Diversity of arbuscular mycorrhizal fungi along a sand dune stabilization gradient: A case study at Praia da Joaquina, Ilha de Santa Catarina, South Brazil

Species diversity of arbuscular mycorrhizal fungi (AMF) was assessed along a dune stabilization gradient (embryonic dune, foredune and fixed dune) at Praia da Joaquina, Ilha de Santa Catarina. The dunes were chosen as a case study to assess whether diversity and mycorrhizal inoculum potential (MIP) increase along the gradient. Ten soil samples were collected from each stage and pooled, and then six 100-g soil sub-samples were taken to identify and enumerate spores. Twelve AMF species were detected, and all three families in Glomales were represented. Gigasporaceae species dominated the embryonic dune, while Glomaceae species dominated the fixed dune. Total spore numbers and richness increased as the dunes became more stabilized. However, indices of Margalef, Simpson and Shannon reached maximal values at different stages, suggesting that species abundance was different among stages. In both embryonic and fixed dunes, species abundance data fit the broken stick model, while in the foredune the log series model best described the data. The MIP followed spore numbers and increased along the gradient, suggesting that spores are important in initiating root colonization in this system. Relationships between edaphic factors and functional roles of Glomales families as determinants of AMF distribution are discussed. This document was subjected to peer and administrative reviews of the U.S. EPA at the National Health and Environmental Effects Research Laboratory, Western Ecology Division, and was approved for publication. Mention of trade names or commercial products in this paper does not constitute endorsement or recommendation of use.     

Neosparton darwinii (Verbenaceae), a restricted endemic species. Is it also endangered?

Neosparton darwinii Benth. & Hook. is a ramose, almost leafless shrub, whose growth is restricted to an area on the southwestern coast of Buenos Aires province (Argentina). Its limited distribution could imply risks for its survival. In the present study, we evaluated population characteristics relevant to an assessment of its conservation status and made a preliminary characterization of its habitat. Historical data seem to indicate that the species has undergone a severe reduction in its geographic distribution. We estimated the actual population size to be around 44,000 plants, distributed in a clumped pattern. We found no significant differences between the environments immediately associated with the plants and other similar distant sites, in terms of position on the dune profile, percentage of bare soil and the richness and composition of accompanying plant species. A high proportion of the seeds produced each year is destroyed by parasite bruchid beetles. We have not seen seedlings of N.darwinii in the area. All the laboratory germination essays done to date have produced negative results. The species grows in an area intensively used by tourists. We can foresee quantitative and qualitative reductions in habitat availability. This information points out that N.darwinii is not just a rare species, but its survival is a matter for serious consideration. We suggest certain steps towards effective management to ensure its conservation.     

Does seed dispersal limit initiation of primary succession in desert playas?

To investigate the initiation of primary succession in a cold-desert playa-dune complex, we studied the large-scale (2000 m) seed (diaspore) dispersal patterns at Mono Lake, California. Seeds of seven of the ten species reaching the barren playa had wind-dispersal adaptations. Rates of dispersal (numbers of seeds per square metre per day) were as much as three orders of magnitude lower on the playa than in the diverse dune vegetation. However, seed input appeared sufficient to reach potential safe sites on the playa, with a peak input of 66 ± 8 total seeds·m·d. The smooth playa surface, the virtual absence of aboveground barriers, and the high windspeed environment promote the long-distance dispersal of seeds (at least 1300 m for Chrysothamnus spp. and at least 700 m for Sarcobatus vermiculatus). The large spatial scale of sampling revealed a relatively high seed input onto the playa by the dominant pioneer species S. vermiculatus, despite the low abundance of parent vegetation in this region. All of these results implicate low rates of seed entrapment as an obstacle to establishment on this desert playa, rather than a lack of seed input.     

Different ecological strategies during the seed germination phase of nine grasses inhabiting the hyper‐arid Arabian desert

The effect of photoperiod, thermoperiod and their interaction on seed germination and its rate was studied for nine grasses growing in the Arabian desert. Germination tests were conducted under two photoperiods and three thermoperiods. Germination of light‐incubated seeds of Hyparrhenia hirta, Pennisetum divisum, Stipacapensis, Centropodia forsskaolii, Stipagrostis plumosa, Cymbopogon parkeri and Panicum turgidum was significantly higher than that detected in the darkness. Photoperiod did not influence the seed germination of Aristida adscensionis and Imperata cylindrica. Seeds of all species, except P. divisum, C. parkeri and I. cylindrica, germinated indepen dently of the tested temperature. Our results indicate that species belonging to the same family and growing in the same hyper‐arid desert habitat may influence and act in different ways during the seed germination phase, causing species‐specific effects, and therefore might affect the ecology of each taxon in this harsh environment.     

Density and environmental effects on shell size in some sand dune snail populations

Populations ol three species of land snail, Helicella itala. Candidula intersecta and Cochlicella acuta are studied on sand dunes on Coll in the Inner Hebrides.
Population density and mean shell size were estimated on 18 sample sites. The sites were ranked for six environmental factors. Environmental factors which are related to the dune vegetational succession account for much of the variation in the densities of C. intersecta and C. acuta . The density of H. itala , however, shows no strong association with these factors. Both snail density and shell size are reactively independent of total soil calcium levels. For each of the three species, mean shell size is negatively associated with population density; the environmental factors account for little of the variation in shell size.
Four possible mechanisms are suggested to account for the variation of shell size with density. It is argued that a direct influence of density on shell size, possibly mediated by mucus conditioning of the environment is the most probable mechanism. There is some evidence to suggest an inter-specific effect whereby C. intersecta density affects H. itala shell size.     

The Lepidoptera of White Sands National Monument, Otero County, New Mexico, USA 4. A new species of Schinia Hübner, 1818 (Lepidoptera, Noctuidae, Heliothinae)

In 2006 the U.S. National Park Service initiated a long term study of the Lepidoptera at White Sands National Monument, Otero County, New Mexico. Schinia pogueisp. n., described here, was discovered in 2007, the second year of the study. The male and female adult moths and genitalia are illustrated.     

Biotic soil factors affecting the growth and development of Ammophila arenaria

Summary To study the origin of replant disease of Ammophila arenaria (L.) Link the growth and development in sand originating from the rhizosphere of a natural Ammophila vegetation was compared with the growth in sand from the sea-floor. In a greenhouse experiment, the growth of Ammophila seedlings in rhizosphere sand, when compared with that in sea sand, was significantly reduced. As sterilization by means of gamma-irradiation increased the biomass production of Ammophila seedlings significantly, it was concluded that the rhizosphere sand contained biotic factors that were harmful to Ammophila. In rhizosphere sand the roots of Ammophila were brown and poorly developed, and the specific uptake rates of N, P and K were reduced. The shoot weight proportion of the total plant dry matter was hardly influenced. In an outdoor experiment with Ammophila seedlings and cuttings, using both sands, the mortality was high and the plants were feeble in rhizosphere sand whereas plants in sea sand grew vigorously. It seems plausible that the plants in rhizophere sand were dessicated because the root system was shallow and badly developed. In the greenhouse experiments, Ammophila cuttings were less sensitive to the inhibiting factors in the rhizosphere than seedlings. This was confirmed in the outdoor experiment. Calammophila baltica (Fluegge ex Schrader) Brand, however, was hardly affected by the harmful biotic factors in the greenhouse. These results are discussed with reference to the ecology of Ammophila. It is assumed that the catching of fresh windblown sand provides Ammophila with a way to escape from harmful biotic soil factors, and it was concluded that degeneration of Ammophila is caused mainly by self-intolerance due to these biotic soil factors.