bluuebunny/crossref_metadata_2025_split huggingface dataset:
Number and proportion of southern bird species in Norway in relation to latitude, spring temperature and respiration equivalent
Authors: Heggberget Thrine Moen 
Published: July 2006

Numbers and proportions of southern bird species in Norway were analyzed, mainly using data from the literature. Southern, regularly breeding, bird species constituted 18% of water/wetland birds and 45% of landbirds. This difference is related to the opposing latitudinal gradients in species richness. Also, the majority of southern water/wetland bird species in Norway are associated with a habitat type that covers small areas, in contrast to southern landbird species.Correlation analysis showed that May temperature and respiration equivalent (a measure of potential for plant growth and ripening) each could account for about 85% of the variation in proportion of southern passerine species, and about 75% in proportion of southern wader species.Significant second‐order, partial correlations were found between proportion of southern passerines and latitude. May temperature and respiration equivalent. It is suggested that the northern distributional limits of passerines, may be indirectly causally related to May temperature and respiration equivalent, and also directly causally related to May temperature. Evidence of causal relationships between northern distributional limits of waders and May temperature or respiration equivalent was not found. For May temperature this may be because of insufficient number of wader censuses.
Variation of reproductive traits in a population of the lizard Lacerta vivipara
Authors: Bauwens Dirk , Verheyen Rudolf F. 
Published: July 2006

Variation in reproductive traits (sexual maturity, clutch size, clutch weight, mean egg mass, newborn weight) was studied during a four year period in a population of the live‐bearing lizard Lacerta vivipara. Sexual maturity was associated with attaining a minimum body size. Clutch size increased with female body length and litter weight increased with clutch size. A major component of the within year variation in these reproductive traits was attributable to female size. Analysis of successive clutches in individual females indicated that a significant fraction of the variation in litter size, adjusted for female length, was due to consistent differences between individuals. Newborn weight varied within and among litters, but no relations between hatchling mass or mean egg mass in a litter and other traits were detected.Size‐adjusted reproductive performances remained constant during the course of this study, even though environmental conditions (weather factors, food availability) varied annually. Observed among year variations in reproductive characteristics were attributable to differences in the body size distributions of the adult females.
Spatial structuring and dispersal in a high density population of the California vole Microtus californicus
Authors: Heske Edward J. 
Published: July 2006

Space use patterns of California voles are described from intensive live‐trapping data obtained during the late breeding season in a peak density year. Operational sex ratios were strongly female biased. Breeding males had mutually exclusive home ranges that overlapped the home ranges of one to several females. The average male home range was larger than the average female home range and tended to encompass female home ranges in their entirety. Breeding females had home ranges that often overlapped extensively with the home ranges of other breeding females. The degree of overlap, however, tended to be either very high or very low, indicating that groups of females may act territorially among themselves. Family groups that may include members of sequential litters formed at high density. Males on experimental removal grids had larger home ranges than males on the high density grids and some became wanderers while most females had home ranges comparable to those on the high density grids.Dispersers onto low density grids were not a random sample of the high density population; large breeding adults and small juveniles were under‐represented. No sex differences in dispersal were noted. Immigration into the high density populations was probably negligible.
Dispersal routes of small mammals at an abandoned field in central Sweden
Authors: Hansson Lennart 
Published: July 2006

Small mammals dispersing in habitat corridors to and from an abandoned field in south‐central Sweden, at the forest edge and inside the forest, were continuously sampled during 1977–81. Altogether 967 specimens of ten species were obtained. Number and dynamics of grassland species were censused intensively in the centre of the abandoned field and extensively on other abandoned fields nearby. Numbers of resident and dispersing animals correlated positively.Grassland field voles Microtus agrestis were almost only obtained in the corridors and woodland bank voles Clethrionomys glareolus mainly in the forest and in narrow grassland corridors. Both these species are folivorous. Granivorous‐insectivorous Apodemus and Sorex species moved more on a broad front through various habitats. Different population categories did not show any elear differences in dispersal routes. The findings of different dispersal strategies in a species gradient are discussed in relation to the local dynamics of subpopulations belonging to metapopulations inhabiting whole landscapes. Implications for pest management and conservation of endangered species are considered.
Spatio‐temporal organization of the bird communities in two Mediterranean montane forests
Authors: Carrascal Luis M. , Potti Jaime , Sanchez‐Aguado Francisco J. 
Published: July 2006

Seasonal changes of bird communities and use of foraging substrates by the birds were studied in two forests with contrasting vegetation structure in montane and subalpine levels of central Spanish mountains throughout complete annual cycles. Common factors contributing most to foraging segregation among species were found to be the foraging on the ground vs that on vegetation and use of proximal vs distal tree parts. A complete dissimilarity exists between the composition of the respective foliage‐gleaning guilds, the converse being true for the trunk‐searchers.Temporal distribution of bird species is to a great extent determined by their use of space, thus existing a gradient of seasonality with maxima for ground‐searchers, minima for trunk‐gleaners and intermediate positions for foliage‐gleaners. A close relationship among temporal variability, mean annual density and niche breadth is found for the subalpine pinewood community, but not for that from the montane oakwood, this being related with their contrasting migratory patterns and the structural stability of vegetation in each wood. The pattern of covariation in community parameters mirrors the summed response of individual bird species to the changing environmental conditions. Increases in community richness, density and diversity are related to temporal invasion by ground and foliage‐gleaners of these highly seasonal Mediterranean habitats.
The effects of inundation on marine littoral Collembola
Authors: Witteveen J. , Joosse E. N. G. 
Published: July 2006

The impact of inundation was studied on two marine littoral collembolan species: Isotoma viridis and Hypogastrura viatica.The unwettable integument causes the collembolans to drift on the water surface during inundation. When trapped under water they try to climb up from below the water level. Their survival on the water surface is higher than under water. H. viatica, occurring in a habitat that is inundated relatively frequently and over a long time, had a greater ability to survive on the water surface than I. viridis.The mortality on the water surface was caused by starvation. A strong correlation between the mortality and the metabolic rate was shown. The highest mortality was found at lower salinities, where oxygen consumption of the animals is highest. The metabolic rate and mortality was lower at salinities up to 75% S.W. At 100% S.W. there was again a rise in metabolic rate and mortality. This is probably due to energy‐demanding processes concerning internal osmotic and ionic regulation.After flooding, transport by sea currents can play a role in the distribution of the species. Reproductive synchronization after inundation is considered to be a mechanism for restoring a disturbed population.
Microcrustacean community structure and biomass in marsh and lake habitats of the Okefenokee Swamp: seasonal dynamics and responses to resource manipulations
Authors: Schoenberg Steven A. 
Published: July 2006

Microcrustacean community and biomass dynamics were studied for two years in a Nymphaea‐Eriocaulon macrophyte marsh and a nearby shallow lake which lacked macrophytes in the Okefenokee Swamp. In this blackwater, acidic wetland, microcrustacean diversity and biomass were similar to other circumneutral lakes and littoral areas, contributing to a productive fish assemblage. In the lake, the annual biomass pattern (15–1627 μg 1−1) was unimodal and was dominated by the crustaceans Diaptomus sinuatus and Eubosmina tubicen. Rotifers were occasionally important, constituting up to 55% of total biomass. Over the long term, mean annual biomass in this post‐drought study are higher than in pre‐drought years. In the marsh, biomass (11–777 μg 1−1) fluctuated biomodally with late winter depressions corresponding to low temperatures and midsummer declines indicative of increasing fish predation. Summer dominance shifted between years from Macrothricidae in 1982 to Sididae in 1983. Variation in biomass correlated most strongly with algal chlorophyll in the marsh and with bacterial density in the lake.In field enclosure experiments in which primary production was reduced by shading, microcrustacean responses varied between lake and marsh habitats and with season. Lake zooplankton were consistently suppressed by reduced algal resources in winter, spring and summer experiments, with greatest responses to shading in the summer. Marsh microcrustacea were most affected in the winter experiment and became less sensitive to manipulated resource levels in spring and summer. Decoupling of these consumers from autotrophic resources in the marsh, but not in the lake, coincides with times of high macrophyte turnover and warming temperatures which promote the conversion of detritus into heterotrophic resources such as bacteria. The conflict between interactions implied by the experimental approach vs statistical criteria emphasizes a need to interpret resource dependence from seasonal dynamics of field populations with caution.
The influence of precocious sexual maturation on survival to adulthood of river stocked Baltic salmon, Salmo salar, smolts
Authors: Lundqvist H. , Clarke W. C. , Johansson H. 
Published: July 2006

During three consequtive years, 1975–1977, Individually tagged Baltic salmon Salmo salar smolts of sexually immature male and female fish (n = 35027, mean size: 15.2 cm) and precocious males (n = 6518, mean size: 14.2 cm) were released into Umeälven (Ume river), northern Sweden. Rate of survival (% captured adults) based on 3714 recoveries was significantly higher (p < 0.01) for smolts from immature fish (10.2%) than those from smolts of early maturing males, i.e. precocious males (2.2%). corresponding to an average yield of 474 and 85 kg per KHX) smolts released, respectively. Gain in survival was on average 2.5% and 1.4% per cm increase in smolt size for immature smolts and smolts from precocious males, respectively. The poor survival among smolts of precocious males is suggested to he related to an interaction between sexual maturation and smolting linked to incompletely resorbed gonads leading to a non migratory behaviour. These non migratory males are then suggested to suffer heavily by predation in the river.The two smolt categories had a similar growth pattern in sea. Smolts from precocious males did not mature early in sea indicating no relation to grisling, i.e. sexually maturing fish returning after first winter in sea. Adult weight of fish returning the fourth summer after release was related to smolt size (P < 0.05). Our Response Surface Model (RSA) predicted that large smolts (19.0 cm) had a higher specific growth rate over their life‐span compared to small smolts (<15.0 cm), 0.86% d−1 and 0.46% d−1, respectively. Large smolts (19.0 cm) attained a size of 3.0 kg during their second winter in sea about six months earlier than small smolts (13.0 cm). The paper discusses alternative release strategies that can be employed if the ultimate goal of salmon stocking is maximizing yield.
Faunal diversity and vegetation structure of some deciduous forests in South Sweden
Authors: Gerell Rune 
Published: July 2006

The relationships of faunal diversity and vegetation structure were studied in twenty deciduous forest plots in South Sweden, all of them managed. Following animal groups were censused: shrews (Soricidae), bats (Chiroptera), voles (Cricetidae), fieldmice (Muridae), birds (Aves), groundliving beetles (Coleoptera), spiders (Araneida), and harvestmen (Opilionidae). The analysis of the 22 vegetation variables was made by means of repeated and rotated PCA. Rarefaction was used to ordinate the bird species richness of the different forest plots.The multivariate vegetational analysis resulted in three distinct and readily interpretable components: horizontal and vertical spatial heterogeneity, and mean basal area. The number of small mammal species (except bats) was greatest in forests with great amount of understory while the number of bat species increased with increasing mean basal area. The number of bird species in a fixed number of territories was also highly correlated with the mean basal area. Hence, maximum bird species richness was obtained in mature forests but not in those with greatest vertical heterogeneity. The invertebrate communities showed very few distinct relationships to the vegetation structure.Dominance decreased as vegetation complexity increased. Dominance also decreased with increasing species richness in all faunal communities studied.
Emergence phenology and ecology of aquatic and semi‐terrestrial insects on a boreal raised bog in Central Finland
Authors: Paasivirta Lauri , Lahti Tapani , Perätie Timo 
Published: July 2006

Emergence of peatland insects was studied in Central Finland by sampling insects on a raised bog with tent traps from five different surfaces: muddy hollow without vegetation; hollow covered with Sphagnum; deep (0.7–0.9 m) open‐water pool; shallow (about 0.3 m) pool with bottom covered by Carex vegetation; shallow (about 0.3 m) pool with bare muddy bottom. The material was collected at two‐days intervals from 13 May until 31 August in 1981.Biomass emerging from the sites varied considerably. In general, aquatic sites were clearly more productive than semi‐terrestrial sites. Corrected total biomass values for deep pools, shallow Carex pools, and shallow mud pools were 2.471, 1.066, and 0 514 g m−2, respectively. The corresponding values for muddy and Sphagnum hollows were 0.208 and 0.236 g m−2, respectively.All chironomids, chaoborids and trichopterans from the aquatic sites were identified to species, and their emergence phenology and habitat preferences are discussed. 14 species were considered as eurytopic littoral species, 9 species showed strong preference for the bog pools or polyhumic lakes, and 8 species were of diverse origin. Differences in emergence patterns and habitat preferences are probably connected with species‐specific resistances to freezing and oxygen and nutrient requirements. The role of emerging insects in the peatland food webs, especially as food for breeding birds, is briefly discussed.
Changing female spacing behaviour and demography in an enclosed breeding population of Clethrionomys glareolus
Authors: Ylönen Hannu , Kojola Taina , Viitala Jussi 
Published: July 2006

The social organization of Clethrionomys glareolus Schreber was studied by live trapping in an enclosure of 0.8 ha in Central Finland between the years 1982–1986. The enclosure consisted of three habitats: abandoned field, brushwood, and moist spruce heath forest.The population density increased from 50 voles ha−1 in 1982 and 1983 to 150 ha−1 in 1984 and 1985. In the summer of 1986 the population crashed to almost zero. In the summer of 1984 after winter breeding the number of breeding females grew to 22 compared with 6–7 in previous years. In 1984 the mature females changed from territorial to group behaviour.During the high population density in 1984 and 1985 breeding stopped already in late July – early August, thus preventing any fence effect.The present study supports the hypothesis stating that microtine social organization is an opportunistic strategy reacting phenotypically to changing environmental – especially food – conditions.
Intraspecific variation in nitrogen status and photosynthetic capacity within mountain birch populations
Authors: Karlsson P. S. , Nordell K. O. 
Published: July 2006

The relative variation in leaf nitrogen concentration and photosynthetic capacity among individuals and sites are compared for mountain birch populations (Betula pubsecens Ehrh. ssp tortuosa (Ledeb.) Nyman).Leaf nitrogen concentration and photosynthetic capacity showed significant differences among individuals; 35 and 26% of the total sum of squares respectively, was attributable to differences among individuals. Two measures of leaf morphology also showed differences among individuals (35–58% of total variation). The variation attributable to site differences ranged from 13% (leaf shape, P = 0.11) to 36% (leaf N concentration and photosynthetic capacity, P≤0.01). Of the variation in photosynthetic capacity, 51% was related to leaf nitrogen concentration. Possible causes for and consequences of the differences found are discussed.
Flowering and seasonal changes in flower sex ratio and frequency of flower visitors in a population of Saxifraga hirculus
Authors: Olesen J. M. , Warncke E. 
Published: July 2006

The open, dish‐shaped flowers ofSaxifraga hirculusreflected ultraviolet and yellow light, contained very small amounts of nectar, and contained an average of about 75300 pollen grains per flower. Almost 11% of the pollen was inviable. Stigmatic pollen loads and seed set decreased during the course of the season. The plant appeared to be fully between‐ramet compatible and partially within‐ramet compatible. Seed set for the population was 30.3%. The protandrous flower opened during the day and had male and female phases of nine and three days, respectively. The protandrous system reduced the number of pollination days by a third.At least 26 species of insects, 16 of which were syrphids, visited the flowers. Based on the number of flower visits, four species were the dominant visitors ofS. hirculus: Eurimyia lineataandNeoascia tenur(Diptera: Syrphidae);Asindulum nigrum(Diptera: Mycetophilidae), andZygaena trlfolii(Lepidoptera: Zygaenidae).Eurimyia lineatawas the most frequent visitor (51% of all visits). As the season advanced, the visits byE. lineatadecreased, whereas the visits byA. nigrumincreased.Z. trifollidisappeared completely towards the end of the season. Only two thirds of the pollination days were “good” foraging days for these visitor species. The four major visitor species spent an average of 11.7, 27.4, 30.7 and 22.6 s per flower, respectively. Estimates suggest that about 6.5 visits (which is equal to 2.6 min of flower‐visiting) and 2100 grains of pollen were required to produce one seed.
Year class splitting in the woodlouse Philoscia muscorum explained through studies of growth and survivorship
Authors: Grundy A. J. , Sutton S. L. 
Published: July 2006

Year class splitting has been observed in a population of the terrestrial isopod Philoscia muscorum (Scopoli) in a fixed dune grassland. In this population, individuals born in one season differentiate into two forms, one of which grows to maturity in one year, the other in two.Laboratory investigations of growth, fecundity and survivorship of individuals showed fundamental positive relationships between rate of growth and the ambient temperature/day light regime and between parental size and the number of offspring produced. Size also affected survivorship, with adults surviving better than juveniles. A link between survivorship and the temperature/day light regime was only obvious in small juveniles.No direct physiological cause for the year class split could be derived from the laboratory studies, but a trade‐off between the need for delayed or early breeding could result in the patterns of growth and reproduction observed in the field population. Delayed breeding allows continued growth of adults and hence larger numbers of offspring. Early breeding allows more growth of juveniles which greatly improves their chances of winter survival.
Comparative analysis of temporal and spatial variability in above‐ground production in a deciduous forest and prairie
Authors: Briggs J. M. , Seastedt T. R. , Gibson D. J. 
Published: July 2006

Production patterns of tallgrass prairie and adjacent eastern deciduous forest were summarized for a five to seven year period. Each system responded differentially to annual or growing season rainfall and solar energy (measured by pan water evaporation). Overall, forest productivity was negatively correlated with annual precipitation; the prairie exhibited no relationship with precipitation. These differences probably reflect the lack of water limitation of the forest and the “downstream” position of the forest.Wood and seed production in the forest were the most variable components measured in our study. Neither variable was related to forest foliage production. Seed production in the prairie was also variable within and between years but was related to prairie foliage production. Prairie seed production was not correlated with seed production of the forest.The two ecosystems respond differentially and independently of each other within the range of climatic variation observed here. Such differences have potential significance to consumers who use both systems for habitat or resources.
Thermal ecology and spatio‐temporal distribution of the Mediterranean lizard Psammodromus algirus
Authors: Carrascal Luis M. , Díaz José A. 
Published: July 2006

We studied summer activity patterns and thermoregulation in the Mediterranean lizard Psammodromus algirus in a holm oak wood in Central Spain. The circadian rhythm curve was bimodal, with a pronounced peak after sunrise, a minimum at noon and a second lower peak in the afternoon. Increased activity in the morning could be explained by insolation levels, whereas the midday low was caused by the rise in temperature.There was a strong positive correlation between body temperature and both air and ground temperatures. Nevertheless, there was no significant correlation between body and air temperatures when the effect of radiation was removed, which was done by considering only individuals in the shade at high temperatures.Activity showed a bell‐shaped relationship with body and air temperatures, with maximum activity at 24.5°C (air temperature) and 31.4°C (body temperature). The spatial distribution pattern of P. algirus (selection of sunny areas and distance to the vegetation edge) reflects the environmental temperatures that are optimal for activity; the lizards show a strong preference for sunny patches when air temperature is lower than the optimum. We conclude that heliothermy is the only viable thermoregulation pattern in Mediterranean forest environments, with heat conduction playing a negligible rote.