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Late May (late + may)
Selected AbstractsInfluence of hatch duration and individual daily growth rates on size structure of age-0 smallmouth bass cohorts in two glacial lakesECOLOGY OF FRESHWATER FISH, Issue 3 2008Q. E. Phelps Abstract,,, We assessed hatch dates and daily growth rates of age-0 smallmouth bass from two glacial lakes over a 3-year period. Hatching durations (19,27 days among years) of smallmouth bass occurred from late May until late June. Mean daily growth rate of age-0 smallmouth bass ranged from 0.56 to 1.56 mm·day,1. Correlation analysis indicated that hatch date had little effect on daily growth rates. Hatch date was significant in explaining variation in total length (TL) of age-0 smallmouth bass at time of capture in only three of six cases and hatch date never explained >50% of the variation in bass length. Daily growth rate significantly explained variation in smallmouth bass TL at time of capture in all six models, accounting for 31,86% of the variability in bass length. Our findings suggest that size structure of age-0 cohorts in some populations may be more strongly regulated by variation in individual daily growth rate than by hatch timing. [source] Long-term variation in brown trout, Salmo trutta L., stocking success in a large lake: interplay between availability of suitable prey and size at releaseECOLOGY OF FRESHWATER FISH, Issue 4 2005P. Hyvärinen Abstract , Factors affecting long-term variation in brown trout, Salmo trutta L., stocking success were examined in a large lake, Lake Oulujärvi, in central Finland. Brown trout were stocked in spring (late May to early June) in 1974,1991 and in summer (late June to early July) in 1992,2001. The biomass of the vendace, Coregonus albula (L.), population (prey) at release time had the largest positive effect on stocking success within both periods: biomass of adult vendace in spring and both 0+ and adult vendace in summer. Increasing the size of stocked fish had a positive effect if the vendace available at release were only adults. The increasing trend of predator-catch-per-unit-effort (CPUE) [combined CPUE of northern pike Esox lucius L., burbot Lota lota (L.), and pike-perch Stizostedion lucioperca (L.)] through the study period and its negative effect on trout stocking success suggested an increasing effect of predation within the entire time series. Resumen 1. Dado lo impredecible que son los resultados de las repoblaciones, se hace necesario conocer los mecanismos que afectan el éxito de los peces soltados para minimizar los riesgos de error en altas inversiones de repoblaciones. Podría existir una ventana óptima para las sueltas que produzca las condiciones más favorables - tales como la ausencia de predadores en la zona de suelta y la disponibilidad de presas apropiadas - bajo las que cualquier pez soltado pueda sobrevivir y generar una producción máxima. El fin de este estudio fue examinar como factores tales como la abundancia de las poblaciones de presas y predadores, y las tasas, tamaños y estaciones de repoblación pueden explicar las variaciones anuales a largo plazo (años 1974,1991) en el éxito de repoblación de Salmo trutta L. en el Lago Oulujärvi (928 km2, Finlandia central). 2. Individuos de S. trutta fueron repoblados en primavera (finales de Mayo , principios de Junio) durante los años 1974,1991 y en verano (finales de Junio , principios de Julio) durante los años 1992,2001. Los resultados de análisis de regresión por pasos mostró que la biomasa de Coregonus albula (L.) adultos (i.e., presas) en el momento de la suelta tuvieron el mayor efecto positivo sobre el éxito de la repoblación en dos períodos: la biomasa de adultos de C. albula en primavera y ambos dos, juveniles 0+ y adultos en verano. Incrementar el tamaño de los peces repoblados tuvo un efecto positivo si los C. albula disponibles en el momento de la suelta fueron solamente adultos (repoblaciones primaverales). La tendencia a incrementar los CPUE-predadores (CPUE combinadas de Esox lucius L., Lota lota (L.), y Stizostedion lucioperca (L.)) a lo largo del periodo de estudio y su efecto negativo sobre el éxito de las repoblaciones de S. trutta sugirió un mayor efecto de la predación sobre la series temporales completas. 3. Concluimos que el momento de la repoblación juega un papel más importante como determinante de la mejor ventana para la repoblación de S. trutta de lagos. Individuos de S. trutta de tamaños <200 g deberían ser repoblados solo si presas de pequeño tamaño (individuos 0+ de C. albula en verano) son también abundantes en el momento y en el área de la suelta. Si las presas disponibles son solos grandes (adultos de C. albula en primavera), el tamaño de repoblación debería ser mayor con individuos de S. trutta claramente mayores de 200 g porque el mayor tamaño amplia el rango de tamaños de las presas disponibles. [source] Behavioral observation of two fungivorous beetles (Coleoptera: Tenebrionidae) on wood-decaying bracket fungus Cryptoporus volvatusENTOMOLOGICAL SCIENCE, Issue 1 2010Kohmei KADOWAKI Abstract The behavior of two sympatric beetles, Parabolitophagus felix Lewis and Ischnodactylus loripes Lewis (Tenebrionidae: Coleoptera), specialists of a bracket fungus Cryptoporus volvatus (Peck) Shear, was studied in Kyoto, central Japan. A sporocarp of C. volvatus has a distinct white volva, and a small elliptical ostiole near the base. Adults of two tenebrionids use the volval chambers of a sporocarp as mating space. Adults walked across closely located sporocarps infrequently on a tree at night (19.30,20.30 h). Field observation showed that the occupancy patterns of the volval chambers in the two species were temporally segregated: Parabolitophagus felix occupied them until May, while I. loripes occupied them in late May to early June [source] Colonization of beech leaves by two endophytic fungi in northern JapanFOREST PATHOLOGY, Issue 2 2000N. Sahashi Summary Leaves of Japanese beech (Fagus crenata) were collected monthly during the vegetation period at five sites in the Tohoku district in Japan to isolate endophytic fungi. Leaves were also collected only once at two additional sites. Two endophytic fungi were dominant, a Discula species and a sterile mycelium. This result strongly suggests that these two fungi are generally associated with leaves of the Japanese beech at different sites. At most sites the isolation frequency of Discula sp. was greatest in June and gradually decreased from July to October whereas the isolation frequency of the sterile mycelium increased during the vegetation period and remained at a high isolation frequency in October. Spores of Discula sp. were released for a very short time in late May, just after the disappearance of the snow cover on the forest floor. These spores may be important for the infection of newly sprouting leaves. [source] The effects of water-level manipulation on the benthic invertebrates of a managed reservoirFRESHWATER BIOLOGY, Issue 5 2010DANIEL C. McEWEN Summary 1. Reservoir creation and management can enhance many ecological services provided by freshwater ecosystems, but may alter the natural conditions to which aquatic biota have adapted. Benthic macroinvertebrates often reflect environmental conditions, and this community may be particularly susceptible to water-level changes that alter sediment exposure, temperature regime, wave-induced sediment redistribution and basal productivity. 2. Using a before,after control,impact experimental design, we assessed changes in macroinvertebrate community structure corresponding with changes in water-level management in two lentic systems in the Voyageurs National Park, Minnesota, U.S.A. Littoral zone (depths 1,5 m) benthic macroinvertebrate assemblages were sampled in Rainy Lake (control system) and Namakan Reservoir (impact system) in 1984,85, and again in 2004,05 following a change in water-level management that began in January 2000. The new regime reduced the magnitude of winter drawdown in Namakan Reservoir from 2.5 to 1.5 m, and allowed the reservoir to fill to capacity in late May, a month earlier than under the prior regime. Rainy Lake water levels were not altered substantially. 3. We found changes in macroinvertebrate community structure in Namakan Reservoir relative to Rainy Lake at 1,2 m depths but not at 3,5 m depths. These shallower depths would have been most directly affected by changes in sediment exposure and ice formation. 4. In 2004,05, Namakan Reservoir benthos showed lower overall abundance, more large-bodied taxa and an increase in non-insect invertebrates relative to 1984,85, without corresponding changes in Rainy Lake. 5. Changes in the benthic community in Namakan may reflect cooler water in spring and early summer as well as lower resource availability (both autochthonous production and allochthonous inputs) under the new regime. [source] Effects of mute swan grazing on a keystone macrophyteFRESHWATER BIOLOGY, Issue 12 2007MATTHEW T. O'HARE Summary 1. This study describes the early summer foraging behaviour of mute swans (Cygnus olor) on the River Frome, a highly productive chalk stream in southern England in which Ranunculus penicillatus pseudofluitans is the dominant macrophyte. 2. A daily maximum of 41 ± 2.5 swans were present along the 1.1 km study reach during the study period (late May to the end of June). The river was the primary feeding habitat. Feeding activity on the river at dawn and dusk was much lower than during daylight, but we cannot rule out the possibility that swans fed during the hours of darkness. 3. The effects of herbivory on R. pseudofluitans biomass and morphology were quantified. Biomass was lower in grazed areas and swans grazed selectively on leaves in preference to stems. A lower proportion of stems from grazed areas possessed intact stem apices and flowering of the plant was reduced in grazed areas. 4. A model, based on the swans' daily consumption, was used to predict the grazing pressure of swans on R. pseudofluitans. The model accurately predicted the number of bird days supported by the study site, only if grazing was assumed to severely reduce R. pseudofluitans growth. The proportion of the initial R. pseudofluitans biomass consumed by a fixed number of swans was predicted to be greater when the habitat area was smaller, initial R. pseudofluitans biomass was lower and R. pseudofluitans was of lower food value. 5. We concluded that the flux of N and P through the study reach was largely unaffected by swan activity. The quality of R. pseudofluitans mesohabitat (the plant as habitat for invertebrates and fish) was significantly reduced by grazing which also indirectly contributed to reduced roughness (Manning's n) and by inference water depth. Wetted habitat area for fish and invertebrates would also be lowered over the summer period as a consequence of the reduction in water depth. It was estimated that, while grazing, an individual swan may eat the same mass of invertebrates per day as a 300-g trout. 6. There is a need to manage the conflict between mute swans and the keystone macrophyte, R. pseudofluitans, in chalk streams, and the modelling approach used here offers a potentially useful tool for this purpose. [source] Nitrogen utilization by Hylocomium splendens in a boreal forest fertilization experimentFUNCTIONAL ECOLOGY, Issue 3 2006Å. FORSUM Summary 1Nitrogen uptake in the terricolous bryophyte Hylocomium splendens (Hedw.) B.S.G. was studied in a boreal forest long-term N-treatment experiment including control plots, N-addition plots (50 kg N ha,1 year,1 for 8 years) and recovery plots (50 kg N ha,1 year,1 for 5 years and thereafter no N addition for 3 years). 2A main objective was to explore whether the N treatments changed bryophyte uptake of different inorganic and organic N forms. In addition, we estimated the contribution of N from throughfall precipitation to the bryophyte N supply. 3The results demonstrated that bryophyte N uptake was similar in all the long-term N-treatment plots. Hylocomium splendens took up more 15N labelled than or glycine when these N forms were applied in situ by the spraying of solutions with N concentrations similar to those in precipitation. 4Analysis of the precipitation collected beneath the closed tree canopy from late May to early October revealed that it contributed 2·0 kg N ha,1 during the period studied, distributed between (78%), amino acid N (17%) and (5%). 5The study highlights that, in addition to analyses of and (normally included in standard environmental monitoring of precipitation), analysis of amino acid N must be performed to account fully for the precipitation N input to bryophytes in boreal forest ecosystems. [source] Diurnal and seasonal variation in methane emissions in a northern Canadian peatland measured by eddy covarianceGLOBAL CHANGE BIOLOGY, Issue 9 2010KEVIN D. LONG Abstract Eddy covariance measurements of methane (CH4) net flux were made in a boreal fen, typical of the most abundant peatlands in western Canada during May,September 2007. The objectives of this study were to determine: (i) the magnitude of diurnal and seasonal variation in CH4 net flux, (ii) the relationship between the temporally varying flux rates and associated changes in controlling biotic and abiotic factors, and (iii) the contribution of CH4 emission to the ecosystem growing season carbon budget. There was significant diurnal variation in CH4 emission during the peak of the growing season that was strongly correlated with associated changes in solar radiation, latent heat flux, air temperature and ecosystem conductance to water vapor. During days 181,215, nighttime average CH4 efflux was only 47% of the average midday values. The peak value for daily average CH4 emission rate was approximately 80 nmol m,2 s,1 (4.6 mg CH4 m,2 h,1), and seasonal variation in CH4 flux was strongly correlated with changes in soil temperature. Integrated over the entire measurement period [days 144,269 (late May,late September)], the total CH4 emission was 3.2 g CH4 m,2, which was quite low relative to other wetland ecosystems and to the simultaneous high rate of ecosystem net CO2 sequestration that was measured (18.1 mol CO2 m,2 or 217 g C m,2). We estimate that the negative radiative forcing (cooling) associated with net carbon storage over the life of the peatland (approximately 2200 years) was at least twice the value of positive radiative forcing (warming) caused by net CH4 emission over the last 50 years. [source] Net grassland carbon flux over a subambient to superambient CO2 gradientGLOBAL CHANGE BIOLOGY, Issue 7 2001P. C. Mielnick Abstract Increasing atmospheric CO2 concentrations may have a profound effect on the structure and function of plant communities. A previously grazed, central Texas grassland was exposed to a 200-µmol mol,1 to 550 µmol mol,1 CO2 gradient from March to mid-December in 1998 and 1999 using two, 60-m long, polyethylene- covered chambers built directly onto the site. One chamber was operated at subambient CO2 concentrations (200,360 µmol mol,1 daytime) and the other was regulated at superambient concentrations (360,550 µmol mol,1). Continuous CO2 gradients were maintained in each chamber by photosynthesis during the day and respiration at night. Net ecosystem CO2 flux and end-of-year biomass were measured in each of 10, 5-m long sections in each chamber. Net CO2 fluxes were maximal in late May (c. day 150) in 1998 and in late August in 1999 (c. day 240). In both years, fluxes were near zero and similar in both chambers at the beginning and end of the growing season. Average daily CO2 flux in 1998 was 13 g CO2 m,2 day,1 in the subambient chamber and 20 g CO2 m,2 day,1 in the superambient chamber; comparable averages were 15 and 26 g CO2 m,2 day,1 in 1999. Flux was positively and linearly correlated with end-of-year above-ground biomass but flux was not linearly correlated with CO2 concentration; a finding likely to be explained by inherent differences in vegetation. Because C3 plants were the dominant functional group, we adjusted average daily flux in each section by dividing the flux by the average percentage C3 cover. Adjusted fluxes were better correlated with CO2 concentration, although scatter remained. Our results indicate that after accounting for vegetation differences, CO2 flux increased linearly with CO2 concentration. This trend was more evident at subambient than superambient CO2 concentrations. [source] The relationship between tiller appearance in spring and contribution to dry-matter yield in perennial ryegrass (Lolium perenne L.) cultivars differing in heading dateGRASS & FORAGE SCIENCE, Issue 2 2005A. S. Laidlaw Abstract The relative contribution of tillers present in April and those appearing in consecutive periods in spring was assessed for perennial ryegrass cultivars in the three maturity groups (early, intermediate- and late-heading). Each group was represented by two diploid and one tetraploid cultivar each in plots in their third (2000) and fourth (2001) harvest years in three replicated blocks receiving an average of 325 kg N ha,1 and cut seven (in 2001) or eight (in 2000) times annually. ,Main' tillers and their daughters were marked with colour-coded PVC-covered wire loops in early April as were daughters which appeared in consecutive periods between harvests, the loop colour identifying the period of origin of the tiller. Tillers were harvested at cutting height (5 cm) before the plots were harvested and the herbage from tillers with the same colour code bulked per plot. Tillers were identified retrospectively as ,reproductive' if they had been decapitated at the previous harvest. Dry-matter yield was higher in the early than late-heading cultivars in April and early May but this was reversed in harvests in late May and June. The early heading group had a lower lamina content than the late-heading group during reproduction growth, both due to the reproductive tillers (mainly those which overwintered) having a lower leaf content and to their being fewer and smaller vegetative tillers during the reproductive phase than for the late-heading group. Turnover of tillers was high in spring due to decapitation of reproductive tillers and rapid post-flowering tillering. This was particularly pronounced in the early heading group which also had slightly more tillers marked in April which were subsequently decapitated than in the other maturity groups, i.e. 0·56 compared with 0·44 for the late-maturing group. Mean ratios of rate of death: rate of tillering for 3 years (1999,2001) for the early and late-heading groups were 0·8 and 0·4, respectively, for April,May and 1·1 and 2·4, respectively, for June indicating the different patterns in tiller turnover for the two extreme maturity groups. Information on tiller origin and contribution to yield can be used to refine tiller-based grass growth models. [source] Setting management limits for the production and utilization of herbage for out-of-season grazingGRASS & FORAGE SCIENCE, Issue 1 2000Laidlaw Three experiments were carried out on perennial ryegrass-dominant swards to provide a basis for recommendations for the limits to (a) building up and timing of utilization of a herbage ,bank' for out-of-season grazing and (b) duration and intensity of early spring grazing in the United Kingdom and Ireland. In experiment 1, the effect of regrowth interval (from 7 September, 20 October, 17 November or 15 December) in autumn on herbage accumulation, leaf turnover and on subsequent spring growth was investigated. Swards regrown from early September reached maximum herbage mass (about 3 t ha,1 DM) and leaf lamina content in mid-November, by which time senescence rate exceeded rate of production of new leaves. New leaf production and senescence rates were greater in swards remaining uncut until December than in those cut in October or November. Time of defoliation up to December had no effect on spring herbage mass in the subsequent spring. Defoliating in March reduced herbage mass in late May by less than 20%. Experiment 2 investigated the progress in herbage growth and senescence in swards regrowing from different times in late summer and autumn to produce herbage for utilization beyond the normal grazing season. Treatments in a randomized block design with three replicates were regrowths from 19 July, 8 August, 30 August and 20 September. Based on a lower ceiling of leaf and total herbage mass being reached with progressively later regrowths, beyond which leaf senescence generally exceeded leaf production and herbage mass declined, it was concluded that currently recommended rotation lengths for this period should extend from 3 weeks in late July to 8 weeks for swards previously grazed in mid-September. In both experiments, leaf senescence commenced earlier (by one leaf-age category) than previously published estimates and so brought forward the time at which senescence rates balanced leaf growth rates. In experiment 3, designed to evaluate the effect of daily grazing period and intensity in early spring on herbage regrowth, dairy cows grazed successive plots (replicates) for 2 or 4 h each day at two intensities (target residual heights of 5 or 7 cm) in March to mid-April. Regrowth rate was similar in all treatments including the ungrazed control, despite soil moisture content being relatively high on occasions. Tiller density was significantly reduced in May by grazing plots in early or mid-April. It is concluded that in autumn there are limits to which rotation lengths should be extended to produce herbage for out-of-season grazing owing to attainment of ceiling yields. Although utilization in early spring may reduce herbage availability in spring, out-of-season utilization need not reduce herbage growth rates in early spring. [source] Influence of climate and reproductive timing on demography of little brown myotis Myotis lucifugusJOURNAL OF ANIMAL ECOLOGY, Issue 1 2010Winifred F. Frick Summary 1. Estimating variation in demographic rates, such as survival and fecundity, is important for testing life-history theory and identifying conservation and management goals. 2. We used 16 years (1993,2008) of mark,recapture data to estimate age-specific survival and breeding probabilities of the little brown myotis Myotis lucifugus LeConte in southern New Hampshire, USA. Using Kendall & Nichols' (1995) full-likelihood approach of the robust design to account for temporary emigration, we tested whether survival and breeding propensity is influenced by regional weather patterns and timing of reproduction. 3. Our results demonstrate that adult female survival of M. lucifugus ranged from 0·63 (95% CL = 0·56, 0·68) to 0·90 (95% CL = 0·77, 0·94), and was highest in wet years with high cumulative summer precipitation. First-year survival [range: 0·23 (95% CL = 0·14, 0·35) to 0·46 (95% CL = 0·34, 0·57)] was considerably lower than adult survival and depended on pup date of birth, such that young born earlier in the summer (c. late May) had a significantly higher probability of surviving their first year than young born later in the summer (c. mid-July). Similarly, the probability of young females returning to the maternity colony to breed in the summer following their birth year was higher for individuals born earlier in the summer [range: 0·23 (95% CL = 0·08, 0·50) to 0·53 (95% CL = 0·30, 0·75)]. 4. The positive influence of early parturition on 1st-year survival and breeding propensity demonstrates significant fitness benefits to reproductive timing in this temperate insectivorous bat. 5. Climatic factors can have important consequences for population dynamics of temperate bats, which may be negatively affected by summer drying patterns associated with global climate change. 6. Understanding long-term demographic trends will be important in the face of a novel disease phenomenon (White-Nose Syndrome) that is associated with massive mortalities in hibernating bat species, including M. lucifugus, in the northeastern United States. [source] Reproductive cycle and sex inversion in razor fish, a protogynous labrid in the southern Mediterranean SeaJOURNAL OF FISH BIOLOGY, Issue 6 2004G. Candi The reproductive biology of the Mediterranean razor fish Xyrichthys novacula was investigated by demographic data and histological analysis of the female, intersexual and male gonads. Specimens were collected by bottom trawl on a monthly basis between June 2000 and July 2001 in a sandy bay in southern Thyrrenian. Gonad histology confirmed that the Mediterranean razor fish is a monandric, protogynous hermaphrodite. Females reached first sexual maturity at 100 mm (LT) and the estimated mean LT at first maturity (L50) was 125 mm. Females exhibited asynchronous ovarian development and multiple ovulations occurred over the spawning period. Vitellogenesis started in early May and spawning occurred from late May until late September. Sexual transition involved a large-scale atresia of all oocyte stages and a massive degeneration of ovarian tissue followed by primordial germ cells proliferation. Sex change began at spawning time (June) but transitional individuals tended to cluster at the end of the reproductive period (September). They accounted for 17·1% of the population sampled and were found in a broad size range (105,150 mm LT). [source] Behavioural responses of dairy cattle to the stable fly, Stomoxys calcitrans, in an open field environmentMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2006B. A. Mullens Abstract., Individual cows (25 in each of four herds) were monitored 8,10 times weekly for 12 weeks (stable fly season) on a southern California dairy, with 100 observations per cow. The numbers of biting stable flies, Stomoxys calcitrans (L.) (Diptera: Muscidae) on the front legs and the frequencies of four fly-repelling behaviours per 2-min observation period [head throws, front leg stamps, skin twitches (panniculus reflex) and tail flicks] were recorded. Fly numbers varied, peaking at 3.0,3.5 flies per leg in week 9 (late May). Weekly herd mean frequencies of fly-repelling behaviours were highly dependent on fly numbers, with a linear regression r2 > 0.8. Head throws and stamps were less frequent than skin twitches and tail flicks. Individual cows differed in numbers of stable flies and behaviours. Behaviours were correlated with flies for individual cows, but at a lower level than were herd means (r = 0.3,0.7). Cows that stamped more within a herd tended to have lower fly counts; other fly-repelling behaviours were less effective. Cows maintained ranks within a herd with regard to fly numbers (r = 0.47), head throws (0.48), leg stamps (0.64), skin twitches (0.69) and tail flicks (0.64). Older cows tended to harbour higher fly numbers and to stamp less relative to younger adult cows. Ratios of leg stamps and head throws to fly numbers dropped significantly through time, suggesting habituation to pain associated with fly biting. Tail flicks were not effective for repelling Stomoxys, but were easiest to quantify and may help in monitoring pest intensity. At this low,moderate fly pressure, no consistent impacts on milk yield were detected, but methods incorporating cow behaviour are recommended for future studies of economic impact. [source] A very low response rate in an on-line survey of medical practitionersAUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 3 2008Campbell Aitken Abstract Objective: To report on the response rate achieved in a survey of medical practitioners and discuss the reasons for it. Method: An on-line (internet-based) survey of all 609 registered pharmacotherapy prescribers in Victoria and Queensland; invitations to participate were sent by mail in late April 2007, and one reminder letter in late May 2007. Results: Six hundred and nine invitation letters were mailed, nine were returned to sender, and 52 questionnaires completed, making the overall response rate 52/600 = 8.7%. The response rate in Queensland was 13.2% (16/121), and in Victoria 7.5% (36/479). Conclusion(s): Despite utilising sound techniques, our response rate was much lower than those achieved in recent Australian paper-based surveys of medical practitioners. It is possible that the issue being addressed (injecting-related injuries and diseases) was not of high priority for many invitees, leading to reduced response. Implications: On-line surveys are not yet an effective method of collecting data from Australian medical practitioners; researchers should continue to use paper questionnaires for maximum response. [source] | |||||||||||||||||||||||||