Distribution of C4 plants in sand habitats of different climatic regions

Sand dunes of warm regions provide suitable habitats for C4 plants because of their water and nitrogen use efficiency under high temperature and their high tolerance to ecological stress such as salinity, aridity and disturbance. We studied the distribution patterns of C4 plant species in five habitat types of sand dune ecosystems in three climatic regions (Mediterranean, Irano-Turanian and Hyrcanian). We compared the relative abundance of C4 plants in terms of richness and cover and aimed at identifying their habitat preferences in sand ecosystems. Our results revealed that C4 species notably contribute to the vegetation cover, despite their rather low contribution to the richness in comparison with C3 species. Generally, C4 plants were more prominent in mobile dunes, saltmarshes and disturbed sandy ground, but they showed regional differences in habitat preference. In northern and central Iran, C4 plants had the highest relative abundance in mobile dunes whereas in northeastern Greece they dominated disturbed sandy ground. The abundance of C4 plants appears to be influenced by climatic conditions. Central Iran, the driest and warmest among our study regions, has the highest proportion of C4 species in terms of number and cover. We observed an increasing trend in richness and cover of C4 plants with increasing aridity. As the number of C4 species alone may not fully reflect their role in a given area, the C4 plant total vegetation cover is shown to be an additional important parameter in ecological studies.     

Effects of fire on the structure and composition of open eucalypt forests

Abstract Fires are integral to the healthy functioning of most ecosystems and are often poorly understood in policy and management, however, the relationship between floristic composition and habitat structure is intrinsically linked, particularly after fire. The aim of this study was to test whether the variability of habitat structure or floristic composition and abundance in forests at a regional scale can be explained in terms of fire frequency using historical data and experimental prescribed burns. We tested this hypothesis in open eucalypt forests of Fraser Island off the east coast of Australia. Fraser Island dunes show progressive stages in plant succession as access to nutrients decreases across the Island. We found that fire frequency was not a good predictor of floristic composition or abundance across dune systems; rather, its affects were dune specific. In contrast, habitat structure was strongly influenced by fire frequency, independent of dune system. A dense understorey occurred in frequently burnt areas, whereas infrequently burnt areas had a more even distribution of plant heights. Plant communities returned to pre‐burn levels of composition and abundances within 6 months of a fire and frequently burnt areas were dominated by early successional species of plant. These ecosystems were characterized by low diversity and frequently burnt areas on the east coast were dominated by Pteridium. Greater midstorey canopy cover in low frequency areas reduces light penetration and allows other species to compete more effectively with Pteridium. Our results strongly indicate that frequent fires on the Island have resulted in a decrease in relative diversity through dominance of several species. Prescribed fire represents a powerful management tool to shape habitat structure and complexity of Fraser Island forests.     

Contrasting responses of native and alien plant species to soil properties shed new light on the invasion of dune systems

在陆地生态系统中，沿海沙丘特别容易受到外来植物的入侵。许多研究将沙丘生境的入侵归因于人为因素，但对土壤性质和植物性状在植物 入侵中的作用却知之甚少。本研究考察了沙丘系统土壤特征与外来植物入侵的关系，重点研究了土壤养分、土壤盐分和植物功能特征之间的相互作 用。研究地点是马拉诺和格拉多泻湖(北亚得里亚海)的沙质堰洲岛。根据沙丘系统生态梯度上的主要生境(前沙丘、后沙丘和盐沼)，在10 个区域内选择100个地块(4 m × 4 m)。在每个地块中记录所有植物物种的发生和丰度，并收集一个土壤核。对每个土壤样品进行土壤质地、电导率(代表土壤盐 分)、有机碳和氮含量分析，并与本地和外来植物的种类数和覆盖度相关联。分析外来和本地物种主要的生殖功能和营养功能性状在生境中的变化。研究结果表明，土壤性质对外来物种库和本地物种库的影响不同，与植物整体多样性密切相关。在后沙丘(最易入侵)的生境中，高的土壤导电性限制了外来物种的数量，但土壤有机碳含量随着外来植物丰度的增加而增加，这也表明植物入侵与土壤之间存在潜在的反馈过程。只有在后沙丘生境中，随着环境条件的改善和植物竞争的加剧，本地植物和外来植物的功能性状谱有显著的趋同。本研究结果表明，在恶劣条件下，只有本地特有植物才能茁壮成长，而在中等条件下，土壤特性梯度与植物特性协同作用，抑制/促进外来植物丰富度。     

不同沙丘生境主要植物比叶面积和叶干物质含量的比较

研究了生长在不同沙丘生境中 (流动沙丘 ,半固定沙丘和固定沙丘 ) 2 0个植物种 (10个 1年生植物种和 10个多年生植物种 )的比叶面积 (SL A)和叶干物质含量 (L DMC)的变化 ,并且分析了各个沙丘生境的土壤养分特征。结果表明 ,各个植物种的平均 SL A和 L DMC在植物种之间差异显著 ;多数在两种或 3种沙丘生境均有分布的植物其 SL A在不同沙丘生境之间差异显著 ,但是仅有 6个植物种的 L DMC在不同沙丘生境之间表现出差异 (p<0 .0 5 )。与许多研究结果类似 ,1年生植物的 SL A显著大于多年生植物的 SL A,而且两者之间 L DMC存在一定的差异。 1年生植物 SL A和 L DMC之间相关性不显著 ,但多年生植物SL A和 L DMC之间呈显著负相关。综合所有 2 0个植物种可以发现 ,SL A增大时 ,L DMC有下降的趋势     

Effects of long‐term grazing management on sand dune vegetation of high conservation interest

Question: Can long‐term grazing management maintain and restore species‐rich sand dune plant communities within a sand dune site of high conservation interest? Location: Newborough Warren, North Wales, UK. Methods: Vegetation changes that occurred between 1987 and 2003, subsequent to grazing by domestic livestock being introduced to the site after decades with little or no stock grazing, were analysed using data collected from permanent monitoring quadrats over a 16‐year period. Results: At the plant community level, grazing brought about a shift from a tall‐grass dominated, species‐poor community to a more species‐rich community in the dry dunes, but did not change community type in dune slacks. However, at the species level, grazing enhanced the abundance of some desired perennial, annual and biennial species, graminoids and bryophytes in both habitat types. The increased frequency of positive indicator species for habitat condition suggests that grazing was beneficial for species of conservation interest. Ellenberg nitrogen (N) values decreased after grazing in dry habitats but showed no long‐term change independent of grazing, suggesting no increase in site fertility over the study period. Surprisingly, light (L) values also decreased in the dry dunes after grazing. Conclusions: Long‐term grazing management can play an important role for the conservation of dune communities and associated species. Because of its positive effects on species diversity, plant communities and habitat condition in sand dunes, livestock grazing is recommended for conservation management.     

Restoration of riverine inland sand dune complexes: implications for the conservation of wild bees

1.  The evaluation of restoration measures is an important task of conservation biology. Inland sand dunes and dry, oligotrophic grasslands have become rare habitat types in large parts of Central Europe and their restoration and management is of major importance for the preservation of many endangered plant and insect species. Within such habitats, it is important to restore key ecosystem services, such as pollination networks. As wild bees are the most important pollinators in many ecosystems, they represent a suitable key group to evaluate restoration measures. Furthermore, the recent decline of many bee species and the potential ecological and economic consequences are currently topics of strong scientific interest.
2.  We studied the succession of bee communities in response to restoration measures of sand dunes and sand grasslands and compared these communities with those of old sand dune complexes.
3.  Our results show that wild bees respond rapidly to restoration measures indicated by a high species richness and abundance. The community structure of bees at restoration sites converged only slightly to those of the target sites. A higher similarity was found between bee communities at the restoration sites (sand dunes and grasslands), indicating that their close proximity was an important determinant of species overlap. Environmental factors such as the number of entomophilous plant species and moisture had a strong influence on wild bee species composition.
4.   Synthesis and applications . The restoration of inland sand dune complexes provides opportunities for colonization by a diverse wild bee community. Although it is difficult to establish a given target community, restoration measures gave rise to a high pollinator diversity and abundance, suggesting that community function can be re-established.     

A comparison of seed banks across a sand dune successional gradient at Lake Michigan dunes (Indiana,USA)

In habitats where disturbance is frequent, seed banks are important for the regeneration of vegetation. Sand dune systems are dynamic habitats in which sand movement provides intermittent disturbance. As succession proceeds from bare sand to forest, the disturbance decreases. At Indiana Dunes National Lakeshore, we examined the seed banks of three habitat types across a successional gradient: foredunes, secondary dunes, and oak savanna. There were differences among the types of species that germinated from each of the habitats. The mean seed bank density increased across the successional gradient by habitat, from 376 to 433 to 968 seeds m⁻², but with foredune and secondary dune seed bank densities being significantly lower than the savanna seed bank density. The number of seeds germinated was significantly correlated with soil organic carbon, demonstrating for this primary successional sequence that seed density increases with stage and age. The seed bank had much lower species richness than that of the aboveground vegetation across all habitats. Among sites within a habitat type, the similarity of species germinated from the seed banks was very low, illustrating the variability of the seed bank even in similar habitat types. These results suggest that restoration of these habitats cannot rely on seed banks alone.     

Woody plant encroachment impacts on soil carbon and microbial processes: results from a hierarchical Bayesian analysis of soil incubation data

Quantitative methods were used to examine soil properties and their spatial heterogeneity in a 0-year fenced mobile dune (MD0), an 11-year fenced mobile dune (MD11) and a 20-year fenced mobile dune (MD20) in Horqin Sandy Land, Northern China. The objective of the study was to assess the effect of vegetation restoration on heterogeneity of soil properties in sand dunes and to provide a concept model to describe the relationship between vegetation succession and spatial heterogeneity variation of soil properties in the dunes. The results showed that the average values of vegetation cover, species number and diversity, soil organic carbon (C), total nitrogen (N), and electrical conductivity (EC) increased with the increase in fenced age of mobile dunes, while soil water content (0–20 cm) showed the reverse trend. Geostatistical analysis revealed that the spatial heterogeneity of soil organic C, total N, EC, very fine sand content, and soil water content (0–20 cm) increased from MD0 to MD11 with succession from sand pioneer plant to shrub species then decreased from MD11 to MD20 due to continuous development of herbaceous plants. Canonical correspondence analysis (CCA) showed that there was a relatively high correspondence between vegetation and soil factors, suggesting that the major gradients relating soil organic C, total N, EC, pH, slope, very fine sand content, and soil water content are the main factors for the distribution of dune plants and account for 68.1% of the species-environment relationship among the three sites. In addition, the distribution of the sand pioneer plant was positively related to the relative height of the sampling site and soil water content, and that of most herbaceous plants were determined by soil organic C, total N, EC, pH, and very fine sand content in mobile dunes. The conceptual model of relationship between vegetation succession and spatial heterogeneity of soil properties in mobile dunes suggests spatial patterns of soil properties are most strongly related to plant-induced heterogeneity in dune ecosystems prone to wind erosion, and conversely, the magnitude and degree of spatial heterogeneity in soil properties can influence the plant distribution pattern and vegetation succession of mobile dunes.     

Contrasting effects of plant inter‐ and intraspecific variation on community trait responses to restoration of a sandy grassland ecosystem

Changes in plant community traits along an environmental gradient are caused by interspecific and intraspecific trait variation. However, little is known about the role of interspecific and intraspecific trait variation in plant community responses to the restoration of a sandy grassland ecosystem. We measured five functional traits of 34 species along a restoration gradient of sandy grassland (mobile dune, semi‐fixed dune, fixed dune, and grassland) in Horqin Sand Land, northern China. We examined how community‐level traits varied with habitat changes and soil gradients using both abundance‐weighted and non‐weighted averages of trait values. We quantified the relative contribution of inter‐ and intraspecific trait variation in specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon content (LCC), leaf nitrogen content (LNC), and plant height to the community response to habitat changes in the restoration of sandy grassland. We found that five weighted community‐average traits varied significantly with habitat changes. Along the soil gradient in the restoration of sandy grassland, plant height, SLA, LDMC, and LCC increased, while LNC decreased. For all traits, there was a greater contribution of interspecific variation to community response in regard to habitat changes relative to that of intraspecific variation. The relative contribution of the interspecific variation effect of an abundance‐weighted trait was greater than that of a non‐weighted trait with regard to all traits except LDMC. A community‐level trait response to habitat changes was due largely to species turnover. Though the intraspecific shift plays a small role in community trait response to habitat changes, it has an effect on plant coexistence and the maintenance of herbaceous plants in sandy grassland habitats. The context dependency of positive and negative covariation between inter‐ and intraspecific variation further suggests that both effects of inter‐ and intraspecific variation on a community trait should be considered when understanding a plant community response to environmental changes in sandy grassland ecosystems.     

Environmental factors and ground disturbance affecting the composition of species and functional traits of ground layer lichens on grey dunes and dune heaths of Estonia

A unique, species‐rich and endangered lichen biota can be found on European coastal and inland sand dunes. However, it is increasingly affected by natural succession as well as by anthropogenic disturbances. We studied lichen diversity on the grey dunes and dune heaths of coastal and inland regions of Estonia. A total of 28 study plots were investigated; in each 0.1 ha study plot general environmental variables and anthropogenic disturbances were described and all epigeic lichen species were identified. We found 66 lichenized fungus (lichen) species, including several rare and ten red‐listed lichens. Multivariate analysis (DCA, CCA) was performed to examine gradients in species composition and to relate variation in species data to environmental factors. In addition, we used redundancy analysis (RDA) to relate variation in species’ trait composition to environmental factors. Species composition on grey dunes differed significantly from that on dune heaths. The characteristic species for grey dunes are, besides several Cladonia species, foliose lichens, e.g. Hypogymnia physodes, Parmelia sulcata and Peltigera spp. Also species’ traits composition was different for either habitat, indicating that sorediate lichens, foliose lichens, lichens with cyanobacterium as the main photobiont, and sparsely branched Cladonia species dominate on grey dunes, while esorediate, green‐algal, crustose and richly branched fruticose lichens are common on dune heaths. Soil pH was the most essential environmental variable for determining both species composition and species’ traits composition. The composition of lichen species was also significantly influenced by forest closeness, soil Mg content and cover of bare sand; the effect of ground disturbances was low compared to the effect of these environmental factors. To protect and conserve the species‐rich lichen biota, it is necessary to protect the dune habitats from building activity, to avoid overtrampling in recreation areas and to regularly remove shrubs and trees.     

If you build it,will they come? Use of restored dunes by beach mice

Restoration of coastal habitat fragmented, degraded, or destroyed by development and climate‐related processes such as sea level rise and storm surge usually involves planting native plants to restore habitat structure, but whether and how restored areas benefit taxa other than plants is rarely reported. Installing restoration plantings is one method used to build habitat such as beach dunes where dunes have been lost, potentially creating habitat for dune‐dependent species. We compared use of natural vegetated dunes, open sand gaps, and restoration plantings (habitat treatment) by Perdido Key beach mice (Peromyscus polionotus trissyllepsis) over 3 years using tracking tubes to assess the value of restoration plantings for beach mice. Tubes were monitored in two seasons (early and mid‐summer), and under new and full moon conditions. Mice used restoration plantings less than natural vegetated dunes but more than open sand gaps, which suggests restoration plantings may facilitate movement of mice across fragmented areas. Both season and moon phase influenced the effect of habitat treatment, interactions which may be attributable to perceived risk associated with movement under a combination of different conditions of ambient light, vegetation cover, and habitat novelty. Our results show restoration plantings provide habitat for movement and foraging, and may ameliorate some consequences of sea level rise and storms for beach mice and potentially other dune‐dependent species into the future.     

Interactions between mycorrhizal colonization and plant life forms along the successional gradient of coastal sand dunes in the eastern Mediterranean, Turkey

The mycorrhizal status of dune plant species in relation to their plant life forms was surveyed along a successional gradient of sand dune on the southern Mediterranean coast of Turkey. Roots of 64 dune plant species belonging to 30 families were collected from sand dune communities at four different successional stages: embryonic dunes (ED), mobile dunes (MD), fixed dunes (FD), and remnant dunes (RD). Of the plant species surveyed in all successional stages, 54 (84%) had formed mycorrhizal associations. Nonmycorrhizal plants with cryptophyte life forms predominated in the earlier successional stages (ED and MD), whereas the number and percent coverage of mycorrhizal plant species belonging to hemicryptophytes, phanerophytes, and chamaephytes generally increased with the stabilization of sand dunes. Arbuscular mycorrhizal (AM) colonization was found to be the dominant mycorrhizal type in ED, MD, and RD. But phanerophytes with dual colonization, AM and ectomycorrhizal, became the dominant life form with high plant coverage in the FD stage. Total percentage of mycorrhizal root length colonization showed significant positive correlations relating to soil parameters such as organic matter and nitrogen content, while negatively correlating to high soil reaction (pH).     

Plant functional diversity mediates the effects of vegetation and soil properties on community-level plant nitrogen use in the restoration of semiarid sandy grassland

Species-rich plant communities use nitrogen (N) more efficiently in grassland ecosystems; however, the role of plant functional diversity in affecting community level plant N-use has received little attention. We examined plant N content, stock and N-use efficiency at community-level along a restoration gradient of sandy grassland (mobile dune, semi-fixed dune, fixed dune and grassland) in Horqin Sand Land, northern China. We used the functional trait-based approach to examine how plant functional diversity, reflected by the most abundant species’ traits (community-weighted mean, CWM) and the dispersion of functional trait values (FDis), affected N-use efficiency in sandy grassland restoration. We further used the structure equation model (SEM) to evaluate the direct or indirect effects of plant species richness, biomass, functional diversity and soil properties on community-level plant N-use efficiency. We found that plant biomass and its N stock increased following sandy grassland restoration, and there were lower plant N content and higher N-use efficiency in semi-fixed dune, fixed dune and grassland as compared with mobile dune. N-use efficiency was positively associated with plant species richness, biomass, CWM plant height, CWM leaf C:N, FDis and soil gradient, but SEM results showed that species richness, CWM leaf C:N, plant biomass and FDis controlled by soil properties were the main factors exerting direct effects. CWM plant height also had a positive effect on N-use efficiency through its indirect effect on plant biomass. Soil gradient increased N-use efficiency through an indirect effect on vegetation rather than a direct effect. Final SEM models based on different plant functional diversity explained over 74% of variances in N-use efficiency. Effects of plant functional diversity on N-use efficiency supported both the mass ratio hypothesis and the complementarity hypothesis. Our results clearly highlight the important role of plant functional diversity in mediating the effects of vegetation and soil properties on community level plant N-use in sandy grassland ecosystems.     

Ecological Assessment of Dune Restorations in the Great Lakes Region

Because of the economic and environmental importance of stabilizing fragile sand dune habitats, restoration of dunes has become a common practice. Restoration efforts in the Great Lakes and East Coast regions of North America often consist of planting monocultures of the dominant native grass species, Ammophila breviligulata. We evaluated 18 dune restoration projects in the Great Lakes region conducted over the past 25 years. We characterized attributes of diversity (plants and insects), vegetation structure (plant biomass and cover), and ecological processes (soil nutrients and mycorrhizal fungi abundance) in each restoration, and we compared these measures to geographically paired natural dune communities. Restoration sites were similar to reference sites in most measured variables. Differences between restorations and reference sites were mostly explained by differences in ages, with the younger sites supporting slightly lower plant diversity and mycorrhizal spore abundance than older sites. Plant community composition varied little between restored and reference sites, with only one native forb species, Artemisia campestris, occurring significantly more often in reference sites than restored sites. Although it remains unclear whether more diverse restoration plantings could accelerate convergence on the ecological conditions of reference dunes, in general, traditional restoration efforts involving monoculture plantings of A. breviligulata in Great Lakes sand dunes appear to achieve ecological conditions found in reference dunes.     

Plant functional composition and ecosystem properties: the case of peatlands in South Africa

The assumption that ecosystems with similar emergent properties consist of similar functional groupings of plant species is tested by comparing three peatlands from different bioregions across South Africa. They are Mfabeni Swamp in the subtropical coastal region, Wakkerstroom on the inland plateau, and Goukou wetland in the Winter Rainfall region of the Western Cape. In each of the three peatlands, about 400 small vegetation plots have been made from which the abundance of each species per wetland can be assessed. The most dominant species in these plots have been investigated for 17 traits. The functional composition of the vegetation types has been compared across the three peatlands and Functional Diversity has been calculated, taking the dominance of each species into account. One peatland differed greatly from the other two, since the dominant species was of a functional type (“Palmiet/woody sedge”) that was very divergent from any other peatland species found in the study. This functional type can be considered an ecosystem engineer and the effects that this functional type has on the ecosystem results in the occurrence of many other functional types that do not occur in the other peatlands. When we consider emergent traits of an ecosystem as a function of all the plant functional traits that occur in that ecosystem, then peatlands can be regarded as a heterogeneous group of ecosystems. Even if emergent properties such as peat formation are similar between ecosystems, those ecosystems may still consist of very different functional groups. Ecosystem engineers have an impact on the final functional composition of an ecosystem and the degree in which ecosystem engineering plays a role in peatlands differs between different peatlands.     

Conservation management of coastal dunes for Orthoptera has to consider oviposition and nymphal preferences

Dune and heathland ecosystems can harbour a multitude of specialized insect species. To assess the habitat quality of these ecosystems, the presence of specialized insect species may act as a useful indicator. The Orthoptera species Myrmeleotettix maculatus, Decticus verrucivorus, and Platycleis albopunctata present such umbrella species. Because knowledge of oviposition and nymphal habitats of these species is insufficient, we conducted a combined study consisting of an outdoor oviposition experiment and a field survey analyzing nymphal habitat preferences during summer 2009 on the Baltic island of Hiddensee, Germany. The oviposition experiment showed, that all three species mostly avoid oviposition under lichens (= mature grey dunes). M. maculatus preferred bare ground for oviposition, D. verrucivorus favoured both bare ground and mosses, and P. albopunctata laid most eggs into mosses. Young nymphs of both M. maculatus and P. albopunctata preferred initial grey dunes with a high proportion of bare ground and moss-rich grey dunes. Old nymphs were related to moss-rich and lichen-rich grey dunes with more dense vegetation. Based on our results, early seral stages of dune succession with bare ground and mosses as keystone structures are crucial for the conservation of the three studied umbrella species. Because old nymphs and adults additionally require more dense grey dune vegetation or adjacent heath stands, practical dune and heathland management measures should aim to maintain a mosaic-like pattern of different grey dune and dwarf-shrub vegetation stands.     

Together but different: co-occurring dune plant species differ in their water- and nitrogen-use strategies

Stress factors may severely constrain the range of plant physiological responses in harsh environments. Convergence of traits is expected in coastal dunes because of environmental filtering imposed by severe abiotic factors. However, the wide range of morphological and phenological traits exhibited by coexisting dune species suggests considerable variation in functional traits. We hypothesized that the constraints imposed by structural traits ought to translate into physiological differences. Five dominant species with different morphological traits, but coexisting in a homogeneous dune area in Northwest Spain, were selected for study. Soil characteristics and leaf functional traits were measured in April, June and November 2008. Integrated water-use efficiency (assessed by C isotope discrimination) and N acquisition and use strategies (estimated by N isotope composition) varied significantly among species and the differences changed over time. Species differences in specific leaf area, relative water content, leaf N and C:N ratio, also varied over time. The species differed in stomatal density but not in soil characteristics, with the exception of pH. Species differences in functional traits related to the use of resources suggest species niche segregation. Species-specific temporal effects on the use of these resources support temporal niche differentiation. Somewhat in contrast to the findings of previous studies on harsh environments, this study revealed a considerable level of functional diversity and complexity, suggesting that dune plant species have evolved species-specific strategies to survive by partitioning growth-limiting resources.     

Temporal development of vegetation and geomorphology in a man-made beach-dune system by natural processes

Twenty-four yrs of primary succession in a man-made beach-dune system at the Baltic coast of Denmark, built of calcareous, marine sand and the dune planted with Ammophila arenaria , was studied by qualitative observations, quantitative records in permanent plots, levelling and soil analysis within a selected area of 0.75 ha. The aim of the study was to discuss whether human initiated and influenced beach and dune dynamics mimick natural beach and dune processes, and to discuss the relationship between succession and zonation. During the study period, which started in 1979, the man-made dune stabilized rather fast. In the stabilized dune, a sand-pararendzina with a thin A-horizon developed. The beach expanded by accretion of less calcareous, marine sand. On the beach new dunes, 3 m high, successively developed. The number of species in the study area increased from 16 to 55, accompanied by species and life form dynamics, characteristic for primary succession on sandy coasts. A gradual change in species composition of the permanent plots, which appeared by a DCA analysis, could by using TWINSPAN be structured into four groups or plant communities, which reflect succession as well as zonation. Two groups represent the vegetation of sandy beaches with annual dicotyledon species, and mobile dunes dominated by rhizomatous geophytes, especially A. arenaria. The two other groups represent stabilized, calcareous dune, dominated by hemicryptophytes, specially Festuca rubra , and less stabilized dune with F. rubra and the invasive alien Rosa rugosa. It was concluded, that the main trends in the geomorphological and vegetational development of the man-made beach-dune system is similar to the development in natural dunes. In the future, further accretion and seaward dune formation may be expected, but is it also expected, that larger parts of the area gradually will be covered by low scrubs of R. rugosa.     

Green beach vegetation dynamics explained by embryo dune development

Sandy coastlines are dynamic environments with potential for biodiverse habitats, such as green beaches. Green beach vegetation can develop on nutrient-poor beaches landward from embryo dunes. It is characterised by low-dynamic coastal wetland habitat such as salt marshes and dune slacks. It has been hypothesised that the establishment of green beach vegetation is facilitated by the shelter provided by embryo dunes, however evidence is lacking.We explored the importance of geomorphology and soil conditions on the species richness and turnover of green beach vegetation over a time period of 10 years. We recorded 107 plots along 11 transects over a gradient from beach to dune on the island of Schiermonnikoog, the Netherlands. We characterised transect geomorphology at transect level and soil conditions and vegetation at plot level in 2006 and 2016.We found that the green beach vegetation was highly dynamic, total plant cover increased by 62% within 10 years. In 2006 beach width was an important factor in explaining species richness, with the highest number of species occurring on narrow beaches with a large volume of embryo dunes. In 2016, species richness was positively associated with the build-up of organic matter. Overall species richness declined relative to 2006 and was accompanied by an increase in elevation due to sand burial and the expansion of embryo dune volume.Our data suggests that geomorphology influenced the vegetation indirectly by affecting sand burial rate. Plant species richness declined less at sheltered conditions where sand burial was limited, allowing the build-up of organic matter. This indicates a time-dependent relationship between the development of embryo dunes and plant species richness: embryo dunes can be a source of shelter, thus increasing species richness, but can compete for space over time, lowering species richness again. Our results are relevant for engineering and management of biodiverse sandy shores.     

Mesophilic Actinomycetes in the Natural and Reconstructed Sand Dune Vegetation Zones of Fraser Island, Australia

The natural coastal habitat of Fraser Island located in the State of Queensland, Australia, has been disturbed in the past for mining of the mineral sand ilmenite. Currently, there is no information available on whether these past mining disturbances have affected the distribution, diversity, and survival of beneficial soil microorganisms in the sand dunes of the island. This in turn could deleteriously affect the success of the natural regeneration, plant growth, and establishment on the sand dunes. To support ongoing restoration efforts at sites like these mesophilic actinomycetes were isolated using conventional techniques, with particular emphasis on the taxa previously reported to produce plant-growth-promoting substances and providing support to mycorrhizal fungi, were studied at disturbed sites and compared with natural sites. In the natural sites, foredunes contained higher densities of micromonosporae replaced by increasing numbers of streptomycete species in the successional dune and finally leading to complex actinomycete communities in the mature hind dunes. Whereas in the disturbed zones affected by previous mining activities, which are currently being rehabilitated, no culturable actinomycete communities were detected. These findings suggest that the paucity of beneficial microflora in the rehabilitated sand dunes may be limiting the successful colonization by pioneer plant species. Failure to establish a cover of plant species would result in the mature hind dune plants being exposed to harsh salt and climatic conditions. This could exacerbate the incidence of wind erosion, resulting in the destabilization of well-defined and vegetated successional dunal zones.