Open Dune Research Articles

Shrubs as ecosystem engineers in a coastal dune: influences on plant populations, communities and ecosystems

Question: How do two shrubs with contrasting lifehistory characteristics influence abundance of dominant plant taxa, species richness and aboveground biomass of grasses and forbs, litter accumulation, nitrogen pools and mineralization rates? How are these shrubs ‐ and thus their effects on populations, communities and ecosystems ‐ distributed spatially across the landscape? Location: Coastal hind-dune system, Bodega Head, northern California. Methods: In each of 4 years, we compared vegetation, leaf litter and soil nitrogen under canopies of two native shrubs ‐ Ericameria ericoides and the nitrogen-fixing Lupinus chamissonis ‐ with those in adjacent open dunes. Results: At the population level, density and cover of the native forb Claytonia perfoliata and the exotic grass Bromus diandrus were higher under shrubs than in shrub-free areas, whereas they were lower under shrubs for the exotic grass Vulpia bromoides. In contrast, cover of three native moss species was highest under Ericameria and equally low under Lupinus and shrub-free areas. At community level, species richness and aboveground biomass of herbaceous dicots was lower beneath shrubs, whereas no pattern emerged for grasses. At ecosystem level, areas beneath shrubs accumulated more leaf litter and had larger pools of soil ammonium and nitrate. Rates of nitrate mineralization were higher under Lupinus, followed by Ericameria and then open dune. At landscape level, the two shrubs ‐ and their distinctive vegetation and soils ‐ frequently had uniform spatial distributions, and the distance separating neighbouring shrubs increased as their combined sizes increased. Conclusions: Collectively, these data suggest that both shrubs serve as ecosystem engineers in this coastal dune, having influences at multiple levels of biological organization. Our data also suggest that intraspecific competition influenced the spatial distributions of these shrubs and thus altered the distributionoftheir effects throughout the landscape.

Changes in landscape and vegetation of coastal dunes in northwest Europe: a review

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.

Predicted effects of climate change, vegetation and tree cover on dune slack habitats at Ainsdale on the Sefton Coast, UK

Dune slack habitats are highly dependent on the availability of water to support flora and fauna. Typically this is provided by shallow groundwater. This paper describes the seasonal and long term variation in groundwater levels in part of the Sefton coastline between 1972 and 2007. The effects of climate change, vegetation management and coastline realignment on groundwater levels are modelled. The observed annual water table levels rise and fall with an amplitude of 1.5 m, but longer term variations and trends are apparent. A stochastic water balance model was used to describe the changes in water table levels in slack floors in the open dunes and also in areas afforested with pine trees. It was found that the pine trees evaporated 214 mm/year more than open dunes vegetation, resulting in the water table being 0.5–1.0 m lower under the trees than under the open dunes. The effects of climate change on the ground water was simulated using predictions of future climate conditions based on the UKCIP02 medium high emissions scenario. The increase in temperature and change in rainfall patterns will result in a decrease in mean ground water levels by 1.0–1.5 mm in the next 90 years. Typical patterns consist of sequences of 5–10 years of low water table levels interspersed by infrequent sequences consisting of 2–5 years of relatively high or “normal” levels. These results indicate that that flora and fauna that cannot survive a 5–10 year period of water table levels >2.5 m below ground level are unlikely to survive or persist in many slack areas and a change in the ecology of these slack may become inevitable. Other effects of climate change include sea level rise which will result in a gradual rise in water table levels. Coastal erosion will increase the water table gradient to the sea and result in a slight lowering of the ground water levels. Conversely coastal accretion will reverse this process. The spatial distribution of coastal erosion and accretion along the Sefton coastline and its likely impacts on groundwater levels are discussed. The modelling work described in this paper has identified the factors which have the largest effect on groundwater levels in temperate coastal dune systems.

Occurrence and habitat of the endangered white flower moth, Schinia bimatris (Lepidoptera: Noctuidae), in Manitoba

AbstractThe only known Canadian population of the white flower moth, Schinia bimatris Harvey, a federally listed endangered species, was rediscovered in 2003 in the dune area of Spruce Woods Provincial Park and Canadian Forces Base Shilo in Manitoba. Little is known about the biology or habitat requirements of this moth in North America. The dune area in Manitoba was surveyed for adult and immature stages of the species during July 2007 using light traps and daytime visual searches. A detailed vegetation survey was also completed in areas where moths were active. Whereas individuals caught in light traps were predominantly males, both females and males were observed to be very active during daylight hours. This is the first record of diurnal activity of the white flower moth in Canada. Adults were observed flying above dune crests and also resting on vegetation between open dunes. Although the current population appears robust, given the number of adults observed, a previous population approximation of up to 5000 individuals may be an overestimate because sand-dune habitat is limited. We were unable to locate immature stages or determine which host plant(s) were utilized by larvae.

Comparative Analysis of Plant and Ground Dwelling Arthropod Communities in Lacustrine Dune Areas with and without Centaurea Biebersteinii (Asteraceae)

ABSTRACT Open dune systems are being degraded through human development and exotic species invasions. The Grand Sable Dunes, Pictured Rocks National Lakeshore, Michigan, are protected from development but not from the spread of exotic species. The invasive exotic spotted knapweed, Centaurea biebersteinii, has invaded significant portions of this dune system. Areas without spotted knapweed had higher native plant diversity than areas with spotted knapweed, as well as lower exotic plant diversity. Of native plant species occurring in the highest frequencies along transects in both spotted knapweed infested and non-spotted knapweed infested areas, four out of the five species were more likely to be encountered along transects in non-spotted knapweed areas than along transects in spotted knapweed areas. Insect families Curculionidae and Formicidae were captured more often in areas with spotted knapweed. Increased dune stabilization increased the ability of exotic plant species not adapted to the actively shif...

Carbon‐13 and nitrogen‐15 enrichment in coastal forest foliage from nutrient‐poor and seabird‐enriched sites in southern New Zealand

To assess the effect of nutrient inputs from breeding seabirds on forest foliage δ13C and δ15N, we collected foliage samples from two contrasting locations. Olearia lyallii forest on North East Island at The Snares hosts large numbers of (in particular) breeding sooty shearwaters (Puffinus griseus). At Mason Bay (Rakiura/Stewart Island), samples of Brachyglottis rotundifolia, Griselinia littoralis, and Dracophyllum longifolium were collected from two strata within diverse dune forest and one stratum from the open dunes. The δ13C results were typical of C3 plants and did not differ significantly between Mason Bay and North East Island. In contrast, the δ15N results from Mason Bay (mean ± standard deviation, ‐6.1 ± 1.7‰) were significantly lower than expected for temperate forest (95% confidence interval of difference, 2.7–3.9‰), and dramatically lower (19.1–21.5‰) than North East Island where enrichments (+14.2 ±3.1 ‰) were among the highest ever reported for vegetation.

Effects of the expansion by Hippophaë rhamnoides on plant species richness in coastal dunes

AbstractQuestion: Is the expansion of Hippophaë rhamnoides in coastal dunes associated with a decline in plant species richness, and is this decline best described by a hump‐backed relationship between species number and shrub cover?Location: Grey and yellow dunes on the East Frisian islands Spiekeroog and Norderney.Methods: Total plant species richness as well as the number of herbaceous and cryptogam species were determined in 2001 using plots of 16 m2 size. We compared shrubland plots with varying cover of Hippophaë with neighbouring dune grassland plots without shrubs as reference sites. Soil samples were collected to determine the values of some important edaphic variables (pH, organic matter, nitrogen).Results: The shrubland plots with Hippophaë had or tended to have lower soil pH and C/N ratios and higher contents of organic matter and nitrogen than the grassland plots. Total species richness was marginally significantly related to the cover of Hippophaë in a hump‐backed manner on both islands. The pattern was more pronounced for mosses and lichens than for herbaceous species. For all species groups on Spiekeroog and for the herbaceous species on Norderney, the hump‐backed relationship was much improved when using the difference in species number between shrubland and grassland plot as a dependent variable. Relationships could be improved by including the soil parameters as co‐variables. Species richness was highest at moderate levels of shrub expansion, while it was much reduced in very dense shrubland. The decrease in species number is caused by the decline in grassland species typical of the open dunes, including some rare taxa.Conclusions: The expansion of Hippophaë rhamnoides is a serious threat to the plant species richness of open coastal dunes, and needs to be counteracted by management measures.

Effects of the expansion by Hippophaë rhamnoides on plant species richness in coastal dunes

Question: Is the expansion of Hippophaë rhamnoides in coastal dunes associated with a decline in plant species richness, and is this decline best described by a hump-backed relationship between species number and shrub cover? Location: Grey and yellow dunes on the East Frisian islands Spiekeroog and Norderney. Methods: Total plant species richness as well as the number of herbaceous and cryptogam species were determined in 2001 using plots of 16 m2 size. We compared shrubland plots with varying cover of Hippophaë with neighbouring dune grassland plots without shrubs as reference sites. Soil samples were collected to determine the values of some important edaphic variables (pH, organic matter, nitrogen). Results: The shrubland plots with Hippophaë had or tended to have lower soil pH and C/N ratios and higher contents of organic matter and nitrogen than the grassland plots. Total species richness was marginally significantly related to the cover of Hippophaë in a hump-backed manner on both islands. The pattern was more pronounced for mosses and lichens than for herbaceous species. For all species groups on Spiekeroog and for the herbaceous species on Norderney, the hump-backed relationship was much improved when using the difference in species number between shrubland and grassland plot as a dependent variable. Relationships could be improved by including the soil parameters as co-variables. Species richness was highest at moderate levels of shrub expansion, while it was much reduced in very dense shrubland. The decrease in species number is caused by the decline in grassland species typical of the open dunes, including some rare taxa. Conclusions: The expansion of Hippophaë rhamnoides is a serious threat to the plant species richness of open coastal dunes, and needs to be counteracted by management measures.

Seasonal variation in heat shock proteins Hsp70 and Hsp90 expression in an exposed and a shaded habitat ofIris pumila

Seasonal variation in heat shock proteins Hsp70 and Hsp90 expression was studied in the leaves of two naturally growing Iris pumila populations, one inhabiting an open dune site, and the other the understorey of a Pinus silvestris stand. The Hsps were quantified by an immunoblotting procedure. The level of the Hsps was found to vary significantly both across seasons and between habitats. The mean Hsp70 concentration was significantly greater at the open area than in the woodland understorey, reaching its maximum in the summer, especially in plants experiencing full sunlight. Two Hsp90 isoforms, referred to as Hsp90a (86 kDa) and Hsp90b (84 kDa), were detected. At both habitats, the level of Hsp90a was highest in autumn, that of Hsp90b in spring, whereas both of them reached a nadir in summer. Throughout the growing season, the relative abundance of Hsp90b was higher in plants growing under vegetation canopy in comparison to those inhabiting the open dune site. An inverse relationship between the phenotypic variation in specific leaf area and the level of Hsp90b over seasons at both habitats was observed, suggesting the role of this protein in buffering phenotypic variation in the wild.

Phenotypic plasticity in response to an irradiance gradient in Iris pumila: adaptive value and evolutionary constraints

Adaptive values of plasticity in Iris pumila leaf traits (morphological: SLA, specific leaf area; anatomical: SD, stomatal density; LT, leaf thickness; VBN, vascular bundle number; SW, sclerenchyma width; CW, cuticle width, and physiological: ChlT, total chlorophyll concentration; ChlA/B, chlorophyll a/b ratio) were tested at three irradiance levels in a growth-room. Siblings from 28 full-sib families from an open dune site and a woodland understory responded similarly to variation in light availability: SLA gradually increased, while anatomical and physiological traits decreased with light reduction. In the Dune population, standardized linear selection gradients were significant for SLA and ChlT at high light, VBN along the entire light gradient, SW at high- and low-, and ChlA/B at low-irradiance. In the Woods population, the significant standardized linear selection gradients were observed for SLA and LT at low- and VBN at both high- and low-irradiance. A significant nonlinear selection gradient was recorded for SD and LT at medium irradiance. Comparisons of the plastic responses to each light quantity with the phenotypes favored by selection in that environments revealed that only an increased SLA value at low light in the Woods population was ecologically significant (adaptive). In the Dune population, SD and VBN entailed plasticity costs at low irradiance, while a cost of homeostasis was recognized for ChlT and ChlA/B at medium light, SD and CW at high- and low-, and SLA at high- and medium-light level. In the shaded population, CW and ChlA/B incurred plasticity costs at high irradiance, while for ChlT plasticity costs appeared under medium- and low-light conditions. In all leaf traits, genetic variation for plasticity was statistically undetectable. Genetic correlations between these traits were mostly insignificant, implying that they possess a capability for relatively independent evolution by natural selection across different light environments.

Centipede communities on the inland dunes of eastern Flanders (Belgium)

During a year-round pitfall sampling campaign on twelve inland dunes in eastern Flanders, a total number of thirteen centipede species were caught. The encountered centipede fauna, with Lithobius calcaratus as the most ubiquitous species, was related to that of the Campine region that is also characterized by acid sandy soils. Community analysis on the basis of species composition revealed that the woody stations had a higher species diversity than the more open heath lands and moss dunes. Brachygeophilus truncorum and Cryptops hortensis were most characteristic for the woody stations whereas Lamyctes fulvicornis and Lithobius microps were more common in the open sites.

Conservation and management of the mediterranean coastal sand dunes in Israel

The aims of this study are to review the current situation of the Israeli Mediterranean coastal sand dunes, to examine the causes for this situation, and to propose options for future conservation and management of the protected dune areas based on ecological, environmental, landscape and recreational demands and interests. The coastal dunes of Israel are characterized by diverse plant communities, with 173 plant species occurring on sand (8.2% of the total flora of Israel) including many endemic species (26% of all endemic species in Israel). Most of the species are annuals. The importance of the coastal strip as a centre of floral and faunal speciation is also manifested in the existing sand-bound animals. However, many species are rare. This is mainly due to the extensive industrial and urban development along the coastal plain and the direct and indirect destruction of the remaining open dune areas by tourism, recreation and sand mining. Only ca. 17% of the Israeli coastal dunes are still of good or reasonable ecological value, while < 5% of this area has been designated as protected area. Management policies differ from place to place and depend on local objectives. These objectives derive mainly from the knowledge and data that exist for each location, and its statutory status. Since 1995 several projects, which aim to develop integrated management tools for nature conservation and recreation uses for all coastal sand dunes in Israel have been conducted. These projects are summarized in the present paper.

Geomorphologic and palaeoenvironmental development of holocene perched coastal dune systems in brittany, france

Two perched dune systems are investigated in the Baie d'Audierne (Finistère, Brittany, northwest France). A maximum age of 4545–4160 cal. yr bp for the onset of sand accretion is provided through radiocarbon (14C) analysis of an organic‐rich basal palaeosol, corresponding closely to deceleration, but before stabilisation, of regional Holocene relative sea levels (RSLs). Molluscan analysis through the dune sand indicates an initial bare sand or sparsely vegetated surface, subsequently maturing and colonised by scrub vegetation, and finally returning to more open dune grassland conditions. These data suggest a three‐stage Perched Dune Development Model (PDDM), which may be applicable to perched dunes on at least a regional scale: (1) initial sand sheet inundation as RSL rises; (2) stabilisation of RSL allowing dune to mature; and (3) sea‐level stabilisation stimulates cliff formation, perching and progressive landward retreat of the dune shore. This study recognises that perched dunes hold greater potential for establishing chronologies for regional Holocene dune development than the more widely studied lowland dune systems, where evidence for early sand inundation may be obscured or lost by modest rises in sea level.

Testing the adaptive plasticity of Iris pumila leaf traits to natural light conditions using phenotypic selection analysis

A multivariate selection analysis has been used to test the adaptiveness of several Iris pumila leaf traits that display plasticity to natural light conditions. Siblings of a synthetic population comprising 31 families of two populations from contrasting light habitats were grown at an open dune site and in the understory of a Pinus nigra stand in order to score variation in phenotypic expression of six leaf traits: number of senescent leaves, number of live leaves, leaf length, leaf width, leaf angle, and specific leaf area. The ambient light conditions affected the values of all traits studied except for specific leaf area. In accordance to ecophysiological expectations for an adaptive response to light, both leaf length and width were significantly greater while the angle between sequential leaves was significantly smaller in the woodland understory than at the exposed dune site. The relationship between leaf traits and vegetative fitness (total leaf area) differed across light habitats as predicted by functional hypotheses. The standardized linear selection gradient (β′) for leaf length and width were positive in sign in both environments, but their magnitude for leaf length was higher in the shade than under full sunlight. Since plasticity of leaf length in the woodland shade has been recognized as adaptive, fitness cost of producing plastic change in leaf length was assessed. In both of the available methods used, the two-step and the multivariate regression procedures, a rather high negative association between the fitness value and the plasticity of leaf length was obtained, indicating a cost of plasticity. The selection gradient for leaf angle was weak and significant only in the woodland understory. Genetic correlations between trait expressions in contrasting light environments were negative in sign and low in magnitude, implying a significant genetic variation for plasticity in these leaf traits. Furthermore, leaf length and leaf width were found to be genetically positively coupled, which indicates that there is a potential for these two traits to evolve toward their optimal phenotypic values even faster than would be expected if they were genetically independent.

Nitrogen availability in relation to vegetation changes resulting from grass encroachment in Dutch dry dunes

The encroachment of some tall grass species in open dune vegetation, as observed in a Dutch dry dune area, is considered unfavourable from a conservation viewpoint. This paper investigates differences in vegetation and soil properties between grass-dominated and still existing open dune grassland plots at four locations along the coast. Soil properties studied include nitrogen and phosphorus pools and nitrogen availability by mineralization. Vegetation properties included are above and below-ground biomass and nitrogen and phosphorus concentrations in above-ground biomass.

Effects of grass-encroachment on vegetation and soil in Dutch dry dune grasslands

The encroachment of tall grass species in open dune vegetation, as observed in the Dutch dry dune area, is considered unfavourable for nature conservation. The effects of grass-encroachment on the vegetation and the availability of light and its relation to nutrients were investigated through a comparative study of grass-dominated and open dune grassland plots at ten locations along the Dutch coast. Grass-dominated plots have a low species diversity and number of species, especially of mosses and lichens. This is associated with a high biomass and a low availability of light at soil surface. In addition, nutrient availability seems to be important. Root biomass and the amounts of both ectorganic and endorganic matter are significantly higher in grass-dominated plots, which may account for the higher nutrient uptake in the vegetation. It is likely that a grass-dominated system can maintain and consolidate itself because of the better competition for light and nutrients. The relevance of these results for restoration management is briefly discussed.

Persistence of British natterjack toad Bufo calamita Laurenti (Anura: Bufonidae) populations despite low genetic diversity

Like other amphibians native to Britain, the natterjack toadBufo calamitamust have colonized the islands during the relatively short period between the end of the last glaciation and the separation of Britain from mainland Europe by rising sea levels. Unlike the other native amphibians, however,B. calamitais a habitat specialist at the north-westerly edge of its biogeographical range and for most of the 8000–10000 years since its colonization has probably been restricted to open dunes, heathlands and upper saltmarshes, as isolated populations in a few discrete areas of the country. We have investigated the genetic diversity and relatedness of six widely separated British natterjack populations by allozyme analysis, and shown that all have very low diversity (OverallP95% = 2·7%, H = 0·004) by comparison with other anurans, including natterjack populations in mainland Europe and common frogs (Rana temporaria, L) in Britain. Eighty percent of loci were fixed for the same allele in all six British natterjack populations and genetic differentiation between colonies was extremely low. The possible significance of these findings to the persistence of small isolated populations at range edges is discussed.

New species of Cucumis (Cucurbitaceae) from northeast tropical Africa

The new species Cucumis hastatus (widespread in southern Somalia, in deciduous bushlands), C. pubituberculatus (central Somalia, on open coastal dunes), C. Jeffrey-anus (southwestern Somalia and eastern Ethiopia, on alluvial soils), and C. baladensis (south-central Somalia, on fixed dunes), are described and illustrated. C. figarei is shown to be illegitimate, the correct name for the species apparently being C. pustulatus.

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.

Growth Response to Different Levels of Soil Moisture and Soil Fertility in Four Winter Annual Species during Their Life-Cycle

The effect of three different soil moisture levels and two soil fertility levels on the growth, biomass allocation and reproductive effort of four winter annual plant species from the open dune habitat i.e. Aira praecox, Cerastium arvense, Erophila verna , and Veronica arvensis , has been investigated. Soil moisture has a considerable effect on the growth and reproduction of all species except Veronica arvensis , in which an increasing soil fertility seems to be of overriding importance. In the experimental period (27-30weeks), only Cerastium semidecandrum and Erophila verna completed their life-cycle and produced seeds. In these species absolute seed biomass and number per plant are markedly depressed by a low soil moisture level. In contrast to Erophila verna , the values of these parameters increase in Cerastium semidecandrum when the soil fertility is high. Mean seed weight was not affected by the treatments. Regarding the different niches of these winter annual species in the dune habitat, we discuss in how far the niches of these annuals represent different strategies or may be considered one particular strategy sensu G rime (1979).