Ammophila Arenaria Research Articles

Community analysis of arbuscular mycorrhizal fungi associated with Ammophila arenaria in Dutch coastal sand dunes.

A polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) approach for the detection and characterization of arbuscular mycorrhizal fungi (AMF) 18S ribosomal DNA (rDNA) was developed and applied to the study of AMF communities associated with the main sand-stabilizing plant species of the Dutch sand dunes, marram grass (Ammophila arenaria, L.). DNA was extracted directly from plant roots, soil or isolated AMF spores, and prominent bands resulting from AMF-specific DGGE profiles were excised for sequence analysis. This strategy provided a robust means of detecting and identifying AMF-like species without the use of trap plant cultivation methods. A number of Glomus-like and Scutellospora-like sequences was detected, including a putatively novel Glomus species, and differences were observed in the dominant AMF-like populations detected in healthy vs. degenerating stands of A. arenaria and in bulk sand dune soil. It has previously been suggested that plant pathogens, such as fungi and nematodes, may contribute to the decline of A. arenaria. Although no causal relationship can be drawn between the observed differences in the dominantly detected AMF-like populations and the vitality of plant growth, these results indicate that mutualistic interactions between this plant and AMF should not be overlooked when examining the role of soil-borne microorganisms in vegetation dynamics. In addition, there were discrepancies observed between the AMF-like groups detected in spore populations vs. direct 18S rDNA analysis of root material, corroborating previous suggestions that spore inspection alone may poorly represent actual AMF population structure.

The search for indigenous dune stabilizers: Germination requirements of selected South African species

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 species Ammophila 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 ger- mination requirements of the native Arctotheca populifolia, Ipomoea pes-caprae, Myrica cordifolia and Scaevola 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 of I. pes-caprae, M. cordifolia and S. plumieri, whereas the seeds of A. populifolia were not dormant. Seeds of I. pes-caprae and M. cordifolia had induced an innate dormancy, respectively, whereas the type of dor- mancy in seeds of S. plumieri dormancy processes remained unknown.

Interpretation of bioassays in the study of interactions between soil organisms and plants: involvement of nutrient factors

Summary Increased plant growth in sterilized soil is usually ascribed to the elimination of (often unidentified) soil‐borne pathogens. Plant–soil bioassays are reported here for three dune soils and two plant species (Ammophila arenaria and Carex arenaria). Dynamics of plant growth, availability and uptake of nutrients were compared in sterilized (25 kGy gamma‐irradiation) vs control soils. Plant growth, availability and acquisition of nutrients, for example P, even when provided in apparent excess, were significantly enhanced in gamma‐irradiated calcareous dune sands. With A. arenaria, the positive sterilization effect occurred independently of initial plant dry mass. The addition of extracts of planted soils to A. arenaria growing in unsterilized sand caused an increase in root growth that could not be related to either nutrients or pathogens. Increased availability and acquisition of nutrients in sterilized soil may contribute to nonsterile : sterile ratios of plant growth that are < 1. Any ecological speculation involving the role of soil‐borne biological factors should be based on fully validated plant–soil bioassays, which account for nutritional or other nonpathogen‐related side‐effects induced by soil sterilization.

The role of European marram grass in dune stabilization and succession near Cape Agulhas, South Africa

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.

Behaviour and transport of radionuclides in soil and vegetation of a sand dune ecosystem

A sand dune ecosystem in the vicinity of the British Nuclear Fuels reprocessing plant at Sellafield, Cumbria, UK was used to examine the spatial, temporal and depth distributions of 134Cs, 137Cs, 238Pu, 239+240Pu and 241Am in soil and in two species of vegetation ( Festuca rubra, Ammophila arenaria). Core samples showed evidence of the accumulation of radionuclides derived mainly from sea-to-land transfer. Accumulated deposits of radioactivity (0–0.1 m) lie within the range: 1.1–3.4 Bq kg −1 ( 134Cs), 260–440 Bq kg −1 ( 137Cs), 31–40 Bq kg −1 ( 238Pu), 150–215 Bq kg −1 ( 239+240Pu) and 190–240 Bq kg −1 ( 241Am). Soil profiles showed greater activity concentrations in their deeper regions and this is attributed to leaching of radionuclides in percolating drainage water accentuated by the coarse texture, low organic matter and clay mineral content of coastal sands.Radionuclide activity concentrations in F. rubra and A. arenaria were similar, in the ranges 20–70 Bq kg −1 ( 137Cs), 1–5 Bq kg −1 ( 238Pu), 10–30 Bq kg −1 ( 239+240Pu) and 10–65 Bq kg −1 ( 241Am). Clear temporal and spatial variations were observed in both species of vegetation, reflecting the weather conditions antecedent to the sampling period and the influence of sea-to-land transfer. Concentration ratios (vegetation:soil) for activity concentrations in the two species were similar, in the ranges: 0.05–0.14 ( 137Cs), 0.025–0.097 ( 238Pu), 0.022–0.057 ( 239+240Pu) and 0.025–0.212 ( 241Am).

The effect of sea-water submergence on rhizome bud viability of the introducedAmmophila arenaria and the nativeLeymus mollis in California

Ammophila arenaria, an invasive European beach grass, dominates most United States Pacific coast beaches north of San Francisco Bay, and it appears to severely reduce opportunities for regeneration of native plant species, including American beach grass,Leymus mollis. The knowledge of how longAmmophila rhizomes can survive in sea-water is important for long-tern management strategies, which must consider the probability of reinvasion of areas whereAmmophila has been eradicated. The bud viability of bothAmmophila arenaria andLeymus mollis remained high following submergence in sea-water for 7 days, andLeymus bud viability was still high after 13 days submergence. In fact,Leymus bud viability appears to be enhanced slightly by submergence for 7 days in sea-water. SinceAmmophila rhizomes retain a mean bud viability of >50% following submergence for 7 days, there is clearly the potential for long distance dispersal to other beaches. Even after 13 days of submergence,Ammophila rhizomes still had a mean bud viability of 8.5%. Assuming near-shore current speeds of 5–45 cm/sec, viableAmmophila rhizomes can be transported up to 505 km in 13 days.

Rapid identification of cyst (Heterodera spp., Globodera spp.) and root-knot (Meloidogyne spp.) nematodes on the basis of ITS2 sequence variation detected by PCR-single-strand conformational polymorphism (PCR-SSCP) in cultures and field samples.

Cyst and root-knot nematodes show high levels of gross morphological similarity. This presents difficulties for the study of their ecology in natural ecosystems. In this study, cyst and root-knot nematode species, as well as some ectoparasitic nematode species, were identified using the second internal transcribed spacer (ITS2) sequence variation detected by polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP). The ITS2 region was sufficiently variable within the taxa investigated to allow species to be separated on the basis of minor sequence variation. The PCR primers used in this study were effective for 12 species with three genera within the Heteroderinae (Globodera pallida, G. rostochiensis, Heterodera arenaria/avenae, H. ciceri, H. daverti, H. hordecalis, H. mani, H. schachtii, H. trifolii, Meloidogyne ardenensis, M. duytsi and M. maritima). However, pathotypes of Globodera pallida and G. rostochiensis could not be distinguished. The method was tested at two coastal dune locations in The Netherlands (one in the lime-poor dunes of the north and one in calcareous dunes of the south) to determine the population structure of cyst nematodes. At each site, cyst nematodes were associated with three plant species: two plant species on the foredune (Elymus farctus and Ammophila arenaria) and one plant species occurring further inland (Calamagrostis epigejos). Two species of cyst nematodes, H. arenaria and H. hordecalis, were found. H. arenaria associated with vigorous A. arenaria and H. hordecalis in association with degenerating A. arenaria and C. epigejos. The field survey demonstrated that in coastal dunes abiotic factors may be the important affecting the distribution of cyst nematodes.

Does Coastal Foredune Stabilization with Ammophila arenaria Restore Plant and Arthropod Communities in Southeastern Australia?

AbstractIn this study we examine whether stabilization of denuded coastal foredunes in southeastern Australia with the exotic grass species Ammophila arenaria (marram grass) restores plant and ground‐active arthropod assemblages characteristic of undisturbed foredunes. Vascular plants and arthropods were sampled from foredunes that had been stabilized with marram grass in 1982, and from foredunes with no obvious anthropogenic disturbance (control dunes). All arthropods collected were sorted to Order, and ants (81.5% of all specimens) were further sorted to morphospecies. Abundance within arthropod Orders, as well as richness, composition, and structure of the plant and ant assemblages from control and stabilized dunes, were compared. The abundance of Diptera was significantly greater on stabilized dunes, while the abundance of Isopoda was significantly greater on control dunes. There were no significant differences in morphospecies richness or composition of ant assemblages on the two dunes types, although some differences in the abundances of individual morphospecies were observed. By contrast, stabilized dunes exhibited lower plant species richness and highly significant differences in plant species composition, due mainly to the large projected foliage cover of marram grass. The study revealed that after 12 years, the vegetation composition and structure of stabilized dunes was still dominated by marram grass and, as a result, invertebrate assemblages had not been restored to those characteristic of undisturbed foredunes.

Koeleria macrantha (Ledeb.) Schultes (K. alpigena Domin, K. cristata (L.) Pers. pro parte, K. gracilis Pers., K. albescens auct. non DC.)

<i>Koeleria macrantha</i> (Ledeb.) Schultes (<i>K. alpigena</i> Domin, <i>K. cristata</i> (L.) Pers. pro parte, <i>K. gracilis</i> Pers., <i>K. albescens</i> auct. non DC.)

Use of Ammophila arenaria for Dune Stabilization in South Africa and Its Current Distribution-Perceptions and Problems.

/ This paper examines the use of the European dune pioneer plant Ammophila arenaria (marram or European beach grass) for dune stabilization in South Africa in the past and present, its present distribution in South Africa, and the perceptions of coastal management agencies and the public about its further use. The planting of A. arenaria became the most important means of dune stabilization, by human intervention, along the South African Cape coast in this century. Its modern distribution from the semiarid west coast to the subtropical shores of the Eastern Cape extends through various climatic zones. Although historical data are missing for some areas, there is no indication of its unaided spread. A. arenaria occurs at most sites because of its prior planting. The South African climate appears to affect its vigor. However, concern about the use of the alien grass has been raised since it has proved to be a highly invasive species in other parts of the world, particularly along the North American west coast and in Tasmania. While the CSIR (Council of Scientific and Industrial Research) promotes its use, CNC (Cape Nature Conservation) follows a policy that restricts the use of any alien plant, including A. arenaria, and requests further research on its invasive properties. Although a questionnaire survey shows that stabilization sites featuring large areas of A. arenaria are accepted by the South African public, current coastal management practices need to be analyzed critically. A thorough investigation of the potential invasiveness of A. arenaria on South African coastal dunes will be essential and shed new light on the American A. arenaria problem.KEY WORDS: Ammophila arenaria; Marram; European beach grass; Dune stabilization; South Africa; Coastal managementhttp://link.springer-ny.com/link/service/journals/00267/bibs/24n4p467.html</HEA

Indigenous and Ammophila arenaria‐dominated dune vegetation on the South African Cape coast

Abstract. Communities formed by the potentially invasive European Ammophila arenaria (marram grass) are compared with those dominated by indigenous dune plant species in coastal dune systems. Sampling of communities was carried out along the Cape coast for species richness, species diversity, importance values and species associations. The influence of soil and other environmental factors on vegetation were also compared. While species richness values in A. arenaria communities appear similar to those of indigenous dune plant communities, diversity indices are significantly lower. However, on the basis of importance values of individual species, A. arenaria does not show extreme dominance to the exclusion of other species, as it does on the North American Pacific coast, where it has also been introduced. Because of its growth in dense tufts, A. arenaria is accompanied mostly by small chamaephytes and therophytes, while indigenous stands support more phanerophytes. Moreover, A. arenaria forms weaker species associations than dominant indigenous dune plant species. The alien status of A. arenaria in South Africa is confirmed by applying classification and ordination analyses which failed to differentiate A. arenaria communities according to their geographical origin as achieved with indigenous communities. This may be attributed to the lack of vigorous indigenous plants in A. arenaria communities, which accounts for the low variety in species composition of A. arenaria communities along the coastline. With regard to environmental factors, A. arenaria communities were observed to be less sensitive to extrinsic factors, such as climate, than indigenous dune plant communities. Results confirm that A. arenaria is an alien plant species in South Africa, but do not imply its invasiveness in the present or near future.

Vertical migration of nematodes and soil-borne fungi to developing roots of Ammophila arenaria (L.) link after sand accretion

Ammophila arenaria benefits from regular burial of windblown beach sand as it allows escape from soil-borne pathogens (nematodes and fungi). The present study was done to obtain more insight into the timing and order of migration of the soil organisms towards the newly formed roots. Accordingly, plants were grown in non-sterilized root zone soil, buried by 20 cm of beach sand and harvested periodically during one growing season. Plants were buried in November. After 17 weeks, the internodes of the planted seedlings elongated and again 10 weeks later, in May, new roots began to develop. The majority of plant parasitic nematodes remained in the original core until root formation started in the deposited layer. Juveniles of Heterodera spp. successfully infected the roots, formed cysts and produced an offspring in October, resulting in high numbers of larvae at the end of the experiment. In February, at the first harvest of plants, fungi were isolated from soil and buried shoots in the whole deposited layer, although it was still winter. During the growing season a shift in the community of fungi in soil and buried shoots occurred in both the original core and the deposited layer. In both layers, the plant pathogenic fungi were gradually replaced by saprophytes. As all fungal and nematode species were able to colonize the deposited sand layer within one year, we conclude that both fungi and nematodes in the root zone of A. arenaria are very well adapted to sand deposition. Because of the fast migration rate of both pathogenic fungi and parasitic nematodes, the window for A. Arenaria to escape in time from its soil-borne pathogens seems to be narrow.

Endogone maritima, a new species in the Endogonales from Poland

Endogone maritima sp. nov. is described and illustrated. This fungus was recovered from around the roots of endomycorrhizal Ammophila arenaria, Corynephorus canescens, Juncus balticus, J. articulatus , and ectomycorrhizal Pinus sylvestris colonizing a deflation hollow of the Slowinski National Park in Poland. Endogone maritima produces sunflower to brownish yellow zygosporangia enveloped by a separable hyphal mantle consisting of interwoven hyphae appearing in section as a dense net. The zygosporangia occur both singly in the soil and in small, non-peridial sporocatps typically containing 2-7 zygosporangia.

Suppression of hyphal growth of soil‐borne fungi by dune soils from vigorous and declining stands of Ammophila arenaria

A study was carried out to determine whether expansion of marram‐grass stands (Ammophila arenaria (L.) Link) on acidic inner Dutch coastal dunes was caused by suppressiveness of soils from these stands against three potential pathogenic fungi of marram grass, namely Fusarium culmorum (W. G. Sm.) Sacc., Phoma exigua Desm. and a Ulocladium sp. The suppressiveness of the acidic inner dune soils was compared with that of lime‐rich dune soils from vigorous and declining marram‐grass stands. Suppressiveness of the dune soils against the saprotrophic fungi Chaetomium globosum Kunze: Fr, Mucor hiemalis Wehmer and Trichoderma harzianum Rifai was also determined. All fungi had been isolated from marram‐grass roots. Suppressiveness was determined by comparing the formation of hyphae from potato–dextrose agar discs into (layer method) or on top of (surface method) dune soils with that of controls consisting of sterile, acid‐washed beach sand. The growth of the three root‐infecting fungi was strongly inhibited in all soils regardless of the method used. Hence, there were no indications that the potential pathogenic fungi were selectively suppressed by the acidic dune soils and, consequently, the results did not give any indication for the involvement of a fungal component in the decline of marram grass. Growth of the saprotrophs C. globosum and M. hiemalis was much less inhibited than that of the root‐infecting fungi. Growth of T. harzianum was strongly inhibited in alkaline soils but not in the acid ones. The suppression of fungal growth could be partly or completely eliminated by a microwave treatment, indicating that biological components of the soil were essential to suppressiveness. The suppression of the fungi by colonies of dune soil micro‐organisms on water‐agar differed considerably from soil alone. Yet, all methods indicated the occurrence of general suppressiveness against fungi by dune soils, irrespective of the origin of the soil samples. This suppressiveness was probably not due to direct competition with other soil micro‐organisms for nutrients but to inhibiting compounds produced by the soil micro‐organisms.

Redescription of the Root-Knot Nematode Meloidogyne Maritima Jepson, 1987 (Nematoda: Heteroderidae), a Parasite of Ammophila Arenaria (L.) Link

The root-knot nematode, Meloidogyne maritima, a parasite of marram grass (Ammophila arenaria), is redescribed from the type locality, a coastal dune near Perranporth, UK. This species is characterized by second-stage juvenile 471 μm long, hemizonid posterior to excretory pore, tail 71.5 μm long, hyaline tail terminus indistinct; male head tapering, not set off, labial disc elevated, rounded and fused with crescent shaped medial lips, lateral lips present, stylet 20.5 μm long, with relatively small rounded knobs, slightly sloping backwardly, lateral field areolated; female stylet curved dorsally, 14.2 μm long, with rounded to transversely ovoid shaped knobs, slightly sloping backwardly, excretory pore located near level of stylet knobs, perineal pattern relatively small, rounded to ovoid and dorsal arch low with lateral field distinct. A malate dehydrogenase pattern, N1a type, and a VS1-S1type of esterase isozyme pattern were detected. Meloidogyne duytsi Karssen et al., 1998, was found on Elymus furctus in the foredunes of the type locality.

Vegetation development in coastal foredunes in relation to methods of establishing marram grass (Ammophila arenaria)

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.

Detection and characterization of fungal infections of Ammophila arenaria (marram grass) roots by denaturing gradient gel electrophoresis of specifically amplified 18s rDNA.

Marram grass (Ammophila arenaria L.), a sand-stabilizing plant species in coastal dune areas, is affected by a specific pathosystem thought to include both plant-pathogenic fungi and nematodes. To study the fungal component of this pathosystem, we developed a method for the cultivation-independent detection and characterization of fungi infecting plant roots based on denaturing gradient gel electrophoresis (DGGE) of specifically amplified DNA fragments coding for 18S rRNA (rDNA). A nested PCR strategy was employed to amplify a 569-bp region of the 18S rRNA gene, with the addition of a 36-bp GC clamp, from fungal isolates, from roots of test plants infected in the laboratory, and from field samples of marram grass roots from both healthy and degenerating stands from coastal dunes in The Netherlands. PCR products from fungal isolates were subjected to DGGE to examine the variation seen both between different fungal taxa and within a single species. DGGE of the 18S rDNA fragments could resolve species differences from fungi used in this study yet was unable to discriminate between strains of a single species. The 18S rRNA genes from 20 isolates of fungal species previously recovered from A. arenaria roots were cloned and partially sequenced to aid in the interpretation of DGGE data. DGGE patterns recovered from laboratory plants showed that this technique could reliably identify known plant-infecting fungi. Amplification products from field A. arenaria roots also were analyzed by DGGE, and the major bands were excised, reamplified, sequenced, and subjected to phylogenetic analysis. Some recovered 18S rDNA sequences allowed for phylogenetic placement to the genus level, whereas other sequences were not closely related to known fungal 18S rDNA sequences. The molecular data presented here reveal fungal diversity not detected in previous culture-based surveys.

HOW SOIL-BORNE PATHOGENS MAY AFFECT PLANT COMPETITION

A role for pathogens in plant competition has often been suggested, but examples are rare and, in the case of soil pathogens, virtually absent. In this paper we examine if and how soil-borne pathogens may play a role in plant competition. As a model, two successional plant species from coastal sand dunes were used: Ammophila arenaria (marram grass) and Festuca rubra ssp. arenaria (sand fescue). The root zone of A. arenaria contains pathogens that contribute to the degeneration of their host when dunes become stabilized. These pathogens (plant parasitic nematodes and pathogenic fungi) are relatively harmless to the immediate successor F. rubra. We tested the hypothesis that F. rubra, when grown in a mixed culture with A. arenaria, will be favored when A. arenaria is exposed to soil-borne pathogens from its own root zone. In a greenhouse, seedlings of both species were grown in replacement series in sterilized (pathogen-free) and unsterilized (pathogen-containing) soils originating from the root zone of natural A. arenaria. Nutrient additions, soil moisture, and the length of the experiment were based on two pilot studies. When exposed to its soil-borne pathogens, A. arenaria was outcompeted, especially when it constituted <50% of the planted mixture. Nutrient limitation enhanced the replacement of A. arenaria by F. rubra especially in unsterilized soil. This was due to reduced plasticity of A. arenaria in responding to nutrient limitation when exposed to its pathogens. The present results support previous suggestions that soil pathogen-driven competition may be an important mechanism in species replacement in coastal foredune vegetation.

Vegetation development in coastal foredunes in relation to methods of establishing marram grass (Ammophila arenaria)

Vegetation development in coastal foredunes in relation to methods of establishing marram grass (Ammophila arenaria)

How Soil-Borne Pathogens May Affect Plant Competition

A role for pathogens in plant competition has often been suggested, but examples are rare and, in the case of soil pathogens, virtually absent. In this paper we examine if and how soil-borne pathogens may play a role in plant competition. As a model, two successional plant species from coastal sand dunes were used: Ammophila arenaria (marram grass) and Festuca rubra ssp. arenaria (sand fescue). The root zone of A. arenaria contains pathogens that contribute to the degeneration of their host when dunes become stabilized. These pathogens (plant parasitic nematodes and pathogenic fungi) are relatively harmless to the immediate successor F. rubra. We tested the hypothesis that F. rubra, when grown in a mixed culture with A. arenaria, will be favored when A. arenaria is exposed to soil-borne pathogens from its own root zone. In a greenhouse, seedlings of both species were grown in replacement series in sterilized (pathogen-free) and unsterilized (pathogen-containing) soils originating from the root zone of natural A. arenaria. Nutrient additions, soil moisture, and the length of the experiment were based on two pilot studies. When exposed to its soil-borne pathogens, A. arenaria was outcompeted, especially when it constituted <50% of the planted mixture. Nutrient limitation enhanced the replacement of A. arenaria by F. rubra especially in unsterilized soil. This was due to reduced plasticity of A. arenaria in responding to nutrient limitation when exposed to its pathogens. The present results support previous suggestions that soil pathogen-driven competition may be an important mechanism in species replacement in coastal foredune vegetation.