Variations in mountain vegetation use by reindeer (Rangifer tarandus) affects dry heath but not grass heath

Question: Are differences in landscape use of semi‐domesticated reindeer reflected in the vegetation of summer grazing grounds? Location: Alpine heaths, central east Sweden. Methods: Dry heath and grass heath vegetation plots with inferred grazing intensities (high, intermediate and low) were selected a priori from an interpolated pellet count map compiled in 2002. In each plot, faecal pellets were counted, environmental variables measured and vegetation sampled by listing presence and absence. Species composition was compared with a detrended correspondence analysis, and a canonical correspondence analysis was used to infer relations between species composition and environmental variables. Plots were also clustered to provide groupings for an indicator species analysis. Results: Significant differences in faecal pellet count were present between the highest and lowest grazing intensities for both vegetation types, showing that the pattern in the interpolated pellet maps was robust. Differences in species composition between grazing intensities were found for the dry heath only. Here, there was an apparent grazing gradient, with lichens and mosses in the low‐use plots and grasses and herbs in the high‐use plots. No such gradient was found for the grass heath. Conclusions: Within the dry heath vegetation type, grazing levels had a subtle effect on the vegetation, while no effects were seen in the grass heath, probably as a result of the dominance of more grazing‐tolerant graminoids. Even in the dry heath, species richness did not differ between grazing levels, but the relative abundances of species differed.     

The Effect of Habitat Changes on the Endangered Ground Beetle Carabus Nitens (Coleoptera: Carabidae)

Carabus nitens, one of the most endangered ground beetles in Central Europe, was investigated with pitfall traps at 30 sampling sites in 17 heath fragments of the largest German heath landscape under nature conservation (nature reserve 'Lüneburger Heide'). The preference for damp Erica heaths and dry Calluna heaths in the building phase was thereby evident. Calluna heaths in the mature and degenerate phase, with and without extensive coverage by Avenella flexuosa, are either not inhabited or are avoided. The results of ovary dissections indicate that the populations in two successive spring seasons consisted mainly of animals which had already reproduced and were therefore older than one and a half years. Allozyme electrophoreses revealed variation for three of the nine investigated enzyme loci, and large differences in the allele frequency at one of these loci indicated genetic drift and fluctuations in the size of local populations. According to these results and statements in the literature, the loss of heathland areas and habitat quality are both responsible for the decline of the species. Suitable measures for preserving the species are (1) restoration of building phases of the Calluna heaths and (2) interconnection of at least the smaller heath fragments. Finally, recommendations are given for reintroductions.     

The phytogeography of European and Mediterranean heath species (Ericoideae, Ericaceae): a quantitative analysis

The geographic ranges of heath species in Europe and the Mediterranean and their relationships with environmental (climatic and ecogeographic) variables and biological features are analysed by means of multivariate methods. In particular, twinspan classifications into floristic elements and floristic regions, DCA floristic ordinations, CCA environment-constrained ordinations and CCA biology-constrained ordinations are carried out. Results of the analyses show a correspondence with conventional regionalization analyses based on broader criteria, and less correspondence with numerical analyses of other taxonomic groups at a similar scale. This lack of fit depends on the particular history and ecology of the taxonomic groups under study. A number of climatic (temperature and water stress) and geographic (coast length) variables are associated with different types of heaths according to their geographical ranges (continental, Mediterranean, Atlantic). Biological features of heaths account for a small part of the variation in range, but the association of temperate heaths with a preference for acid soils, of Mediterranean heaths with pubescence, and of Atlantic heaths with plant height is of interest. Heath species richness throughout Europe and the Mediterranean is analysed by multiple regression analyses and, apart from a strong influence of area size, a significant effect of water conditions, temperature and proximity to sea is detected. The area with the highest heath species richness is Western Mediterranean. Additional classification, ordination and multiple regression analyses of heaths in the Iberian Peninsula (Spain and Portugal, the areas with the highest heath diversity) revealed similar patterns to those found in Europe and the Mediterranean. The effect of heterogeneity of the studied units at this latter scale is removed in the Iberian analysis because of the relative homogeneity of the units considered at this scale.     

Early stages of Calluna vulgaris regeneration after burning of coastal heath in central Norway

Questions: How does Calluna vulgaris regenerate after burning wet and dry heaths of different age? Location: Central Norway. Methods: Patches of Calluna dominated old and young wet heath and old dry heath were burned. The mean temperatures reached in the categories of heath were measured. Cover, frequency, height and number of seedlings of Calluna were studied in plots. Results: The mean burning temperatures varied from 680 to 740°C, and were highest in wet heath that had not been burned for at least 50 years. Regeneration of Calluna was evident in the year of burning, but only from seeds. Even heath with a short burning interval lacked vegetative regeneration. Calluna cover increased yearly and exceeded 50 % three years after burning. Regeneration was evident in the year of burning, and was highest in heath with a short burning interval. The height increased regularly at all sites, but was most rapid in dry heath, probably because of better microclimatic conditions. There were more seedlings in the heath with a short burning interval. Conclusions: Calluna only regenerates from seeds afterburning in central Norway. The density of Calluna increased rapidly, which is positive for the conservation and management of coastal heaths in central Norway.     

Experimental evidence that ground‐disturbance benefits Woodlark Lullula arborea

To determine whether ground‐disturbance increased Woodlark Lullula arborea abundance, we examined responses over 3 years to four treatments varying in establishment method (shallow‐ or deep‐cultivated) and complexity (homogeneous or ‘complex‐mosaics’ comprising fallow and recently cultivated subplots), plus controls, replicated across the largest lowland grass‐heath in the UK. Abundance increased through the study and was higher on plots closer to woodland and across all treatments. Within complex‐mosaics, Woodlark preferentially used recently cultivated subplots over 1‐ or 2‐year‐old fallows. Regardless of treatment detail, providing suitable foraging habitat within c. 45 m of woodland, through annual ground‐disturbance, can increase Woodlark abundance within lowland grass‐heaths characterized by closed swards.     

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.     

Influence of soil and microclimate on species composition and grass encroachment in heath succession

Aims and Methods Mostly due to land use changes, European heathlands have become increasingly rare. In addition, the increasing amount of atmospheric nitrogen deposition has resulted in an encroachment of grasses and a loss in species diversity. Despite many investigations, information about the precise environmental parameters that determine the development and maintenance of heathland vegetation is still insufficient. In order to determine the environmental factors that control heath succession and grass encroachment, and to develop appropriate management schemes, we studied the influence of several soil and microclimate parameters on species composition and vegetation characteristics in five successional stages in a coastal heathland on the island of Hiddensee, north-east Germany, where the encroachment of Carex arenaria has become a major problem.Important findings We recorded the highest plant species richness in grey dune and birch forest plots, while the encroachment of C. arenaria let to a significant decline in plant species richness. The most important environmental factors influencing species richness and distribution of single species were microclimate, soil moisture, soil pH and the C/N ratio. While many studies reported the importance of differences in nutrient availability, we found no significant correlations between soil nutrient availability and vegetation pattern. Environmental conditions in dense C. arenaria stands, especially soil properties (e.g. soil pH), showed great differences in comparison to the other successional stages. However, no correlations between the encroachment of C. arenaria and single environmental factors were found. Our results show that not only soil nutrients are important abiotic factors in heaths but that also microclimate and soil moisture play an important role and that many factors are involved in heath succession and in the promotion of grass encroachment. Management plans for the conservation and restoration of heathlands should therefore focus on the specific site conditions and should take several abiotic and biotic factors into account.     

Long‐term influence of sod cutting depth on the restoration of degraded wet heaths

Temperate heaths have an unfavorable conservation status in most European biogeographical regions. Increasing nitrogen levels promote competitive grass species such as Molinia caerulea, which is a main threat to heathland conservation in Europe. This article investigates the long‐term influence of sod cutting and the resulting changes in soil properties on the heath composition, integrity, and structure. In 15 nature reserves across the northern half of Belgium, we used (1) a large number of plots (203); (2) a broad range of sod cut depths (2–40 cm), and (3) a temporal dimension that describes how long the effects of sod cutting persist (census up to 19 years after sod cutting). Multivariate analyses were used in order to explore the influence of sod cut depth and time after sod cutting on the soil and vegetation properties. There was a positive relationship between sod cut depth and soil pH and water level, and a negative relationship with Al³⁺, NH₄⁺, and total organic matter (TOM). However, only a limited number of typical (target) species appeared after sod cutting, and then only weakly. Most of the time they remained a minor component of the restored vegetation. Moreover, M. caerulea reappeared and its cover significantly increased during the years following sod cutting. Although we were able to show that sod cut depth has a differential effect on soil properties and vegetation recovery, it also appeared that sod cutting does not restore wet heaths in the long term when applied in regions with high nitrogen deposition.     

The contribution of grazing to plant diversity in alpine grassland and heath

Abstract Grazing on transplants of a grass, a forb and a tree was examined in low-diversity grassland and more diverse heath in Australia's Snowy Mountains. Transplants were surrounded by 2 mm mesh netting. In one grassland plot, grazers (probably soil invertebrates) attacked 40–90% of tree and forb seedlings but no grass seedlings. In heath, which had about half the grass cover of grassland, grazers consumed grasses but not trees or forbs. The results suggest that grazers can depress diversity in grassland by attacking species other than grass. In heath, they may promote diversity by attacking only grass and releasing other species from competition.     

Plant coexistence in coastal heaths: Habitat segregation in the post-fire environment

Abstract Previous studies of heaths on Pleistocene coastal sands showed consistent variation in patterns of floristic composition between areas on ridges and slopes but not within them. A large wild-fire that swept this system provided an opportunity to observe temporal processes in habitat segregation of species. Ridges and slopes were found to differ in species richness of seedlings in 0.0625 m2 quadrats and there was no evidence that the species richness in the two habitats was converging over 3 years. This suggests that initially these processes differ in space between the two habitats with more species in the wet heath being packed into a smaller area than in the dry heath. Seed-banks of species did not saturate available space for recruitment in either habitat, but seedling densities differed asymmetrically between habitats across two pairs of species studied. Experimental manipulation of seeds among habitats also showed distinct differences in establishment and survival among representative species from different habitats. The presence of seed-banks of wet-heath species in dry heath suggested that recruitment of their seedlings may occur there, but experiments showed that seedlings that arise from them do not survive there. Conversely, although no seed-bank of either dry-heath species studied was found in wet heath, our manipulations showed that their seedlings could grow there. Thus, superficially, physiological tolerance appeared to limit regeneration of wet-heath species in dry heath. However, there appeared to be no physiological limit for dry-heath plants to survive in wet heath. This paper shows that segregation of species may operate at either of two stages of the life cycle: at dispersal when safe sites for establishment are required, and at recruitment after seedlings have established. These findings highlight the importance of the regeneration niche in structuring community composition in coastal heaths, and contrast with traditional explanations of species segregation invoking physiological tolerance and competition at later life-history stages.     

Effects of N-deposition on ion trapping by B-horizons of Danish heathlands

Coastal and inland heaths constitute a dominating fraction of the relatively few semi-natural ecosystems in Denmark. At the inland heath, the soil forming factors have been active with the same vegetation type during the last 2000 years, whereas at the coastal heath, these soil forming factors have only been active over a couple of hundred years, due to the activity of windblown sand. Effects on ion-balance and soil processes of nitrogen deposition on a young dune heath and an old inland heath have been investigated. Different levels of NH₄NO₃have been applied to the two heathlands, and rain, throughfall water and soil water chemistry below the experimental plots have been analysed. Results show that the ability to retain added, as well as deposited, nitrogen requires the presence and the integrity of a humifyed H-subhorizon. When the mor-layer for some reason breaks down, the nutrients will be retained by the B-horizons as a kind of back-up, and most probably be reused by the new vegetation. One year after destructive heather beetles attack on the inland heath, the mor-layer started to decompose. A large translocation of organic compounds, complexed associated cations and nitrogen-species, started from the mor-layer to the top of the B-horizon where they precipitate. The podzolic B-horizons can be seen as nutrient trap to the mor-layer. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ecology of heath communities dominated by Cassiope tetragona at Alexandra Fiord, Ellesmere Island, Canada

At a high arctic lowland on Ellesmere Island, heath communities dominated by Cassiope tetragona were widespread, and occurred in a variety of habitats that differred in time of snowmelt, relative site moisture, soil thaw depth, and air and soil temperature. Cover, standing crop, and production were dominated by woody plants, notably Cassiope tetragona and Dryas integrifolia . The Cassiope -dominated heaths were similar in composition to those at other Canadian high arctic localities, but were less similar to localities in Greenland and Spitzbergen. Compositional relationships among Cassiope -dominated heaths in different habitats at the study site may be largely determined by two interrelated environmental factors, time of snowmelt and site moisture.
Aboveground vascular plant biomass was concentrated near the ground surface, resulting in simple vertical structure that takes advantage of relatively warm soil and air temperatures in summer, and a protective snow cover in winter. Aboveground vascular plant standing crop was largely comprised of attached dead tissue, and there were equal proportions of above- and belowground biomass. Low community production was due to dominance by long-lived, slow-growing species, and to short growing seasons and cold temperatures. Overall character of Cassiope -dominated heaths reflects the conservative, stress tolerant growth strategy of the dominant species, Cassiope tetragona .     

A phytosociological study of a mid-altitude heath in County Durham, Northern England

A phytosociological survey of Hedleyhope Fell, a mid-Durham heath, was carried out. Much of the Fell is rank Nardus grassland, with damper Juncus and Eriophorum patches. Disturbed areas to the west are covered by poor Agrostis/Trifolium/Festuca grasslands. The eastern end of the Fell forms a locally valuable area of heathland. 115 relevés were taken and 131 species of plant recorded. Classification by two-way indicator species analysis suggested the delimitation of 19 noda. The principal ordination axes, produced by detrended correspondence analysis, emphasised the importance of soil moisture gradients, organic/mineral soil gradients and levels of disturbance in determining the vegetation. The Fell, at 300 m, falls between the lowland heaths of southern England and the upland mires of the north. Indeed, its vegetation contains some assemblages and species characteristic of both habitats. The heaths of central, mid-altitude County Durham are found where the coal measures lie close to the surface and so this habitat type has suffered extensively from opencast mining activity in the recent past. Proposed opencast sites, if they go ahead, will destroy the Fell.     

Climatic warming increases isoprene emission from a subarctic heath

Emissions of isoprene, a reactive hydrocarbon, from Subarctic vegetation are not well documented. However, the Arctic is likely to experience the most pronounced effects of climatic warming, which may increase temperature-dependent isoprene emission. Here, we assessed isoprene emission from a Subarctic heath subjected to a 3-4 degrees C increase in air temperature and mountain birch (Betula pubescens ssp. czerepanovii) litter addition for 7-8 yr, simulating climatic warming and the subsequent expansion of deciduous shrub species and migration of the treeline. The measurements were performed using the dynamic chamber method on a wet heath with a mixture of shrubs, herbs and graminoids. Isoprene emissions averaged across the treatments were 36 +/- 5 microg m(-2) h(-1) in 2006 and 58 +/- 7 microg m(-2) h(-1) in 2007. The experimental warming increased the emissions by 83% in 2007 (P = 0.021) and by 56% in 2006 (P = 0.056), while litter addition had no significant effects. The net ecosystem CO(2) exchange was significantly decreased by warming in 2007. These results show that isoprene emissions from Subarctic heaths are comparable to those from Subarctic peatlands. Climatic warming will increase the emissions, and the amount of carbon lost as isoprene, from Subarctic heath ecosystems.     

Local adaptation,genetic divergence,and experimental selection in a foundation grass across the US Great Plains’ climate gradient

Many prior studies have uncovered evidence for local adaptation using reciprocal transplant experiments. However, these studies are rarely conducted for a long enough time to observe succession and competitive dynamics in a community context, limiting inferences for long‐lived species. Furthermore, the genetic basis of local adaptation and genetic associations with climate has rarely been identified. Here, we report on a long‐term (6‐year) experiment conducted under natural conditions focused on Andropogon gerardii, the dominant grass of the North American Great Plains tallgrass ecosystem. We focus on this foundation grass that comprises 80% of tallgrass prairie biomass and is widely used in 20,000 km² of restoration. Specifically, we asked the following questions: (a) Whether ecotypes are locally adapted to regional climate in realistic ecological communities. (b) Does adaptive genetic variation underpin divergent phenotypes across the climate gradient? (c) Is there evidence of local adaptation if the plants are exposed to competition among ecotypes in mixed ecotype plots? Finally, (d) are local adaptation and genetic divergence related to climate? Reciprocal gardens were planted with 3 regional ecotypes (originating from dry, mesic, wet climate sources) of Andropogon gerardii across a precipitation gradient (500–1,200 mm/year) in the US Great Plains. We demonstrate local adaptation and differentiation of ecotypes in wet and dry environments. Surprisingly, the apparent generalist mesic ecotype performed comparably under all rainfall conditions. Ecotype performance was underpinned by differences in neutral diversity and candidate genes corroborating strong differences among ecotypes. Ecotype differentiation was related to climate, primarily rainfall. Without long‐term studies, wrong conclusions would have been reached based on the first two years. Further, restoring prairies with climate‐matched ecotypes is critical to future ecology, conservation, and sustainability under climate change.     

Geographical separation of two Ulex species at three spatial scales: does competition limit species' ranges?

It is a common assumption that species' ranges are limited by their physiological tolerances to climatic factors, Biotic factors, such as competition, are rarely considered. We investigated the distributions of Ulex minor and U. gallii at three spatial scales from geographic ranges to individual heaths - to examine whether the species are negatively associated, as predicted by the hypothesis that the ranges of the species are limited by competition with each other. Distribution maps for the British Isles and France (100 400 km² survey units) show the two species have largely separated, but slightly overlapping ranges. A region of range overlap on the heaths of Dorset, southern England was mapped using 4 ha survey squares. There was strong negative association between the species, and the heaths could be divided into zones where one species was dominant. There was some indication of edaphic differences between the U. minor -dominated zones and the U. gallii zones. The few heaths where the species co-occurred were surveyed using 4 m² quadrats placed along transects. Usually one species was widespread over the heath, while the other occurred in patches. The species were strongly negatively associated in all transects. Therefore, the two species showed strong negative associations at three mapping scales. Apparent co-occurrences detected at one spatial scale largely disappeared when species were mapped at finer scales, emphasising the fractal nature of distributions. This provides evidence that the distributions of the two species are not independent and that they cannot coexist, and therefore that their ranges are limited by competition. Over their ranges, competitive superiority is probably determined by the climate. At the range boundaries in the region of overlap, climate is not important, but other physical factors such as edaphic conditions may determine the outcome of competition.     

Response of carabid beetles (Coleoptera: Carabidae) and spiders (Araneae) to coastal heathland succession

We analyzed the impacts of succession and grass encroachment on carabid beetle and spider assemblages in a coastal heathland. Further, indicator species for different successional stages (grey dunes, dwarf-shrub heath, grassy heath, heath with shrubs, birch forest) were identified, and their relations to habitat parameters were analyzed. The study was conducted on the Baltic island of Hiddensee, Germany. Ground-dwelling arthropods were sampled using pitfall traps along a successional gradient containing five stages. Ordination by nonmetric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) revealed a clear separation of species composition among the successional stages. Both in carabid beetles and spiders, most indicator species were obtained in the youngest stage (grey dunes) and fewest in the intermediate stages (grassy heath, heath with shrubs). Also the proportion of endangered species was highest in grey dunes. Based on our results, conservation management of coastal heathlands should preserve a mosaic of different successional stages with a clear preference on younger stages (grey dunes and dwarf-shrub heath).     

Seedling emergence after sod cutting in grass heath

Abstract. Experimental plots in grass heath, previously subjected to various sod cutting treatments, contained a seed store of ericoid dwarf shrubs, but seeds of grasses of the former grass heath were not found. The density of emerging dwarf-shrub seedlings in the plots was determined mainly by soil moisture, but with density of seeds stored in the soil and soil acidity as modifying factors. It is concluded that the restoration of a dwarf-shrub heathby sod cutting is relatively successful, as compared to other measures, because the grass seeds become obsolete.     

Diet and habitat use of the Dotterel Charadrius morinellus in Scotland

The feeding ecology of Dotterel Charadrius morinellus adults and chicks was studied on three Scottish breeding areas. On the basis of 2324 prey items identified from 234 faeces, we show that (i) birds feed selectively and (ii) age-related and seasonal differences in food selection occur.
The diet comprised mainly beetles (Coleoptera), sawflies (Symphyta) and the adults and larvae of Tipula montana. The faeces of adult Dotterel contained a high proportion of beetles, whereas chick faeces had more soft-bodied prey. However, when T. montana adults emerged en masse (every second year) both adults and chicks took more tipulids. On one area, larval T. montana comprised much of the diet soon after the birds arrived on their breeding grounds and just before leaving in autumn. The preferred feeding habitats were flat or gently sloping Racomitrium lanuginosum or Juncus trifidus heaths or the transition zone between moss heath and montane bog. Dwarf-shrub, grass-dominated and single bog communities were avoided. The preferred feeding habitats were those in which pitfall trap catches of the main prey were highest. A close juxtaposition of montane bog and R. lanuginosum heaths met the feeding requirements of both chicks and adults, respectively. Recent changes in the breeding distribution of Dotterel in Britain may be related to de- terioration in feeding and breeding habitat due to overgrazing by sheep and greater habitat acidification.