Animals on marine flowers: does the presence of flowering shoots affect mobile epifaunal assemblage in an eelgrass meadow?

Eelgrass, Zostera marina, produces two types of shoots: morphologically simple vegetative shoots and highly branched flowering (reproductive) shoots, the latter found only in summer months. We examined whether the abundance and diversity of mobile epifaunal assemblage are affected by the presence of flowering shoots in an eelgrass meadow of Otsuchi Bay, northeastern Japan. Comparisons of epifauna in natural vegetation revealed that density and species richness did not differ significantly between sites consisting of both flowering and vegetative shoots, and those only of vegetative shoots. A transplant experiment, conducted to examine the colonization rates of epifauna to defaunated eelgrass planted with different combination of vegetative and flowering shoots, showed no obvious variation in abundance and species richness. At species level, the density of some species such as a tanaid Zeuxo sp. and a polychaete Platynereis sp. was higher at sites and/or treatments with flowering shoots, whereas that of some gastropods, such as Lirularia iridescens and Siphonacmea oblongata was higher at sites without flowering shoots. The species-specific response led to dissimilarity of epifaunal assemblage between sites and among treatments with different densities of vegetative and flowering shoots. Similar patterns observed for natural vegetation and the transplant experiment suggest that the variation in assemblage structure is caused by habitat selection of each species, for example, the utilization of flowering shoots as feeding ground and nursery by Zeuxo sp.     

Ruffed grouse brood habitat on reclaimed surface mines in West Virginia

Human-imprinted ruffed grouse (Bonasa umbellus) chicks were used to evaluate grouse brood food and cover conditions on reclaimed surface mines in northern West Virginia. Reclaimed surface-mined areas did not provide the quality of habitat for ruffed grouse chicks that unmined land provided. On the surface-mined areas, grasslegume reclamation provided the poorest cover and next to the lowest feeding rates. Of the surface-mined areas a 25-year-old reclaimed mine planted to autumn olive had canopy provided a more favorable micro-climate for insects and herbaceous vegetation was established around the edge. Planting rows of shrubs in addition to the current practice of planting grasses and legumes on surface-mined areas is suggested to create ruffed grouse brood habitat.     

Innovation in wildland shrub establishment

Fluid drilling has the potential to improve establishment of direct seeded shrubs. This paper briefly reviews some fluid drilling equipment and reports two studies addressing the problems of shrub fluid drilling. Study one demonstrates the potential for fluid drilling in establishing shrubs which require cold-moist treatment to break dormancy. This study also provides evidence of water soluable substances which inhibit the dormancy breaking process in some species. The existence of these inhibitors is postulated. The second study found that land imprinting significantly improved seedling establishment of fluid drilled surface germinating seeds such as those ofEurotia. Fluid drilling is a means to increase our control and manipulation of the seed and its environment, while retaining the capability for extensive low cost dispersal.     

Screening bamboo species for salt tolerance using growth parameters,physiological response and osmolytes accumulation as effective indicators

Bamboos are potential species for reclamation of saline soils and water. In this study, the performances of three bamboo species, namely Dendrocalamus strictus (S1), Dendrocalamus longispathus (S2) and Bambusa bambos (S3), were investigated for salinity stress tolerance. After 14 days of treatment with 100?mM NaCl, reduction in shoot length was 66%, 100%, 77%, root length was 77%, 100%, 57%, number of leaves was 50%, 100%, 73% and fresh weight was 30%, 72%, 14% in S1, S2 and S3 species, respectively. Relative water content (RWC) in S1 and S3 species was 1.26 and 1.07 folds higher in 50?mM NaCl in comparison to control. In S2 species, total chlorophyll, chlorophyll_a and chlorophyll_b degradation were the highest (40.4%, 42.7%, 16.32%, respectively) in comparison to S3 (18.18%, 23%, 16.4%) and S1 (23.5%, 25%, 19.17%) species. In S3 and S1 species, the Chl_a/Chl_b ratio was maintained showing stabilisation of the net photosynthetic rate. Proline played a more important role than glycine betaine for salt tolerance of these bamboo species. On account of vegetative growth, proline accumulation and RWC, it is inferred that S1 and S3 species are salt tolerant while S2 is a sensitive species.

Abbreviations: SL: shoot length; RL: root length; NL: number of leaves; FW: fresh weight; RWC: relative water content; Chl_a: chlorophyll_a; Chl_b: chlorophyll_b; TC: total chlorophyll; GB: glycine betaine     

Concentrations of arsenic and heavy metals in vegetation at two abandoned mine tailings in South Korea

Untreated abandoned mines may result in hazards to ecosystems due to dispersion of various toxic elements such as arsenic (As) and lead (Pb). Phytoremediation is an alternative of remediation for large scale mine dumps. Plant species were sampled from two abandoned gold (Au) mines in South Korea. Plant samples were digested following the guidelines of US EPA Method 3050 (US-EPA, 1996) and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Concentrations and bioaccumulation factors of plants are reported and out-performing species are summarized. Poplar trees (Populus davidiana) growing on the Myoungbong tailings were suggested to be a potential species for revegetation of large scale Au mine tailings. Arsenic accumulations of bracken ferns (Pteridium aquilinum) sampled from the Duckum tailings were far lower than those of the reported hyperaccumulators, but the possible chronic adverse effects on residents through daily diet are of concern.     

Species-specific defense strategies of vegetative versus reproductive blades of the Pacific kelps <Emphasis Type="Italic">Lessonia nigrescens</Emphasis> and <Emphasis Type="Italic">Macrocystis integrifolia</Emphasis>

Chemical defense is assumed to be costly and therefore algae should allocate defense investments in a way to reduce costs and optimize their overall fitness. Thus, lifetime expectation of particular tissues and their contribution to the fitness of the alga may affect defense allocation. Two brown algae common to the SE Pacific coasts, Lessonia nigrescens Bory and Macrocystis integrifolia Bory, feature important ontogenetic differences in the development of reproductive structures; in L. nigrescens blade tissues pass from a vegetative stage to a reproductive stage, while in M. integrifolia reproductive and vegetative functions are spatially separated on different blades. We hypothesized that vegetative blades of L. nigrescens with important future functions are more (or equally) defended than reproductive blades, whereas in M. integrifolia defense should be mainly allocated to reproductive blades (sporophylls), which are considered to make a higher contribution to fitness. Herein, within-plant variation in susceptibility of reproductive and vegetative tissues to herbivory and in allocation of phlorotannins (phenolics) and N-compounds was compared. The results show that phlorotannin and N-concentrations were higher in reproductive blade tissues for both investigated algae. However, preferences by amphipod grazers (Parhyalella penai) for either tissue type differed between the two algal species. Fresh reproductive tissue of L. nigrescens was more consumed than vegetative tissue, while the reverse was found in M. integrifolia, thus confirming the original hypothesis. This suggests that future fitness function might indeed be a useful predictor of anti-herbivore defense in large, perennial kelps. Results from feeding assays with artificial pellets that were made with air-dried material and extract-treated Ulva powder indicated that defenses in live algae are probably not based on chemicals that can be extracted or remain intact after air-drying and grinding up algal tissues. Instead, anti-herbivore defense against amphipod mesograzers seems to depend on structural traits of living algae.     

Indirect Effects of Biological Control on Plant Diversity Vary across Sites in Montana Grasslands

Abstract:  Biological control with specialist, nonindigenous, herbivorous insects is an important option for controlling invasive exotic plants in wildlands and nature reserves. It is assumed that biological control agents will reduce the dominance of the target weed, thereby increasing the native diversity of the associated plant community. However, this hypothesis has rarely been tested. We introduced Aphthona nigriscutis into grassland sites infested with the invasive exotic species Euphorbia esula L. on a nature reserve in Montana (U.S.A.). Two sites with better soil had been treated previously with herbicide, whereas two other sites had not. We measured the density and biomass of Euphorbia vegetative and flowering stems and number of native and exotic shrubs, grass-like plants, and forbs in 48 microplots in Aphthona release and control macroplots at each site. After 5 years, Aphthona release was associated with a 33–39% decline in Euphorbia aboveground biomass compared with controls at all sites. Other effects of the biocontrol depended on the site. Biocontrol slowed the recovery of species diversity at the sites previously treated with herbicide but slowed the loss of diversity at sites without a history of herbicide. Biocontrol introduction was not associated with a disproportionate increase in nontarget exotic species. Release of Aphthona caused a decline in the biomass of flowering stems relative to controls at good-soil, previous-herbicide sites but was associated with a relative increase in flower stem mass at poor-soil, no-herbicide sites. Our results suggest that biocontrol reductions in weed dominance will not always be associated with increased species diversity. More emphasis should be placed on conserving desirable communities and less on simple weed control. Monitoring of community-level effects should accompany biocontrol introductions on nature reserves.     

Dynamics of parrotfish grazing scars

Parrotfishes exhibit a range of feeding modes. These species vary in both feeding morphology and behaviour, but the vast majority of species leave distinctive scars on the substratum when feeding. Although the role of parrotfishes in reef resilience is well documented, the basis of this role and the effect of their grazing scars on the benthic community structure remain unclear. This study evaluated the dynamics of grazing scars of large adult Scarus rivulatus and Chlorurus microrhinos on an inshore reef in the Great Barrier Reef (GBR). These species represent the most abundant scraping and excavating parrotfish species on inshore reefs. Grazing scars of each species were marked, measured and observed for seven consecutive days. S. rivulatus grazing scars were smaller in area and volume and more rapidly reoccupied by algae than those of C. microrhinos. However, because of the higher abundance and feeding frequency of S. rivulatus at the study site, this species had higher algal removal rates than C. microrhinos. These species appear to play distinctly different functional roles in shaping the benthic community of inshore GBRs. S. rivulatus is primarily responsible for algal dynamics dominated by vegetative regrowth. In contrast, C. microrhinos opens relatively large areas which remain clear for several days. These scars may represent settlement sites which are relatively free from algae and sediment. This study provides new information on the differences between scraping and excavating parrotfishes and, in a system with just one abundant large excavating species, emphasizes the potential for low functional redundancy in high diversity coral reef systems.     

Interspecific acoustic interactions of the neotropical treefrog Hyla ebraccata

Summary Hyla ebraccata, H. microcephala and H. phlebodes commonly occur together in Panama. The three species have calls exhibiting broad frequency overlap and call during the same season and time of day from similar microhabitats, frequently in close proximity. The vocal repertoires of the three species are structurally and functionally similar. All employ multi-part advertisement and aggressive calls which consist of a primary note followed by a variable number of clicks. H. ebraccata males often responded to heterospecific calls with multi-note synchronized responses, and calls with primary notes greater than 150–200 ms were most effective in eliciting synchrony. Playback experiments with synthetic 1-note advertisement calls of different durations and both synthetic 1-note advertisement calls and 200 ms tones of different frequencies demonstrated that H. ebraccata males will synchronize with stimuli which are similar in frequency and duration to conspecific calls. Data from a two-choice experiment with female H. ebraccata demonstrate that calls of individual H. microcephala can reduce the attractiveness of a H. ebraccata male's calls if primary notes overlap. By synchronizing response calls to those of H. microcephala, a H. ebraccata may reduce the chances that his calls are rendered less attractive to potential mates.Aggressive calls of these species are graded and are characterized by higher pulse repetition rates and often longer durations than advertisement calls. H. ebraccata males respond to aggressive calls of H. microcephala and H. phlebodes as they do to their own calls. Heterospecific aggressive interactions probably occur because the species interfere acoustically. Our results demonstrate that H. ebraccata males behave in ways which enhance their ability to communicate in a noisy assemblage of conspecific and heterospecific males.     

Simulation of the cyclical process of heathlands: induction of mosaic structures, evolution to irreversible states

A simulation (random process with a discrete control of time) of cyclical regeneration of the monospecific heathlands established on the volcanic Chaîne des Puys (Massif Central, France) after the general and sudden surrender of grazing in the middle of this century, is proposed. On the high sloping zones on the south and south-west, spontaneous regressive dynamics of the heathlands appears, causing intense erosion. In other cases, some mosaic structure (Calluna vulgaris-Brachypodium pinnatum) cover the volcanoes. This highly simplified model takes into account the following processes: (i) the senescence process and vegetative reproduction of Calluna, (ii) the reproduction and intraspecific competition of Pinus sylvestris, (iii) erosion. The main results demonstrate that such a system exhibits an oscillatory behaviour. This phenomenon is strongly dependent on the initial parameters of the Calluna populations and may or may not reach an interior equilibrium: a stationary phase. An activity state function, taking into account the average transformation rapidity and modifications with constant surfaces, allows following the whole activity of the system. The origin of the mosaics could lie in this behaviour and could be more clearly topologic than strictly ecological. The oscillatory behaviour induces a multiple-steps settlement by pines. The suspension of grazing in several times would favour the health colonization by multimodal age-population of Calluna and then lessen the oscillations as well as erosion and regularizes pine colonization. The optimal density of the initial pool of pines seems to be equivalent to 1 tree per 700 m².     

Distribution of arsenic compounds in Plantaginaceae and Cyperaceae plants growing in contaminated soil

The ability of plant species to accumulate arsenic (As) species in the biomass from As-contaminated soils is variable. Among the plants widely grown at the As-contaminated locations, Plantaginaceae and Cyperaceae families belong to the frequent ones. In this study, the ability of Plantago lanceolata (Plantaginaceae) and three wetland plant species representing the family Cyperaceae (Carex praecox, Carex vesicaria, and Scirpus sylvaticus) naturally occurring in the soils with an elevated As in the Czech Republic were investigated. The plants were cultivated under controlled conditions in an As-contaminated soil reaching 735?mg?kg^?1 of the total As. The total As in plants reached up to 8.3?mg?kg^?1 in leaves, and up to 155?mg?kg^?1 in roots of C. praecox. Dominant As compounds were arsenite and arsenate with a small abundance of dimethylarsinic acid (DMA) in all the plant species. In Cyperaceae, small percentages of arsenobetaine (AB) and arsenocholine (AC) were detected, suggesting the ability of these plants to transform As into less toxic compounds. Moreover, the important role of As(V) sequestration on iron plaque on the root surface of Cyperaceae was confirmed. In this context, root washing with oxalic acid partially disrupted the iron plaque for the better release of arsenate.     

根表铁膜对水稻铅吸收转运的影响

通过温室土壤盆栽试验研究不同生育期水稻根表铁膜形成对水稻吸收和转运Pb的影响。结果表明,两种水稻根表铁膜形成量(以DCB-Fe含量计)及铁膜中吸附的Pb量均随着生育期的延长而减少。水稻根表铁膜Fe含量与铁膜吸附的Pb量呈显著的正相关关系(r=0.798,p0.01)。水稻根系和茎叶吸收积累Pb随着不同品种和不同生育期而变化。品种NK57籽粒Pb含量显著高于品种YD6,前者为后者的1.9倍。从富集系数和分配比率来看,Pb主要富集在水稻的铁膜和根系中,而积累在茎叶和籽粒中的比率较少。Pb从水稻根表铁膜、根系和茎叶向籽粒中的转运系数在两个水稻品种间差异均不显著。水稻分蘖期和孕穗期根表铁膜量与根系Pb含量均呈显著的正相关关系(p0.05),但是成熟期水稻根表铁膜量与根系、茎叶和籽粒中Pb含量相关性均不显著,说明根表铁膜形成对水稻分蘖期和孕穗期吸收积累Pb有一定影响,但对水稻成熟期根系、茎叶和籽粒吸收积累Pb影响不大。     

Promoting late-fall establishment of tall fescue with artificial soil covers to minimise soil erosion

Frequently, turfgrass seedings have been sown in the late fall, which usually results in a poor vegetative stand and the possibility of soil erosion the following spring. This study evaluates the effects of a spun-bonded polyester soil cover placed over a late-fall seeding on subsequent seedling growth and overwintering. Clemfine, Mustang, Rebel, and Rebel II cultivars of tall fescue (Festuca arundinacea Schreb.) were sown on a silt loam soil in late fall (on 17 October in 1989 and 19 October in 1990) and allowed to grow with and without a soil cover until June. In the spring the temperature under the soil cover was greater than 2°C warmer than the uncovered soil from mid-April through May. Over the winter, leaf and root weights showed no detrimental effects from being under the cover. Individual cultivars grown under the cover produced 2 to 11 times greater leaf yields and 38 to 270% better stand establishment than those sown on the exposed soil. However, plant winter injury was observed under the soil cover in small soil depressions which accumulated water originating from thawing. All cultivars had similar amounts of growth under the cover. However, leaf yields for Rebel were 30-55% less than the other cultivars when grown under the cover and this was probably related to a low seed germination rate. The covers also promoted weed growth, which comprised from 34–65% of total leaf weights and was found to be negatively correlated (r = –0.66) to the yields of the sown grass. The soil cover was found to be beneficial to improving the success of seedling establishment of late seedings of tall fescue in cold areas.     

Egg release and settlement patterns of dioecious and hermaphroditic fucoid algae during the tidal cycle

The timing of gamete release by fucoid algae, although known to be restricted to calm days is not clearly understood within a circadian time scale. The need for externally fertilizing species to avoid gamete dilution suggests that in wave-exposed areas spawning may occur during particular tidal phases. However, this may differ between mating systems, as selfing species may be less affected by gamete dilution. In this study, two different approaches were used to determine when egg release occurs during the tidal cycle in two sister species with different mating systems. First, egg settlement of Fucus vesiculosus (dioecious) and Fucus spiralis (selfing hermaphrodite) was quantified on removable substrates (egg settlement disks) every day for 2 months and settlement patterns were used to statistically estimate the radius of a circle that would encompass 99% of each patch of settled eggs (the egg dispersal radius). Also, egg release was quantified every 2 h during the tidal cycle. A significantly larger egg dispersal radius (P < 0.02) was found for F. spiralis than F. vesiculosus, and this difference was somewhat site dependent with a greater difference between species in exposed sites. The egg dispersal radius was negatively correlated with significant wave height and positively correlated with sea surface temperature for both the species (P < 0.05), with a greater effect of both the factors for F. spiralis than for F. vesiculosus. Egg release during the tidal cycle was variable between species and experiments, with F. vesiculosus releasing more eggs, later in the day, and at a lower tide, than F. spiralis, which released fewer eggs, throughout the day and at all tides. The dioecious species, F. vesiculosus, may have developed a specific adaptation for timing the egg release to periods when emersed in exposed habitats to avoid rapid dilution of gametes that require outcrossing for fertilization. On the other hand, egg release for F. spiralis, which can self-fertilize, occurred both when emersed and immersed, suggesting this species has developed less synchrony with specific environmental factors. Site dependence also suggests local wave conditions can modulate timing of release. The data are consistent with the relaxation of the selective constraints of water motion on fertilization success in a selfing hermaphrodite, relative to an obligate outcrossing species. Results support the idea that species with different mating systems evolve different sensitivities to environmental cues for gamete release with specific implications for inbreeding and successful external fertilization in the ocean.     

Herbivores on a dominant understory shrub increase local plant diversity in rain forest communities

Indirect effects of trophic interactions on biodiversity can be large and common, even in complex communities. Previous experiments with dominant understory Piper shrubs in a Costa Rican rain forest revealed that increases in herbivore densities on these shrubs caused widespread seedling mortality as a result of herbivores moving from Piper to seedlings of many different plant genera. We tested components of the Janzen-Connell hypothesis by conducting focused studies on the effects of specialist and generalist Piper herbivores on local seedling diversity. Whereas specialist herbivores are predicted to increase mortality to neighboring seedlings that are closely related to the source plant, true generalists moving from source plants may cause density-dependent mortality of many species, and possibly increase richness if new species replace abundant species that have been thinned by herbivores. Therefore, we hypothesized that seedling richness would be greater in understory control plots created in patches of Piper that had normal densities of generalist herbivores compared to plots from which we removed generalist herbivores manually from all Piper shrubs. After 15 months, generalist-herbivore-removal plots had > 40% fewer seedlings, > 40% fewer species, and 40% greater seedling evenness, on average, than control plots with generalist herbivores intact. Using a complementary approach in unmanipulated plots in four forests, we used path analysis to test for a positive association between seedling diversity and herbivore damage on Piper species. In unmanipulated plots, for both generalist and specialist herbivores, our data were significant fits to the causal model that Piper herbivores decrease evenness and increase plant species richness, corroborating the experimental results. Because herbivores changed how individuals were apportioned among the species and families present (lower evenness), one interpretation of these associations between herbivores on Piper shrubs and local seedling richness is that high seedling mortality in dominant families allowed the colonization or survival of less common species. If interspecific or apparent competition allowed for a relative increase in species richness, then the Janzen-Connell hypothesis may extend its predictions to generalist seedling predators. We speculate that apparent competition may explain some of the deviations from neutral model predictions, especially at small scales.     

Growth and survival differences among native,introduced and hybrid blue mussels (<Emphasis Type="Italic">Mytilus</Emphasis> spp.): genotype,environment and interaction effects

The Mytilus species complex consists of three closely related mussel species: Mytilus trossulus, Mytilus edulis, and Mytilus galloprovincialis, which are found globally in temperate intertidal waters. Introduction of one or more of these species have occurred world-wide via shipping and aquaculture. Stable hybrid zones have developed in areas where these species have come into contact, making the invasion process complex. On the east coast of Vancouver Island (VI), British Columbia (BC), Canada, the native (M. trossulus) and introduced species (M. edulis and M. galloprovincialis), as well as their hybrid offspring, occur sympatrically. This study used a common environment experiment to quantify growth and survival differences among native, introduced, and introgressed mussels on VI. Mussels were collected from an area of known hybridization and reared in cages from May to August 2006. The cages were deployed at a local site as well as a remote site (approximately 150 km apart), and the mussels were genotyped at two species-specific loci. Growth and survival, as fitness measures, were monitored: native, introduced, and introgressed individuals were compared between and within sites to determine whether growth and survival were independent of site and genotype. Overall, mussels reared at Quadra Island performed better than locally-reared mussels at Ladysmith. Specifically, introgressed mussels reared at Quadra Island performed better than all genotypes reared at Ladysmith, as well as better than native mussels reared at Quadra Island. Differences in survival and growth among the native, introduced and introgressed mussels may serve to explain the complex hybridization patterns and dynamics characteristic of the VI introgression zone.     

Resource acquisition in two intertidal fucoid seaweeds, Fucus serratus and Himanthalia elongata : seasonal variation and effects of reproductive development

Seasonal variations and the effect of reproductive development on resource acquisition by two intertidal fucoid species, the iteroparous Fucus serratus L. and the semelparous Himanthalia elongata (L.) S. F. Gray were examined. The oxygen-exchange characteristics of vegetative apical tissue of both non-fertile and fertile plants and receptacle tissue were compared at monthly intervals throughout reproductive development. Respiratory rates in non-fertile F. serratus varied seasonally between 1.5 and 8.0 μmol g⁻¹ fresh wt h⁻¹; in fertile plants the receptacle had a significantly lower respiratory rate than the vegetative tissue. The respiratory rate of the vegetative button of fertile H. elongata displayed less seasonal variation and was lower than that of the receptacle, which varied from a maximum of 9.5 μmol g⁻¹ fresh wt h⁻¹ at receptacle initiation in October to a minimum of 2.0 μmol g⁻¹ fresh wt h⁻¹ in February. The maximum photosynthetic rate (P _max) of non-fertile plants of both species did not vary in a distinct seasonal manner (∼60 μmol g⁻¹ fresh wt h⁻¹ for F. serratus and ∼12 μmol g⁻¹ fresh wt h⁻¹ for H. elongata). In fertile plants, the P _max of the receptacle tissue was (∼50% lower in F. serratus, and at its peak three times higher in H. elongata, than that of vegetative tissue. The stable carbon-isotope ratio (δ¹³C) did not differ between different tissue types in F. serratus, but values did vary seasonally, being less negative in the summer than in the winter (−13.5‰ compared to −18‰). The receptacle tissue of H. elongata also displayed a distinct seasonal variation in δ¹³C values (−12‰ in summer, −16‰ in winter), whilst the δ¹³C of the vegetative button did not vary seasonally. The rate of uptake of inorganic nitrogen by the vegetative thallus was lower in H. elongata than in F. serratus. The receptacle tissue of F. serratus had lower uptake rates than the vegetative tissue, whilst the uptake rate by H. elongata receptacle tissue was higher than that of the vegetative button. Received: 14 March 1997 / Accepted: 22 April 1997     

Numerical and wind tunnel modeling on the windbreak effectiveness to control the aeolian erosion of conical stockpiles

There are many industrial sites where open aggregate conical piles exist to store granular materials, like coal, industrial residuals, or other minerals. Usually these storage piles are placed in open areas, making them susceptible to wind erosion, which can create health, environmental, and/or economical concerns. It is common to minimize the dust emission through the placement of windbreaks in the vicinity of the storage piles, which reduces the wind speed in the vicinity of the pile’s surface. In this work, some experimental results from a wind tunnel study on the erosion of a conical sand pile, exposed or protected by a fence with porosities of 0, 70, and 83%, are shown. For the sheltered cases, the windbreak was placed at several distances from the pile’s leading edge, ranging from H to 4H, where H is the initial height of the non-eroded pile. The evolution of the shape of the sand pile is shown, at different instances in time, and the pile deformation quantified, using a novel experimental setup developed for wind erosion studies. This information might be regarded as a useful dataset for the benchmark of computational models aiming to produce the transient simulation of the aeolian erosion of stockpiles. The CFD results are comprised of the modeling of several experimental scenarios. The computational results for the surface wind velocity show a good correlation with the initial deformation of the pile. Based on the results, the isocontours of (u _s /u _r ) presented might be regarded as a good basis for the estimation of the pile shear velocity.     

The use of legumes for reclaiming copper mine wastes in the Southwestern USA

Seeds of three legumes, blue lupine (Lupinus hirsutus L.), sesbania (Sesbania macrocarpa Muhl.), and alfalfa (Medicago sativa L.) were broadcast planted on four soil materials (desert soil, overburden, overburden plus tailings, and tailings) associated with copper mines near Tucson, Arizona. Experiments were conducted to study the effects of the four soil materials on germination (emergence), seedling establishment, and growth over a two-year period (1974 and 1975). All species grew best on desert soil, followed by overburden, overburden plus tailings, and tailings, in decreasing order. The presence of copper in overburden plus tailings and in tailings may have created a toxicity effect that limited the growth of plants in these two soil materials. Alfalfa was superior on all soil materials. Sesbania and blue lupine grew equally well. All three species were able to adapt to the different soil materials. For revegetation on copper mine wastes, it is desirable to plant a variety of plant species rather than a single species, to help blend the disturbed areas into the surrounding environmentApproved for publication as Arizona Agricultural Experiment Station Research Contribution No. 3100.     

Allelopathic effect of Cylindrospermopsis raciborskii extracts on the germination and growth of several plant species

Cylindrospermopsis raciborskii is an invasive cyanobacterium and a potential producer of the alkaloid toxin cylindrospermopsin (CYN). Extracts of two strains of C. raciborskii were tested for their effects on the germination and growth of Lactuca sativa, Phaseolus vulgaris, Pisum sativum and Solanum lycopersicum. Germination was not significantly inhibited for any of the plant species tested, but growth was affected, depending on the species. Root and stem growth in L. sativa was generally stimulated by both strains. Ph. vulgaris root growth was stimulated by both strains but no effect was visible in stem growth. S. lycopersicum root growth was inhibited by both strains and stem growth was inhibited only by the CYN strain. P. sativum root growth was also inhibited by both strains but stem growth was stimulated. CYN accumulation was also differential with toxin transfer to the stem. Ph. vulgaris accumulated the highest CYN concentration. This study suggests that plants behave differently in their response to this toxin and that roots and stems also show different abilities to react and accumulate the toxin. Knowledge of the impact of CYN- and non-CYN-producing cyanobacteria in different plant species and translocation of the toxin to different plant parts is essential for the avoidance of human as well as environmental health hazards.