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Substrate Type (substrate + type)
Selected AbstractsSeedling Growth and Heavy Metal Accumulation of Candidate Woody Species for Revegetating Korean Mine SpoilsRESTORATION ECOLOGY, Issue 4 2008Kyung Won Seo Abstract Selecting plant species that can overcome harsh soil and microclimatic conditions and speed the recovery of degraded minelands remains a worldwide restoration challenge. This study evaluated the potential of three woody species and various organic and inorganic fertilization treatments for revegetating abandoned metalliferous mines in Korea. We compared survival, growth, and heavy metal uptake of species common to Korean minelands in two spoil types and a reference forest soil. Substrate type and fertilization both influenced seedling growth and metal concentrations substantially, but they had little effect on seedling survival. Fertilization increased the growth of all three species when grown in mine spoils but influenced the growth of seedlings grown in forest soil only marginally. Initial seedling survival and growth indicate that the study species can tolerate the heavy metal concentrations and other soil constraints of metalliferous spoil types. We estimate that plants can stabilize 2,22% of various heavy metals contained in spoil materials into plant biomass during 20 years of plantation growth. Combined with the erosion control and site amelioration benefits of mineland reforestation, stabilization of heavy metals in forest biomass justifies this treatment on abandoned Korean metalliferous mines. [source] Bilby distribution and fire: a test of alternative models of habitat suitability in the Tanami Desert, AustraliaECOGRAPHY, Issue 6 2007Richard Southgate The distribution of the bilby Macrotis lagotis was assessed in the Tanami Desert using stratified random plots, repetitively sampled transects, aerial survey transects, and ground truth plots. Compared to a previous assessment of distribution, the extent of occurrence has changed little in the last 20 yr. However, the area of occupancy is small relative to the extent of occurrence and <25% of the current geographic range has bilby sign <20 km apart. Generalised linear modelling was used to determine the strength of association between bilby occurrence and habitat variables and identify refugia characteristics. Four competing candidate models were examined to determine whether bilby occurrence associated significantly with productive substrates and introduced herbivores, the distribution of key predator species, the pattern of fire, and climatic gradients including rainfall and temperature. For the entire study area, bilby presence associated most strongly with variables of mean annual rainfall, substrate type and the probability of dingo occurrence. Proximity to recently burnt habitat formed a significant predictor of bilby occurrence in a model derived for a reduced part of the study area where most sign was found. The work suggested that the current frameworks underpinning understanding of biotic distributions in arid Australia are deficient, and that climatic gradients, lateritic and rocky systems, and predators need to be incorporated into our thinking in the future. The extent of occurrence based on outlier records from opportunistic reports provided a misleading indication of the true status of the bilby. [source] Habitat characteristics at bluegill spawning colonies in a South Dakota glacial lakeECOLOGY OF FRESHWATER FISH, Issue 4 2006N. J. C. Gosch Abstract,,, Bluegill (Lepomis macrochirus) primarily reproduce in spawning colonies. We assessed habitat characteristics at 15 bluegill spawning colonies in a South Dakota glacial lake. Nesting sites were visually identified and angling was used to verify the species of nesting fish. Habitat characteristics were measured at each nesting site and compared with those measured at 75 randomly selected sites. In Lake Cochrane, mean water depth of spawning colonies was 1.0 m. Of the 13 habitat characteristics measured, four (substrate type, substrate firmness, vegetation density and dissolved oxygen levels) were significantly different (P , 0.05) between nesting and random sites. Every bluegill nest site contained gravel substrate, despite the availability of muck, sand and rock. Substrate firmness was indexed at 0-cm penetration and vegetation density was low at all nesting sites. Additionally, bluegills selected nesting locations with relatively moderate dissolved oxygen levels. Lake Cochrane bluegill nest sites consisted of shallow, gravel areas with short, low-density, live submergent Chara vegetation. [source] Seasonal and substrate preferences of fungi colonizing leaves in streams: traditional versus molecular evidenceENVIRONMENTAL MICROBIOLOGY, Issue 2 2005Liliya G. Nikolcheva Summary Aquatic hyphomycetes are the main fungal decomposers of plant litter in streams. We compared the importance of substrate (three leaf species, wood) and season on fungal colonization. Substrates were exposed for 12 4-week periods. After recovery, mass loss, fungal biomass and release of conidia by aquatic hyphomycetes were measured. Fungal communities were characterized by counting and identifying released conidia and by extracting and amplifying fungal DNA (ITS2), which was subdivided into phylotypes by denaturing gradient gel electrophoresis (DGGE) and terminal-restriction fragment length polymorphism (T-RFLP). Mass loss, fungal biomass and reproduction were positively correlated with stream temperature. Conidial diversity was highest between May and September. Numbers of different phylotypes were more stable. Principal coordinate analyses (PCO) and canonical analyses of principal coordinates (CAP) of presence/absence data (DGGE bands, T-RFLP peaks and conidial species) showed a clear seasonal trend (P, 0.002) but no substrate effect (P, 0.88). Season was also a significant factor when proportional similarities of conidial communities or relative intensities of DGGE bands were evaluated (P, 0.003). Substrate was a significant factor determining DGGE band intensities (P = 0.002), but did not significantly affect conidial communities (P = 0.50). Both traditional and molecular techniques suggest that strict exclusion of fungi by substrate type is rare, and that presence of different species or phylotypes is governed by season. Biomasses of the various taxa (based on DGGE band intensities) were related to substrate type. [source] Seasonal variation in habitat use by salmon, Salmo salar, trout, Salmo trutta and grayling, Thymallus thymallus, in a chalk streamFISHERIES MANAGEMENT & ECOLOGY, Issue 4 2006W. D. RILEY Abstract, A portable multi-point decoder system deployed in a tributary of the River Itchen, a southern English chalk stream, recorded the habitats used by PIT-tagged juvenile salmon, Salmo salar L., trout, Salmo trutta L. and grayling, Thymallus thymallus L., with a high degree of spatial and temporal resolution. The fishes' use of habitat was monitored at 350 locations throughout the stream during September/October 2001 (feeding period) and January/February 2002 (over-wintering period). Salmon parr tended to occupy water 25,55 cm deep with a velocity between 0.4 and 1.0 m s,1. During both autumn and winter, first year salmon (0+ group) were associated with gravel substrate during the daytime and aquatic weed at night. In autumn, 1+ salmon were strongly associated with hard mud substrates during the day and with marginal tree roots at night. In winter, they were located on gravel substrate by day and gravel and mud at night. Trout were associated with a greater range of habitats than salmon, generally occupying deeper and faster water with increasing age. During the autumn, 0+ trout were located along shallow (5,10 cm) and slow (,0.1,0.4 m s,1) margins of the stream, amongst tree roots by day and on silty substrates at night. During winter the 0+ trout occupied silty substrates at all times. As age increased, trout increasingly used coarse substrates; hard mud, gravel and chalk, and weed at night. All age groups of grayling (0+, 1+ and 2+) tended to occupy hard gravel substrate at all times and used deeper and faster water with increasing age. The 1+ and 2+ groups were generally found in water 40,70 cm deep with a velocity between 0.3 and 0.5 ms,1, whilst the 0+ groups showed a preference for shallower water with reduced velocity at night, particularly in the winter. There were greater differences in the habitats used between species and age groups than between the autumn and winter periods, and the distribution of fish was more strongly influenced by substrate type than water depth or velocity. The results are discussed in relation to the habitat requirements of mixed salmonid populations and habitat management. [source] Asymmetric Reduction of Activated Alkenes by Pentaerythritol Tetranitrate Reductase: Specificity and Control of Stereochemical Outcome by Reaction OptimisationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Anna Fryszkowska Abstract We show that pentaerythritol tetranitrate reductase (PETNR), a member of the ,ene' reductase old yellow enzyme family, catalyses the asymmetric reduction of a variety of industrially relevant activated ,,,-unsaturated alkenes including enones, enals, maleimides and nitroalkenes. We have rationalised the broad substrate specificity and stereochemical outcome of these reductions by reference to molecular models of enzyme-substrate complexes based on the crystal complex of the PETNR with 2-cyclohexenone 4a. The optical purity of products is variable (49,99% ee), depending on the substrate type and nature of substituents. Generally, high enantioselectivity was observed for reaction products with stereogenic centres at C, (>99% ee). However, for the substrates existing in two isomeric forms (e.g., citral 11a or nitroalkenes 18,19a), an enantiodivergent course of the reduction of E/Z -forms may lead to lower enantiopurities of the products. We also demonstrate that the poor optical purity obtained for products with stereogenic centres at C, is due to non-enzymatic racemisation. In reactions with ketoisophorone 3a we show that product racemisation is prevented through reaction optimisation, specifically by shortening reaction time and through control of solution pH. We suggest this as a general strategy for improved recovery of optically pure products with other biocatalytic conversions where there is potential for product racemisation. [source] Caddisfly diapause aggregations facilitate benthic invertebrate colonizationJOURNAL OF ANIMAL ECOLOGY, Issue 6 2003Declan J. McCabe Summary 1We used natural and manipulative field experiments to examine the effects of caddisfly (Trichoptera) diapause aggregations on benthic macroinvertebrates communities in a Vermont river. 2Natural substrates with aggregations of Neophylax and Brachycentrus (Trichoptera: Uenoidae and Brachycentridae) had higher species richness than did substrates lacking aggregations. Aggregations of caddisfly cases added to artificial substrates (bricks) also accumulated greater abundance, species density (number of species per unit area), and species richness (number of species per standard number of individuals) than did control bricks. 3Low-density, uniformly spaced, Brachycentrus cases accumulated higher species density and species richness than did an equivalent density of clumped cases. Similarly, empty Neophylax cases accumulated higher diversity than did cases still occupied by Neophylax pupae. 4Although natural substrates had higher species richness than artificial substrates, substrate type did not change qualitatively the effect of caddisfly aggregations on species richness. 5We subsampled individuals randomly from aggregations and control surfaces to provide an estimate of species richness unbiased by abundance. Expected species richness was higher in aggregations than on control surfaces. These results suggest that caddisfly aggregations increase species density by altering the shape of the species,abundance distribution as well as by accumulating individuals and species passively. 6We conclude that caddisfly diapause aggregations increase habitat complexity and facilitate colonization of other benthic species. [source] Efficiency of point abundance sampling by electro-fishing modified for short fishesJOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2003M. Scholten Summary The assessment of fish densities using point abundance sampling by electro-fishing requires information about the size of the sample area. For electro-fishing the effective fishing range depends on biological effects such as species and length of fish as well as physical effects like conductivity of water or substrate type. The present study investigates systematically the impact of conductivity and substrate type on the extension of the electrical field of a battery-powered electro-fishing gear (DEKA 3000, Marsberg, Germany), modified for larval and juvenile fishes. Threshold values for galvanotaxis were examined for juvenile fishes of five species in terms of current densities. Based on 71 experiments a general function relating body length to current density threshold values was developed. Optimal electrical current flow periods of 10 s were determined. For three different substrate types (gravel, sand, mud) a formula has been developed to quantify biological and physical effects on the effective fishing range. Each equation included information on the length of fish and the ambient conductivity. An increase in the effective fishing range of about 10% every 0.1 mS cm,1 was established. Reduction of the fishing range over muddy substrate was about 20,30% compared with coarse gravel or sand. This study provides a sufficient tool to calculate area-related densities of larval and juvenile fishes in different habitat types of a large river system using point abundance sampling by electro-fishing. Finally, calculated fish densities were evaluated by different types of fishing gear. [source] Rain forest invasion of eucalypt-dominated woodland savanna, Iron Range, north-eastern Australia: II.JOURNAL OF BIOGEOGRAPHY, Issue 8 2004Rates of landscape change Abstract Aim, To explore rates of rain forest expansion and associated ecological correlates in Eucalyptus -dominated woodland savanna vegetation in north-eastern Australia, over the period 1943,91. Location, Iron Range National Park and environs, north-east Queensland, Australia. This remote region supports probably the largest extent of lowland (< 300 m) rain forest extant in Australia. Rainfall (c. 1700 mm p.a.) occurs mostly between November and June, with some rain typically occurring even in the driest months July,October. Methods, Interpretation of change in lowland rain forest vegetation cover was undertaken for a 140 km2 area comprising complex vegetation, geology and physiography using available air photos (1943, 1970 and 1991). A GIS database was assembled comprising rain forest extent for the three time periods, geology, elevation, slope, aspect, proximity to streams and roads. Using standard GIS procedures, a sample of 6996 10 × 10 m cells (0.5% of study area) was selected randomly and attributed for vegetation structure (rain forest and non-rain forest), and landscape features. Associations of rain forest expansion with landscape features were examined with logistic regression using the subset of cells that had changed from other vegetation types to rain forest, and remained rain forest over the assessment period, and comparing them with cells that showed no change from their original, non-rain forest condition. Results, Rain forest in the air photo study area increased from 45 km2 in 1943 to 78.1 km2 by 1970, and to 82.6 km2 by 1991. Rainfall (and atmospheric CO2 concentration) was markedly lower in the first assessment period (1943,70). Modelled rates of rain forest invasion differed predominantly with respect to substrate type, occurring faster on substrates possessing better moisture retention properties, and across all elevation classes. Greatest expansion, at least in the first assessment period, occurred on the most inherently infertile substrates. Expansion was little constrained by slope, aspect and proximity to streams and roads. On schist substrates, probability of invasion remained high (> 60%) over distances up to 1500 m from mature rain forest margins; on less favourable substrates (diorite, granites), probability of expansion was negligible at sites more than 400 m from mature margins. Main conclusions, (i) Rain forest expansion was associated primarily with release from burning pressure from c. the 1920s, following major disruption of customary Aboriginal lifestyles including hunting and burning practices. (ii) Decadal-scale expansion of rain forest at Iron Range supports extensive observations from the palaeoecological literature concerning rapid rain forest invasion under conducive environmental conditions. (iii) The generality of these substrate-mediated observations requires further testing, especially given that landscape-scale rain forest invasion of sclerophyll-dominated communities is reported from other regions of north-eastern Australia. [source] Classification and Antihypertensive Activity of Angiotensin I-Converting Enzyme Inhibitory Peptides Derived from Food ProteinsJOURNAL OF FOOD SCIENCE, Issue 4 2000H Iroyukifujita ABSTRACT: Angiotensin I-converting enzyme (ACE)-inhibitory peptides from the thermolysin digest of chicken muscle and the peptic digest of ovalbumin were isolated. However, some of them failed to show antihypertensive activity in spontaneously hypertensive rats (SHR). To clarify this discrepancy, ACE-inhibitory peptides from various sources were preincubated with ACE before measurement of ACE-inhibitory activity and classified into 3 groups: (1) inhibitor type, IC50 values of peptides that are not affected after preincubation with ACE; (2) substrate type, peptides that are hydrolyzed by ACE to give peptides with weaker activity; and (3) prodrug-type inhibitor, these peptides are converted to true inhibitors by ACE or gastrointestinal proteases. Peptides belonging to the 1st and the 3rd groups exert antihypertensive activities even after oral administration in SHR. [source] Survival and growth responses of eight Everglades tree species along an experimental hydrological gradient on two tree island typesAPPLIED VEGETATION SCIENCE, Issue 4 2010Susana L. Stoffella Abstract Questions: How are the early survival and growth of seedlings of Everglades tree species planted in an experimental setting on artificial tree islands affected by hydrology and substrate type? What are the implications of these responses for broader tree island restoration efforts? Location: Loxahatchee Impoundment Landscape Assessment (LILA), Boynton Beach, Florida, USA. Methods: An experiment was designed to test hydrological and substrate effects on seedling growth and survivorship. Two islands , a peat and a limestone-core island representing two major types found in the Everglades , were constructed in four macrocosms. A mixture of eight tree species was planted on each island in March of 2006 and 2007. Survival and height growth of seedlings planted in 2006 were assessed periodically during the next two and a half years. Results: Survival and growth improved with increasing elevation on both tree island substrate types. Seedlings' survival and growth responses along a moisture gradient matched species distributions along natural hydrological gradients in the Everglades. The effect of substrate on seedling performance showed higher survival of most species on the limestone tree islands, and faster growth on their peat-based counterparts. Conclusions: The present results could have profound implications for restoration of forests on existing landforms and artificial creation of tree islands. Knowledge of species tolerance to flooding and responses to different edaphic conditions present in wetlands is important in selecting suitable species to plant on restored tree islands [source] Effect of sandy and muddy substrates on the growth and survival of the freshwater clam Galatea paradoxa (Born 1778)AQUACULTURE RESEARCH, Issue 9 2010Daniel Adjei-Boateng This study was conducted to determine the effect of a sandy and muddy substrate on the growth and survival of three size-classes of Galatea paradoxa (Born 1778). The experiment was conducted over a 6-month period in a 1000 m2 pond at the research farm of the Faculty of Renewable Natural Resources. Three size classes (shell length) of G. paradoxa categorized as small (20,30 mm), medium (31,40 mm) and large (>40 mm) were used to ascertain the effect of a sandy and muddy substrate on growth performance. Growth in general was very slow, between 1.4 and 2.4 mm over the 6-month experimental period. The lengths measured at the end of the experiment were also significantly different. However, the mean length gained and the specific growth rate for the three size classes in the two substrates (sandy and muddy) were not significantly different (P>0.05). The results of this study indicate that the pond environment is not suitable for the culture G. paradoxa as the species is adapted to life in a river with its filter-feeding activity dependent on the water current. The effect of the substrate type on growth was not significant. However, the substrate type did affect survival, with sandy substrates yielding in better survival than muddy ones. [source] Experimental manipulation reveals the importance of refuge habitat temperature selected by lizardsAUSTRAL ECOLOGY, Issue 3 2010MICHA ANDERSSON Abstract Refuges provide shelter from predators, and protection from exposure to the elements, as well as other fitness benefits to animals that use them. In ectotherms, thermal benefits may be a critical aspect of refuges. We investigated microhabitat characteristics of refuges selected by a heliothermic scincid lizard, Carlia rubrigularis, which uses rainforest edges as habitat. We approached lizards in the field, simulating a predator attack, and quantified the refuge type used, and effect of environmental temperatures (air temperature, substrate temperature and refuge substrate temperature) on the amount of time skinks remained in refuges after hiding (emergence time). In respone to our approach, lizards were most likely to flee into leaf litter, rather than into rocks or woody debris, and emergence time was dependent on refuge substrate temperature, and on refuge substrate temperature relative to substrate temperature outside the refuge. Lizards remained for longer periods in warmer refuges, and in refuges that were similar in temperature to outside. We examined lizard refuge choice in response to temperature and substrate type in large, semi-natural outdoor enclosures. We experimentally manipulated refuge habitat temperature available to lizards, and offered them equal areas of leaf litter, woody debris and rocks. When refuge habitat temperature was unmanipulated, lizards (85%) preferred leaf litter, as they did in the field. However, when we experimentally manipulated the temperature of the leaf litter by shading, most skinks (75%) changed their preferred refuge habitat from leaf litter to woody debris or rocks. These results suggest that temperature is a critical determinant of refuge habitat choice for these diurnal ectotherms, both when fleeing from predators and when selecting daytime retreats. [source] Lysosomal cysteine proteases (cathepsins): promising drug targetsACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2003an Turk Papain-like lysosomal cysteine proteases are processive and digestive enzymes expressed in organisms from bacteria to humans. Their ubiquity alone makes them potential drug targets, with the assumption that appropriate specificities may be achieved. These enzymes have rather short active-site clefts, comprising three well defined substrate-binding subsites (S2, S1 and S1,) and additionally have comparatively broad binding areas (S4, S3, S2,, S3,). This geometry distinguishes them from other protease classes, such as serine and aspartic proteases, with six and eight substrate-binding sites, respectively. Exopeptidases (cathepsins B, C, H and X), in contrast to endopeptidases (such as cathepsins L, S, V and F), possess structural features that facilitate binding of N- and C-terminal groups of substrates in the active-site cleft. Other than a clear preference for free chain termini in the case of exopeptidases, the substrate-binding sites exhibit no strict specificities. Instead, their subsite preferences arise more from specific exclusions of substrate type. This presents a challenge for the design of inhibitors to target a specific cathepsin: only the cumulative effect of an assembly of inhibitor fragments can produce the desired result. The small number of papain-like lysosomal cysteine proteases (11 human enzymes are known) and the small number of substrate-binding sites calls for a innovative and empirical approach. [source] Distribution of myrmecochorous species over the landscape and their potential long-distance dispersal by emus and kangaroosDIVERSITY AND DISTRIBUTIONS, Issue 1 2008María Calviño-Cancela ABSTRACT Topographical heterogeneity can create a mosaic of substrate types leading to the formation of isolated plant populations. Seed dispersal then becomes crucial for the colonization of such suitable but remote substrate types. We surveyed the distribution of seven elaiosome-bearing species (myrmecochores) over 5 km2 of natural heathland in southwestern Australia. Ants are the standard means of dispersal of these species, which provide limited dispersal (usually of a few metres). Six species were associated with particular substrate types (dune or swale) and all occurred as discrete populations, on average 270,500 m apart, with closest dune edges 280 m apart. We evaluated the possible roles of emus and kangaroos as alternative agents of long-distance seed dispersal between substrate types. Their droppings contained viable seeds of three of the target species, as well as other myrmecochores, and were evenly distributed over the substrate types. While migration of these plant species between preferred substrate types seems unlikely when considering only their standard dispersal agents (ants), it is highly likely in the presence of emus (in particular) and kangaroos that act as non-standard dispersers. This may have important consequences for plant species conservation by increasing habitat connectivity and favouring regional persistence. [source] Arboreal substrates influence foraging in tropical antsECOLOGICAL ENTOMOLOGY, Issue 4 2010NATALIE A. CLAY 1. Physically complex substrates impart significant costs on cursorial central-place foragers in terms of time spent outside the nest and total distance travelled. Ants foraging in trees navigate varied surfaces to access patchy resources, thus providing an appropriate model system for examining interactions between foraging efficiency and substrates. 2. We expected that the speed of recruitment, body size distribution and species richness of foraging arboreal ants would differ predictably among common substrate types occurring on tropical tree trunks. We measured changes in ant abundance and species composition over time at baits placed on bare tree bark, moss-covered bark, and vine-like vegetation appressed to bark. We also measured average body size and body size frequency on the three substrate types. Ants discovered baits sooner and accumulated at baits relatively faster when using vine substrates as the primary foraging trail. Average body size was smaller on vine substrates than on bark. Experimental removal of vine and moss substrates nullified these differences. Contrary to our predictions, species richness and body size distributions did not differ among the three substrate types, due in part to the frequent presence of a few common ground-nesting species at baits on bare bark. 3. Our results collectively indicate that linear substrates facilitate access of foraging ants to patchy resources. Ant use of vine-like substrates appears to be opportunistic; vine use is not confined to certain species nor constrained by body size. [source] Competition for food between Eurasian perch (Perca fluviatilis L.) and ruffe (Gymnocephalus cernuus [L.]) over different substrate typesECOLOGY OF FRESHWATER FISH, Issue 4 2004A. Dieterich Abstract,,, Food consumption by Eurasian perch (Perca fluviatilis L.) and ruffe (Gymnocephalus cernuus [L.]) was studied in single and mixed-species treatments in the laboratory, where alternative food resources, chironomids and zooplankton, were offered simultaneously. The effects of structural complexity, which was represented by substrate grain size, and of feeding level on food consumption were analysed. Across all experiments, the outcome of competition between perch and ruffe depended on food abundance and on the structural complexity of the environment. Perch and ruffe both changed their food consumption in the presence of a heterospecific competitor. With high food supply, perch consumed more benthic food than ruffe. With low food supply, the consumption of perch decreased strongly, while that of ruffe remained high on fine sediment. Under all conditions tested, the mechanism of competition appeared to be of interference rather than of exploitative nature. It is suggested that with decreasing lake productivity caused by re-oligotrophication, habitat shifts of both species will occur, which will alleviate interspecific competition. Ruffe will forage over fine sediment and perch over coarse sediment, whereby both species will achieve the highest foraging efficiency under conditions of low food supply. Resumen 1. Hemos estudiado el consumo alimenticio de Perca fluviatilis L. y Gymnocephalus cernuus (L.) en condiciones de laboratorio. Bajo tratamientos de especies individuales y mezcladas, les ofrecimos, simultáneamente, varios recursos alimenticios alternativos (quironómidos y zooplancton). 2. Analizamos los efectos de la complejidad estructural - representada por el tamaño del sustrato (arena, grava, y guijo) - y del nivel alimenticio, sobre el consumo alimenticio. Pusimos especial atención a la potencial influencia de competidores hetero-específicos sobre los patrones alimenticios de ambas especies, tanto en términos cualitativos como cuantitativos. Además, dado que en un futuro cercano una menor productividad general en lagos debida a re-oligotrofia, probablemente aumente la competición por el alimento en muchos lagos donde ambas especies co-existen, los experimentos se llevaron a cabo bajo niveles de abastecimiento alimenticio alto y bajo. 3. En los experimentos, la aparición de competencia entre P. fluviatilis y G. cernuus dependió de la abundancia del alimento y de la complejidad estructural del ambiente. El consumo de quironómidos por P. fluviatilis dependió del tipo de sustrato a niveles altos de abastecimiento alimenticio pero no a niveles bajos, mientras que en G. cernuus observamos lo contrario. 4. Ambas especies cambiaron el consumo alimenticio en presencia de un competidor hetero-específico. A altos niveles de abastecimiento alimenticio, P. fluviatilis consumió más bentos que G. cernuus. A niveles bajos, el consumo de P. fluviatilis decreció substancialmente mientras que el de G. cernuus permaneció alto en sedimento fino. Bajo todas las condiciones experimentales analizadas, los mecanismos de competición parecieron ser de interferencia más que de naturaleza explotativa. 5. Finalmente, presentamos un escenario sobre como P. fluviatilis y G. cernuus pueden competir por alimento bentónico en lagos con variado sustrato de fondo. Sugerimos que a altos niveles de abastecimiento alimenticio, G. cernuus forrajee más sobre arena y grava mientras que P. fluviatilis puede utilizar todos los sustratos disponibles. Al decrecer el abastecimiento alimenticio por re-oligotrofia, pueden producirse cambios en el hábitat de ambas especies que minimizarán la competencia inter-específica. G. cernuus forrajeará básicamente sobre sedimento fino, allá donde sea claramente superior a P. fluviatilis. Esta última especie forrajeará predominantemente sobre sedimento más grueso donde se enfrentará a competencia intra- e inter-específica. A través de estos cambios de hábitat, ambas especies podrían alcanzar la mayor eficiencia de forrajeo bajo condiciones de bajo abastecimiento alimenticio. [source] Dynamics of yeast populations recovered from decaying leaves in a nonpolluted stream: a 2-year study on the effects of leaf litter type and decomposition timeFEMS YEAST RESEARCH, Issue 4 2007Ana Sampaio Abstract Here we report on the results of a survey of the yeast populations occurring on submerged leaves (alder, eucalyptus and oak) in a natural mountain stream, during different phases of their decomposition and through two consecutive years. Leaf litter mass loss, total yeast counts, Shannon,Weiner index (H,), yeast community structure and physiologic abilities were analyzed to evaluate the dynamics of yeast communities during decay. Seventy-two yeast taxa were recorded, and in all litter types, species of basidiomycetous affinity predominated over ascomycetous ones. Discriminant analysis of presence/absence data (yeast species) showed significant differences both among substrate types (P<0.0026) and with decomposition time (P<0.0001). Carbon and nitrogen source utilization by yeast strains also varied with the substrate (P<0.0001) and decomposition time (P<0.0001). Further conclusions were that: (1) all litter types have in common ubiquitous yeast species, such as Cryptococcus albidus, Debaryomyces hansenii and Rhodotorula glutinis, among the common 20 yeast species; (2) only a few species were dominant, and most species were rare, being recorded once or twice throughout decomposition; and (3) the order of yeast appearance, and their substrate assimilation patterns, strongly suggest a succession phenomenon. Finally, explanations for the distribution patterns and variations in yeast communities are discussed. [source] Modular Furanoside Phosphite-Phosphoroamidites, a Readily Available Ligand Library for Asymmetric Palladium-Catalyzed Allylic Substitution Reactions.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009Origin of Enantioselectivity Abstract A library of furanoside phosphite-phosphoroamidite ligands has been synthesized and screened in the palladium-catalyzed allylic substitution reactions of several substrate types. These series of ligands can be prepared efficiently from easily accessible D -xylose and D -glucose. Their modular nature enables the position of the phosphoroamidite group, configuration of C-3 of the furanoside backbone and the substituents/configurations in the biaryl phosphite/phosphoroamidite moieties to be easily and systematically varied. By carefully selecting the ligand components, therefore, high regio- and enantioselectivities (ees up to 98%) and good activities have been achieved in a broad range of mono- and disubstituted hindered and unhindered linear and cyclic substrates. The NMR studies on the palladium-,-allyl intermediates provide a deeper understanding about the effect of the ligand parameters on the origin of enantioselectivity. They also indicate that the nucleophilic attack takes place predominantly at the allylic terminal carbon atom located trans to the phosphoroamidite moiety. [source] Efficiency of point abundance sampling by electro-fishing modified for short fishesJOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2003M. Scholten Summary The assessment of fish densities using point abundance sampling by electro-fishing requires information about the size of the sample area. For electro-fishing the effective fishing range depends on biological effects such as species and length of fish as well as physical effects like conductivity of water or substrate type. The present study investigates systematically the impact of conductivity and substrate type on the extension of the electrical field of a battery-powered electro-fishing gear (DEKA 3000, Marsberg, Germany), modified for larval and juvenile fishes. Threshold values for galvanotaxis were examined for juvenile fishes of five species in terms of current densities. Based on 71 experiments a general function relating body length to current density threshold values was developed. Optimal electrical current flow periods of 10 s were determined. For three different substrate types (gravel, sand, mud) a formula has been developed to quantify biological and physical effects on the effective fishing range. Each equation included information on the length of fish and the ambient conductivity. An increase in the effective fishing range of about 10% every 0.1 mS cm,1 was established. Reduction of the fishing range over muddy substrate was about 20,30% compared with coarse gravel or sand. This study provides a sufficient tool to calculate area-related densities of larval and juvenile fishes in different habitat types of a large river system using point abundance sampling by electro-fishing. Finally, calculated fish densities were evaluated by different types of fishing gear. [source] Palaeocology of Hard Substrate Faunas from the Cretaceous Qahlah Formation of the Oman MountainsPALAEONTOLOGY, Issue 1 2001Mark A. Wilson Skeletal encrusters and carbonate hardgrounds are rare in siliciclastic sands and gravels because of high levels of abrasion and sediment movement. An exception to this is the Maastrichtian Qahlah Formation of the Oman Mountains, a sequence of coarse siliciclastic sediments deposited on a shallow marine shelf above wavebase and at an equatorial palaeolatitude. This unit contains intercalated carbonate hardgrounds and other hard substrates which were encrusted and bored. The hard substrates, comprising carbonate and silicate clasts, calcareous bioclasts (mollusc shells and coral fragments) and wood, supported a diverse encrusting and boring fauna dominated in biomass by the oyster Acutostrea. There are twelve bryozoan species and at least two serpulid worm species, most living cryptically. Other encrusters on exposed surfaces include the agglutinated foraminiferan Placopsilina and several species of colonial corals. Borings in the carbonate clasts and shells are predominantly those of bivalves (Gastrochaenolites), with subsidiary clionid sponge (Entobia) and acrothoracican barnacle (Rogerella) borings. The woodgrounds are thoroughly bored by teredinid bivalves (Teredolites). Of the common substrate types, carbonate hardground clasts support the greatest number of taxa, followed by chert clasts, with limestone rockground pebbles being depauperate. Clast composition and relative stability probably explain these differences. Individual clasts probably had variable and typically long colonisation histories. Detailed palaeoecological interpretation is constrained by taphonomic loss, time-averaging and clast transportation and reorientation. Evidence from the Qahlah Formation shows that tropical rocky-shore biotas in the Cretaceous were not impoverished as previously believed. [source] Electrical and structural properties of p -type nanocrystalline silicon grown by LEPECVD for photovoltaic applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Gabriel Micard Abstract p-doped hydrogenated nanocrystalline silicon (p-nc-Si:H) is one of the most critical layers in thin film silicon solar cells. LEPECVD is a new technique for the growth of nc-Si at high growth rate without compromising the layer quality, using a dense but low energy plasma. Thin p-nc-Si:H layers are grown on glass and ZnO:Al coated glass and their structural and electrical properties are investigated as a function of the silane dilution (d) and of the doping ratio (DR). The influence of the substrate on the structural properties is investigated and discussed. The incubation layer is clearly observed on both substrate types and its thickness is estimated. LEPECVD distinguishes itself from other high growth rate methods by a very low impurity distribution coefficient to obtain a comparable conductivity and boron density. The conduction path is shown to be dependent on the density of boron in the layer while a significant decrease of conductivity at high DR is not observed in the studied range (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Settlement and Survival of the Oyster Crassostrea virginica on Created Oyster Reef Habitats in Chesapeake BayRESTORATION ECOLOGY, Issue 2 2007Janet A. Nestlerode Abstract Efforts to restore the Eastern oyster (Crassostrea virginica) reef habitats in Chesapeake Bay typically begin with the placement of hard substrata to form three-dimensional mounds on the seabed to serve as a base for oyster recruitment and growth. A shortage of oyster shell for creating large-scale reefs has led to widespread use of other materials such as Surf clamshell (Spisula solidissima), as a substitute for oyster shell. Oyster recruitment, survival, and growth were monitored on intertidal reefs constructed from oyster and Surf clamshell near Fisherman's Island, Virginia, U.S.A. and on a subtidal Surf clamshell reef in York River, Virginia, U.S.A. At the intertidal reefs, oyster larvae settlement occurred at similar levels on both substrate types throughout the monitoring period but higher levels of post-settlement mortality occurred on clamshell reefs. The oyster shell reef supported greater oyster growth and survival and offered the highest degree of structural complexity. On the subtidal clamshell reef, the quality of the substrate varied with reef elevation. Large shell fragments and intact valves were scattered around the reef base, whereas small, tightly packed shell fragments paved the crest and flank of the reef mound. Oysters were more abundant and larger at the base of this reef and less abundant and smaller on the reef crest. The availability of interstitial space and appropriate settlement surfaces is hypothesized to account for the observed differences in oyster abundance across the reef systems. Patterns observed emphasize the importance of appropriate substrate selection for restoration activities to enhance natural recovery where an underlying habitat structure is destroyed. [source] Systematics and phylogeography of a threatened tortoise, the speckled padloperANIMAL CONSERVATION, Issue 3 2010S. R. Daniels Abstract This study investigated the systematics and phylogeography of a threatened tortoise of South Africa, the speckled padloper Homopus signatus. Sixty three specimens were collected from 17 localities that covered the distributional range of the two subspecies in western South Africa and a north-eastern population that was recently discovered near Pofadder. The Pofadder sample could not be assigned to either subspecies based on morphology. The samples were sequenced for two partial mtDNA fragments, nicotinamide adenine dinucleotide dehydrogenase component four and cytochrome b, which yielded ,1.1 kb, while a subset of the samples were sequenced for a 390 bp nuclear DNA (nDNA) fragment of prolactin. Phylogenetic analyses of mtDNA using minimum evolution, maximum parsimony and Bayesian inferences supported the monophyly of H. signatus and revealed that the Pofadder specimen was basal in the topology and sister to the remainder. The phylogenetic analyses did not support the recognition of two subspecies; there was statistical support for a Homopus signatus signatus clade but Homopus signatus cafer was not monophyletic. The nDNA analysis showed no difference between the subspecies and placed the Pofadder sample distant but not distinct from H. s. signatus. The mtDNA and the nDNA data suggest that the subspecies are invalid taxonomic units. The structure of the mtDNA network corresponded to the geographical distribution of populations. The north-western populations formed one haplocluster, corresponding to H. s. signatus, whereas the south-western populations formed three haploclusters, corresponding to H. s. cafer. The Pofadder sample was unconnected to the network. The morphology of the northern and southern morphotypes probably reflects selection for crypsis on the different substrate types of the regions, granites and sedimentary rocks, respectively. These results highlight that subspecies designations should be authenticated by molecular techniques because morphological plasticity can obfuscate phylogenetic relationships. We consider the western H. signatus populations as one taxonomic unit and recommend wider sampling of the Pofadder locality to clarify the taxonomic status of this lineage. [source] Survival and growth responses of eight Everglades tree species along an experimental hydrological gradient on two tree island typesAPPLIED VEGETATION SCIENCE, Issue 4 2010Susana L. Stoffella Abstract Questions: How are the early survival and growth of seedlings of Everglades tree species planted in an experimental setting on artificial tree islands affected by hydrology and substrate type? What are the implications of these responses for broader tree island restoration efforts? Location: Loxahatchee Impoundment Landscape Assessment (LILA), Boynton Beach, Florida, USA. Methods: An experiment was designed to test hydrological and substrate effects on seedling growth and survivorship. Two islands , a peat and a limestone-core island representing two major types found in the Everglades , were constructed in four macrocosms. A mixture of eight tree species was planted on each island in March of 2006 and 2007. Survival and height growth of seedlings planted in 2006 were assessed periodically during the next two and a half years. Results: Survival and growth improved with increasing elevation on both tree island substrate types. Seedlings' survival and growth responses along a moisture gradient matched species distributions along natural hydrological gradients in the Everglades. The effect of substrate on seedling performance showed higher survival of most species on the limestone tree islands, and faster growth on their peat-based counterparts. Conclusions: The present results could have profound implications for restoration of forests on existing landforms and artificial creation of tree islands. Knowledge of species tolerance to flooding and responses to different edaphic conditions present in wetlands is important in selecting suitable species to plant on restored tree islands [source] The Role of the Conserved Threonine in P450BM3 Oxygen Activation: Substrate-Determined Hydroxylation Activity of the Thr268Ala MutantCHEMBIOCHEM, Issue 2 2008Max J. Cryle Dr. Abstract The hydroxylation activity of the Thr268Ala mutant of P450BM3 has been shown to occur to varying degrees with small alterations in the structure of a fatty-acid substrate. Ten substrates were investigated, including straight chain, branched chain and cis -cyclopropyl substituted fatty acids with a straight-chain length that varied between 12 and 16 carbon atoms. The efficacy of the hydroxylation activity appeared to be governed by the chain length of the substrate. Substrates possessing 14 to 15 carbons afforded the highest levels of activity, which were comparable with the wild-type enzyme. Outside of this window, straight-chain fatty acids showed reduced activity over the other substrate types. These results provide a cautionary tale concerning the loss of ferryl activity in such cytochrome P450 threonine to alanine mutants, as the nature of the substrate can determine the extent to which hydroxylation chemistry is abolished. [source] | |||||||||||||||||||||||||||||||