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One Season (one + season)
Selected AbstractsOf squeezers and skippers: factors determining the age at moult of immature African Penguins Spheniscus demersus in NamibiaIBIS, Issue 2 2005JESSICA KEMPER We used banding and resighting records of 391 African Penguins Spheniscus demersus banded as chicks and later resighted during immature moult to explain the roles of date of fledging and age at moult in determining the season of moult and its timing within the season. Breeding was continuous, but immature moult occurred mainly during spring and summer. Age at immature moult extended over 11 months, from 12 to 23 months after hatching. Birds that fledged during summer and early autumn generally moulted during the next moult season (squeezers), whereas birds that fledged in late autumn, winter and spring skipped the next moult season to moult only the following season (skippers). There was a significant relationship between age at moult and moult date, with young birds moulting later in the season than older birds. The age at moult of immature birds appears to be constrained by minimum age, moult seasonality and plumage wear. Birds that fledged over nearly 2 years moult during one season. Counts of moulting immature African Penguins have not been used to estimate year-class strength and post-fledging survival owing to the wide range of ages at immature moult. Our results provide the means of assigning recruits to specific age groups. [source] Interannual variability of the Tropical Atlantic independent of and associated with ENSO: Part II.INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 14 2006The South Tropical Atlantic Abstract Two dominant ocean,atmosphere modes of variability on interannual timescales were defined in part I of this work, namely, the North Tropical Atlantic (NTA) and South Tropical Atlantic (STA) modes. In this paper we focus on the STA mode that covers the equatorial and sub-tropical South Atlantic. We show that STA events occurring in conjunction with ENSO have a preference for the southern summer season and seem to be forced by an atmospheric wave train emanating from the central tropical Pacific and travelling via South America, in addition to the more direct ENSO-induced change in the Walker Circulation. They are lagged by one season from the peak of ENSO. These events show little evidence for other-than-localised coupled ocean,atmosphere interaction. In contrast, STA events occurring in the absence of ENSO favour the southern winter season. They appear to be triggered by a Southern Hemisphere wave train emanating from the Pacific sector, and then exhibit features of a self-sustaining climate mode in the tropical Atlantic. The southward shift of the inter tropical convergence zone that occurs during the warm phase of such an event triggers an extra tropical wave train that propagates downstream in the Southern Hemisphere. We present a unified view of the NTA and STA modes through our observational analysis of the interannual tropical Atlantic variability. Copyright © 2006 Royal Meteorological Society. [source] Climate variability in Malawi, part 1: dry summers, statistical associations and predictabilityINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 11 2002M. R. Jury Abstract Climate variability and predictability over tropical southern Africa is studied using a Malawi summer rainfall index. Thermodynamic and circulation patterns are examined and statistical associations are analysed. Links with El Niño,southern oscillation (ENSO) and quasi-biennial oscillation (QBO) phase are significant and consistent with those found for southern Africa. Correlations are mapped with respect to the Malawi rainfall index, and the regional expression of ENSO emerges quite clearly. Negative r values for sea-surface temperature (SST) in the west Indian Ocean contrast with positive r values in the east Atlantic and Agulhas region. The thermodynamic pattern ,anchors' a standing Rossby wave, comprised of northwest,southeast-oriented centres of action across the Mozambique Channel and southern Africa, and east of Madagascar to East Africa. A meandering of the sub-tropical jet stream is an expression of the standing Rossby wave, leading to vertical motions over southern Africa. The pattern develops at least one season in advance, and predictive indices are extracted in the July,September season for use in a multivariate model to predict the Malawi summer rainfall. The three-area SST index, formulated to capture the ENSO-modulated Rossby wave pattern, is the most influential predictor, followed by air pressure over the east Indian Ocean and the stratospheric zonal wind anomaly (QBO). Skilful results are found, with a 55% hindcast fit and two-thirds of tercile categories correctly forecast in independent tests. Copyright © 2002 Royal Meteorological Society. [source] Breeding habitat selection in cliff swallows: the effect of conspecific reproductive success on colony choiceJOURNAL OF ANIMAL ECOLOGY, Issue 1 2000Charles R. Brown Summary 1.,One way that animals may select breeding sites is by assessing the reproductive success of conspecifics in one season and settling the next year in those habitat patches where success collectively had been greatest. This sort of habitat assessment may promote the formation of colonies at high quality sites. 2.,We examined whether cliff swallows, Petrochelidon pyrrhonota, in south-western Nebraska used conspecific breeding performance to choose colony sites. 3.,Reproductive success at colony sites varied spatially within seasons and between seasons, and was autocorrelated at a site from one year to the next, but not over longer time intervals. Cliff swallows thus met the conditions for potential use of information on conspecific breeding performance. 4.,Among sites re-used in consecutive years, those with highest collective success in one season showed the greatest rates in colony growth the next season, including the greatest influx of immigrants. 5.,The probability of colony-site re-use in successive years increased with collective reproductive success and average breeder body mass (a measure of individual condition) the previous season. 6.,Cliff swallows probably use conspecific breeding performance in selecting colonies. This mechanism is one component of habitat selection that also includes attraction to conspecifics and assessment of an individual's own success. [source] High hybrid fitness at seed and seedling life history stages in Louisiana irisesJOURNAL OF ECOLOGY, Issue 3 2003Jill A. Johnston Summary 1,Relative fitness of hybrid genotypes will determine the role that hybrids can play in the evolution of a plant species complex. To realistically evaluate hybrid fitness and how environmental variation affects fitness in a long-lived species, all life stages must be considered. 2,We evaluated germination, seedling survival and growth of two Louisiana iris species and their early generation hybrids in several experimental environments created by manipulating light and water levels. 3,Species and hybrids all required similar moist conditions for germination. The proportion of germinated seeds was highest in shade and seedling survival highest in sun. 4,Iris brevicaulis exhibited the lowest germination and seedling survival overall, yet those individuals that survived grew vigorously. Iris fulva had high levels of germination and seedling survival, but yielded the smallest plants at the end of one season of growth. 5,Germination rates, seedling survival and seedling growth of hybrids equalled or exceeded one or both parent species, indicating that hybrids in this system have high relative fitness at seed and seedling stages in several environmental conditions. 6,We conclude that Iris fulva and I. brevicaulis share a common regeneration niche and similar early stage relative fitness with their hybrids. Thus, environment-dependent fitness in this system is due primarily to selection at adult stages. [source] Single-season heteroscedasticity in time seriesJOURNAL OF FORECASTING, Issue 3 2007Yorghos Tripodis Abstract We consider seasonal time series in which one season has variance that is different from all the others. This behaviour is evident in indices of production where variability is highest for the month with the lowest level of production. We show that when one season has different variability from others there are constraints on the seasonal models that can be used; neither dummy and trigonometric models are effective in modelling this type of behaviour. We define a general model that provides an appropriate representation of single-season heteroscedasticity and suggest a likelihood ratio test for the presence of periodic variance in one season.,,Copyright © 2007 John Wiley & Sons, Ltd. [source] Effect of Seasonality on Distribution of Macroalgae in a Stream System (Xin'an Spring) in Shanxi Province, North ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 8 2006Bian-Fang Hu Abstract A survey of the seasonal distribution of macroalgae in a stream system in Shanxi Province, north China, was undertaken from July 2004 to April 2005. The relative abundance and percentage cover of macroalgae, and several environmental factors were monitored along a 20-m stretch at each of four sites, at intervals of approximately three months (one sampling per season). Several stream conditions were relatively constant over the sampling period (pH, maximum width and maximum depth), whereas others exhibited a distinct seasonal pattern (water temperature and specific conductance), and some fluctuated with no discernable seasonal pattern (current velocity and dissolved oxygen). Forty-two species of macroalgae were found, with a predominance of Chlorophyta (26 species, 61.9%). Rhodophyta and Charophyta represented the smallest proportion (1 species each, 2.38%). Six macroalgae species were the most widespread, occurring in all four sampling sites. Twelve species were found at only one site each. In terms of seasonality, eight species occurred throughout the year, whereas 16 species were found in only one season each. The macroalgal community at Xin'an Spring was species rich relative to other streams. Species richness per sampling site was negatively correlated with pH. Principal component analysis revealed that no single variable had much influence on the macroalgal seasonal dynamics. We calculated Sorensen similarity indices to compare our study with other continent-wide surveys of stream macroalgae, but the similarity indices were all very low. This study also shows that macroalgae in different locations have significant reproductive isolation. (Managing editor: Ya-Qin Han) [source] A RESIDENT POPULATION OF INDO-PACIFIC BOTTLENOSE DOLPHINS (TURSIOPS ADUNCUS) IN AMAKUSA, WESTERN KYUSHU, JAPANMARINE MAMMAL SCIENCE, Issue 1 2002Miki Shirakihara Abstract Residency patterns and population size were examined for Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the coastal waters of Amakusa-Shimoshima Island, western Kyushu, Japan, from summer 1994 to fall 1998. A total of 203 individuals were identified. The number of newly identified individuals barely increased after the first 1.5 yr. The identified individuals in one season were frequently resighted with percentages of mostly over 60% during the subsequent seasons. Most of the dolphins off Amakusa were yearround residents, although the total range of their habitat was unknown. The population size estimated by the mark-recapture technique was 218 individuals with a CV of 5.41% in 1995,1997. The group commonly consisted of more than 100 individuals. The large group size was thought to be a response to feeding on schooling fishes. [source] Population genetic structure of Plasmopara viticola in the Western Cape Province of South AfricaMOLECULAR PLANT PATHOLOGY, Issue 6 2007TREVOR KOOPMAN SUMMARY Plasmopara viticola populations in South Africa were studied for two consecutive grape growing seasons, in an organically managed and a conventional fungicide-sprayed vineyard. Three to four samplings in each season were genotyped with four microsatellite markers (GOB, CES, ISA and BER). Population differentiation (Fst) between the conventional fungicide-sprayed vineyard and organically managed vineyard was low (0.004 and 0.016) in both growing seasons, suggesting one metapopulation. However, differences in the relative contribution of the predominant and new genotypes to epidemics in the two vineyards suggested that fungicide applications may have selected for reduced pathogen diversity. In both years and vineyards, sexual (oosporic) reproduction and/or migration occurred throughout the year and contributed between 12 and 74% to the epidemic. Hardy,Weinberg analyses suggest that South African P. viticola populations are randomly mating. Epidemics in both years and vineyards were dominated by one or two genotypes that each contributed between 14 and 67% to the epidemic through asexual reproduction. The remaining genotypes showed low levels of asexual reproduction, with most genotypes never being able to reproduce asexually. However, for some genotypes asexual reproduction was important, as it enabled survival of the genotypes from one season to the next. In total, ten genotypes were able to survive asexually or vegetatively from one season to the next. The populations were further characterized by the presence of a high frequency of isolates that most likely have elevated ploidy levels. [source] Long-term monitoring in IC4665: fast rotation and weak variability in very low mass objectsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2009Alexander Scholz ABSTRACT We present the combined results of three photometric monitoring campaigns targeting very low mass (VLM) stars and brown dwarfs in the young open cluster IC4665 (age ,40 Myr). Each of our observing runs covers time-scales of ,5 d in the seasons 1999, 2001 and 2002, respectively. In all three runs, we observe ,100 cluster members, allowing us for the first time to put limits on the evolution of spots and magnetic activity in fully convective objects on time-scales of a few years. For 20 objects covering masses from 0.05 to 0.5 M,, we detect a periodic flux modulation, indicating the presence of magnetic spots co-rotating with the objects. The detection rate of photometric periods (,20 per cent) is significantly lower than in solar-mass stars at the same age, which points to a mass dependence in the spot properties. With two exceptions, none of the objects exhibits variability and thus spot activity in more than one season. This is contrary to what is seen in solar-mass stars and indicates that spot configurations capable of producing photometric modulations occur relatively rarely and are transient in VLM objects. The rotation periods derived in this paper range from 3 to 30 h, arguing for a lack of slow rotators among VLM objects. The periods fit into a rotational evolution scenario with pre-main sequence contraction and moderate (40,50 per cent) angular momentum losses due to wind braking. By combining our findings with literature results, we identify two regimes of rotational and magnetic properties, called C- and I-sequence. Main properties on the C-sequence are fast rotation, weak wind braking, H, emission and saturated activity levels, while the I-sequence is characterized by slow rotation, strong wind braking, no H, emission and linear activity-rotation relationship. Rotation rate and stellar mass are the primary parameters that determine in which regime an object is found. We outline a general scheme to understand rotational evolution for low-mass objects in the context of these two regimes and discuss the potential as well as the problems of this picture. [source] Rodents, plants, and precipitation: spatial and temporal dynamics of consumers and resourcesOIKOS, Issue 3 2000S. K. Morgan Ernest Resource/consumer dynamics are potentially mediated by both limiting resources and biotic interactions. We examined temporal correlations between precipitation, plant cover, and rodent density, with varying time lags using long-term data from two sites in the Chihuahuan desert of North America: the Sevilleta Long-term Ecological Research site (LTER), New Mexico, USA and a site near Portal, Arizona, USA. We also calculated the spatial correlations in precipitation, plant cover, and rodent dynamics among six sites, five at Sevilleta and one at Portal. At Sevilleta, all three variables were temporally correlated, with plant cover responding to precipitation during the same growing season and rodent populations lagging at least one season behind. At Portal, plant stem count was also correlated with precipitation during the same growing season, but there was no significant correlation between rodents and either precipitation or plant growth. Spatial correlations in plant cover and rodent populations between sites reflected the localized nature of summer rainfall, so that sites with highly correlated summer precipitation exhibited higher correlations in plant cover and rodent populations. In general, our results indicate that limiting resources influence consumer dynamics, but these dynamics also depend crucially on the biotic interactions in the system. [source] Carbon and nitrogen dynamics in acid detergent fibre lignins of beech (Fagus sylvatica L.) during the growth phasePLANT CELL & ENVIRONMENT, Issue 4 2002J. Dyckmans Abstract To study the incorporation of carbon and nitrogen in different plant fractions, 3-year-old-beech (Fagus sylvatica L.) seedlings were exposed in microcosms to a dual-labelling experiment employing 13C and 15N throughout one season. Leaves, stems, coarse and fine roots were harvested 6, 12 and 18 weeks after bud break (June to September) and used to isolate acid-detergent fibre lignins (ADF lignin) for the determination of carbon and nitrogen and their isotope ratios. Lignin concentrations were also determined with the thioglycolic acid method. The highest lignin concentrations were found in fine roots. ADF lignins of all tissues analysed, especially those of leaves, also contained significant concentrations of nitrogen. This suggests that lignin-bound proteins constitute an important cell wall fraction and shows that the ADF method is not suitable to determine genuine lignin. ADF lignin should be re-named as ligno-protein fraction. Whole-leaf biomass was composed of 50 to 70% newly assimilated carbon and about 7% newly assimilated nitrogen; net changes in the isotope ratios were not observed during the experimental period. In the other tissues analysed, the fraction of new carbon and nitrogen was initially low and increased significantly during the time-course of the experiment, whereas the total tissue concentrations of carbon remained almost unaffected and nitrogen declined. At the end of the experiment, the whole-tissue biomass and ADF lignins of fine roots contained about 65 and 50% new carbon and about 50 and 40% new nitrogen, respectively. These results indicate that significant metabolic activity was related to the formation of structural biopolymers after leaf growth, especially below-ground and that this activity also led to a substantial binding of nitrogen to structural compounds. [source] | ||||||||||