Coastal Sand Dune System Research Articles

Grazing is the key to the conservation ofGentianella campestris(L.) Börner (Gentianaceae): evidence from the north Merseyside sand-dunes

AbstractPopulations and habitat of the internationally-declining Gentianella campestris (L.) Borner were studied on a calcareous coastal sand-dune system at Ainsdale in north-western England. The total of 140,700 plants is thought to be the largest population in Britain and may be of European significance. In recent years, this species has greatly increased at Ainsdale, especially within a ‘Dune Restoration Area’ where pine trees and scrub were removed in the 1990s, followed by sheep-grazing. G. campestris was mainly found in dry-slacks where patches of short grassy vegetation are maintained by rabbits within areas largely dominated by Salix repens (UK National Vegetation Classification SD16d: Salix repens–Holcus lanatus dune-slack, Agrostis stolonifera sub-community). There was a close coincidence between G. campestris occurrence and compartments fenced for winter sheep-grazing, but plants were absent from older, more acidic, slacks in the eastern part of the study area. It is inferred that the recent po...

Patterns in Species Diversity during Succession of Coastal Dunes

The humped-back relationship in species diversity during succession was tested using vegetation in a coastal sand dune system of the German Wadden Sea island of Spiekeroog. Permanent plots were studied over 15 years along a spatial chronosequence from young grey dunes to old brown dunes. Species diversity, succession rate, and environmental indicator value were used to evaluate multitemporal dynamics of the ecosystem. Long-term development of the dune vegetation was reflected along the chronosequence, whereas fluctuations of plant communities were analyzed by short-term changes of each permanent plot. The study confirmed the intermediate stress theory, whereas highest species diversity was reached at the transition zone of the environmental gradients. Total species richness showed humped-back relations along the xerosere. Hotspots in species diversity varied with the life form group. Highest richness of herbaceous plants was reached in semidynamic young grey dunes, whereas highest richness of bryophytes and lichens shifted due to competition effects to the driest parts of the dune gradient in older successional stages. Moreover, the study confirmed the biodiversity-stability theory, with highest ecosystem stability at highest diversity. More stable environments showed lower succession rates than dynamic, disturbed environments. Thus, during secondary succession with probably repeated disturbance, the succession rate was higher and no clear direction of vegetation development was found in comparison to primary succession. The succession rate in a primary series represented a unimodal relation with total species richness. Thus, species-poor vegetation often dominated by one species, such as heathlands, as well as species-rich vegetation, showed lowest succession rates. These communities probably are more stable due to a balanced species combination represented by higher evenness.

Does the Seed Bank Reflect Plant Distributions in a Coastal Dune?

The spatial patterns in the seed bank were examined within a coastal sanddune system. Soil samples were collected from vegetated and bare plots in three zones, each dominated by different plant species. The total number of seeds and species diversity in the seed bank were low. There were no significant patterns in total seed number. However, there were significant differences in species composition. Seeds of Artemisia campestris (Tall Wormwood) were more abundant in vegetated plots and were found in all zones, although adults are more spatially restricted. Fruits of Cyperus grayii (Gray's Sedge) were most common where adults are found. Dominant species from the site were absent from the seed bank. Overall, composition of the seed bank does not reflect composition of the adult community.

Have we neglected the societal importance of sand dunes? An ecosystem services perspective

Abstract Coastal sand dunes are widespread worldwide, including around the coasts of the British Isles and Europe, providing a wide range of functions some of which are recognized for their socio‐economic benefits. In some localities, their contribution to coastal defence and to tourism and regional character have been acknowledged in local plans, but this is far from ubiquitous. A rapid assessment was undertaken of the range of ecosystem services provided by coastal sand dune systems, using the Millennium Ecosystem Assessment ecosystem services classification augmented with habitat‐ and locally‐appropriate additions. Sand dunes were shown to provide a wide range of provisioning, regulatory, cultural and supporting services, many of which remain substantially overlooked. Although the importance of coastal sand dune for a diversity of characteristic and often rare organisms from a variety of taxa has been addressed, many of the broader ecosystem services that these habitats provide to society have been overlooked. This suggests that coastal sand dune systems are neglected ecosystems of significant and often under‐appreciated societal value. Copyright © 2010 John Wiley & Sons, Ltd.

Ontogenetic shifts in interactions of two dominant shrub species in a semi‐arid coastal sand dune system

AbstractQuestion: How does the interaction between two dominant shrub species in a coastal sand dune community change during their life history? Does this interaction influence their population dynamics?Location: A semiarid coastal sand dune system in southeast Spain.Methods: For 3 years we monitored physiological status, growth and reproductive effort of Juniperus phoenicea and Pistacia lentiscus, the dominant shrub species, growing either alone or in close spatial association. We also recorded adult mortality patterns and characterized seedling survival, soil properties and microclimate conditions beneath canopies and in bare ground.Results and conclusions: There was a strong bi‐directional interaction between the two studied species, with a net balance that changed in sign with increasing plant development. While mature individuals facilitated the establishment of seedlings of both species, adult mortality patterns suggested asymmetric competition at later life stages. The interaction with Pistacia negatively affected growth of juniper and contributed to its high mortality rates, while juniper had almost no effect on mature Pistacia individuals. Physiological data suggested that Pistacia had a competitive advantage over juniper, most likely because of differences in rooting patterns and tolerance to salinity, which may determine the source of water available for each species. Community dynamics are governed by facilitation at the seedling stage and shaped by differences in physiological traits in adult plants. Plant‐plant interactions, which are strongly affected by environmental gradients, are important drivers of community dynamics in this system.

Belowground mutualists and the invasive ability of Acacia longifolia in coastal dunes of Portugal

The ability to form symbiotic associations with soil microorganisms and the consequences for plant growth were studied for three woody legumes grown in five different soils of a Portuguese coastal dune system. Seedlings of the invasive Acacia longifolia and the natives Ulex europaeus and Cytisus grandiflorus were planted in the five soil types in which at least one of these species appear in the studied coastal dune system. We found significant differences between the three woody legumes in the number of nodules produced, final plant biomass and shoot 15N content. The number of nodules produced by A. longifolia was more than five times higher than the number of nodules produced by the native legumes. The obtained 15N values suggest that both A. longifolia and U. europaeus incorporated more biologically-fixed nitrogen than C. grandiflorus which is also the species with the smallest distribution. Finally, differences were also found between the three species in the allocation of biomass in the different studied soils. Acacia longifolia displayed a lower phenotypic plasticity than the two native legumes which resulted in a greater allocation to aboveground biomass in the soils with lower nutrient content. We conclude that the invasive success of A. longifolia in the studied coastal sand dune system is correlated to its capacity to nodulate profusely and to use the biologically-fixed nitrogen to enhance aboveground growth in soils with low N content.

Genetic Diversity of Rhizobia Associated with Acacia longifolia in Two Stages of Invasion of Coastal Sand Dunes

We examined the genetic diversity of root nodule bacteria associated with the Australian legume Acacia longifolia in two stages of invasion of a coastal sand dune system. All isolates belonged to the genus Bradyrhizobium. A higher diversity was found in the long-established trees. The results suggest the introduction of exotic bradyrhizobia with the plant.

Geological controls and tidal forcing of submarine groundwater discharge from a confined aquifer in a coastal sand dune system

Submarine groundwater discharge (SGD) into the ocean is increasingly recognized as an important component of land‐ocean interaction. Numerous geological settings may be the source of terrestrially derived SGD, including spatially extensive sand dune systems, which are a common coastal setting in tropical, subtropical, and temperate regions throughout the world. Within the catchment of the Great Barrier Reef lagoon, numerous large‐scale sand dune systems exist. Creeks and rivers draining these systems are largely absent; however, terrestrially derived groundwater discharges from discrete springs in the intertidal zone. The geological and hydrological controls of the discharge were investigated, using a combination of geological, geophysical, and hydrological methods. From sedimentary and geoelectric data it is inferred that a unit of sandy clay provides a confinement of the shallow aquifer system in the dune complex, with groundwater discharging where this layer is breached. Groundwater discharge flux was inversely correlated with tidal water level, but remained positive throughout the tidal cycle. A simple hydrological model indicates that the continuous discharge is the result of a change in hydraulic pressure of the confined aquifer in response to tidal forcing at the seaward limit of the aquitard, which is a previously undescribed effect of tidal modulation of SGD. The observed groundwater discharge is likely to have a significant effect on the biogeochemistry of the coastal environment, particularly in the absence of surface water drainage.

Using earth observation data from multiple sources to map rare habitats in a coastal conservation area

Kenfig NNR (National Nature Reserve) is a coastal sand dune system in south Wales, UK. The site is an important location for the conservation of the fen orchid Liparis loeselii, a significant proportion of the UK population is found solely on the site. Approaches to the mapping and monitoring of the habitats at Kenfig NNR using EO (Earth Observation) meth- ods are investigated. Typical airborne EO missions over such sites produce more than a single source of EO data; these may include various optical imaging sensors with different spectral ranges, film cameras and ranging devices to measure topography. Conservation managers are thus presented with the problem of which sources of data to use when producing a land cover map of the site of interest. Using a data set gathered over the Kenfig NNR site, we investigate land cover mapping methods for conservation. The land cover types of interest typically cover small areas within a much larger site so they present a hard problem for the EO data and associated classification methods to solve. Land cover classifications produced from the data sets provide a set of competing hypotheses of land cover type for the site. Methods we use to resolve this competition between the data sets include voting methods, data fusion methods and a method utilising fuzzy logic to aggregate information. This paper is intended to act as an introduction to some of the issues involved in using EO data for habitat mapping in highly heterogeneous coastal dune environments and to present some preliminary results of the performance of each method.

The sands of Forvie (Scotland): A case study in geomorphology and conservational management

The Sands of Forvie, National Nature Reserve, Scotland is a complex coastal sand dune system which is associated with the dynamic estuary of the River Ythan. The dune system has developed over more than 5000 years. The south part is a peninsula of dunes, sand hills, sand arcs, erosion and deflation surfaces. The north part is superimposed on a rock plateau with a cliff coastline. This plateau is covered in glacial deposits and is essentially an upland heath landscape. Some of the best examples of large active parabolic dunes in Britain are found in North Forvie. The sequence of geomorphic development is described. As a nature reserve with a rich ecology it has been managed for conservational purposes since 1960s. As such it is an excellent case study of how conservational management has changed to become more flexible and more aware of the importance of dynamic processes.

Vegetation development influenced by grazing in the coastal dunes near The Hague, The Netherlands

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.

Adaptations of plants to burial in coastal sand dunes

One of the most obvious features on the foredunes and strands of coasts and lakes is recurrent burial in sand. Burial levels vary in different coastal sand dune systems and influence the physical and biotic microenvironment of the plant and soil. Foredune plants along coasts possess numerous adaptations to withstand burial. Studies show that below a certain threshold level of burial, the growth of all foredune plant species is stimulated probably because of multiple factors, namely improved soil resources, increase in soil volume, reactive plant growth, and enhanced mycorrhizal activity. However, as the level of burial increases, the positive response starts to decline until it becomes a negative value. For example, burial may reduce seed germination, seedling emergence, survival, and growth of seedlings and adult plants. At the community level, burial acts as a filter and selectively eliminates susceptible species, reduces the relative abundance of less tolerant species, and increases the abundance of tolerant and sand-dependent species. However, if sand deposition continues unabated, even the sand-dependent species are eliminated and a bare area is created. The emergence of a plant from a burial deposit primarily depends on the energy reserves in its storage organs and the speed, depth, and frequency of burial. Upon burial the plants shift resources from the belowground to the aboveground parts. Different plants show varied morphological responses to sand accretion. For example, the culms of grasses emerge by an increase in the number of nodes per culm and the elongation of internodes. Similarly, the emergent trunks and woody branches of tolerant trees and shrubs produce new buds and suckers at a higher level on the stem. In response to burial, the coastal sand dune species produce shootborne roots close to the new soil surface probably because of decreased oxygen levels.Key words: sand accretion, adaptations to burial, zonation of vegetation, burial of seeds, plant vigour, impact on communities, modes of emergence.

Vegetation of a coastal sand dune system in southern New Zealand

The introduction of vigorous exotic species has destroyed much of the native sand dune vegetation along the coasts of South Island, New Zealand. However, some dunes built by the native cyperad Desmoschoenus spiralis still remain in the southwest.The dunes at Cole Creek, on the West coast of South Island, were chosen as a relatively pristine study area. 15 transects were laid through semi‐fixed dunes into dwarf forest. Environmental measurements were taken at regular intervals through the dunes: pH, soil moisture, organic matter, conductivity, nutrient status and elevation. Classification and ordination of these data demonstrated that two major environmental areas were present ‐ open dune and dwarf forest ‐ with an abrupt ecotone between them. Vegetation analyses revealed a loosely‐banded pattern, parallel to the sea. Vegetation types with few but constant species such as Desmoschoenus spiralis and Calystegia soldanella, predominated in the open dune. Forest species were rarely found seaward of the dune/forest boundary, though there was evidence the Spatial Mass Effect was operating.Multiple regression and canonical correlation of the vegetation and environmental factors showed that the main factors affecting vegetation patterns were the environmental complex related to distance from the sea, elevation above mean tide, soil alkalinity and moisture.

Mycorrhizas and nutrient cycling in sand dune ecosystems

SynopsisThe extent of occurrence, the form and the function of mycorrhizal infection are shown to change with successional development across coastal sand dune systems. The interrelationships between these changes and the prevailing physico-chemical conditions are explored and clear patterns are recognised in terms of both type and function of the infection. The periodically disturbed and nutritionally enriched high tide line is colonised by non-mycorrhizal ruderal species. There follows a sequence of plant communities, each characterised by the presence of a dominant mycorrhizal type and a distinctive nutritional limitation. In the foredunes, pioneer grasses are normally infected with vesicular-arbuscular (VA) mycorrhizal fungi. Plants such as Ammophila, Leymus and Uniola, all of which have extensive root systems, appear, when fully grown, to be only facultatively mycorrhizal. However, experimental evidence suggests that infection is important for the early growth of such plants and it is suggested that in these, as in many other dune species, mycorrhizas may be essential at critical stages in the life cycle, most notably during the phase of seedling establishment. Here, phosphorus (P) is the most important growth-limiting nutrient. The extensive mycelial network of VA hyphae not only facilitates capture of this element but also provides the aggregation of sand grains necessary for dune stabilisation. In semi-fixed dune pastures, as sand inputs are reduced, productivities are low and species diversity increased. Phosphate limitation persists and the majority of the characteristic species show VA infection. Experimental studies using microcosms of dune sand containing an assemblage of species typical of such communities suggest that the maintenance of the species richness is dependent upon mycorrhizal fungi which produce a large absorptive mycelial network into which the roots of germinating seedlings become incorporated as they are infected. Accumulation of organic matter in dune-slacks leads to reduction of pH. Nitrification is inhibited, ammonium becomes the major mineral nitrogen (N) source and N replaces P as the key growth-limiting element. Here plants with ecto-mycorrhizal infection predominate. Salix repens produces a shrub layer enriched with litter in which a guild of species interconnected by a common mycorrhizal mycelium occurs. The functional basis of this guild structure is explored, the ability of some of its mycorrhizal fungi to mobilise nutrients from organic macro-molecules being seen as a vital attribute. Where organic matter accumulation and base depletion are most strongly developed in the oldest parts of the succession, plants with ericoid mycorrhizas become important. The ability of their mycorrhizal fungi to liberate N and P from acidic organic complexes, as well as to assimilate or exclude, and hence detoxify, organic acids and metal ions facilitates vigorous growth of ericaceous species in soil conditions which are inimical to plants important earlier in the succession. Since the attributes of each mycorrhizal type are relevant to a specific suite of edaphic properties the formation of appropriate symbiotic associations is likely to be a prerequisite for successional change. It is concluded that mutualism contributes significantly to fitness in the sand dune ecosystems, the further understanding of which will be dependent upon more effective collaboration between the microbiological and ecological disciplines.

Classification and ordination of coastal sand dune vegetation along the Gulf and Caribbean Sea of Mexico

A classification is presented of community types found in the coastal sand dune systems along the Gulf coast and the Caribbean Sea of Mexico. Twenty-eight dune systems were sampled along transects using the Braun-Blanquet approach. A total of 4444 releves were subjected to agglomerative classification and table arrangement (program TABORD). Synoptic species values were calculated for the 396 clusters obtained. They were arranged in two new data sets, one comprising the material from Tamaulipas and Veracruz and the other Yucatan and Quintana Roo. These data sets were again subjected to classification and ordination (detrended correspondence analysis) programs. Final community types are based on the basic clusters, 59 types for the Gulf area and 31 for the Caribbean. Their geographical and ecological distribution is interpreted.

Sand movement as a factor in the distribution of plant communities in a coastal dune system

The semi-mobile coastal sand dune system El Morro de La Mancha at the Gulf of Mexico was studied phytosociologically and ecologically. The floristic gradient resulting from a releve ordination was correlated with the amount of sand movement occurring on the site of each releve, and the topography of the dune.

The Fungi of a Coastal Sand Dune System

Le littoral (Danemark) est divise en 5 zones refletant la transition entre milieu marin, zone intercotidale et conditions terrestres