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1.
Ammophila arenaria (marram grass) is the most important plant species for sand stabilization in European coastal foredunes. Stand degeneration
due to poor supply of wind-blown sand enhances the susceptibility for wind erosion when successional species do not become
established. ReplantedA. arenaria often fails to become established.
In the present study we examined whether management practices such as mowing, fertilizing, burning or below-ground cutting
of plants may be applied to re-establish the vigour ofA. arenaria. Field experiments performed at exposed sites, where naturally succeeding plant species are not supposed to become established
due to salt spray, showed that none of the applied methods resulted into enhanced tiller density ofA. arenaria. Thus, further studies are necessary to solve this type of management problem.
At the leeward side of foredunes, the successional speciesFestuca rubra ssp.arenaria andElymus athericus could be established successfully as both pre-grown seedlings and planted bundles of cuttings (all further experiments were
fertilized). When planted in spring, cuttings of successional plant species established less than those planted in early winter.
Water repellency of the sand surface is supposed to be the main cause for this. Pre-grown seedlings were less susceptible
for the season of planting. Direct sowing was not effective. Rabbit browsing had to be omitted to obtain successful establishment.
When living rhizomes of successional plant species were still present in the soil profile, fencing alone turned out to be
effective to re-establish vegetation at initially bare sites. 相似文献
2.
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
3.
A grazing experiment was started in 1984 and 1989 respectively, in two parts of a dune grassland in the nature reserve ‘Zwanenwater’,
North Holland; a third part with similar geology and topography was used as a control area and not grazed. An evaluation of
the effects of grazing on vegetation patterns, species composition, vegetation structure and humus form was made with the
help of vegetation maps from 1986 and 1992 as well as field surveys.
Dense tall-grass communities dominated byAmmophila arenaria increased over the period 1986–1992 in the grazed areas, and especially in the non-grazed area (increase in area to 20 %,
22 % and 50 %, respectively). Open communities decreased in the grazed areas, but are still prevalent, while in the ungrazed
area they virtually disappeared, with the result that the present percentage areas are 53 %, 38 % and 17 %.
Field survey data were classified by TWINSPAN producing four vegetation types. These occur more or less equally in grazed
and ungrazed areas, albeit with different percentage areas: (1) open vegetation dominated byCorynephorus canescens; (2) open vegetation characterized byKoeleria macrantha; (3) heathland dominated byEmpetrum nigrum; and (4) tall-grass communities dominated byAmmophila arenaria. Within a vegetation type, species composition was only marginally affected by grazing regime.
Within the open communities the number of species, vegetation height, vegetation cover and soil organic horizons were not
affected by grazing. In the tall-grass communities the number of species was significantly larger and the height of the vegetation
significantly lower in the area grazed since 1984. In the heathland community the number of species and cover of the moss
layer were significantly higher in the 1984 area and ectorganic and endorganic horizons significantly thicker in the ungrazed
area.
It is suggested that these effects are the result of an increased availability of light, but possibly also of a decreased
stock of organic matter and nutrients, due to a decreased input of litter and accelerated rates of decomposition.
Nomenclature: Van der Meijden et al. (1992) for phanerogams; Corley et al. (1981) for mosses; Grolle (1983) for hepatics. 相似文献
4.
A grazing experiment was started in 1984 and 1989 respectively, in two parts of a dune grassland in the nature reserve ‘Zwanenwater’,
North Holland; a third part with similar geology and topography was used as a control area and not grazed. An evaluation of
the effects of grazing on vegetation patterns, species composition, vegetation structure and humus form was made with the
help of vegetation maps from 1986 and 1992 as well as field surveys.
Dense tall-grass communities dominated byAmmophila arenaria increased over the period 1986–1992 in the grazed areas, and especially in the non-grazed area (increase in area to 20%,
22% and 50%, respectively). Open communities decreased in the grazed areas, but are still prevalent, while in the ungrazed
area they virtually disappeared, with the result that the present percentage areas are 53%, 38% and 17%.
Field survey data were classified by TWINSPAN producing four vegetation types. These occur more or less equally in grazed
and ungrazed areas, albeit with different percentage areas: (1) open vegetation dominated byCorynephorus canescens; (2) open vegetation characteized, byKoeleria macrantha; (3) heathland dominated byEmpetrum nigrum; and (4) tall-grass communities dominated byAmmophila arenaria. Within a vegetation type, species composition was only marginally affected by grazing regime.
Within the open communities the number of species, vegetation height, vegetation cover and soil organic horizons were not
affected by grazing. In the tall-grass communities the number of species was significantly larger and the height of the vegetation
significantly lower in the area grazed since 1984. In the heathland community the number of species and cover of the moss
layer were significantly higher in the 1984 area and ectorganic and endorganic horizons significantly thicker in the ungrazed
area.
It is suggested that these effects are the result of an increased availability of light, but possibly also of a decreased
stock of organic matter and nutrients, due to a decreased input of litter and accelerated rates of decomposition. 相似文献
5.
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. 相似文献
6.
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
7.
The coastline of South Africa is characterized by extensive dune fields which are threatened by development, and thus the
demand of stabilization of drift sand will increase. The non-invasive alien grass speciesAmmophila arenaria is at present the dominant sand stabilizer. Due to its foreign origin and invasiveness in North America its use was criticized
and indigenous sand-binding species would be preferred. The germination requirements of the nativeArctotheca populifolia, Ipomoea pes-caprae. Myrica cordifolia andScaevola plumieri were investigated. The results showed that for all four species the total germination time and germination phase could be
shortened and germination success (number of germinated seeds) improved. The different scarification and stratification treatments
broke the dormancy ofI. pes-caprae, M. cordifolia andS. plumieri, whereas the seeds ofA. populifolia were not dormant. Seeds ofI. pes-caprae andM. cordifolia had induced an innate dormancy, respectively, whereas the type of dormancy in seeds ofS. plumieri dormancy processes remained unknown. 相似文献
8.
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
9.
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
10.
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
11.
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
12.
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
13.
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
14.
M. Laurence M. Jones Alwyn Sowerby Peter M. Rhind 《Journal of Coastal Conservation》2010,14(2):127-137
Newborough Warren is a large calcareous west coast UK dune system, which has experienced rapid vegetation spread in the last 70 years. Information from two high resolution chronosequences for dry and wet dune habitats, 0–145 years, was used to answer the following questions: Does climate influence colonisation of vegetation on bare sand? What are the timescales and sequences of successional change in the vegetation? Analysis of aerial photographs showed that stabilisation of the dune system since 1945 has occurred in three main phases. The onset of stabilisation predated myxomatosis by 10 years; while stabilisation virtually halted during the period 1964–1978. Periods of rapid stabilisation were coincident with higher values of Talbot’s Mobility index (M)?>?0.3. Successional development was apparent in both dry and wet habitats. Fixed dune grassland started to replace earlier successional communities at around 40 years, and could persist to 145 years. Linear succession in dune slacks was less apparent, but a separation between communities typically regarded as ‘younger’ and ‘older’ occurred at around 40 years. Species richness in dry dune habitats increased with age to a maximum on soils around 60 years old, then declined again. Species richness was unrelated to age or soil development in wet dune slacks. The influence of climate suggests that conservation managers can only operate within the constraints imposed by natural climatic conditions. Vegetation growth and soil development are closely linked and maintaining some open areas is key to preventing soil development and over-stabilisation. 相似文献
15.
Benthic filter feeding macrofauna organisms may be an important factor linking sediment and water column. Transport of water and concomitantly of suspended matter is directly related to the size of the benthic filter feeding population. This paper aims to determine the potential for water transport by the bivalve Mya arenaria along a coastal stretch of roughly 100 km length in the southern Baltic Sea. Quantification of population filtration rates specific to the area is based on distribution, abundance and biomass of M. arenaria and calculated according to previously published filtration rate–biomass relations. Calculated rates range up to >8 m3 m–2 day–1 (at 5–20 m water depth in sandy sediment) with the potential to locally process a volume of water equivalent to the water column within <1 day. Data from 1991–2002 at one site suggest that the area-specific potential population filtration rate remains remarkably constant in time despite changes in population structure of M. arenaria. The related impact on pore water exchange within the permeable sediment associated with the leakage of water from the gape of M. arenaria valves is discussed.Communicated by L. Hagerman, Helsingør 相似文献
16.
Ammophila arenaria (marram grass) was introduced to South Africa from Europe as a means of stabilizing the Cape Flats in the 1870s, but was
only successfully established in the 1890s as it was found that seeds from the first introductions did not readily germinate.
By the end of the last century, it was successfully used as a dune stabilizing grass. It is now widely used in stabilization
projects along the Cape coastline, being established by planting cuttings or whole plants. Because of problems experienced
of marram becoming invasive, especially on the west coast of North America, and the fact that we have many invasive species
which threaten our indigenous dune fields, studies have been initiated on this plant in South Africa. Most work to date has
involved investigating the methods used to establish the plant in stabilization sites, and very little has been done on the
biology of the species in this country. Marram is generally thought not to seed in South Africa, and thus its spread has been
limited.
However, in the light of recent reports of successful germination of the seed, detailed studies on the phenology of seed production
and establishment in natural areas will be undertaken. Studies on the natural control by fungal species and nematodes will
be carried out in conjunction with work done in the Netherlands, so that a comparison of the biology of the species in South
Africa can be made with that in Europe, where it is used extensively to stabilize dunes.
Nomenclature: Arnold & de Wet (1993) for vascular plants. 相似文献
17.
Summary This contribution presents an attempt to measure the path of habitat and vegetation succession in a coastal dune system (Kenfig
Burrows, South Wales) using remote sensing and GIS. The loss of slack habitats associated with the continuing stabilization
of this dune system is a major cause for concern. These habitats support a range of plant species, including the rare fen
orchid,Liparis loeselii, as well as other hydrophytes. A decrease in their areal extent implies a reduction in biodiversity. To quantify the overall
rate and spatial dimension of these changes, a series of aerial photographs dating from 1962 to 1994 were digitized and analysed
in an image processing system. The resultant maps. transferred to a vector-based GIS, were used to derive a transition matrix
for the dune system over this period of time. The results indicate that there has been a marked reduction in the total area
of bare sand (19.6% of the dune system in 1962, but only 1.5% in 1994) and a decline in both the areal extent and the number
of dune slacks. Over the same period of time, there has been an increase inSalix repens dominated habitats, at the expense of pioneer species. Analysis of the habitat maps, together with hydrological data, within
the GIS suggests that even the dry slacks have the potential for further greening and to support invasive species. In terms
of habitat management however, there is still scope to restore many of the slacks to their original state. It is estimated
that at least 24% of the area occupied by partially and moderately vegetated slacks could be rehabilitated. 相似文献
18.
Soil microarthropods (Acari, Collembola) were analyzed along transects from shore to brown dune in two sandy coastal sites
of the North Sea (Jutland, Denmark, and Spiekeroog, East Frisian island, Germany). Predatory mites (Acari: Gamasina) and Collembola
were determined to species. The Jutland and the Spiekeroog sites each yielded 22 Gamasina species, 10 of which are common
to both areas. Collembola were identified from the Spiekeroog samples only (also 22 species).
Largest mite abundances were found in Jutland in primary dunes (419 tsd. ind./m2) and on Spiekeroog in old brown dunes (314 tsd.ind./m2). Compared to the mites, Collembola abundances are low, with maxima of 77 tsd.ind./m2 in Jutland (yellow dune) and only 18 tsd. ind./m2 on Spiekeroog (old vellow dune).
The communities of predatory mites (Gamasina) and Collembola along transects from shore inland to brown dune are quite specific.
High similarities are found for the predatory mites between the specific dune sites of the two North Sea areas, particularly
for yellow dune.
Additionally, preliminary data are presented for the southern Baltic Coast. The findigns are discussed in a broader context.
Arguments focus on conservation and biogenic dune stabilization. 相似文献
19.
Laan D. van der Tongeren O. F. R. van Putten W. H. van der Veenbaas G. 《Journal of Coastal Conservation》1997,3(1):179-190
In coastal foredunes marram grass (Ammophila arenaria) is used to stabilize windblown sand. The development of traditionally plantedAmmophila into a more natural foredune vegetation may take 5–10 yr. For economic reasons, traditional planting may be replaced by alternative
techniques such as planting seeds or disk-harrowing rhizome fragments. In this paper, we compare the initial vegetation development
of traditionally planted stands with stands established from seeds and from rhizomes.
The experiments were conducted on an artificial foredune originating from dredged sea sand. The total experimental area covered
more than 100 ha and the vegetation development was studied for 6 yr. The data were analysed bya priori grouping of plant species according to their ecology, as well as by Principal Components Analysis (PCA) and Redundancy Analysis
(RA) of the percentage ground cover per plant species.
Comparing ecological groups of plants showed that all planting methods delivered equal numbers of plant species that are indicative
for coastal dunes. PCA and RA showed that methods based on the use of rhizome material resulted in a higher percentage cover
of clonal perennials (Calammophila baltica, Festuca rubra ssp.arenaria, Carex arenaria andCirsium arvense) than the traditionally planted stands and the stands obtained from seeds. The latter two were characterized by the dominance
of annuals, bi-annuals and (mostly nonrhizomatous) perennials.
Initially, the rates of succession were highest in the stands obtained from rhizomes. However, after 3–6 yr there were no
differences between the various stands. During the first four years, the percentage cover by rhizomatous foredune plants developed
faster than that of annuals, bi-annuals and perennials. After 6 yr, the latter contributed almost as much to the percentage
cover as the clonal species. 相似文献
20.
Ammophila arenaria (marram grass) was introduced to South Africa from Europe as a means of stabilizing the Cape Flats in the 1870s, but was
only successfully established in the 1890s as it was found that seeds from the first introductions did not readily germinate.
By the end of the last century, it was successfully used as a dune stabilizing grass. It is now widely used in stabilization
projects along the Cape coastline, being established by planting cuttings or whole plants. Because of problems experienced
of marram becoming invasive, especially on the west coast of North America, and the fact that we have many invasive species
which threaten our indigenous dune fields, studies have been initiated on this plant in South Africa. Most work to date has
involved investigating the methods used to establish the plant in stabilization sites, and very little has been done on the
biology of the species in this country. Marram is generally thought not to seed in South Africa, and thus its spread has been
limited.
However, in the light of recent reports of successful germination of the seed, detailed studies on the phenology of seed production
and establishment in natural areas will be undertaken. Studies on the natural control by fungal species and nematodes will
be carried out in conjunction with work done in the Netherlands, so that a comparison of the biology of the species in South
Africa can be made with that in Europe, where it is used extensively to stabilize dunes. 相似文献