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1.
A change in the vegetation of UK moorland from Calluna vulgaris-dominated heath to Molinia caerulea- or Nardus stricta-dominated grassland is frequently deemed undesirable on economic and biodiversity grounds. Moorland vegetation restoration is an increasingly practiced management option. However there has been little research on the effectiveness of such management for aiding the restoration of other aspects of moorland biodiversity such as associated insect populations.We sampled Hemiptera and Lepidoptera assemblages from restored, degraded and C. vulgaris-dominated (target) moorland at eight restoration sites in England and Scotland. Vegetation assemblages and additional environmental variables were sampled at the same locations.Vegetation restoration aided the reassembly of moorland insects to a variable extent. Hemiptera restoration success was greatest at mechanically restored sites dominated by C. vulgaris. In addition to treatment, latitude best explained variation in the Hemiptera assemblage. A range of plant species, all either dwarf shrubs or graminoids, acted as further determinants. Lepidoptera restoration success was correlated most closely with the success of restoring the full diversity of the vegetation assemblage and was highest at sites restored by grazing control.The results demonstrate that vegetation restoration brings wider biodiversity benefits and that the form these take may depend on the restoration method used and consequent characteristics of the resultant vegetation assemblage.  相似文献   

2.
Many upland areas of the British Isles have seen declines in the area and condition of heather (Calluna vulgaris)-dominated heathland vegetation. To reverse this decline, management regimes must be designed to rehabilitate areas that have seen this decline. As most of this heathland vegetation is primarily managed by grazing, such management has to determine what stocking levels can maintain the vegetation in a desired state. This paper describes how to reverse this decline through suitable grazing management.A degraded ‘wet-heath’ system, previously grazed at 2.1 sheep ha−1, was subject to a range of grazing treatments over a 5-year period. Treatments varied in intensity (0-1.4 sheep ha−1) and timing (summer only, winter only, or year round) of grazing. Grazing levels were maintained at 2.1 sheep ha−1 outside the fenced areas. Vegetation composition remained stable outside the fenced treatments. All the fenced treatments showed an increase in the relative frequency of the evergreen Calluna vulgaris, with the greatest increase being in the ungrazed treatment, and the least in the year round 1.4 sheep ha−1 treatment. This increase was in line with a reduction in heather utilisation to relatively low and sustainable levels. Other species that benefited from reduced grazing included Carex nigra, Deschampsia flexuosa and to a lesser extent Galium saxatile and Erica tetralix, whereas a range of moss species including Hypnum jutlandicum and Rhytidiadelphus loreus were more frequent at higher grazing levels. Though the recovery of heather was similar in the two seasonally grazed treatments, the vegetation showed different overall trajectories. Winter only grazed allowed a substantial increase in the cover of the deciduous Molinia caerulea, whereas this species was kept in check by summer only grazing. A stocking level of between 0.7 and 1.4 sheep ha−1 appears to be appropriate to maintain and even enhance the cover of heather on degraded wet heath. Complete removal is not necessary. Grazing restricted to the winter period is inappropriate in areas where M. caerulea occurs. Setting appropriate stocking levels to maintain the condition of the vegetation must take into account site conditions, especially the presence of species that can affect the utilisation of heather.  相似文献   

3.
Upland heather moors are high priority biotopes for conservation in Britain, but are under threat from a number of sources. One such threat is a change from a vegetation dominated by dwarf shrubs, mainly Calluna vulgaris, to a grassland dominated by Molinia caerulea. Restoration of a dwarf shrub community has proved problematic with studies showing that herbicide use may be necessary to control Molinia. Previously the non-selective herbicide, glyphosate, has been recommended, but this herbicide may damage Calluna and other moorland species severely. Here, we tested a range of selective herbicides (graminicides) for use in an herbicide-based conservation strategy under field conditions. Two selective herbicides, propaquizafop and quizalofop-ethyl, gave a short-term check to Molinia and another, cycloxydim, provided a reduction for at least 1 year, but this effect disappeared after 3 years. Damage to Calluna was less than that caused by glyphosate, and the selective herbicides had little effect on other moorland species present. Our findings suggest that selective herbicides have a potential role in reducing Molinia during moorland restoration, although follow-up applications, and appropriate moorland management, will also be needed.  相似文献   

4.
The UK Biodiversity Action Plan has identified the creation of lowland heathland as an important objective. Heathland restoration studies have identified soil pH, elevated soil nutrients and large weed seed banks as major problems in the restoration of heathland vegetation on ex-arable land. Heathland vegetation is usually found on nutrient-poor acidic soils. Creating acidic soil conditions on ex-arable sites thus may produce a suitable environment for the establishment of heath vegetation. Soil acidification by the addition of sulphur has been shown to reduce the soil pH and the availability of nutrients in arable soils. A series of experiments was established to investigate the effects of soil acidification using sulphur on the establishment of Calluna vulgaris and the development of weed vegetation. The application of sulphur at 0.24 kg m−2 to an arable soil was found to increase the survival rate of C. vulgaris cuttings planted in it. The mechanism of increased C. vulgaris survival appeared to be by sulphur application significantly reducing the cover of arable weeds arising from the soil seed bank. Higher rates of sulphur application (0.36 and 0.48 kg m−2) resulted in the death of many C. vulgaris plants. However C. vulgaris seedlings were able to establish successfully on these ex-arable soils within 18-24 months following the addition of these levels of sulphur. The application of sulphur appears to offer a practical solution to heathland creation on ex-arable land. However, it may be necessary to provide an interval of between 18 and 24 months between the application of sulphur and the addition of C. vulgaris plants or seeds for the successful establishment of heathland vegetation.  相似文献   

5.
Calluna vulgaris-dominated heaths and moorlands are habitats of international conservation importance. Degradation has occurred throughout their range with Calluna typically being replaced by grass species. The cessation of grazing is often impractical and rarely results in the recovery of Calluna abundance when it is initially present at low cover. Thus the development of restoration methods is required; these should be practical at a large-scale, in remote areas and create suitable conditions for Calluna germination and establishment, whilst still allowing grazing to occur. A replicated field experiment was established on Nardus stricta and Molinia caerulea-dominated moorlands to test the efficacy of different grazing regimes and intervention techniques aimed at establishing Calluna. Disturbance (rotavation and trampling by animals) to create bare ground increased Calluna establishment. On the Nardus site, Calluna establishment was equally successful on rotavated and trampled plots, but rotavation was more successful on the Molinia site. Seeding with Calluna increased Calluna establishment irrespective of whether a seed-bank was present. At the Nardus site, 0.5 cow/ha for two months in summer led to Calluna establishment and growth similar to that of ungrazed plots and was more successful than a mixed grazing regime (1 ewe/ha plus 0.5 cow/ha for 2 months) or a sheep only regime (1.5 ewes/ha). The creation of small patches of bare ground, seed addition and low intensity grazing enabled the rapid establishment of Calluna on grass-dominated moorlands; such techniques may also be applicable in other habitats where restoration requires the addition of a single/few species and minimal intervention.  相似文献   

6.
Eutrofication is a threat against nutrient-poor habitats as increased amounts of nutrients in ecosystems may cause changes in the vegetation. Nitrogen (N) deposition leads to conversion of Calluna heathlands into graminoid dominated heath, but low availability of P may hinder or slow down this process.In this study the soil properties under two dominant heathland plants, the dwarf shrub Calluna vulgaris and the grass Deschampsia flexuosa, were investigated, with focus on nutrient content in the organic top soil and soil microbes during the main growing season and effects of nutrient amendments. The concentration of inorganic and dissolved organic N was significantly higher under D. flexuosa than C. vulgaris all though there were the same amounts of total N in the soil below the two species. N and P amendment enhanced available N and P in the soil, but added nutrients had little direct effects on microbes. The microbial biomass on the other hand was positively related to soil water content in fertilized plots indicating that this was due to an indirect effect of enhanced nutrient availability. Microbial N and P pools were respectively 1000 and 100 times higher than the pool of inorganic N and P, and microbes therefore may play an important role in regulating plant nutrient supply. Judged from responses of inorganic and microbial N and P concentrations to added N and P, N seemed to limit C. vulgaris and soil microbes below while P seemed to limit D. flexuosa and soil microbes below this species. There were lower rates of net nitrification, net ammonification and DOC and DON production rates during winter in the soil under C. vulgaris than below D. flexuosa, although all these rates were equal under the two species on an annual basis. This indicates that these microbial processes were taking place during winter but were affected by exudates from C. vulgaris.  相似文献   

7.
In the Yucatan, cenotes or water sinkholes formed by the dissolution of limestone and surrounded with a characteristic dense layer of heterogeneous vegetation, are the main sources of water for plant and animal assemblages. We investigated their importance to bats by comparing the assemblage structure and diversity between tropical forest and pastureland, with and without cenotes. We set ground level mist nets, sub-canopy nets and harp traps for 96 nights and caught 2819 bats of 26 species and six families. Forest had a greater bat species diversity and abundance than pastureland, as well as rare and threatened species. In forest, sites with and without cenotes had a similar bat assemblage structure and diversity, whereas in pastureland there was a greater species diversity and abundance and number of rare and threatened species at cenotes than sites without cenotes. Chrotopterus auritus and Micronycteris schmidtorum, both threatened in Mexico, and Eptesicus furinalis, were exclusively captured at cenotes. We suggest that it may be the vegetation around cenotes rather than the water bodies per se that attracts many bat species in pastureland. Cenotes are threatened by nitrate contamination from untreated domestic and animal waste and fertilizers and the removal of vegetation to allow livestock access to water. In Yucatan’s agricultural landscapes, protection of cenotes and their characteristic vegetation is key not only for bat conservation but also because they represent potential seed sources for the regeneration of the lowland forest, in which bats play key roles as pollinators and seed dispersers.  相似文献   

8.
Regional botanical surveys supported by field experiments suggest that atmospheric nitrogen deposition threatens the balance between species and causes loss of biodiversity within plant communities. Methods are required to monitor the nitrogen status of vegetation at a landscape scale and therefore the potential for ecological change. Remote sensing has the potential to monitor a number of plant biophysical and chemical variables, but its application to monitor the nitrogen status of native vegetation remains limited and untested. Using field spectroscopy, canopy reflectance measurements were taken from two heathland field sites and heather (Calluna vulgaris) plants grown in a greenhouse. The nitrogen concentration was determined through destructive sampling and chemical analysis. Stepwise multiple regression analysis was used to identify the wavebands most associated with nitrogen concentration and despite high variation in the selected wavebands between the three datasets, most of these wavebands were associated with nitrogen and protein absorption features within the spectral region 1,990–2,170 nm. Results highlight the potential of remote sensing as a bio-monitoring technique to estimate foliar nitrogen status in native plants.  相似文献   

9.
This study has compared the phytolith production and soil phytolith assemblages of two native grass communities typical in Argentina, namely the monospecific Paspalum quadrifarium community or “pajonal”, and the Stipa-Piptochaetium community or “flechillar”. Five sites – three of which had been unmanaged while other two had been submitted to fire and fire-grazing management activities – were selected for study. The results show that in these sites a) phytolith production of the plant communities differed due to their diverse floristic composition, b) it was possible to define the type of management or the type of community based on soil phytolith assemblages, c) there were differences between plant communities and soil phytolith assemblages. These results suggest that modern phytolith assemblages are composed not only of local and present vegetation but also of extralocal/regional and probably past vegetation. Hypotheses about the probable processes involved in phytolith incorporation to soil have emerged during the investigation.  相似文献   

10.
Decline of leafy spurge (Euphorbia esula) in the northern Great Plains of the US is generally viewed as a success story for biological control, but quality of the vegetation that survived the infestation is key to recovery of ecosystem function. In addition, effects of other invasive species, notably cool-season exotic grasses, must be taken into account. Objectives of this study were (1) to evaluate direction and significance of changes in biomass of native and exotic grasses, forbs, and leafy spurge and in plant species composition following control of leafy spurge by flea beetles and (2) to evaluate the relative effects of leafy spurge and exotic grasses on biomass of native grasses, biomass of forbs, and richness of native species. We monitored species composition (1998-2003 and 2008) and biomass (2000, 2002, 2003 and 2008) of these groups on spurge-infested and noninfested permanent plots at three sites with unbroken prairie sod in North Dakota, USA. We found little evidence, in terms of species richness or biomass of native grasses or forbs, that leafy spurge was being replaced by desirable native species, although desirable as well as weedy and exotic species were characteristic of 2008 vegetation at all three sites. Structural equation models revealed that leafy spurge had temporally intermittent negative effects on forb biomass and species richness, but no effects on native grasses. In contrast, exotic grass had consistently strong, negative effects on native grass biomass, as well as stronger negative effects than leafy spurge on native species richness. Although substantial native plant diversity remains at these sites, exotic grasses pose an important threat to these crucial building blocks of native prairie ecosystems.  相似文献   

11.
We studied the impact of the invasive plant species Solidago canadensis on the species richness of vascular plants and the abundance, species richness and diversity of butterflies, hoverflies and carabid beetles in herbaceous semi-natural habitats near Ljubljana, Slovenia. The species groups were sampled in sites dominated by S. canadensis and paired nearby sites covered by semi-natural vegetation. Plant species richness and species richness, abundance and diversity of butterfly species were lower in plots dominated by S. canadensis. Hoverfly abundance, diversity and species richness were negatively affected only in July just before the onset of flowering of S. canadensis, but tended to be positively affected in August during the height of flowering of S. canadensis. Only the abundance of carabid beetles was reduced in plots dominated by S. canadensis. The responses of the insect groups seem largely driven by the effects of Solidago on the availability of essential resources like food or larval host plants. Our results suggest that insect species that are closely related to plant species composition are more vulnerable to the effects of invasive plant species than those that are loosely or only indirectly related to plant species composition.  相似文献   

12.
The impact of long-term heavy grazing pressure on montane vegetation and soils was investigated on the Carneddau plateau in North Wales. At this site, historical information suggests that formerly extensive Racomitrium- and Vaccinium-dominated heaths have become degraded and reduced in extent over the last 40-50 years. This coincides with a period when both sheep numbers and atmospheric deposition of nitrogen have greatly increased. Vegetation composition, plant tissue chemistry, soil chemistry and sheep presence were compared between areas of ‘good’ condition Racomitrium and Vaccinium heath and degraded areas. Comparison of species composition data with sheep presence and environmental data showed no significant link between current grazing distribution and species composition in the areas investigated, with all habitats having sheep presence above the recommended maximum for this habitat. Soil chemistry showed several differences between degraded and ‘good’ condition habitats, suggesting that degraded areas had experienced loss of soil organic matter and upper organic horizons. Comparison of soil and vegetation nitrogen content with data from other UK sites suggests a build up of nitrogen has occurred in Carneddau vegetation and soils, possibly related to high levels of nitrogen deposition. It is concluded that restoration of severely degraded areas of montane vegetation may be retarded by deleterious changes in soil properties which could slow recolonisation by montane species. Reductions in stocking density aiming to restore montane communities might have more immediate impact on less degraded areas.  相似文献   

13.
Invasive plants are, simply by occupying a large amount of space in invaded habitats, expected to impose a significant impact on the native vegetation and their associated food webs. However, little is known about the impact of invasive plants both on native vegetation and on different invertebrate feeding guilds at the habitat level. Yet, studies addressing multiple trophic levels, e.g. plant species, herbivores, predators and detrivores, are likely to yield additional insight into how and under which conditions invasive weeds alter ecosystem structures and processes. We set out to assess whether plant species richness and invertebrate assemblages in European riparian habitats invaded by exotic knotweeds (Fallopia spp.) differed from those found in native grassland- or bush-dominated riparian habitats, which are both potentially threatened by knotweed invasion. Our findings suggest that riparian habitats invaded by knotweeds support lower numbers of plant species and lower overall abundance and morphospecies richness of invertebrates, compared to native grassland-dominated and bush-dominated habitats. Total invertebrate abundance and morphospecies richness in Fallopia-invaded riparian habitats were correlated with native plant species richness, suggesting that there is a link between the replacement of native plant species by exotic Fallopia species and the reduction in overall invertebrate abundance and morphospecies richness. Moreover, biomass of invertebrates sampled in grassland and bush-dominated habitats was almost twice as high as that in Fallopia-invaded habitats. Large-scale invasion by exotic Fallopia species is therefore likely to seriously affect biodiversity and reduce the quality of riparian ecosystems for amphibians, reptiles, birds and mammals whose diets are largely composed of arthropods.  相似文献   

14.
We assessed the effects of a range of experimental restoration treatments on the diaspore bank (seed and spores) on an upland moor infested by dense Pteridium aquilinum, 9 years after implementation. Experimental treatment included both Pteridium control (cutting, spraying and combinations) and restoration treatments (grazing, seeding); both univariate and multivariate analyses of variance were used to assess significant effects. The seed bank was made up largely of Calluna vulgaris, Juncus effusus and Agrostis capillaris with the majority germinating from the litter (38 per cent) and upper soil layer (53 per cent). Soil depth influenced species composition and density, with greatest numbers near the surface, in keeping with a negative exponential response. In the lowest soil depth only ferns were abundant. A. capillaris seed density was greater in the most disturbed treatment (cut twice yearly with grazing), whereas C. vulgaris was greater in the low‐disturbance treatment (herbicide application only). The diaspore bank composition response identified that certain treatment combinations had a grass‐heath composition in the upper soil layer, which may assist future restoration. There was a significant effect of C. vulgaris seed addition detected in the Pteridium litter layer suggesting that this litter acted as a barrier to seed transfer to the soil. There was little evidence of coupling developing between the diaspore bank and vegetation. The most successful treatment combination was cutting twice per yr with low grazing plus C. vulgaris addition as brash. Where seed is added the Pteridium litter should be disturbed. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

15.
We investigated ways of optimising the establishment of Calluna vulgaris-dominated heathland vegetation following removal of pines from afforested heathland using a randomised block experiment. Removal of the litter layer, or both the litter and humic layers, resulted in a higher initial establishment rate of C. vulgaris compared to in the control plots. The effect of adding heathland clippings suggested that the rate of establishment of C. vulgaris was limited by seed availability in plots from which both the litter and humic layers had been removed, but not in those from which just the litter layer had been removed. Removal of both the litter and humic layers did, though, result in a long-term reduction in the depth of the humic layer, a lower loss-on-ignition and lower level of nitrate and total nitrogen compared to in the control plots. The optimal method for establishing heathland vegetation at a site will depend on: (1) whether there is a viable seedbank of C. vulgaris and other desirable heathland species present; (2) the importance of quickly establishing a high cover of desirable heathland species; (3) the likely long-term effects of soil nitrogen levels on the maintenance of C. vulgaris dominance; (4) the practicality of removing and disposing of the litter and humus layers.  相似文献   

16.
Grasslands are often characterized by small-scale spatial heterogeneity due to the juxtaposition of grass tufts and bare ground. Although the mechanisms generating plant spatial patterns have been widely studied, few studies concentrated on the consequences of these patterns on belowground macrofauna. Our objective was to analyze the impact of grass tuft (Brachiaria bryzantha cv. marandu) spatial distribution on soil macrofauna diversity in Amazonian pastures, at a small scale (less than 9 m2). Soil macrofauna was sampled among B. bryzantha tufts, which showed a variable spatial distribution ranging from dense to loose vegetation cover. The vegetation configuration explained 69% of the variation in total soil macrofauna density and 68% of the variation in total species richness. Soil macrofauna was mainly found in the upper 10 cm of soil and biodiversity decreased with increasing distances to the nearest grass tuft and increased with increasing vegetation cover. The size of the largest grass tuft and the micro-landscape connectivity also had a significant effect on biodiversity. The density and species richness of the three principal soil ecological engineers (earthworms, ants and termites) showed the best correlations with vegetation configuration. In addition, soil temperature significantly decreased near the plants, while soil water content was not influenced by the grass tufts. We conclude that soil macrofauna diversity is low in pastures except close to the grass tufts, which can thus be considered as biodiversity hotspots. The spatial arrangement of B. bryzantha tussocks influences soil macrofauna biodiversity by modifying soil properties in their vicinity. The possible mechanisms by which these plants could affect soil macrofauna are discussed.  相似文献   

17.
North American beavers (Castor canadensis) were introduced into southern South America in 1946. Since that time, their populations have greatly expanded. In their native range, beavers shape riparian ecosystems by selectively feeding on particular plant species, increasing herbaceous richness and creating a distinct plant community. To test their effects as exotic engineers on sub-Antarctic vegetation, we quantified beaver impacts on tree canopy cover and seedling abundance and composition, as well as their impacts on herbaceous species richness, abundance and composition on Navarino Island, Cape Horn County, Chile (55°S). Beavers significantly reduced forest canopy up to 30 m away from streams, essentially eliminating riparian forests. The tree seedling bank was greatly reduced and seedling species composition was changed by suppressing Nothofagus betuloides and Nothofagus pumilio, but allowing Nothofagus antarctica. Herbaceous richness and abundance almost doubled in meadows. However, unlike beaver effects on North American herbaceous plant communities, much of this richness was due to invasion by exotic plants, and beaver modifications of the meadow vegetation assemblage did not result in a significantly different community, compared to forests. Overall, 42% of plant species were shared between both habitat types. Our results indicate that, as predicted from North American studies, beaver-engineering increased local herbaceous richness. Unlike in their native range, though, they did not create a unique plant community in sub-Antarctic landscapes. Plus, the elimination of Nothofagus forests and their seedling bank and the creation of invasion pathways for exotic plants together threaten one of the world’s most pristine temperate forest ecosystems.  相似文献   

18.
Changes over a period of 10–30 years in the vegetation of some Dutch heathlands were studied, using aerial photographs and information derived from observations and permanent plots. The sites studied are situated in (formerly) Calluna vulgaris-dominated heathlands, known to be infested in the past by the heather beetle Lochmaea suturalis, Thoms., followed by a Calluna die-off. No interference by management practices had interrupted the natural changes in the vegetation following the infestation. Evidence for both seral and cyclical changes is presented. It is concluded that abiotic factors, i.e. physiographically controlled minor differences in the soil type, determine whether a cyclical or seral change will occur.  相似文献   

19.
对黄土丘陵区退耕地植被特征的时空变异性进行了研究.结果表明,不同植被类型区植被特征之间差异不是很显著,仅延安与安塞在物种丰富度之间和安塞与吴旗在物种多样性之间存在较显著的差异(0.01<p<0.05),其它的两两之间的差异并不明显.延安森林带北缘→安塞森林草原带植被指数呈下降趋势,降幅最大为17.65%,变异系数呈增大趋势,增幅最大为21.49%;安塞森林草原带→吴旗草原带物种丰富度指数及其变异系数都呈增大趋势,而物种多样性和均匀度指数呈减小趋势,其变异系数呈增大趋势.植被指数随退耕年限的变化趋势图都有两个明显的峰值,并在退耕20年左右后植被群落逐渐稳定.  相似文献   

20.
Overabundance of wild ungulates, especially exotic species, is a major threat to several ecosystems worldwide. While the response of forest vegetation to high density of herbivores has been well studied, far less is known about peatland vegetation. In this paper, we assessed the long term impact of white-tailed deer (Odocoileus virginianus) on plant communities of ombrotrophic (bog) and minerotrophic (fen) peatlands in eastern North America. Vegetation of five peatlands that have experienced high deer densities for at least 75 years was compared with that of five peatlands situated at proximity but on deer-free islands. We investigated deer impacts on plant species composition and cover, shrub height and cloudberry (Rubus chamaemorus) fruit/flower production and morphology. In bogs, white-tailed deer had no long-term impact on plant species assemblages, but reduced lichen cover and increased sedges and grasses cover as well as the surface area of bare peat. On the other hand, the floristic composition of fens differed significantly between sites where deer were present or absent. Plant diversity was greater in undisturbed fens than in disturbed fens, especially for shrubs, sedges and liverworts. No detrimental effects of browsing on shrub height were observed. Conversely, deer browsing seemed to have deleterious impacts on cloudberry fruit/flower production as well as on the number of leaves per individual. Overall, our results suggest that white-tailed deer had some important impacts on the vegetation of peatlands that could be harmful for the long-term conservation of peatland plant diversity.  相似文献   

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