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1.
The negative impact of grass and moss encroachment on the botanical diversity of West European coastal dunes attracted increasing
attention in the 1990s. This paper focuses on moss encroachment during primary succession in the xeroseries. Until the mid-1970s,
vegetation types rich in species of the lichen generaCladonia andCladina were found on the fixed,Corynephorus canescens-dominated, so-called grey dunes all over the island of Terschelling, The Netherlands. In addition, species ofHypogymnia, Parmelia andUsnea, which usually grow on trees, occurred here terrestrially on moss carpets or bare sand. These vegetation types are still
present on the Noordsvaarder, a nature reserve in the western part of the island. They occur on parts of seven dune ridges
parallel to the coast and form a chronosequence in which age increases with distance from the sea.
Our study found the highest lichen diversity on the second and third dune ridges in a stage of primary succession that can
be assigned to theViolo-Corynephoretum. The changes from lichen-rich to moss-dominated stadia were significantly related to soil development and acidification in
connection with the ageing of the dune soil.
The superficial cutting of sods in moss-encroached vegetation appeared to be unsuccessful as a management technique for restoring
the biodiversity of cryptogams. Our findings suggest that the best option for maintaining lichen vegetation in theViolo-Corynephoretum is the blow-in of sand with a subneutral or neutral pH from reactivated and natural blowouts or from foredunes, with increasing
lime content respectively.
Nomenclature: Van der Meijden (1990) for higher plants; Touw & Rubers (1989) for mosses; Purvis et al. (1992) for lichens. A set of lichen
specimens has been deposited at the herbarium of Dr. A. Aptroot (C.B.S. Baarn) — herbarium code ABL (Taxon 44: 258). 相似文献
2.
In the asperillo dune system, Southwest Spain, lichen vegetation covering the dune sand, has a low species diversity but is
an important component of the perennial vegetation, providing stability, nutrients, and moisture to the soil layer. The Asperillo
dunes harbour (1) natural ecosystems, (2) disturbed systems affected by forestry activities where the natural vegetation is
eliminated, and (3) pine forest resulting from afforestation withPinus pinea since the end of the 1940s where the composition and abundance of the lichen flora has been drastically changed.
Our hypothesis was that the lichen species composition and distribution are influenced by the type and period of human intervention.
To test this hypothesis a 1.2 km × 1.1 km area, which includes zones with different degrees of conservation and perturbation,
consisting of five different habitats, was selected: well preservedJuniperus woodland,Pinus pinea plantations with dense scrub, dense scrub,P. pinea plantations cleared from scrub, and pioneer scrub in recent pine afforestation. In each area, randomly located 5m × 5 m homogeneous
plots were sampled. In each plot the cover of shrub and lichen species was recorded.
The first results show that lichen cover is higher in the most preserved areas,Cladonia mediterranea being the dominant species under theJuniperus phoenicea canopy. The lichen community changes in composition and abundance depending on the time elapsed since the last perturbation. 相似文献
3.
Bridget L. Elliott Graham I. H. Kerley Anton McLachlan 《Journal of Coastal Conservation》2000,6(1):79-88
Dune hummocks (small aeolian dunes formed by sand deposition in and around pioneer plants) are the smallest vegetated dune
unit; they occur along the entire South African coastline but are poorly studied. Structural properties and distribution of
the two main hummock-forming plants:Arctotheca populifolia (a pioneer species with fast growth rate and rapid turnover) andGazania rigens (a later colonizer with slower growth) were investigated. A marked vegetation succession exists across the floor of the slack
as a result of the migration of transverse dune ridges across the slack.Arctotheca hummocks were initiated on the newly exposed eastern margin of the slack, and were replaced about midway across the width
of the slack byGazania hummocks. Hummocks increased in size with distance from the eastern side of the slack.Gazania hummocks attain a greater vegetation height, support a greater vegetation complexity and mass, and attain a larger maximum
size thanArctotheca hummocks. Succession, defined as both the replacement of plant species as well as site modification within the plants over
time, was evident. Since the growth form and dynamics determine (1) the ability of plants to trap wind-borne soil and detritus,
(2) the shape of the hummocks, and (3) the habitat complexity available to spiders and insects, the ecology of the hummocks
is probably determined largely by the vegetation characteristics of the hummock-forming plants. 相似文献
4.
Sam Provoost Carole Ampe Dries Bonte Eric Cosyns Maurice Hoffmann 《Journal of Coastal Conservation》2004,10(1):33-42
Grey dunes are a priority habitat type of the European Union Habitats Directive and demand special attention for conservation
and management. Knowledge of the ecology of coastal grey dunes can contribute to this policy. Dune grassland succession is
initiated by fixation and driven by the complex of soil formation (humus accumulation) and vegetation development. Leaching
and mobilization of CaCO3. which are important in nutrient dynamics, complicate the picture. At present, grass- and scrub encroachment greatly overrules
these fine scaled soil processes and causes substantial loss of regional biodiversity. Belgium has an international responsibility
in grey dune conservation because of the limited range of its characteristic vegetation, flora and fauna. As biomass removal
seems essential in grassland preservation, grazing is an important management tool. Evaluation of management measures focuses
on biodiversity measurements on the levels of landscape, community and species. 相似文献
5.
This study reports the results of restoration management on sand dune environments along the coastal belt of the Castelporziano
nature reserve (Rome, Italy) and the subsequent monitoring phases to test the sustainability of the ‘soft techniques’ applied.
In the area concerned, over a length of ca. 3 km, 40 dunes were built up along with three belts located at <40 m, 40–70 m,
and >70 m, respectively, from the shoreline. On each of 38 dunes 20 individuals ofAmmophila littoralis were planted; this species is one of the local autochthonous species considered particularly suitable for stabilizing sand
dunes. After one year, two years and five years, respectively the changes in height and surface of each dune, the survival
rates ofA. littoralis, and its changes in cover, the appearance of new shoots and the establishment of new species were observed. A progressive
increase in species number, which five years after the restoration amounted to about 60% of those characterizing the natural
dunes, was reported indicating a progressive trend towards populations similar to natural ones. In the colonization of new
species there is a prevalence of theSporobolus-Elymetum farcti and theSalsolo Kali-Cakiletum maritimae association, while the species established successively refer to theEchinophoro spinosae-Ammophiletum arundinaceae association and theCrucianellion maritimae alliance as occurring in natural successions.
This succession runs parallel to the natural dune colonization processes. In particular, the data regarding survival, cover
and number of vegetative shoots indicate that the dune belt between 40 and 70 m from the sea is the one most suitable for
restoration.
Some changes in dune morphology was observed: the height of the artificial dunes tended to decrease considerably in the five
years of observation, whereas a progressive increase in their surface area was observed. During the study period.A littoralis favoured the establishment of new species, but as yet exercises no action on increasing dune height. 相似文献
6.
Bart Wouters Marijn Nijssen Gertjan Geerling Hein Van Kleef Eva Remke Wilco Verberk 《Journal of Coastal Conservation》2012,16(1):89-99
Encroachment of tall grasses and shrubs in coastal dunes has resulted in loss of vegetation heterogeneity. This is expected
to have negative effects on animal diversity. To counteract encroachment and develop structural heterogeneity grazing is a
widely used management practice. Here, we aim to functionally interpret changes in vegetation composition and configuration
following grazing management on habitat suitability for sand lizards. Aerial photographs taken over a period of 16 years were
used to quantify changes in vegetation composition. A GIS-based method was developed to calculate habitat suitability for
sand lizards in a spatially explicit manner, encompassing differences in vegetation structure and patch size. From 1987 to
2003 dune vegetation shifted from small patches of moss and sand to larger patches covered by shrubs and grasses. Grazing
management did not have any significant effect on the overall level of heterogeneity, measured as habitat suitability for
sand lizards. However, on a more local scale highly suitable patches in 1987 were deteriorating whereas unsuitable patches
became more suitable in 2003. This inversion results from a broad shift with shrubs being a limiting habitat element in 1987
to sandy patches being the limiting element in 2003. Future changes are believed to negatively impact sand lizards. The habitat
suitability model has proven to be a useful tool to functionally interpret changes in coastal dune vegetation heterogeneity
from an animal’s perspective. Further research should aim to include multiple species operating on different scale levels
to fully capture the natural landscape dynamics. 相似文献
7.
Topography and vegetation of restored dunes on a developed barrier island were examined after a large-scale beach nourishment
project. Restoration began in 1993 using sand-trapping fences andAmmophila breviligulata Fern. plantings. Subsequent growth of dunes was favored by installing new fences and suspending beach raking to accommodate
nesting birds. Plant species richness, percent cover of vegetation, and height ofA. breviligulata were sampled in 1999 on seven shore perpendicular transects in six dune microhabitats (backdune, primary crest, mid-foredune,
swale, seaward-most fenced ridge, incipient dune on the backbeach).
A total of 26 plant taxa were found at all seven sites. Richness and percent cover were greatest in the backdune and crest,
especially in locations that predated the 1992 nourishment. Richness was greater where fences enhanced stabilization. Fences
initially compensate for time and space and allow vegetation to develop rapidly, but maintenance nourishment is required to
protect against wave erosion and ensure long-term viability of habitat. An expanded environmental gradient is an option, where
beach nourishment provides space for a species-rich crest and backdune to develop, while the incipient dune remains dynamic.
Options where space is restricted include a dynamic, full-sized seaward section of a naturally functioning dune (truncated
gradient) or a spatially restricted sampler of a wider natural dune (compressed gradient) maintained using fences. Expanded
and truncated gradients may become self-sustaining and provide examples of natural cycles of change. Compressed gradients
provide greater species richness and flood protection for the available space, but habitats are vulnerable to erosion, and
resident views may be impaired. 相似文献
8.
A short outline is given of the floristic composition, structure and distribution of coastal dune vegetation found at Malindi
Bay, Kenya. The area was studied by air photo interpretation and field sampling to determine the relationship of plants to
aeolian features. TWINSPAN classification was used to distinguish geomorphological units on the basis of their species composition.
In this paper, an inventory and first quantitative analysis of vegetation distribution is presented. We identified 174 plant
species from 62 families in the sand dunes and several plant communities are distinguished based on the species content and
the connection with morphological units.Papilionaceae with 18 species andPoaceae with 17 species were the most represented families. A distinct zonal distribution of the plant communities was found.
The most important plant species are the pioneer vegetation consisting ofHalopyrum mucronatum, Ipomoea pescaprae andScaevola plumieri. The woody shrub species which have colonized the established primary dunes and hummock dunes areCordia somaliensis, Pluchea discoridis, Tephrosia purpurea (dunensis). Succulent herbs were identified in the dune slacks and salt marsh that are moist and damp environments. 相似文献
9.
Sam Provoost M. Laurence M. Jones Sally E. Edmondson 《Journal of Coastal Conservation》2011,15(1):207-226
In coastal dunes, landscape changes are a rule, rather than an exception. This paper gives an overview of changes in landscape
and vegetation with a focus on the past century. The history of dunes is characterised by phases of sand drift, alternated
with geomorphological stability. The historical development of dune woodland during these stable phases has been documented
for sites all over Europe. Vegetation reconstructions of historical open dune habitats however is very difficult due to limited
preservation of fossil remains. People have drastically altered coastal dune landscapes through centuries of exploitation
and more recently development of the coast. Historical land use has generally pushed vegetation back into a semi-natural state.
During roughly the past century a tendency of increasing fixation and succession is observed on coastal dunes throughout northwest
Europe. Six causes of change are discussed. 1) Changes in land use, mainly abandonment of agricultural practices, have led
to the development of late successional stages such as scrub and woodland. 2) Crashing rabbit populations due to myxomatosis
in the 1950s caused vigorous grass growth and probably stimulated scrub development. 3) A general tendency of landscape fixation
is observed due to both natural and anthropogenic factors. 4) Eutrophication, mainly due to atmospheric nitrogen deposition
is clearly linked to grass encroachment on acidic but also on some calcareous dunes. 5) The impact of climate change on vegetation
is still unclear but probably lengthening of growing season and maybe enhanced CO2 concentrations have led to an acceleration of succession. 6) A general anthropogenisation of the landscape occurs with rapid
spread of non-native species as an important consequence. The reconstruction of a natural reference landscape is considered
largely unattainable because of irreversible changes and the long tradition of human impact, in many cases since the development
of the dunes. Two contradictory elements need reconciliation. First, the general acceleration of succession and scrub and
woodland development in particular is partly caused by a decreased anthropogenic interference in the landscape and deserves
more appreciation. Second, most biodiversity values are largely linked to open, early succession dune habitats and are threatened
by the same tendency. Apart from internal nature management, in which grazing plays an important part, re-mobilisation of
stable, senescent dunes is an important challenge for dune management. 相似文献
10.
The coastline near the southern tip of Africa is characterized by large mobile dunes that are driven along wide beaches by
strong winds throughout the year. This results in the blockage of the river mouths causing severe flooding of the low-lying
farmland of the Agulhas Plain during the rainy winter season. Large parts of the driftsands were stabilized with the European
dune pioneer species Marram grass (Ammophila arenaria), which has proved highly invasive along the North American west coast. In order to establish the potential invasiveness
ofA. arenaria in South African coastal dune systems and its role in the succession of a large stabilization area, studies were carried
out on De Mond Nature Reverve. Using aerial photos, maps and planting records, the vegetation of sites of various ages were
sampled. By means of this chronosequence of stands, there is clear evidence that succession takes place at De Mond. Four communities
are distinguished, varying from recent plantings ofA. arenaria to mature dune thicket or dune fynbos (heath) vegetation. These relate to four different stages of succession,A. arenaria occurring in reduced abundance in the older communities. After 50 years, formerA. arenaria areas are usually covered by dense dune scrub and in some places even in asteraceous dune fynbos. Succession is most rapid
in sheltered, moist dune slacks, butA. arenaria remains vigorous in conditions favourable for its growht, i.e. on exposed, steep dune slopes with strong sand movement.A. arenaria does not appear to spread unaidedly at De Mond and has been successfully used for temporary dune stabilization. 相似文献
11.
In dune slacks in The Netherlands, a decline of rare mesotrophic basiphilous plant species and their plant communities has
been observed in combination with an increase of more productive systems with common, taller acidophilous plant species. This
has been attributed to both natural and anthropogenic changes. In a humid climate with a precipitation surplus, as in The
Netherlands, the calcium carbonate content of a calcareous soil increases with depth. However, soils in coastal dune slacks,
may have a higher carbonate content in the topsoil horizon than in the underlying layers. Carbonates which buffer the pH can
prolong the presence of mesotrophic basiphilous plant communities which are of high conservation value.
To explain the occurrence of calcareous surface horizons in dune slacks, hydrological and micromorphological analyses were
carried out in three dune slacks. Two slacks are situated on the Wadden Sea islands in the northern part of The Netherlands;
one on Schiermonnikoog and one on Texel. The third slack is situated in the dunes on the island of Goeree in the southwestern
part of The Netherlands. In all three slacks, carbonate occurs as mollusc and gastropod fragments (silt- or sand-sized) and
as micritic nodules in the topsoil layer, due to aeolian deposition and sedimentation by water.In situ carbonate accumulation (calcitans and calcareous crusts) due to CO2 release in inundated and/or capillary rise of calcareous groundwater near, or at the soil surface. Accumulation of carbonate
also occurs as a result of biological activity by algae in the topsoil of the Goeree site. In general, hydrological processes
maintaining high levels of calcareous groundwater are a prerequisite for the maintenance of high carbonate levels in topsoils.
Such levels are necessary for the conservation and management of basiphilous pioneer vegetation. 相似文献
12.
Jens Schirmel 《Journal of Coastal Conservation》2011,15(1):159-162
In Europe, acidic coastal dunes are threatened by the invasion of the exotic moss Campylopus introflexus. While the effect of the moss encroachment on the vegetation is well analysed, knowledge of possible impact on arthropods
is lacking. Thus, an experiment was conducted in acidic coastal dunes on the Baltic island of Hiddensee, Germany. Myrmeleotettix maculatus, a common Orthoptera species of open and dry habitats, was sampled by pitfall trapping in eleven plots invaded by C. introflexus and in eleven native, non-invaded plots rich in lichens. Overall, 826 individuals of M. maculatus were captured (266 nymphs, 560 adults). Mean number of adults was significantly higher in native plots. This maybe explained
by a higher proportion of grasses (food supply), a higher availability of shelter (from predators, weather), or more favourable
microclimate conditions in native plots and a higher mortality rate in invaded plots. However, mean number of both young and
old nymphs did not differ significantly between both types. This could imply that invaded areas at least serve as favourable
oviposition sites and larval habitats. The observed negative effect of the moss invasion on M. maculatus remains to be studied on other arthropods. 相似文献
13.
A. J. de Bonte A. Boosten H. G. J. M. van der Hagen K. V. Sýkora 《Journal of Coastal Conservation》1999,5(1):59-68
In 1990, grazing was introduced in a section of Meijendel, a coastal sand dune system near The Hague, The Netherlands. After
five years an evaluation was made of the effects of grazing on vegetation development. Three transects were established, two
in grazed areas and one in an ungrazed area. Field survey data were classified by means of TWIN-SPAN, ordinated with Detrended
Correspondence Analysis and the resulting vegetation types interpreted according to Westhoff & den Held (1969). All associations
were found in both the grazed and the ungrazed areas, but at the subassociation and variant level some communities appeared
to be restricted to the grazed area. These variants were five grassland variants characterized by disturbance indicators such
asSenecio sylvaticus andCynoglossum officinale.
The total number of plant species in the 19 permanent plots, which had been observed to have been decreasing since 1960, showed
a considerable increase after the introduction of horses and cows in 1990. A marked decrease in the cover ofCalamagrostis epigejos andCarex arenaria since 1990 was evident, while in some plots species such asRibes rubrum andViburnum opulus increased considerably.
A series of false-colour aerial photographs were used to compare vegetation structure in the three transects between 1990
and 1995. In the grazed area the tall grass vegetation had almost totally disappeared, whereas the areas of open sand. sand
with moss and lichens, and low grass vegetation had increased and the pattern had become more fine-grained. In the ungrazed
area the area covered by low grass vegetation had increased at the expense of the area of sand with moss and lichens and the
pattern had become more coarse-grained. 相似文献
14.
A review of results of fertilization experiments in wet dune slacks is presented. In most cases the above-ground biomass appeared
to be limited by nitrogen availability. Primary phosphorus limitation was assessed only once in a dune slack where sod cutting
had been applied very recently. In most other case studies phosphorus limits biomass production after nitrogen deficiency
was lifted. Potassium availability is of minor importance for biomass production in this type of ecosystem. Singular nitrogen
additions led to increased dominance ofCarex andJuncus species as well as perennial grasses, such asAgrostis stolonifera andCalamagrostis epigejos. A combined addition of nitrogen and phosphorus led to total dominance of grasses, while the characteristic basiphilous pioneer
species (including mosses) decreased or even disappeared. Certain mechanisms are considered which may maintain nutrient availability
in slacks with basiphilous pioneer vegetation at a low level, despite of the accumulation of nutrients in the developing organic
soil layer. Some implications for management and further research are discussed. 相似文献
15.
At three coastal dune sites at the island of Hiddensee, north-east Germany, vegetation cover was mapped during 2002 and compared
to vegetation surveys from the late 1980s and 1930s. Abiotic and biotic factors, which have been identified as being critical
for coastal dunes in former studies such as disturbance, salt spray or nutrient availability, were measured. Grazing and land-use
history were reviewed by literature and interviews. Tall graminoid communities, mainly Carex arenaria, are a common vegetation unit today. Development, distribution of these dominances and possible causes for its occurrence
have not been analysed. Generally, older successional vegetation units increased and pioneer stages decreased from the 1930s
until 2002. At the geologically youngest site, the southern dunes, grass encroachment by Carex arenaria was highest (ca. 50% cover in 2002), and age and density of trees lower than at the older, central dunes. Land-use changes
such as decrease in grazing pressure, additional feeding of livestock, increase in coastal protection measures and subsequent
decrease in shifting sands as well as varying availability of groundwater and amount of salt spray are relevant factors for
vegetation changes in coastal dunes over the past 70 years. Site-specific land-use differences such as livestock density and
land-use history have a stronger influence than atmospheric N-pollution on the vegetation composition of these acidic, coastal
dunes under low to moderate N-deposition loads of 6–8 kg N ha−1 yr−1. 相似文献
16.
Eduard J. Weeda 《Journal of Coastal Conservation》2010,14(2):75-79
The position of alien plant species in the Dutch coastal dune vegetation is evaluated considering 12 archaeophytes and 20
neophytes (including one moss), all of widespread occurrence in the coastal area of the Netherlands. Almost all archaeophytes
have become part of natural vegetation types. Open scrub communities, in particular Hippophae rhamnoides-Sambucus nigra scrub at the leeside of the outer dunes, and calciphilous moss-dominated pioneer vegetation are relatively rich in archaeophytes.
Among neophyte vascular species a contrast is apparent between herbaceous and woody species. The majority of herbaceous neophytes
are characteristic of man-disturbed habitats and are only infrequently observed in natural vegetation types. However, woody
species (as well as the moss Campylopus introflexus) have entered into natural vegetation on a large scale and behave in an invasive way. 相似文献
17.
Alma V. de Groot Albert P. Oost Roos M. Veeneklaas Evert Jan Lammerts Willem E. van Duin Bregje K. van Wesenbeeck 《Journal of Coastal Conservation》2017,21(3):409-419
The Frisian islands (Southern North Sea) have extensive island tails, i.e. the entire downdrift side of an island consisting of salt marshes, dunes, beaches and beach plains, and green beaches. Currently, large parts of these tails are ageing and losing dynamics, partly due to human influence. This may mean a loss of young stages on the long term, and current management is not enough to counteract this. To aid the development of new interventions aiming at (re)introducing natural dynamics, a conceptual model of island-tail development under natural and disturbed conditions was developed, based on existing data, field visits and literature. The development of an island tail follows the general pattern of biogeomorphic succession. The first phase consists of a bare beach plain. In the second phase, embryonic dunes form. In the third phase, green beaches, dunes and salt marshes form, including drainage by creeks and washovers. In the fourth phase, vegetation succession continues and the morphology stabilises. Human interference (such as sand dikes and embankments) reduces natural dynamics and increases succession speed, leading to a reduction in the diversity in landforms and vegetation types. Both for natural and human-influenced island tails, succession is the dominant process and large-scale rejuvenation only occurs spontaneously when large-scale processes cause erosion or sedimentation. Island tails cannot be kept permanently in a young successional stage by reintroducing natural dynamics through management interventions, as biogeomorphic succession is dominant. However, such interventions may result in local and temporal rejuvenation when tailored to the specific situation. 相似文献
18.
P. D. Jungerius H. Koehler A. M. Kooijman H. J. Mücher U. Graefe 《Journal of Coastal Conservation》1995,1(1):3-16
This paper investigates the effects of mowing and sod removal on vegetation, soil mesofauna and soil profile, and the restoration
of these features in the years following sod removal. The sampling site is located in a primary wet dune slack in the northern
part of the province of North-Holland. The original vegetation is a heathland withEmpetrum nigrum andCalluna vulgaris, underlain by a Gleyic Arenosol with an O, Ah and (B) horizon development. Above-ground, the vegetation in the dune slack
has been mown since 1940. The sod was removed from restricted areas in the slack at various times in the past (1980, 1985,
1987 and 1991).
All three sources of data point to adaptation to wet conditions after mowing and sod removal. The vegetation of the mown area
is related to the vegetation in the original heathland, although some species appear to have disappeared. Below-ground, mowing
drastically reduces the number and depth of occurrence of microarthropoda. Restriction of depth applies also to the Enchytraeidae.
Soil profile development is restricted to an Ah-AC-Cr sequence.
Species diversity both above and below-ground is relatively high in plots where the sod has recently been cut, due to the
rapid colonization by the first pioneer species. A time series for the vegetation is difficult to establish because hydrological
conditions interfere with years since sod removal. Soil profile evolution after sod cutting is poor but consistent, from an
AC-Cr sequence since 1991, to an O-Ah-Cr sequence since 1980.
The management practices were set up with the intention to interrupt the succession to give pioneer species a chance. Neither
the vegetation, nor the soil fauna or soil profile have fully recovered during the 13 yr since the first sod removal. So the
goal has been reached. 相似文献
19.
Urban Šilc Danka Caković Filip Küzmič Danijela Stešević 《Journal of Coastal Conservation》2017,21(1):15-21
Trampling is one of the human activities that are harmful for plant species and communities of sand dune ecosystems. The aim of this study was to compare the vegetation of embryonic and shifting Ammophila sand dunes with and without fencing to limit trampling. Fenced sand dunes appeared to be richer in species but differences were more prominent in embryonic sand dunes. Some species (Cakile maritima, Pancratium maritimum) were missing on trampled embryonic dunes. The positive impact of trampling exclusion on embryonic sand dunes was indicated by a lowered slope in a Whittaker graph as well as by rarefaction curves that showed higher species richness on the lower slope. Changes in the vegetation of more stabilised shifting Ammophila sand dunes due to trampling are not evident, although species composition is also impoverished. Fencing of parts of sand dunes proved to be an effective measure for vegetation conservation. In addition to physical exclusion of visitors, fences can also have symbolic value for raising public awareness. 相似文献
20.
F. P. Sival A. P. Grootjans P. J. Stuyfzand T. Verschoore de la Houssaye 《Journal of Coastal Conservation》1997,3(1):79-86
Basiphilous, open, species-rich vegetation types of young dune slacks have declined throughout Europe in recent years, and
have largely been replaced by often acidophilous, tall marsh and scrub vegetation. This succession appears to be accelerated
by a decrease in the discharge of calcareous groundwater from sandy ridges or small dune hummocks. The present study deals
with spatial and temporal variation in the chemical composition of the groundwater in the upper metres of the soil of a degraded
dune slack complex on the Dutch barrier island of Schiermonnikoog, with emphasis on (1) groundwater composition, (2) water
level and (3) decalcification patterns. The main aim was to assess perspectives for restoring basiphilous vegetation types
which had been abundant in this slack from 1954 to 1977. The depth of decalcification was related to former hydrological conditions
along a transect of 200 m. Acidifying effects of rainfall were reflected in the chemical composition of the groundwater below
small dune hummocks within the slack. Distinct precipitation water lenses, poor in dissolved ions, were formed under the dune
hummocks during a wet period. This microtopography did not contribute to the discharge of calcareous groundwater to lowlying
parts of the slack. Here, groundwater showed decreasing concentrations of the dissolved ions after a rain shower. Except for
the peripheral sections of the slack—where upward seepage of groundwater (exfiltration)still occurs—infiltration conditions
are now dominant in the slack. The consequences of the present hydrological conditions for restoration are briefly discussed. 相似文献