Germination response to temperature,salinity, light and depth of sowing of ten tropical dune species

This study describes the germination responses of ten tropical dune species to several factors to which their seeds are exposed in the field. Species studied were: three sand dune endemics (Amaranthus greggii, Palafoxia lindenii, and Trachypogon gouini), three pantropical coastal species (Sesuvium portulacastrum, Sporobolus virginicus and Ipomoea stolonifera) and four cosmopolitan grasses also found inland (Panicum repens, Panicum maximum, Pappophorum vaginatum and Andropogon glomeratus). Six species germinated when exposed to different constant temperatures. Four required temperature fluctuation (S. portulacastrum, P. lindenii, S. virginicus, P. repens). Light promoted germination of three species (S. Portulacastrum, P. vaginatum, P. lindenii). Species varied in their degree of sensitivity to salinity. Seeds of T. gouini, I. stolonifera, S. portulacastrum, P. repens, P. Maximum and P. vaginatum were able to germinate under some of the salinity concentrations. Not all species were able to recover after being transferred to distilled water. Seedling emergence was inhibited when seeds were buried. This response was related to depth and to seed size. S. portulacastrum and S. virginicus were the most affected. Nitrates only affected germination response of two species. Seed age promoted germination under a wider range of conditions. P. lindenii showed very heterogeneous responses depending on seed cohort. No dormancy mechanisms were found, other than a thermoperiod and/or light requirement for some of the species. Cosmopolitan grasses tolerated both sand burial and salinity, although the endemics were the most successful in emerging from sand burial; coastal pantropicals were very tolerant to high saline concentrations and recovered completely.     

Landscape-level seagrass–sediment relations in a coastal lagoon

We investigated the relationships between sediment (subaqueous soil) properties and eelgrass (Zostera marina L.) distribution to develop landscape-level soil-based strategies for choosing eelgrass restoration locations. Subaqueous soils were sampled and eelgrass cover determined for 14 soil-landscape units within a 116 ha area of Ninigret Pond, a coastal lagoon in Rhode Island, USA. Of the 14 soil-landscape units sampled for eelgrass cover, 52% had virtually no eelgrass cover (<10%), while 18% had high eelgrass cover (>90%). The Lagoon Bottom, Shallow Lagoon Bottom, Flood-tidal Delta Slope, and Barrier Cove subaqueous soil-landscape units had the highest eelgrass cover (66–100%). A weak relationship between eelgrass cover and water depths (r² = 0.10) was observed suggesting that properties other than water depth may also control eelgrass distribution. Subaqueous soils on landscapes with >60% eelgrass cover had relatively high levels of acid-volatile sulfides (>90 μg/g), high soil salinity levels (34–44 ppt), fine textures (silt loam), and relatively high total nitrogen levels (>0.15%). Four principal components accounted for 81% of the variability in eelgrass cover. The first component reflected particle-size distribution (i.e. sand, silt, and clay contents) effects and accounted for 43% of the variability. The other components suggested that eelgrass cover is correlated to carbonaceous remains, non-calcareous rock fragments and soil salinity. These data suggest that the current distribution of eelgrass within the study area is strongly influenced by physical and chemical subaqueous soil characteristics. Soil survey techniques proved useful for the delineation of sediment characteristics (e.g. texture, salinity) that influence eelgrass distribution patterns at landscape-level scales.     

Carbonate facies evolution from the late albian to Middle Cenomanian in Southern Istria (Croatia): influence of synsedimentary tectonics and extensive organic carbonate production

Summary During the Late Albian, Early and Middle Cenomanian in the NW part of the Adriatic Carbonate Platform (presentday Istria) specific depositional systems characterised by frequent lateral and vertical facies variations were established within a formerly homogeneous area, ranging from peritidal and barrier bars to the offshore-transition zone. In southern Istria this period is represented by the following succession: thin-bedded peritidal peloidal and stromatolitic limestones (Upper Albian); well-bedded foreshore to shoreface packstones/grainstones with synsedimentary dliding and slumping (Vraconian-lowermost Cenomanian); shoreface to off-shore storm-generated limestones (Lower Cenomanian); massive off-shore to shoreface carbonate sand bodies (Lower Cenomanian); prograding rudist bioclastic subaqueous dunes (Lower to Middle Cenomanian); rudist biostromes (Lower to Middle Cenomanian), and high-energy rudist and ostreid coquina beds within skeletal wackestones/packstones (Middle Cenomanian). Rapid changes of depositional systems near the Albian/Cenomanian transition in Istria are mainly the result of synsedimentary tectonics and the establishment of extensive rudist colonies producing enormous quantities of bioclastic material rather than the influence of eustatic changes. Tectonism is evidenced by the occurrence of sliding scars, slumps, small-scale synsedimentary faults and conspicuous bathymetric changes in formerly corresponding environments. Consequently, during the Early Cenomanian in the region of southern Istria, a deepening of the sedimentary environments occurred towards the SE, resulting in the establishment of a carbonate ramp system. Deeper parts of the ramp were below fair-weather wave base (FWWB), while the shallower parts were characterised by high-energy environments with extensive rudist colonies, and high organic production leading to the progradation of bioclastic subaqueous dunes. This resulted in numerous shallowing- and coarsening-upwards clinostratified sequences completely infilling formerly deeper environments, and the final re-establishment of the shallow-water environments over the entire area during the Middle Cenomanian.     

Données synchorologiques sur la végétation littorale européenne

Four aspects of the synchorology of plant communites along the European coastline are treated: (1) with examples from sand dunes (Agropyreta and Ammophileta) and salt marshes (Puccinellieta maritimae) synvicariance is elucidated; (2) The increase in synvicariance towards the inner sand dunes is discussed as a result of an increasing effect of autochthonous climatic features; (3) with examples from sand dunes and cliffs the concept of synendemism is elucidated; (4) synvicariance at the landscape (geosigmetum) is discussed with examples from the French coastline.

     

Myrmecochory in Polygala vulgaris L., Luzula campestris (L.) DC. and Viola curtisii Forster in a Dutch dune area

Summary Seed dispersal by ants in Polygala vulgaris, Luzula campestris and Viola curtisii was studied in a primary dune valley on the island of Terschelling, The Netherlands. Normally developed seeds of all three species are taken by the ants into their nests. The ants show a distinct preference for the seeds of the specialized myrmecochore Polygala vulgaris, as compared with the two diplochorous species. It could be demonstrated that the elaiosome is the attractive part of the seed. Mapping studies demonstrate that the dispersal of the seeds by ants has a marked effect on the distribution pattern of the standing population of Polygala and Viola. Adult plants are often found on or close to the active nest mounds of all ant species present, while the growing sites of juvenile individuals and seedlings are practically restricted to the nest environment. The nests of two of the seed-dispersing ant species, viz., those of Lasius niger and Tetramorium caespitum, show differences in soil chemistry with the surroundings. The ant nests are significantly richer in some essential plant macronutrients, such as phosphate, potassium and nitrate. The advantage of myrmecochory in the dune area of Terschelling is discussed.     

Seed mass of Indiana Dune genera and families: Taxonomic and ecological correlates

Summary Several surveys have documented an association among species between habitat type and seed mass, suggesting that habitat attributes impose a direct selective force on seed mass. Previous comparative surveys, however, have not controlled for the statistical effects of shared phylogenetic history (at the genus or family level) and life form when evaluating the relationship between habitat and seed mass. This study of the Indiana Dunes angiosperm flora provides statistical control of genus and family membership by: (i) partitioning out the statistical effect of genus membership prior to measuring the effect of habitat on seed mass, and (ii) seeking an association between habitat and seed mass within eight genera (206 species) and ten families (366 species). To measure the associations between ecological factors, taxonomic membership and seed mass, I examined life form, phenological schedules and seed mass among species in 8 genera distributed among 13 habitat types (assigned to 1 of 4 categories of inferred water and light availability). One-way ANOVAS indicated that genus, life form, habitat, water/light category, the onset of flowering and the duration of flowering accounted for 71%, 51%, 10%, 4%, 14% and 14% of the variance in seed mass, respectively. However, multi-factor ANOVAS measured the variance in seed mass accounted for by each variable independently of the others: only genus explained a significant proportion (11%). Genus membership is strongly associated with the other ecological factors, accounting for the difference between one-way and multi-factor ANOVAS. Within the ecologically widespread genera and families of this study, there was no significant association between water/light category and seed mass, even though this association can be detected across taxa. Among congeners and confamilials, interspecific variation in seed mass (measured as the coefficient of variation) was as high within habitat types as among them, suggesting that habitats do not provide upper limits to the range of seed mass exhibited by the species within them. A previous study of 648 Indiana Dune species showed that species segregate among habitats on the basis of seed size; large-seeded species tend to occupy closed habitats and small-seeded species tend to inhabit open habitats. This segregation creates the ecologically meaningful observation that low-light habitats support larger-seeded species than high-light habitats, even though this pattern cannot be detected independently of taxonomic membership. Generalist taxa may occupy a wide range of habitats for reasons other than their seed size. If this is a common feature of ecological generalists, it may not be possible to detect an association between habitat and seed size independently of taxonomic membership.     

Mayflies,stoneflies, and caddisflies of streams and marshes of Indiana Dunes National Lakeshore,USA

United States National Parks have protected natural communities for one hundred years. Indiana Dunes National Lakeshore (INDU) is a park unit along the southern boundary of Lake Michigan in Indiana, USA. An inventory of 19 sites, consisting of a seep, 12 streams, four marshes, a bog, and a fen were examined for mayflies (Ephemeroptera), stoneflies (Plecoptera), and caddisflies (Trichoptera) (EPT taxa). Volunteers and authors collect 35 ultraviolet light traps during summer 2013 and supplementary benthic and adult sampling added species not attracted by lights or that were only present in colder months. Seventy-eight EPT species were recovered: 12 mayflies, two stoneflies, and 64 caddisflies. The EPT richness found at INDU was a low proportion of the number of species known from Indiana: caddisflies contributed only 32.7% of known state fauna, mayflies and stoneflies contributed 8.4% and 2.3%, respectively. Site EPT richness ranged from one for a seep to 34 for an 8 m-wide stream. Richness in streams generally increased with stream size. Seven new state records and rare species are reported. The number of EPT species at INDU is slightly larger than that found at Isle Royale National Park in 2013, and the community composition and evenness between orders were different.     

Development of vegetation in dune slack wetlands of Cape Cod National Seashore (Massachusetts,USA)

Interdunal seasonal wetlands, known as dune slack wetlands, were mapped and their vegetation surveyed across a large region of dunes within the Cape Cod National Seashore. Wetland sizes and ages were estimated from digitized, georeferenced aerial photographs available from 1938, 1947, 1960, 1986, 1994, and 2001, and from LIDAR elevation data. A total of 346 sites were found, covering an area of ∼45.4 ha., in which 97 species of vascular plants were identified. Vegetation structure and composition exhibited a distinct sequence of development with age, following a pattern of succession from herbaceous, graminoid-dominated communities to shrub- and tree-dominated communities. Floristic variables were not related to proximity to the coast and although wetland size appeared to have some bearing on species richness, the correlation was statistically weak. Soil organic matter determined for a subset of 60 wetlands was positively correlated with age and woody cover but showed no relationship with water depth. The results suggest that vegetation development is primarily driven by the internal mechanisms of succession. Notwithstanding, any changes in the environment that alter the process of succession will collectively influence these wetlands. In addition, stabilization of the dunes resulting in a reduction in the formation of new wetlands, may translate into permanent loss of early and mid-successional dune slack communities. Maintenance of these communities will depend on succession being periodically reset by disturbance or active management.