Ecophysiological adaptations of coastal halophytes from foredunes and salt marshes

Ecophysiological strategies of coastal halophytes from foredunes and salt marshes are discussed. A comparison is made of the factors that limit growth in salt marshes and sand dunes. In salt marshes, zonation and succession are primarily governed by variation in soil salinity, which strongly depends on inundation with seawater. Results are described of experiments which aim at separating salinity and inundation effects on growth, osmotic and mineral relations in a comparison of salt-marsh halophytes. The growth response of plants cannot simply be correlated (and causally explained) with the concentration of Na, Cl, and K in the tissues. Also, the compatible osmotic solutes proline and methylated quaternary ammonium compounds may accumulate both in species with a positive response to increased salinity and in species with a growth reduction under seawater inundation. More likely inadequate adaptation of the plants water potential with these components is partly the cause of retarded growth. Disfunctioning of the plant in this respect may be at three levels: (a) total water potential of the plant, (b) (loss) of turgor pressure potential; (c) regulation at the cellular level. The ecological importance of some factors in seawater other than sodium chloride is considered. In coastal sand dunes airborne rather than soil salinity limits plant growth, together with the effects of abrasion, sand accretion, drought and the poor nutrient status of the dune sand. Adaptations of sand-dune species to these factors may consist of: large seeds with storage tissue germinating in the dark and seedling growth enough to emerge through the accreted sand. Aerial parts must be resistant to mechanical damage (high wind speed and abrasion), possibly by a sclerophyllous and tough structure. Efficient nutrient uptake, translocation and retranslocation seem to help survive sand-dune species in a nutrient-poor rooting medium.     

Vegetation composition of a maritime salt marsh in Qatar in relation to edaphic features

Abstract. Coverpercentage values for plant species were estimated using the line-intercept method along two belt transects starting at the lower mangrove frontier and ending at the upper height of the salt marsh. Twelve perennial species representing five growth forms were recorded with a total cover ranging between 10 and 50 %, depending on the type of substrate. Principal components analysis of the soil data indicated an array of stands, on the basis of which four vegetation zones couldbe distinguished. The procumbent growth form predominating on the salt marsh is related to high salinity levels. The procumbent vegetation shows a zonation related to the degree of waterlogging. The rhizomatous growth form is found on sites with a low bicarbonate content and saturation percentage levels, while the undershrub- and stoloniferous growth forms occupy sites of low salinity level, linked with intermediate values of the other edaphic factors.     

Trajectory analysis of Chinese vegetation types in a multidimensional climatic space

Abstract. The concept of trajectory of a vegetation type is used as a tool to study the position of vegetation types in a multidimensional climatic space. This space was obtained by Principal Component Analysis based on climatic data - based on monthly means. The positions of the main vegetation types distinguished in China were plotted in the climatic space and trajectory lengths and shapes of the types were compared. Three main groups were found, which correspond to: (1) cold and temperate, (2) alpine and mountain, and (3) subtropical and tropical conditions. Within each main category sub-categories were distinguished on the basis of trajectory length and direction. In total, seven trajectory shapes were defined. Based on the correlation between climatic variables and PCA-axes temperature is suggested to be the overriding factor in determining the trajectory shape. But, trajectories can also be affected by the combination of other climatic variables.     

Multi-species pattern analysis of Mediterranean pastures in three stages of ecological succession

Multi-species patterns were analyzed in three stages of ecological succession in oligotrophic pastures in Central Spain using a new method of analysis. The method is based on plotting the species coordinates of principal components analysis undertaken at different block sizes. It allows the detection of any heterogeneity present and reveals both microtopographical and macrotopographical trends in species patterns.Nomenclature follows Tutin et al., 1964–1980, Flora Europaea.     

Investigation of the within- and between-sample colour pattern differentiation in Hydropsyche contubernalis (Trichoptera)

The caddisfly Hydropsyche contubernalis (Trichoptera; Hydropsychidae) occurs in rivers and large streams throughout Europe. The aquatic larvae of this species are highly variable in their head capsule colour patterns. This paper describes the differentiation of such a pattern within and between 13 samples from three different West European river basins. The main aim is to investigate whether differences in colour pattern exist between river basins. Because the head capsule colour patterns of H. contubernalis do not have clear detectable morphs, an image analysis technique is presented to quantify the pattern in the form of mean colour curves expressed as grey levels. These curves are described by mathematical spline functions, and the differences between these functions, which formalize the original data set of colour curves, are analysed by multivariate Between-Group Principal Component Analysis. Our results show that distinct head capsule colour patterns occur in the Loire and Rhône, individuals of the Rhône being darker than individuals of the Loire. However these results also suggest that important differences in such a colour pattern can be detected at smaller scales: along the whole length of the Loire; within a 10km stretch of the Doubs, and also within a single site on the Loire (Amboise). Temporal differences at the same site between different H. contubernalis generations were also recorded. The mechanisms responsible for such differentiation patterns are discussed but still remain unclear. The overall statistical procedure detailed in this paper could potentially be used in numerous other fields of evolutionary biology.     

Microbial Diversity in Soil,Sand Dune and Rock Substrates of the Thar Monsoon Desert,India

A culture-independent diversity assessment of archaea, bacteria and fungi in the Thar Desert in India was made. Six locations in Ajmer, Jaisalmer, Jaipur and Jodhupur included semi-arid soils, arid soils, arid sand dunes, plus arid cryptoendolithic substrates. A real-time quantitative PCR approach revealed that bacteria dominated soils and cryptoendoliths, whilst fungi dominated sand dunes. The archaea formed a minor component of all communities. Comparison of rRNA-defined community structure revealed that substrate and climate rather than location were the most parsimonious predictors. Sequence-based identification of 1240 phylotypes revealed that most taxa were common desert microorganisms. Semi-arid soils were dominated by actinobacteria and alpha proteobacteria, arid soils by chloroflexi and alpha proteobacteria, sand dunes by ascomycete fungi and cryptoendoliths by cyanobacteria. Climatic variables that best explained this distribution were mean annual rainfall and maximum annual temperature. Substrate variables that contributed most to observed diversity patterns were conductivity, soluble salts, Ca²⁺ and pH. This represents an important addition to the inventory of desert microbiota, novel insight into the abiotic drivers of community assembly, and the first report of biodiversity in a monsoon desert system.     

The vegetation of the Puna Belt at laguna de Pozuelos Biosphere Reserve in northwest Argentina

The presence of species and their cover values together with soil and topographic characteristics were recorded at 40 sites along an altitudinal gradient of the Puna Belt at Pozuelos, in the High Andes in northwest Argentina. Classification and ordination of plant assemblages showed that soil and topography were the best predictors of the variation in species distribution. The different plant assemblages which occur along the topographic gradient follow the geographic variation in rainfall in this Andean region. Perennial bushes and grasses colonize the plains and slopes with fine textured soils which retain their water content. In contrast, deciduous bushes and cactuses grow on steep, rocky, dry slopes. Open woods also occur on east-facing steep, rocky slopes which are sheltered from winds.     

种子萌发和幼苗生长对沙丘环境的适应机制

综述了植物沙生适应机制的研究及其进展.一些植物的种子在刚成熟时具有休眠特性.种子需要适度沙埋促进萌发并实现幼苗定居,但过度沙埋则会抑制种子萌发和出苗.在沙层深处,没有萌发的种子会进入休眠状态,形成土壤种子库.幼苗通过增加节数和延长节间来适应沙埋.沙埋深度超过植物的忍耐限度会抑制幼苗生长,甚至导致幼苗死亡.沙生植物必须适应其他环境因子,如盐风与土壤盐分、昆虫采食、土壤养分亏缺等,才能在沙丘上成功生长.沙蚀可导致幼苗根系暴露并干燥脱水.一些沙漠植物的幼苗在萌发后可忍耐一段时期的干燥,水分条件得到满足之后,幼苗能够恢复生长.     

Vegetation analysis of the Mediterranean region of Nile Delta

Thirty-four vegetation clusters identified in the present study, after the application of TWINSPAN and DCA multivariate techniques, were assigned into 8 vegetation types, each of definite vegetation and habitat characters. The suggested vegetation types are well segregated along the DCA axis one which reflects soil moisture, salinity (as indicated by EC values), fertility (as indicated by the organic matter and nitrogen contents) and species diversity gradients. In general, soil moisture and soil fertility increase and species diversity decreases with the following sequence of vegetation types:Echinops spinosissimus-Ononis serrata on inland sand dunes,Pancratium maritimum on coastal sand dunes,Halocnemum strobilaceum-Salsola kali in saline sand deposits,Atriplex halimus-Chenopodium murale along the terraces and slopes of drains,Arthrocnemum glaucum-Tamarix nilotica in salt marshes,Chenopodium murale along the slopes of drains,Phragmites australis along the littoral zones of drains, andLemna gibba-Potamogeton crispus in the water zone. This sequence reflects also a gradient of human interference, starting with the vegetation of the less disturbed habitats (sand dunes and saline sand deposits) and ending with the fully man-made habitats (drain zones).     

Differences between Pinus pinea and Pinus pinaster as bioindicators of polycyclic aromatic hydrocarbons

The potential of Univariate and Multivariate Analysis and specifically Principal Components Analysis (PCA), has been employed to assess the performance of pine needles as bioindicators of polycyclic aromatic hydrocarbons (PAHs) and particularly emphasize the crucial importance of making a distinction between different pine species if more than one is sampled. Four sampling sessions were done in 29 sites and needles of two common pine species (Pinus pinaster Ait. in 19 sites and Pinus pinea L. in 12) were collected and analysed using gas chromatography-mass spectrometry (GC-MS) and PCA. The results obtained indicated significant differences between species, attributed to their different morphology. The mean total PAH concentration of the P. pinaster needles are over two times higher than P. pinea's. This difference is lower when the results are presented in lipid weight, but still statistically significant. Samples from the two sites with adjacent trees reinforce these conclusions, showing significant differences in terms of PAH mean concentration and aromatic ring patterns.     

Cluster analysis of recent benthic foraminifera from the northwestern Mediterranean coast of Egypt

A suite of 74 surface sediment samples, collected from two areas along the Egyptian Mediterranean coast (the Western Harbor of Alexandria and its environs, and the area comprising the Gulf of Kanayis and the Abu Hashafa Bay), have been examined for their benthic foraminiferal faunas. A total of 82 species were identified. Census data were obtained for different species in each sample and the statistically significant fractional abundances values (≥5%) were analyzed using a Q-mode cluster analysis. Samples were segregated into four clusters, each having its peculiar benthic faunal assemblage (biotope), reflecting particular environmental conditions. These clusters are: (1) the Ammonia beccarii forma tepida Biotope, found in samples located in areas with waters of low energy, characterizing semi-closed basin conditions, with muddy or sandy mud bottom sediments (Harbor Proper); (2) the Quinqueloculina spp. Biotope, found in samples collected from depths bathed by turbid inner shelf conditions with some fresh water inflow and sandy bottom sediments (Harbor’s environs); (3) the Peneroplis-Amphistegina Biotope, found in samples collected from depths characterizing marine shelf environments with calcareous algae, and medium to very coarse calcareous sands (the Gulf of Kanayis and the Abu Hashafa Bay); (4) the Triloculina trigonula-Adelosina laevigata Biotope was represented by only one sample (at the far eastern part of the Gulf of Kanayis), collected from a site exhibiting very restricted environmental conditions. The study suggests that nutrients, turbidity, light intensity, type of substrate, and salinity are the main ecological factors controllingthe distribution of benthic foraminifera.     

Vegetation zonation in dune slacks on the Leba Bar,Polish Baltic Sea coast

Vegetation zones in dune slacks on the Leba Bar on the Polish Baltic Sea coast are described. Plant colonization starts on moist sand in eastern ends of slacks, in the wake of receding mobile dunes. Communities on deflation ribs, dominated by psammophytic grasses, sedges and lichens, are structurally simple. Communities in troughs, dominated by species of fresh habitats, become structurally more complex in a western direction and they culminate with the Pinus silvestris forest. The main lines of vegetation variation correlate with groundwa-ter depth, micro topography, soil profile build-up and substrate acidification.     

The impact of grazing on plant communities,plant populations and soil conditions on salt marshes

Grazing an abandoned salt marsh causes retrogressive succession, since mid salt-marsh communities change into lower salt-marsh communities. Grazing and mowing are compared in detail. Both management practices enhance species diversity in an abandoned salt marsh. This can be attributed to the removal of litter. The finding that lower salt-marsh species appear more with grazing than with mowing or abandoning is not related to a higher soil salinity as compared to mowing or abandoning, but probably to locally baring of the soil by grazing animals. Only species of pioneer or unstable environments seem to have a persistent seed bank, for other species seed dispersal seems to be a limiting factor for their establishment.Nomenclature follows Heukels & van Ooststroom (1977) for species; Westhoff & den Held (1969) for syntaxa.Mrs R. Rusthoven analyzed the soil samples, Mr E. Leeuwinga drawed the figures, and Mrs J. O'Brien corrected the English text.     

Relationships Between Hydrology and Soils Describe Vegetation Patterns in Seasonally Flooded Tree Islands of the Southern Everglades, Florida

Tree island ecosystems are important and distinct features of Florida Everglades wetlands. We described the inter-relationships among abiotic factors describing seasonally flooded tree islands and characterized plant–soil relationships in tree islands occurring in a relatively unimpacted area of the Everglades. We used Principal Components Analysis (PCA) to reduce our multi-factor dataset, quantified forest structure and vegetation nutrient dynamics, and related these vegetation parameters to PCA summary variables using linear regression analyses. We found that, of the 21 abiotic parameters used to characterize the ecosystem structure of seasonally flooded tree islands, 13 parameters were significantly correlated with four principal components, and they described 78% of the variance among the study islands. Most variation was described by factors related to soil oxidation and hydrology, exemplifying the sensitivity of tree island structure to hydrologic conditions. PCA summary variables describing tree island structure were related to variability in Chrysobalanus icaco (L.) canopy cover, Ilex cassine (L.) and Salix caroliniana (Michx.) canopy cover, Myrica cerifera (L.) plot frequency, litter turnover, % phosphorus resorption of co-dominant species, and nitrogen nutrient-use efficiency. This study supported findings that vegetation characteristics can be sensitive indicators of variability in tree island ecosystem structure. This study produced valuable, information which was used to recommend ecological targets (i.e. restoration performance measures) for seasonally flooded tree islands in more impacted regions of the Everglades landscape.     

Plant succession and interaction between soil and plants after land reclamation on the west coast of Korea

Plant succession and the interaction between soil and plants after reclamation were investigated on the west coast of Korea. Our study included one natural tidal flat site (Namdong, 3 km²), and five sites that differed in the number of years since being reclaimed: Hyundai A, 6 km² (1 yr); Hyundai B, 5 km² (2 yr); Jangdeog, 5 km² (8 yr); Mado, 2.5 km² (12 yr); and Baegseog, 1 km² (30 yr). The number of plant species occurring at each site was 10, 9, 15, 30, 28, and 38, respectively. Based on distribution ranges of the plants along gradients of salt and moisture contents in the soil, and species associations and life forms, plant succession was divided into two sere groups, hydrarch and xerarch. The major species of the former werePhragmites communis andTypha angustata, but the sequence of the sere could not be identified. Species associated with the latter were [Suaeda japonica] → [Salicornia herbacea, S. japonica, Atriplex subcordata, Suaeda asparagoides] → [Aster tripolium, Carex scabrifolia, Zoysia sinica, Limonium tetragonum] → [Artemisia scoparia, Calamagrostis epigeios, andSetaria viridis] → [Imperata cylindrica var.koenigii, Sonchus brachyotus, S. viridis] → [Aeschynomene indica, Lotus corniculatus var.japonicus, Trifolium repens, and other non-halo-phytes]. In certain circumstances, the first and second stages replacedS. japonica withC. scabrifolia andZ sinica. The progression of interactions between soil and plants through succession was salt leaching → increase in species richness and biomass → increase in soil organic matter → increase in total nitrogen and decrease in bulk density of soil, and/or salt leaching → increase in phytomass → decrease in soil-available phosphorus.     

The validity of burrow counting in estimating the densities of Chiromantes dehaani and Ilyoplax deschampsi in tidal flat at Yangtze Estuary

It has been confirmed that the crabs play significant roles in the structure and function of coastal wetland ecosystems, such as mangroves and salt marshes. However it is not easy to estimate the abundance and density of burrowing crabs effectively, thus a further understanding of roles of crabs in these ecosystems has been lagged. Some studies have discussed the suitability of several census techniques, such as burrow counting method in estimating crab density in mangroves. The validities of burrow counting method and other census techniques in estimating crab density, however, has not been tested in salt marshes, especially where vegetation are dense. In this study, we tested the validity of burrow counting method in estimating the densities of Chiromantes dehaani and Ilyoplax deschampsi in tidal flat with dense vegetation of Phragmites australis and Zizania aquatica at Yangtze Estuary through comparing densities estimated by the burrow counting method and the excavation. Burrow counting averagely underestimated the density of C. dehaani by 15% and the degree of underestimation varied among vegetations and habitats (from an overestimate by 23% to underestimate by 41%). Burrow counting averagely overestimated the density of I. deschampsi by 43% and the degree of overestimate varied from 0% to 133% depending on the vegetations and habitats. The percentage of occupied burrows and the number of crabs sharing one burrow were important factors influencing the validity of estimating crab density through burrow counting method.     

The validity of burrow counting in estimating the densities of Chiromantes dehaani and Ilyoplax deschampsi in tidal flat at Yangtze Estuary

It has been confirmed that the crabs play significant roles in the structure and function of coastal wetland ecosystems, such as mangroves and salt marshes. However it is not easy to estimate the abundance and density of burrowing crabs effectively, thus a further understanding of roles of crabs in these ecosystems has been lagged. Some studies have discussed the suitability of several census techniques, such as burrow counting method in estimating crab density in mangroves. The validities of burrow counting method and other census techniques in estimating crab density, however, has not been tested in salt marshes, especially where vegetation are dense. In this study, we tested the validity of burrow counting method in estimating the densities of Chiromantes dehaani and Ilyoplax deschampsi in tidal flat with dense vegetation of Phragmites australis and Zizania aquatica at Yangtze Estuary through comparing densities estimated by the burrow counting method and the excavation. Burrow counting averagely underestimated the density of C. dehaani by 15% and the degree of underestimation varied among vegetations and habitats (from an overestimate by 23% to underestimate by 41%). Burrow counting averagely overestimated the density of I. deschampsi by 43% and the degree of overestimate varied from 0% to 133% depending on the vegetations and habitats. The percentage of occupied burrows and the number of crabs sharing one burrow were important factors influencing the validity of estimating crab density through burrow counting method.     

Directionality,convergence, and rate of change during early succession in the Inland Pampa,Argentina

Abstract. We tested the following hypotheses forthe first five years of a grassland succession: (a) community changes are mainly directional and related to time after disturbance ratherthanto environmental fluctuations; (b) rates of succession decrease over time, and (c) plant communities in different plots converge on a similar composition within five years of succession. We tested those hypotheses using a Principal Components Analysis applied to data from four successional plots established in successive y ears in a large cropland in the Inland Pampa, Argentina. Community changes were correlated to the age of the plots, and unrelated to rainfall variability, a major environmental variable in grasslands. Successional rates were constant over the five years, probably because of the continued dominance of different annuals; we conclude that successional rates depend on the life history of the dominant species rather than on any emergent community property. We found no evidence of convergence ordivergence; we concluded that the results of successional studies may depend on the temporal and spatial scale of observation.     

Distribution and Contamination Status of Trace Metals in the Mediterranean Coastal Sediments,Egypt

Trace metals concentrations in sediments from the Egyptian Mediterranean coast were determined to evaluate the levels of contamination. The highest concentrations of metals were generally found in the middle region of the coast. Sediment pollution assessment was carried out using Enrichment Factor (EF), Geoaccumulation Factor (Igeo), Contamination Factor (CF), Modified Degree of Contamination (mCd), and Pollution Load Index (PLI). Association of adverse effects to aquatic life was determined using the classification of sediments according to three sets of sediment quality guidelines. The mean EF values were found to fall in the following sequence: Cr > Pb > Ni > Zn > Cu > Mn. The results demonstrated that the EF of metals in the sediments of the middle region was lower than those recorded in the western region and Rafah Station at the eastern region; the difference in the EF levels was significantly correlated with Fe concentrations along the study area. Based on the average Igeo of target elements, the Egyptian Mediterranean coast could be considered not polluted with Cr, Cu, Mn, Ni, Pb, and Zn (Igeo ≤ 0). The modified degree of contamination was >1.5, indicating zero to very low contamination. The calculated PLI were less than 1, indicating only baseline levels of pollution. There were small differences between the results obtained with the three used SQGs. Highly significant correlations were found between the concentrations of Fe, Mn, Co, Cr, and Ni, suggesting similar sources and/or similar geochemical processes controlling the occurrence of these metals in the sediments.     

Lizard herbivory in a sand dune environment: the diet of Angolosaurus skoogi

Summary Early observations of the feeding habits of Angolosaurus skoogi (Andersson), a 50–120 g lizard inhabiting the almost vegetationless dunes of the northern Namib Desert, indicated that this species was herbivorous. Less than two percent of living lizard species are predominantly herbivorous and these species tend to have a high body mass (>100 g). We therefore analysed fecal pellets of A. skoogi to obtain dietary details of this relatively rare lizard. Eighteen food taxa were identified: 81 percent by mass was composed of vegetable matter, of which 56 percent was an endemic, perennial cucurbit Acanthosicyos horrida. Both spatial and temporal variation in dietary composition were apparent. Ready access to water in the form of A. horrida is postulated to have allowed Angolosaurus to occupy this extreme habitat and to forage on components of the windblown detritus, a food source that would probably not be usable in other circumstances.