Soils and vegetation of central Australian sandridges II. Sandridge vegetation in the Uluru National Park Area,Northern Territory,Australia

Belt transects taken over the main sandridges in Uluru National Park, Northern Territory, show a consistent fioristic zonation from swale to dunecrest. On the larger ridges five or six zones are distinguishable and the crest assemblage is largely disjunct; on the lower dunes the pattern is truncated. The Uluru dunefields are representative of the Northern Territory and central Western Australia, though the floristic assemblage differs regionally.     

Environmental Factors Influencing Coastal Vegetation Pattern: New Insights from the Mediterranean Basin

Coastal dune ecosystems show strongly dynamic interactions between abiotic and biotic factors. The relationship between plant communities and environmental factors has been previously studied in oceanic dune systems, but few studies have been conducted along Mediterranean coasts. In this study we analyze the relative contribution of environmental factors associated with two of the main drivers of vegetation zonation: soil and wind. We chose two representative coastal dune systems in the western Mediterranean Basin subject to low levels of human disturbance. Within 54 plots we recorded floristic and environmental data. Vegetation zonation and relationships with environmental variables were investigated through unconstrained and constrained ordinations, correlation, and variance partitioning. Environmental factors shift along the gradient from coastal to inland dunes, concomitantly with the pattern of community types from annual beach communities to shrub-covered fixed dunes. This general gradient is similar both in the Mediterranean and in the oceanic coastal ecosystems, with the same factors that show similar trends along the dune profile. However, our results highlight some peculiarities of the Mediterranean dune systems in relation to the amount of variation explained by environmental factors. While most studies conducted in oceanic ecosystems find that wind-related parameters may control the vegetation zonation, in our study areas we observed a minor importance of the wind-related variables when compared to soil properties. In particular, organic matter and grain-size variability were found to be closely correlated with the distribution of plant communities along the gradient.     

Coastal sand dune vegetation of Tabasco and Campeche,Mexico

Abstract. Sand dune vegetation along the coast of the Mexican states of Tabasco and Campeche was sampled by means of 1501 releves and the data were analyzed with classification and ordination programs. 36 community types were distinguished, which were grouped into 10 higher-order groups. The communities are described in a sequence reflecting the main vegetation zonation. Beach, embryo dune and foredune community groups include 12 community types, the sheltered zone includes 16 types and the fixed dunes 8 types. The ordination results reveal one main vegetation gradient corresponding to the increase in mean distance from the shoreline and elevation, and being covariant with species richness, mean vegetation cover and mean vegetation height. Additional differences are related to the geographical transition between the Gulf and Caribbean coastal vegetation and environmental conditions, mainly type of sand, occurring in the study area. Siliceous sand and a Gulf climate are characteristic for most of Tabasco, and calcareous sand and a Caribbean-type climate are characteristic for Campeche. Disturbance caused by coconut plantations, cattle grazing and tourism favours the invasion of ruderal species from waste places behind the dunes, which attain local dominance in the dunes described here. Consequently some separate community types had to be distinguished. The distribution of community types is analyzed in the context of the transitions between calcareous and siliceous substrates in the study area.     

Transplants along the vegetation gradient on central Australian sandridges

To assess the importance of static catenary factors in controlling the floristic gradient on central Australian sandridges, plant species characteristic of particular topographic zones were transplanted to zones outside their normal topographic range. Both upper-slope species transplanted downslope, and lower-slope species transplanted upslope suffered higher mortality than control plants transplanted within the same topographic zone.     

The role of soil mobility in controlling a vegetation gradient

Mature plants of species which characteristically occupy the mobile crests and upper slopes of the central Australian sandridges are more tolerant of sand burial or undercutting than those of the lower slopes and swales. Seedlings growing on the mobile crest areas are susceptible to sand burial, even during wet years. The young shoots of vegetatively spreading species are less susceptible than individual seedlings of the same size.     

Coastal dune vegetation and pollen representation in south Buenos Aires Province, Argentina

Aim To establish the relationship between coastal dune vegetation and its pollen representation as an aid to interpret Holocene vegetation dynamics and environmental changes from pollen assemblages. Location The study area is situated on the temperate Atlantic coast of south Buenos Aires Province, Argentina (c. 39° S and 61°20′ W). Methods The vegetation of the active dune area adjacent to the beach was described on the basis of its floristic composition from 25 plots. Classification of the vegetation into distinct zones was carried out by cluster analysis. Surface samples were collected from each vegetation stand and analysed for their pollen composition. Pollen percentage data were analysed using principal components analysis in order to investigate the degree to which the different vegetation units can be distinguished by their pollen spectra. Pollen–vegetation relationships for selected taxa were explored using simple scatter plots and indices of association, under‐ and over‐representation. Indices of floristic diversity and palynological richness were used to assess the representation of the vegetation in the pollen spectra. Results and conclusions Five vegetation zones are defined on the basis of species composition and their quantitative variation: back shore, mobile dunes, slacks, semi‐fixed and fixed dunes. Pollen assemblages from back shore, mobile dunes and slacks are clearly differentiated from semi‐fixed and fixed dunes. Pollen assemblages differ considerably from the associated vegetation composition. Major discrepancies are caused by large differences in pollen and vegetation proportion of Hyalis argentea and Discaria americana. There is a considerable proportion of non‐local pollen in every spectrum. Pollen representation in the coastal dunes at Monte Hermoso is influenced by differences in pollen production, dispersal and preservation of individual taxa as well as by the spatial distribution of the vegetation, the topography of the dune system and the wind pattern. The pollen–vegetation relationship established in this study has important implication for understanding and interpreting fossil pollen records from coastal dune environments.     

Floristics and soil relations of upland swamp vegetation near Sydney

Abstract We examined relations between vegetation and soils, using multivariate methods, in hitherto poorly-known upland swamps on the Woronora Plateau, south of Sydney. A major trend in floristic composition was related to the height and cover of the herbaceous stratum and reflected a gradient in soil moisture and nutrients. A second trend in floristic composition was related to the height and cover of the shrub stratum, and may reflect the influence of recurring fires on certain dominant shrub species. Five plant communities were recognized on the basis of floristic composition and were distinguishable by their different soil habitats and/or structural characteristics. We report some of the highest species-richness values in the world (at scales of 1–15 m₂) for shrub/sedge-dominated vegetation, with up to 70 vascular plant species in 15 m2. Variation in species richness is inversely related to the resource gradient and positively related to the penetration of light through the vegetation canopy. This pattern is consistent with resource-competition models and warrants further investigation.     

Vegetation succession on the dunes near Oostvoorne,The Netherlands; a comparison of the vegetation in 1959 and 1980

The vegetation of a 150 ha coastal dune area in the SW Netherlands was carefully analyzed and mapped at a scale of 1:2500 in 1959 and 1980. About 600 relevés were treated numerically. 127 vegetation types were distinguished, the overlap in community composition between the two years was very small. An intermediate level between this community level and the level of the structural-physiognomic formation was adopted. 56 so-called subformations, in which floristic and structural characters are combined, have been recognized and the overlap was then considerably larger, at least in number of types. Ordination results suggest that in each subset: grasslands, dune slacks, woodlands + scrubs, the first axis reflects floristic differentiation along with progression. The ordination of the entire material shows moisture as the main factor underlying the first axis, zonation as the second and nutrient status as the third factor. Change in vegetation was detected through a network overlay with 2 300 points for each of which the transition between 1959 and 1980 was scored. The pattern of change between 1959 and 1980 is apparently multiple pathway in type. This would be one of the few examples of such a pattern to be established on the medium term level of change, which is considered as succession sensu strictu. On an areal basis the change in vegetation is extremely large; even on the subformation level only 15% of the area was found to be unchanged, and on the community level only 4%. The overall trend is progression with a strong increase in the area of tall scrubs and woodlands. Retrogression also occurs, partly as a result of disturbances such as fire, partly due to local death of a dominant woody species. This latter phenomenon is interpreted against the background of the starting point of the succession; a sudden release of the inner dune area from overgrazing by cattle and a subsequent rapid dune development (outer dunes) on the beach in front of the inner dunes. Both species and community diversity increased, which is related to both differentiation under progression and to retrogression.     

Evidence against primary microclimatic control of the dune-swale floristic gradient on central Australian sandridges

There are distinct and consistent soil and vegetation gradients between the dune-crests and swales of the central Australian sandridges. If there is a corresponding dune-swale microclimatic gradient, it is assumed to be controlled by topography. In general, soil characteristics and topography are closely correlated, but where they diverge, vegetation follows soil rather than topography. Hence if any duneswale microclimatic gradient exists, it is not a significant factor in controlling the dune-swale floristic gradient.     

Bryophytes in Mediterranean coastal dunes: ecological strategies and distribution along the vegetation zonation

The bryophytic flora has been widely studied in Atlantic coastal dune environments while bryological literature addressing the Mediterranean bryophytes is still scarce and fragmented, although they are an important component of this area, especially considering their ability to colonize and stabilize sandy soils. The aims of this study were: (i) to analyze the taxonomy, chorology and ecology of coastal dunes bryoflora; (ii) to analyze distribution patterns of bryophytic species along a coastal dune vegetation zonation. We used as coastal dune model system a particularly well-preserved study area of the Sardinian coast (Italy), which includes several habitats listed in European Habitats Directive 92/43/EEC. We conducted a general survey of the area and a random sampling. A total of 20 bryophytic species were detected most of which were acrocarpous mosses and, to a lesser extent, pleurocarpous and liverworts. Most bryophytes are pioneer colonizers, reflecting their adaptation to environments with high levels of stress/disturbance conditions such as those of coastal dunes. Finally, in this study we described for the first time how bryophytic species are distributed along a Mediterranean coastal dune vegetation zonation, focusing also on their chorological and ecological characteristics and on how they seem to follow the sea-land gradient, probably in response to different environmental conditions developing along this gradient.     

Riverain vegetation in the Nile valley in Upper Egypt

Abstract. Naturaland semi-natural plant communities occurring in the Nile Valley in Upper Egypt are described and their position in the zonation along the river bank interpreted. With the help of ordination and classification methods relationships among the 13 community types and their distribution along the predominating moisture gradient are elucidated. The vegetation of the Nile Valley can be described as a series of discrete plant community types on the basis of their floristic composition, structural components and habitat conditions. The communities can be grouped into four higher units, considered as formations: swamp, meadow, thorn-bush and riverain woodland.     

Floristic composition and analysis of spontaneous vegetation of Sabkha Djendli in north-east Algeria

We conducted a phyto-ecological analysis of the Sebkha Djendli located in the semi-arid lands of the north-eastern Algeria in order to contribute in the understanding of flora composition, diversity and factors controlling plant zonation. Eight plots, distributed on the cardinal and intercardinal points of the site, were sampled. A floristic analysis (species richness, life forms, spatial occurrence, plant cover rate and similarity) and an assessment of the effect of soil salinity and pH on the cover of dominant halophytes were performed. The results of the floristic approach showed the presence of 51 species belonging to 21 families and 45 genera. The most frequent biological types were therophytes (58%) followed by chamaephytes (18%). Vegetation cover rate ranged from 50% to 95%. The distribution of vegetation all around the edges of the Sabkha revealed the dominance of halophytic species belonging to the family Chenopodiaceae. The variation of total halophytic vegetation cover over all sampled plots seems to be affected neither by the distance from waterbody nor by plot orientation nor by the electrical conductivity and pH of soil.     

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.     

Zonation of vegetation on lacustrine coastal dunes: effects of burial by sand

More than 50 years ago it was proposed that zonation of major plant species on coastal dunes was determined by salt spray. Here, we argue against this hypothesis because (i) salt concentrations rarely exceed toxic levels; (ii) high precipitation in temperate latitudes washes the salt off the plants; (iii) major salt spray events occur in late autumn and winter when plants are dormant; and (iv) zonation also occurs on lacustrine dunes. Instead, we show evidence that zonation may be caused by burial because plant distribution was correlated with sand deposition and species were eliminated when burial exceeded their limits of tolerance, thus creating zones of different plant species. We conclude that in temperate regions (i) burial by sand may be among the most important factors in zonation, while salt spray may play a secondary role; and (ii) single environmental factors cannot be the determinants of a phenomenon as complex as species zonation.     

沙地植被碳氮磷化学计量特征与物种多样性的关系

植被化学计量特征表征植物营养限制.它是否会影响物种多样性需要进一步探究.本研究以宁夏哈巴湖国家级自然保护区沙地油蒿群落和沙柳群落为对象,计算了植被碳(C)、氮(N)、磷(P)含量,分析了植被C、N、P生态化学计量特征对沙地植物群落物种多样性的影响.结果表明: 在流动沙丘和半固定沙丘生境中的沙柳群落,物种多样性Simpson指数与植被C/N值存在显著的负相关关系,而与植被N/P值的相关性不显著;在半固定沙丘和固定沙丘生境中的油蒿群落,物种多样性Shannon指数与N/P值存在显著正相关关系,而与C/N值存在显著负相关关系.结合C、N、P生态化学计量特征与冗余分析可知,油蒿群落和沙柳群落的植被P含量对物种多样性的影响不同,导致两个群落的植被N/P值对物种多样性产生不同的影响.     

Classification and gradient analysis of the beech forest vegetation of the southern Rodopi (northeast Greece)

Pure and mixed beech forest vegetation of the southern Rodopi range (northeast Greece) was studied using 614 relevés and multivariate analyses (TWINSPAN and DCA). Classification of the relevés resulted in 12 vegetation units, 8 of which were ranked as associations or communities and the rest as subcommunities and variants. DCA diagrams of relevés and taxa indicated that floristic differentiation was attributed mainly to factors such as altitude (affecting temperature and humidity), soil nutrient content and substrate type (affecting physical and chemical soil properties). Differential taxa of vegetation units were chosen based on their phi coefficient values, which were calculated from three different percentage synoptic tables that corresponded to three ranks (ecological groups, associations and communities, and subcommunities and variants) of floristic differentiation. The calculation of phi coefficient on the basis of relative constancy of taxa helps to overcome the problem of the dependence of fidelity values on the number of relevés per vegetation unit and to facilitate the better investigation of the floristic differentiation even of rare vegetation units represented by a small number of relevés. Furthermore, the calculation of fidelity values for different hierarchical levels enables a more detailed and thorough investigation of the floristic differentiation of the vegetation units.     

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.     

The role of landscape structure in determining palynological and floristic richness

The associations between floristic and palynological richness and landscape structure were studied based on modern pollen?Cvegetation data from a patchy cultural landscape in southern Estonia (northern temperate vegetation zone). Nine study sites (small lakes and their surrounding vegetation) represent land cover gradient from closed forest to semi-open vegetation. Floristic richness (number of species) and floristic richness of pollen types (number of pollen-equivalent taxa) were used to describe the vegetation within the radius of 250?m from the pollen sampling sites. Palynological richness was calculated to describe the modern pollen samples diversity. Landscape structure was estimated on the basis of landscape openness and three landscape diversity measures: richness of community patches, Simpson evenness of community patches and Simpson diversity of community patches. To study the effect of the spatial scale of landscapes on the vegetation?Clandscape and pollen?Clandscape associations, landscape structure was estimated within eight radii (250?C2,000?m) around each lake. The results showed that landscape openness was the most important determinant of both floristic richness and palynological richness in southern Estonia and that landscape diversity estimated by Simpson diversity index was also significantly associated with the richness estimates. Floristic and palynological richness were significantly positively correlated with landscape structure within the radii greater than 1,000?m from the pollen sampling sites, which is similar to the estimated Relevant Source Area of Pollen in southern Estonia. We conclude that within one floristic or climatic region, palynological richness gives reliable estimates about the variation in floristic richness and landscape structure; however, caution must be taken when comparing pollen-inferred vegetation diversities from different regions or when interpreting fossil pollen records from times with highly different vegetation associations.