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1.
Over the last two centuries wet heathlands and associated habitats, such as poor fens and bogs, have suffered extensive fragmentation. Recently, large-scale projects aim to restore these rare habitats throughout Europe. To evaluate post-restoration trajectories of wet heathlands, suitable monitoring tools are urgently needed. Here, we investigated whether spider communities are useful tools for evaluating the restoration success of wet heathlands. Ordination revealed that dissimilarity in spider communities between patches of different age classes resulted mainly from vegetation cover and soil moisture. By using a functional trait-approach, we tested if the time since restoration affects trait distribution of spiders in wet heathlands. Typical wet heathland spider species were less common with increasing vegetation encroachment and lower water content. New patches were inhabited by summer active, eurytopic (non-heathland) spiders, while more typical heathland species were found in middle-aged and old patches. Our results suggest that time-related changes in vegetation structure and moistness of restored wet heathlands are clearly reflected by spider communities. Although mobile spiders quickly recolonize the restored heathlands, it takes time for typical heathland spiders to settle. Restoration measures should prevent the negative effects of a vegetation encroachment and a high density of forested edges and should rehabilitate the hydrological cycle in order to preserve rare heathland spiders. We discuss that accounting for responses of spiders provides additional information to guide wet heathlands restoration.  相似文献   

2.
Heathlands, dominated byCalluna vulgaris, are located along the western seaboard of Europe. Most undergo a cyclical succession as the heather plants pass through four definable growth-phases over a period of about 30 years. Examples of upland heathlands are drawn from the North York Moors National Park, an area of Jurassic rocks in the north of England (approximately 54°25N, 0°55W). Botanical diversity is low. In a survey of 10 heathlands selected to encompass the botanical variation of the heathlands of the National Park, only 40 species of higher plants and 31 species of mosses were recorded (2.2% and 4.5% of the British flora, respectively).However, diversity of some invertebrate groups is high. Totals of 54 species of carabid beetles and 127 species of spiders were recorded (15.3% and 20.4% of the British fauna, respectively). At least two environmental gradients appear to influence the species composition of the invertebrate assemblages: a wet-dry gradient and the height of the vegetation (corresponding to the growth-phase of the heather). Experimental areas on three heathlands were burnt and cut, the traditional and more modern methods of heather management. Analysis of both the spider and beetle data indicated that the species assemblages were primarily influenced by the growth-phase of the heather. Some of the nationally rarer species are associated with the open conditions of recently-cut or burnt heathland. An altitudinal effect was also inferred since heathland at 410 m above sea level tended to be less species-rich than heathlands at ca 260 m above sea level.These results present a paradox. Although botanical diversity is extremely low, and although it is a non-natural ecosystem maintained by fire and grazing management to prevent a succession to woodland, arthropod diversity can be extremely high. The discussion focuses on the importance of upland heathlands in the conservation of insect and spider diversity, as well as on the value of these upland areas for conservation more generally.C. vulgaris is seen to be a key species on which many other species depend. One conclusion is that there is insufficient effort, nationally and especially internationally, to conserve the heathlands of Europe.  相似文献   

3.
Findings from nitrogen (N) manipulation studies have provided strong evidence of the detrimental impacts of elevated N deposition on the structure and functioning of heathland ecosystems. Few studies, however, have sought to establish whether experimentally observed responses are also apparent under natural, field conditions. This paper presents the findings of a nationwide field-scale evaluation of British heathlands, across broad geographical, climatic and pollution gradients. Fifty two heathlands were selected across an N deposition gradient of 5.9 to 32.4 kg ha−1 yr−1. The diversity and abundance of higher and lower plants and a suite of biogeochemical measures were evaluated in relation to climate and N deposition indices. Plant species richness declined with increasing temperature and N deposition, and the abundance of nitrophilous species increased with increasing N. Relationships were broadly similar between upland and lowland sites, with the biggest reductions in species number associated with increasing N inputs at the low end of the deposition range. Both oxidised and reduced forms of N were associated with species declines, although reduced N appears to be a stronger driver of species loss at the functional group level. Plant and soil biochemical indices were related to temperature, rainfall and N deposition. Litter C:N ratios and enzyme (phenol-oxidase and phosphomonoesterase) activities had the strongest relationships with site N inputs and appear to represent reliable field indicators of N deposition. This study provides strong, field-scale evidence of links between N deposition - in both oxidised and reduced forms - and widespread changes in the composition, diversity and functioning of British heathlands. The similarity of relationships between upland and lowland environments, across broad spatial and climatic gradients, highlights the ubiquity of relationships with N, and suggests that N deposition is contributing to biodiversity loss and changes in ecosystem functioning across European heathlands.  相似文献   

4.
Many habitat specialist species are originally composed of small, discontinuous populations because their habitats are naturally fragmented or patchy. They may have suffered the long-term effects of natural patchiness. Mediterranean heathlands, a representative habitat in the Strait of Gibraltar region, are associated with nutrient-poor, acidic sandstone soils. Sandstone soil patches in the African side of the Strait (Tangier) are, in general, smaller and more scattered than in the European side (Algeciras). In this study, we analyze the effect of this sandstone patchiness on the population genetic diversity and structure of two Erica species from these Mediterranean heathlands that differ in their edaphic specificity, E. australis, sandstone specialist, and E. arborea, generalist. Average levels of within-population genetic diversity and gene flow between populations were significantly lower in Tangier (high sandstone patchiness) than in Algeciras (low patchiness) for the sandstone specialist, whereas no differences between both sides of the Strait were detected in the edaphic generalist. Since most endemic species in Mediterranean heathlands of the Strait of Gibraltar are sandstone specialists, these results highlight an increased vulnerability to loss of genetic diversity and local extinction of the heathland endemic flora in the Tangier side of the Strait of Gibraltar.  相似文献   

5.
Land-use changes and atmospheric nitrogen deposition have negatively affected heathland biota. Active habitat management is one possible way of counteracting the biodiversity loss associated with these habitat alterations. However, management practices for lowland heathlands often have been transferred to montane heathlands, irrespective of the differences in environmental conditions or assemblage composition. The objective of this study was to evaluate the effects of so-called choppering for the rejuvenation of montane heathland. Choppering involves chaffing and removing the largest part of the organic layer down to the mineral soil. In this study, we compared montane heathlands that were rejuvenated through the application of choppering (CHOPPER) to old-growth montane heathlands (CONTROL). Thirteen years after the rejuvenation measures had been conducted, the environmental conditions between CHOPPER and CONTROL still differed. CHOPPER was characterised by shorter vegetation (herbs/grasses and dwarf shrubs), more bare soil, less litter and higher temperatures. Although, the vascular plants and all studied arthropod groups were affected by the environmental changes, their responses were somewhat different. CHOPPER had a unique assemblage of each taxonomic group that included at least a few heathland species that mainly occurred in this treatment. However, choppering was most beneficial for vascular plants, grasshoppers and carabid beetles. As shown for lowland heathlands, choppering is also a suitable management measure for montane heathland to rejuvenate vegetation with its characteristic arthropod fauna. Due to the intact seed banks and Ericaceae root systems with their mycorrhizas, in combination with the availability of bare soil, heathland vegetation can rapidly regenerate after choppering. The keystone structures that explain the high relevance of CHOPPER, especially for vascular plants, grasshoppers and carabid beetles, are low-growing vegetation and bare soil, which result in light and warm microclimatic conditions. Based on the results of our study, we recommend choppering as a regular management measure to rejuvenate montane heathland.  相似文献   

6.
Questions: Does the diversity of heathland vegetation change when subjected to experimental disturbances such as cutting and nitrogen fertilization? Do changes in the vegetation structure negatively affect the regeneration of the dominant species Calluna vulgaris? Is cutting an alternative method of conserving the diversity and maintaining the structure of heathlands in the Cantabrian Mountains? Location: Calluna vulgaris heathlands on the southern slopes of the Cantabrian Mountain range, NW Spain. Methods: A total of 60 plots were treated with different combinations of cutting and twice the estimated atmospheric deposition of nitrogen (56 kg‐N.ha?1.yr?1). The changes in the cover values of the species present were monitored over a five year study period. The cover values were used to calculate abundance and species richness. Results: Fertilizing with nitrogen allows biodiversity to increase over time. However, the greatest biodiversity is associated with the cutting plus fertilization treatment, since cutting allows gaps to be opened that are easily colonized by pioneer annual species, while fertilization mainly favours an increase in the mean number of perennial herbs (graminoids and forbs). Increased perennial herb richness also corresponds to a rise in their cover values. The recovery of the dominant woody species in these communities, Calluna vulgaris, is not impeded by the increase in perennial herbs species' cover values. Conclusions: In the Calluna vulgaris heathlands studied, cutting plus fertilization allowed an increase in biodiversity over time. No displacement of the dominant woody species, Calluna vulgaris, is observed due to the presence of the perennial herbs. Cutting patches of heathland is recommended as a mechanism for maintaining high vegetation diversity, when grazing is not possible.  相似文献   

7.
Abstract. Diversity relations in Mediterranean heathlands and the understorey of oak woodlands on sandstone-derived substrates were studied at both sides of the Strait of Gibraltar. Trends in species composition and cover were analysed by Detrended Correspondence Analysis; the first axis, assumed to reflect a main environmental gradient, was used to analyse the patterns of three aspects of community diversity. Species richness, i.e. number of species along a 100-m transect, shows a humpbacked trend along the gradient, with the highest values in the understorey of evergreen Quercus suber woodlands, associated with soils of intermediate fertility and moisture status. The number of endemic species is highest in open heathlands, associated with more extreme conditions of acid, infertile soils on exposed ridges. The taxonomic singularity, as measured by the inverse of the average number of species per genus at each site, is highest at the most fertile and moist sites occupied by semideciduous Q. canariensis woodlands. A comparison between northern (Spanish) and southern (Moroccan) sides of the Strait of Gibraltar shows a general concordance of the trends of woody plant communities along the main environmental gradient. However, significant differences of the southern samples are: (1) lack of some differential, habitat-specific species and greater abundance of widespread generalists; and (2) a general reduction in species diversity, number of endemics and taxonomic singularity. We interpret these differences as affected partly by the smaller extent and fragmentation of sandstone areas in the south, and partly by the higher impact of slashing and grazing there.  相似文献   

8.
Abstract. Based on both theoretical and empirical studies there is evidence that different species abundance distributions underlie different species‐area relationships. Here I show that Australian and Californian shrubland communities (at the scale from 1 to 1000 m2) exhibit different species‐area relationships and different species abundance patterns. The species‐area relationship in Australian heathlands best fits an exponential model and species abundance (based on both density and cover) follows a narrow log normal distribution. In contrast, the species‐area relationship in Californian shrublands is best fit with the power model and, although species abundance appears to fit a log normal distribution, the distribution is much broader than in Australian heathlands. I hypothesize that the primary driver of these differences is the abundance of small‐stature annual species in California and the lack of annuals in Australian heathlands. Species‐area is best fit by an exponential model in Australian heathlands because the bulk of the species are common and thus the species‐area curves initially rise rapidly between 1 and 100 m2. Annuals in Californian shrublands generate very broad species abundance distributions with many uncommon or rare species. The power function is a better model in these communities because richness increases slowly from 1 to 100 m2 but more rapidly between 100 and 1000 m2 due to the abundance of rare or uncommon species that are more likely to be encountered at coarser spatial scales. The implications of this study are that both the exponential and power function models are legitimate representations of species‐area relationships in different plant communities. Also, structural differences in community organization, arising from different species abundance distributions, may lead to different species‐area curves, and this may be tied to patterns of life form distribution.  相似文献   

9.
Heather and heathlands   总被引:1,自引:0,他引:1  
GIMINGHAM, C. H., 1989. Heather and heathlands. Studies of the biology and ecology of heather (Calluna vulgaris (L.) Hull) reveal a remarkable combination of characteristics, accounting for its success as a heathland dominant and its ability to persist under traditional forms of use and management. New work on the life history and physiology of the species is helping to explain recent changes in heathlands, and to develop appropriate methods of conservation.  相似文献   

10.
Sandplain heathlands are disturbance-dependent plant communities that occur infrequently in coastal areas of the northeastern United States. We hypothesize that salt spray plays a role in maintaining the composition of the heathland community by excluding salt-intolerant species close to the ocean. We examined the distributions of Solidago nemoralis, Myrica pensylvanica, Pinus rigida, and Quercus spp. in heathlands and conducted greenhouse studies to determine whether different levels of salt spray tolerance explain patterns found in the field. We found that common heathland forb and shrub species grow closer to the ocean than successional woody species. In greenhouse experiments, these species differ in their water status, necrosis, and growth responses to salt spray. The tree species P. rigida and Q. rubra are more susceptible to salt spray than the common heathland species M. pensylvanica. Our results suggest that salt spray may prevent tree species in heathlands from growing close to the ocean and therefore might be an important factor in maintaining the characteristic community composition of these dwarf shrublands in coastal habitats.  相似文献   

11.
The Aljibe Mountains are located in the southern tip of the Iberian Peninsula and have a remarkable biogeographical interest. The complete plant species list (trees, climbers, shrubs, perennial and annual herbs, ferns, lichens, bryophytes and macroscopic algae) was recorded in four 0.1 ha plots from each of the most representative community types (Quercus suber woodland, Q. canariensis forest, open heathland and Q. coccifera shrubland). Up to 119 plant species were found in total in the Q. suber woodland plot. The diversity of woody plants was analysed from 44 samples of cover (100 m line), and the herbaceous layer was explored in 200 quadrats (of 0.5 × 0.5 m). Three biodiversity components (species richness, endemism, and taxonomic singularity) were evaluated in both shrub and herbaceous layers. Open heathlands showed the highest richness of endemic species, both woody and herbaceous. The highest number of woody species was found in the evergreen Q. suber woodland, and of herbaceous species in the semi-deciduous Q. canariensis woodland. Taxonomic singularity was higher in Q. canariensis woodlands and Q. coccifera shrublands for woody species, but there were no significant differences in the herbaceous layer. Local species diversity of heathlands in this region resembles that of South African heathlands (fynbos), despite the obvious geographic and floristic distance, and contrasts with the low diversity of biogeographically closer, European temperate heathlands. The Aljibe Mountains show high diversity values for different life forms (from trees to mosses) and spatial scales (from community to region), and are rich in endemic species. Thus, this area should be recognised as a relevant unit within the Mediterranean plant diversity hot spots.  相似文献   

12.
Open heathlands of the Strait of Gibraltar region constitute a singularvegetation type within the Mediterranean Basin owing to their high biodiversitylevels and distinct features in the biological aspects of endemism. However,they have been traditionally depicted as low profitable, tree-less, barrenlandsand have been either overlooked in conservation policies or included inextensive pine-tree afforestation programmes. Nowadays, most of the existingpine plantations are no longer exploited and have become dense pine woodlands.Here we present the results of a comparative analysis aimed to ascertain theeffects of pine stands on the structure and diversity of the woody component ofthese mediterranean heathlands. Ten sampling sites were located within thestudyarea, each consisting of two adjacent subsamples: an open heathland and aneighbouring heathland under pine-tree cover. Woody species richness andoverallshrub cover was much lower in pine-tree heath understoreys. This drop in coverwas more marked for short-lived species (seeders and withering resprouters),implying a decrease of the life-history diversity and also having noticeableconsequences in homogenizing the floristic composition of heath patches underpine trees. Heathland narrow endemics dropped significantly in pine stands,showing greater sensitivity to afforestation than nonendemics. We suggest thatthe open heathlands of the Strait of Gibraltar should be given furtherattentionin EU and IUCN conservation policies. Programmes should be implemented toprogressively eliminate abandoned pine plantations so as to restore andpreservethese highly diverse mediterranean heathlands.  相似文献   

13.
Anthropogenic impact represents a major pressure on ecosystems, yet little is known about how it affects symbiotic relationships, such as mycorrhizal symbiosis, which plays a crucial role in ecosystem functioning. We analyzed the effects of three human impact types – increasing urbanity, introduction of alien plant species (alienness) and modifications in plant species distribution ranges (as a proxy for naturalness) – on plant community overall mycorrhization (including arbuscular, ecto‐, ericoid and orchid mycorrhizal plants) and arbuscular mycorrhization (indicating the degree of forming mycorrhizal symbiosis at plant community level using the relative abundance of mycorrhizal and arbuscular mycorrhizal plants, respectively). The study was carried out in three habitat types, each dominated by a distinct mycorrhizal type – ectomycorrhizal woodlands, ericoid mycorrhizal heathlands and arbuscular mycorrhizal grasslands – at the regional scale in the Netherlands. The response of community mycorrhization and arbuscular mycorrhization to anthropogenic influence showed contrasting patterns, depending on the specific aspect of human impact. Community mycorrhization responded negatively to urbanity and positively to increasing alienness, while arbuscular mycorrhization showed the reverse trend. More natural heathlands were found to be more mycorrhizal and less arbuscular mycorrhizal. The strongest responses were detected in woodlands and heathlands, while mycorrhization in grasslands was relatively insensitive to human impact. Our study highlights the importance of considering mycorrhizal symbiosis in understanding and quantifying the effects of anthropogenic influence on plant communities, especially in woodlands and heathlands.  相似文献   

14.
North American coastal sandplain heathlands are unique in species composition and vegetation, but the extent to which edaphic factors influence the structure of these communities is currently debated. It was hypothesized that salt spray and edaphic factors maintain the dwarf stature and community composition of heathlands by limiting plant growth and excluding competitively dominant woody species close to the ocean. Field surveys were carried out to investigate the spatial patterns of salt spray accumulation, soil salt and soil moisture. High salt spray correlated significantly with increased leaf necrosis and water stress in Myrica pensylvanica and with decreased plant height. Plant community composition changed across a salt spray and soil gradient, as well. Distinctive sub-communities were identified that separated according to soil salt and soil moisture but salt spray was the main factor affecting sites occupied only by heathland vegetation. Results from this study suggest that salt spray suppresses the growth of heathland plants in close proximity to the ocean, and therefore maintains the low stature in these dwarf shrublands. This research also demonstrates that the physical environment influences the community structure in heathlands, particularly by limiting tree species from growing in high salt spray, low water availability sites.  相似文献   

15.
At the beginning of the 20th century, many montane heathlands were abandoned and became subject to natural succession or afforestation by humans. Thus, the formerly large montane heathlands slowly degraded into small and isolated patches. In this study, we evaluate the influence of restoration measures on leafhopper (Auchenorrhyncha) assemblages of montane heathland ecosystems in Central Europe. Our analyses comprised three different site types that were adjacent to each other: (1) montane heathlands, (2) restoration sites, and (3) control sites. Leafhoppers showed a clear response to montane heathland restoration. Thus, after 4–5 years since implementation of restoration measurements restoration sites were characterized by the highest species richness. However, detailed analyses of leafhopper diversity, species composition, and environmental parameters on the three site types revealed that restoration sites were rather similar to control sites and significantly differing from montane heathlands. We conclude that leafhoppers are excellent bioindicators for restoration measurements because they reflected environmental differences between the three site types. Restoration measurements might only be a useful instrument to promote typical montane heathland leafhopper communities in the long run. Colonization by leafhoppers is, however, dependent on many different factors such as leafhopper mobility, vegetation structure, microclimate, and the establishment of ericaceous dwarf shrubs. Practitioners should establish a management regime (grazing and sod‐cutting) that creates a mosaic of different habitat structures and increases typical heathland vegetation, thus, favoring the colonization of typical heathland leafhoppers.  相似文献   

16.
Questions: How do species composition and abundance of soil seed bank and standing vegetation vary over the course of a post‐fire succession in northern heathlands? What is the role of seed banks – do they act as a refuge for early successional species or can they simply be seen as a spillover from the extant local vegetation? Location: Coastal Calluna heathlands, Western Norway. Methods: We analysed vegetation and seed bank along a 24‐year post‐fire chronosequence. Patterns in community composition, similarity and abundances were tested using multivariate analyses, Sørensen's index of similarity, vegetation cover (%) and seedling counts. Results: The total diversity of vegetation and seed bank were 60 and 54 vascular plant taxa, respectively, with 39 shared species, resulting in 68% similarity overall. Over 24 years, the heathland community progressed from open newly burned ground via species rich graminoid‐ and herb‐dominated vegetation to mature Calluna heath. Post‐fire succession was not reflected in the seed bank. The 10 most abundant species constituted 98% of the germinated seeds. The most abundant were Calluna vulgaris (49%; 12 018 seeds m?2) and Erica tetralix (34%; 8 414 seeds m?2). Calluna showed significantly higher germination the first 2 years following fire. Conclusions: Vegetation species richness, ranging from 23 to 46 species yr?1, showed a unimodal pattern over the post‐fire succession. In contrast, the seed bank species richness, ranging from 21 to 31 species yr?1, showed no trend. This suggests that the seed bank act as a refuge; providing a constant source of recruits for species that colonise newly burned areas. The traditional management regime has not depleted or destroyed the seed banks and continued management is needed to ensure sustainability of northern heathlands.  相似文献   

17.
The effects of sod cutting, a common restoration measure to remove excess nutrients from grass-dominated heathlands, on nitrification were studied in dry and wet Dutch heathlands and in incubation experiments. In the field, soil ammonium and nitrate concentrations were measured after treatment by sod cutting, with or without additional liming. Potential net nitrification was measured by incubating soil samples of all treatments with extra ammonium in a climate chamber at pH 6. Potential net nitrification of heaths dominated by Molinia caerulea was significantly higher than that of dwarf-shrub dominated heaths. Sod cutting of the former areas significantly decreased potential net nitrification, whereas in the latter areas no differences were found. Liming of sod-cut soils greatly increased potential net nitrification and the accumulation of ammonium in the soil up to toxic concentrations could be prevented. Our results show that the combination of sod cutting and liming would create suitable soil conditions for the germination and establishment of endangered plant species of dry and wet heathlands. The success of restoration projects of these areas can thus be increased.  相似文献   

18.
The relationship of environmental and soil-nutrient variables with the floristic composition of Empetrum rubrum heathlands and related communities from northern Tierra del Fuego were studied by means of ordination techniques. A floristic gradient was found which had its axis of major variation closely related to a gradient in soil trophic status. Increases in the densities of Empetrum and other cushion plants (Bolax gummifera, Azorella lycopodioides, Pernettya pumila) along the floristic gradient were: (a) associated with a lower number of species and total cover, and greater soil erosion; (b) positively correlated with the C/N ratio and aluminium content in the soil; and (c) negatively correlated with pH, calcium content and base saturation.Climate, lithology, habitat exposure, and the history of human activity would be key factors in developing the oligotrophic conditions that favoured the establishment of different Empetrum heathlands.  相似文献   

19.
WEBB, N. R., 1989. The invertebrates of heather and heathland. The southern heathlands of Great Britain have long been renowned amongst entomologists. The invertebrates fall into two groups: species which feed on heathland plants–about 40 in the case of Calluna–and a second group which depends on the particular physical conditions provided by heathland, such as hot dry sandy areas or the micro-topography of Sphagnum bogs. The ecology of representative examples will be described, and the effects of fragmentation and isolation of the heathlands on the distribution and abundance of invertebrates discussed.  相似文献   

20.
The coastal heathlands of the Royal National Park are impacted by both fire and herbivory by introduced deer, and to date these two factors have been dealt with independently in the management of natural areas. In recent years, there has been increasing recognition for a more integrated approach to manage these two disturbance agents. Fire and its role in Australian heathlands are well known, while impacts from introduced deer and the combined effects of fire and introduced deer are still poorly understood. In this study, we investigated the effects of fire and Javan rusa deer (Cervus timorensis) on both vegetation cover and floristics. The percentage cover of plants at different height layers and the presence/absence of individual species were recorded at sites representing two different burn histories (1993/1994 and 2000/2001) and deer presence or absence. Fire significantly reduced vegetation cover at low (<50 cm) and intermediate heights (50–100 cm), while deer presence affected grasses and sedges, and low vegetation at more recently burnt sites. Rusa deer also affected composition of the plant species assemblages, but no such effect was found for fire. Understanding the influence of each disturbance factor independently and together in the heathlands will be critical for implementing a more robust framework for future management.  相似文献   

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