgaris and Deschampsia flexuosa, a common heathland grass. The interactive effects of rainfall, nitrogen deposition and management by cutting or rotovating on vegetation dynamics, and particularly relative cover of Calluna and Deschampsia are investigated. Management by cutting or rotovating resulted in more stable vegetation dynamics, with pure Calluna stands being persistent in the longer term and Deschampsia expanding more slowly when management was imposed. Cutting and rotovating management interacted differently with rainfall and nitrogen deposition. A smaller management interval was required to maintain high Calluna cover by cutting when rainfall was low. More frequent cutting was also required under conditions of high nitrogen deposition. This effect was greatest in simulations with moderate to high rainfall. The outcome of management by rotovating was little affected by rainfall or nitrogen deposition. It is concluded that heathlands that experience varying climates may show different responses to nitrogen deposition and management. This variation should be taken into account when defining critical loads or designing management prescriptions.

Within an ombrogenous part of N. Kisselbergmosen, Rodenes, SE Norway, fine-scale changes in species abundance, successional trends relative to the main gradients (as represented by DCA axes), and co-ordinated change within pairs of the bottom layer species are studied. Data sets were sampled twice with a five-year interval, and included species abundance and cover of mud bottom, naked peat and litter in 436 sample plots (16 cm× 16 cm), and species abundance in 6976 subplots (4 cm× 4 cm). Depth from the surface of subplots to the water table was estimated in 1991. Most summers and growing seasons were somewhat drier than normal in the 5-yr period. The area covered by mud-bottom, naked peat and litter increased significantly, as did the frequencies of the dwarf shrubs Calluna vulgaris and Andromeda polifolia in hummocks and upper lawn. Sample plots were significantly displaced downward the peat productivity gradient (DCA 2), reflecting the reduced cover of many bottom layer species, including all Sphagnum spp. Significant coordinated changes in cover of bottom layer species are described. The changes observed in hummocks support the existence of a local regeneration cycle, as suggested by other researchers. Some of the vegetation changes seem parallel to those reported from areas with a higher nitrogen deposition, but it is not likely that nitrogen deposition alone is the major cause of the observed changes. Between-year variation in population size and climatic fluctuations may as well explain the observed changes.

This paper deals with browsing and grazing as forces driving cyclic succession. Between 1989 and 1994 reciprocal transitions between the dwarf shrub Calluna vulgaris and the grass Deschampsia flexuosa were monitored in permanent plots in a cattle grazed grass-rich Dutch heathland on podsolic soils in which tree encroachment was prevented. Heather beetles killed Calluna in four of the nine plots during 1991/1992. The monitoring revealed reciprocal transitions and cycles between Calluna and Deschampsia on a subplot scale. Beetles and cattle had additional and complementary effects on the two competing species. Defoliation by beetles and trampling by cattle-killed Calluna and favoured grass invasion. Grazing and gap creation by cattle in Deschampsia favoured the establishment and recovery of Calluna. Analysis of the causal mechanisms suggests that indirect, resource-mediated herbivory effects may be as important for the replacement processes as direct effects of defoliation and trampling. Herbivory created differential light and nutrient levels in Calluna and Deschampsia gaps. Grazing and browsing improved the resource-capturing abilities of Calluna and its resistance to herbivory and abiotic disturbances. The emerged Calluna-Deschampsia cycle and its driving forces are summarized in a conceptual triangular resource-mediated successional grazing cycle (RSGC) model, a limit cycle involving herbivore-plant-plant resource interactions. It offers a deterministic equilibrium model as alternative for stochastic transitions between the meta-stable states with dominance of Calluna and Deschampsia respectively, The validity range of the RSGC model and its management implications are briefly discussed.

Succession was studied on plots with the upper soil horizon removed in an area affected by acidic air pollu- tion in the Krusne Hory Mts., Czech Republic. 10 permanent 1-m 2 plots were marked and vegetation recorded annually using a grid of 100 subplots from 1989 to 1995. Constrained ordination analyses showed that soil texture is the most important environmental factor influencing the course of suc- cession. Its effect on species composition increases with succes- sional age of the plant community. On fine-grained soils species- poor communities dominated by grasses (Calamagrostis villosa, Deschampsia flexuosa) and on coarse-grained soils species-rich communities dominated by heather (Calluna vulgaris) devel- oped. Succession proceeded from communities where species composition was determined by diaspore availability towards communities where species composition depended on environ- mental conditions. Successional communities after 10 yr are more dependent on soil characteristics and consequently envi- ronmental determination increases over the course of succes- sion and causes the communities to diverge.

The biomass and chemical composition in six domi- nant field and bottom layer species was followed during four years after a fire in a Pinus sylvestris forest in western Norway. Three fire intensity levels were distinguished: low, medium and high. The overall biomass in the different species was estimated from the biomass per shoot, the shoot densities in pure stands of the investigated species and the percentage cover at medium burned sites. Corresponding measurements were made at control plots outside the burned area. A strong post-fire increase in the overall biomass of Calluna vulgaris, Polytrichum spp., Deschampsiaflexuosa and Pteridium aquilinum was found, against a much slower regrowth of Vaccinium myrtillus and V. vitis-idaea. The Vaccinium species and Calluna were the dominant species at the control plot. Accumulation of carbohydrates seemed to take place in green and non-green tissue of Pteridium and Deschampsia. A corre- sponding accumulation of nitrogen was found in green and non- green Calluna and in non-green Vaccinium myrtillus tissue, and of phosphorus in green and non-green tissue of both Vaccinium species and Calluna as a result of fire. The regrowth of Calluna was mainly from seeds that appeared to be present in the soil before the fire. The regeneration of Pteridium and the two Vaccinium species took place almost exclusively vegetatively from below-ground rhizomes that had survived the fire. Three years after the fire the overall biomass at the burned site was higher than at the control site, due to improved light and nutrient conditions. However, the biomass is expected to decrease in the future and the species composition will prob- ably change as nutrients are leached out of the soil and Pinus and deciduous trees (Betula pubescens and Salix caprea) regenerate from seeds and roots, leading to increased compe- tition in the field and shrub layer.

For a 28-week period in late 1987 and early 1988, a study of seed-shedding by several heath species was carried out at the Muir of Dinnet in northeastern Scotland. The dominant species in the heath is Calluna vulgaris. Seed-shedding in Calluna began in early September 1987 and was completed in April 1988, with the period of maximum shedding falling between early November and late December 1987. The total numbers of seeds/m2 deposited in stands of Calluna in its four growth-phases were: pioneer, 18 910; building, 169010; mature, 198580; degenerate, 33900. Substantial loss of potential seeds results from the shedding of immature flowers. A control area close to, but outside the area of Calluna dominance had a deposition rate of 770 Calluna seeds/m2, indicating sufficient seed to colonise nearby available habitats. Seed rain was also recorded for several other heathland species: Erica cinerea, E. tetralix, Carex spp. and Betula pendula. Seeds of Erica cinerea were deposited in all the Calluna stands, 32670/m2 in the pioneer stand, 17600/m2 in building, 3720/m2 in mature, 210/m2 in degenerate (120/m2 in the control area). Numbers were greatest at the start of the sampling period, declining thereafter. This applied also to Betula seeds. Erica tetralix occurred in the degenerate Calluna stand and yielded 640 seeds/m2 (400/m2 in the control area). Seeds of Carex spp. were obtained in the control: 4110/m2. The method of sampling has a significant effect on the figures obtained. A method using tube collectors, emptied frequently, is recommended.

Heathlands in the Paimpont area, Brittany, were ravaged by numerous fires in the summer of 1976. The period in which the fires occurred, and their intensity had important consequences for recolonization processes. In the tall Ulex europaeus heathland described in this paper, fire occurred relatively late (mid-July), and was of high intensity. Colonisation was mainly from propagules, often from species foreign to the original heathland. Plant succession together with vertical and horizontal structure was studied in permanent plots over 13 yr. Three stages were distinguished. Vertical structure varied greatly among the three stages. It was very simple in the colonisation phase, became more complicated during the competition phase, but became simpler again in the stabilisation phase. This was particularly evident for the moss layer, which, 13 yr after the fire, was made up of Polytrichum commune alone. Mosses showed interspecific competition with size as the decisive factor: the large mosses gradually eliminated the smaller ones. Horizontal structure was studied using spatial autocorrelation, which provided some indication of the distinctive -ness and scale of spatial pattern. Some species were weakly aggregated such as Ceratodon purpureus, Polytrichum pili-ferum, and P. juniperinum, whileothers, like the P. formosum-P. commune complex, Agrostis curtisii and Ulex minor were strongly aggregated. In the current community, 13 yr after the fire, a mosaic can be distinguished with three components: (1) a moss layer of Polytrichum commune on which a herbaceous layer, dominated by Agrostis curtisii has developed; (2) a birch wood (both Betulapendula and B. pubescens), which established on the Polytrichum - Agrostis combination; (3) patches of Ulex minor heathland, with a few Frica and Calluna plants. Extreme simplicity and stability are the two prominent features of the present vegetation state.

The availability of maj or plant resources was investigated in three vegetation types that were assumed to represent different stages of a secondary succession on heathland on the Luneburger Heide, northwestern Germany. Canopy transmission and absorption of photosynthetically active radiation (PAR), soil-water availability, and nutrient (Ca, K, Mg, N, P) availability were monitored with high spatial and temporal resolution in (1) a Calluna vulgaris heathland, (2) a pioneer birch-pine forest and (3) a late-successional oak-beech forest, situated close to each other on comparable geological substrate (diluvial). Mean fractional transmission of PAR during summer decreased from 0.48 in the heathland to 0.04 in the oak-beech forest while the fractional canopy absorption increased from 0.49 to 0.92. Soil-water availability as indicated by the soil-water potential, was significantly influenced by differential canopy interception loss and characteristic rooting patterns in the three vegetation types. Annual mean nutrient concentrations in the equilibrium soil solution were similar or, for some elements, increased from the heathland to the birch-pine and the oak-beech forest despite a growing demand. A marked increase was found for the total nutrient pools in the soil-organic layer between early and late successional vegetation types. On the poor glacial parent material, nutrient pools seem to be strongly dependent on stand productivity and litter production which increased with succession. Thus, for nutrients, facilitation seems to be important in this type of succession.

Accumulation of nutrients in leaves of the dominat- ing species of three ecosystems, characterizing the secondary succession from Genisto-Callunetum heathland through Leucobryo-Pinetum birch-pine woodland to mature Querco- Fagetum oak-beech forest, as well as nutrient turnover within these ecosystems was studied. The objective of the study was to establish potential variations in quantity and quality of nutrient supply to the plants with respect to succession dynam- ics. The results show very low leaf nutrient concentrations of all species investigated, coinciding with low nutrient avail- ability in the soil. However, the nutrient content of leaves and leaf litter of Quercus petraea and Fagus sylvatica, which dominate the late succession stages, and in Betula pendula are higher than in the photosynthetic organs (leaves and young shoots) of Calluna vulgaris and Pinus sylvestris. The combination of the higher nutrient content of the leaves and an increasing leaf-litter production during succes- sion results in an increased nutrient turnover via leaf-litter fall.

Understorey vegetation dynamics in Pinus sylvestris L. stands were examined over 30 yr in southern Finland. Data were collected from 112 permanent sample plots twice, first in 1950-1956 and again in 1983 -1986. Between the two surveys 52 stands were clear-felled and in the 60 remaining old stands thinnings of various magnitude were conducted. In the mature, thinned stands species presence remained virtually unchanged. With the exception of a few species, including Vaccinium vitis-idaea, Hylocomium splendens, and Dicranum polysetum, the changes in species cover were also slight. In the clear-felled plots the changes in species presence were minor but the cover of many species changed strongly. The average cover of Vaccinium myrtillus and Hylocomium splendens dropped to near zero and that of Vaccinium vitis- idaea and Pleurozium schreberi decreased 2 - 4 times on all sites. The cover of Calluna vulgaris approximately doubled, and Cladina rangiferina and Cladina arbuscula also increased after canopy removal. In addition to intrinsic successional change, a special interest in this study was to investigate vegetation dynamics in relation to forest land classification methods in which understorey vegetation is used as part of the classification criteria. The results support the Cajanderian site classification approach, in the case of boreal Scots pine stands, that sites can be classified on the basis of understorey vegetation at different successional phases. However, because of the strong succes- sional and site-to-site variation in species cover, it is suggested that site classification be based primarily on species presence.

Relationships between seed deposition, size of soil seed banks and some of the environmental factors affecting them were assessed for Calluna vulgaris throughout its altitudinal range (150-960 m a.s.l.) in eastern Scotland. Seed rain was assessed using pitfall traps, collected every 5-10 wk for 3 yr; germinability was determined by laboratory incubation. Seed bank size was estimated, once only, by counting seedlings emerging from soil cores kept for 50 wk in a glasshouse. Seed deposition varied annually, was related to parent plant cover but always declined with altitude, falling sharply above 600 m a.s.l. Seed bank size was more closely correlated with the proportion of organic matter in the soil than with the amount of seed rain. Seed bank sizes declined gradually with altitude but did not differ significantly between four altitudinal zones. The mean density of buried seeds was less than half the mean annual seed rain at sites below 300 m a.s.l. but was over 200 × greater than annual seed rain ...