bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of sea shore displacement on population age structure of coastal Alnus glutinosa (L.) Gaertn.
Authors: Cramer Wolfgang
Published: July 2006

The age structure of Alnus glutinosa (L.) Gaertn. populations was studied in two areas on the coast of the Baltic Sea. One area, situated in Upplatid, eastern central Sweden, at 60°07′N, has a relative land uplift of 5.3 mm yr−1; the other area, situated in Blekinge, southeastern Sweden, at 56°10′N, is nearly stable. The spatial distribution of 200 Alnus individuals of various age classes at nine sites was analyzed in order to reconstruct establishment history. In the land uplift area, the youngest individuals were found in the lowest parts of the sites, and age and elevation were significantly correlated. In the area without land uplift, no such pattern was found. Regression analysis of the time/space pattern of establishment in the land uplift area showed that the zone where individuals establish follows the moving shore line with roughly constant speed. Alnus glutinosa uses two different regenerative strategies: (1) continuous colonization of emerging land from seeds (with subsequent mortality of the older trees) in the land uplift area, and (2) regeneration from old stem bases, forming multistemmed trees, in the area without land uplift.
Effects on heather of heavy grazing by mountain hares
Authors: Moss Robert , Hewson Raymond
Published: July 2006

Continual heavy grazing of small patches of heather by mountain hares produces conspicuous, short, lawn‐like bushes. Their probable development is described. The shoots of such heather bushes maintained a juvenile appearance, contained more nitrogen and phosphorus than the surrounding heather and, to judge from their chemical composition, were more digestible. The generalization that tree and shrub twigs of juvenile growth form are more unpalatable to hares than twigs of mature growth form did not apply in this case.
Synchronous short‐term population fluctuations of some birds and mammals in Fennoscandia ‐ occurrence and distribution
Authors: Angelstam P. , Lindström E. , Widén P.
Published: July 2006

We examined population fluctuations of the volesMicrotus agrestisL. andClethrionomys glareolusSchreb. by biannual trapping; black grouseTetrao tetrixL., mountain hareLepus timidusL., and red foxVulpes vulpesL. by using bag records from all over Sweden, questionnaires from south‐central Sweden, and population indices from Grimsö Wildlife Research Area in south‐central Sweden. Synchronous population fluctuations between voles as a group and the other species conformed to a 3–4 year periodic pattern in both autumn and spring populations only in northern and central Sweden (the boreal forest region). Spring populations of boreal forest grouse, hare, and probably also fox, lagged one year behind the voles. The northerly areas also formed geographical units of co‐fluctuation within each game species. Using our own data as well as reviewing previous studies in Fennoscandia, we conclude that synchronized 3–4 year population fluctuations of voles and medium‐sized herbivores are confined to the central and northern part of Fennoscandia, although voles may exhibit short‐term population fluctuations further south. The synchronizing link between the herbivores could be (1) food plant quality and/or quantity and/or (2) predation. We could not reject either of these two plausible mechanisms as a cause of interspecifically synchronous fluctuations.
The influence of microtopographic heterogeneity on carbon dioxide efflux from a subarctic bog
Authors: Lukeno J. O. , Billings W. D.
Published: July 2006

Soil carbon dioxide efflux was measured in hummock and hollow niicrohabitals of a subarctic peat bog near Fairbanks, Alaska, during the 1983 growing season. Regardless of the presence of permafrost, hummocks showed a late June or early July peak in soil respiration followed by a gradual decrease. Hollows and wet Carex Lawns showed a gradual increase in soil respiration with no mid‐season peaks. Regression equations using soil temperature and soil moisture as independent variables explained 76% of the variance associated with soil carbon dioxide efflux. Sucrose (100 g m−2) applied to a field plot caused a significant increase in soil respiration but nitrogen (5 g m−2) did not. Sequential effects of nitrogen and phosphorus on peat respiration were demonstrated in a laboratory experiment.
Plastic morphological response to density in Spergularia marina (L.) Griseb.: Leaf demography and meristem activity
Authors: Torstensson Peter , Telenius Anders
Published: July 2006

In order to explain, in terms of a morphologically based plastic response, the absence of density‐dependent mortality, and the regulation of reproduction in the halophilous annual Spergularia marina, leaf demography and the use of meristems were studied in populations of three different densities. Leaf birth and death rates were almost constant at the higher densities, whereas at the lowest density both increased throughout most of the observation period. This increase was caused by the addition of new vegetative shoots, each one resembling the individuals growing at higher densities in having an almost constant leaf birth and death rate. The capacity to adjust leaf death rate to birth rate with density was high. There was no difference in the proportions of meristems used for flowering as the density increased. After the first flower had been produced, each following node produced a flower. The proportions of meristems used for vegetative shoots were strongly density‐dependent; more shoots were produced at lower densities. The regulation of flower production was almost entirely caused by the addition of vegetative shoots.
Consequences of differential utilization of meristems in the annual Spergularia marina and the perennial S. media
Authors: Torstensson Peter , Telenius Anders
Published: July 2006

The differences in vegetative expansion and in reproduction associated with the annual Spergularia marina and the perennial S. media were investigated and explained as a function of their differential utilization of meristems. Plant size and the lime of first reproduction depended on at which node transition of the apical meristems from growth to reproduction took place. Leaf birth‐rate and number of flowers depended on the time of activation and the proportion of axillary meristems used in producing shoots.
Effect of snow cover on seasonal changes in diet, habitat, and regional distribution of raptors that prey on small mammals in boreal zones of Fennoscandia
Authors: Sonerud Geir A.
Published: July 2006

Seasonal changes in spatial distribution of search effort of birds that prey on small mammals were studied in two structurally different coniferous forest habitats in the northern boreal zone in SE Norway. During the season with snow cover both the proportion ofMicrotusrelative to that ofClethrionomysin the predators' diet, and their use of a clear‐cut relative to that of older forest were lower than during the snow‐free season. This was related to a lower relative availability of prey (Microtus agrestisandM. oeconomus) in the clear‐cut when the ground was snow‐covered than when it was snow‐free. Based on this local pattern I suggest the following explanation for differences in migratory strategy between raptors that prey on small mammals in Fennoscandian boreal zones: species that migrate to snow‐free areas in winter are either adapted to hunt by the energetically expensive method of quartering in open grassland habitats, where prey (Microtus) availability is relatively low during periods with snow cover (hen harrierCircus cyaneus, short‐eared owlAsio flammeus, and longeared owlA. otus), or by sit‐and‐wait in open grassland and forest habitats, the latter with relatively high prey availability during periods with snow cover, but unable to locate concealed prey (kestrelFalco tinnuculus, common buzzardButeo huteo, and roughlegged buzzardB. lagopus). In contrast, species that remain in areas with permanent snow cover during winter use the energetically cheap sit‐and‐wait tactic, and are able to hunt in closed forest habitat and localize concealed prey (the remaining owl species). Interspecific differences in prey availability as determined by hunting habitat and hunting mode is probably more important in shaping the migration patterns of Fennoscandian owls than is nest site availability.
Stand structure, variability in growth and intraspecific competition in a peatland stand of black spruce Picea mariana
Authors: Lieffers V. J.
Published: July 2006

Age and size distributions and growth rates of individual trees were examined in a black spruce stand growing on a peatland in Alberta, Canada, 38 years after fire. Both height and basal girth frequency distributions were positively‐skewed, with many small and few large individuals. Age distributions were negatively‐skewed; most trees were recruited five to seven years after fire and there was little recruitment after 25 years. Stem analysis data indicated that increment in height was nearly constant over the life of the trees but larger trees grew faster than smaller trees. The trees which started growth immediately after the fire maintained faster growth than those recruited some years later. At the time of study, above ground competition and canopy shading were not considered to have a large effect on growth rates of individual trees. Several hypotheses are presented to explain these differences in growth of individual trees.
Influence of the food plant, Urtica dioica, on larval development, feeding efficiences, and voltinism of a specialist insect, Inachis io
Authors: Pullin A. S.
Published: July 2006

The development and feeding efficiences of larvae of Inachis io were compared on mature and regrowth leaves of Urtica dioica. The nitrogen and water content of regrowth leaves was higher than in mature leaves. Larvae fed on regrowth leaves both singly and in groups attained higher ECI and ECD values, completed development faster, and attained a greater body weight than larva fed on mature leaves. AD values were not significantly different. The consequences on herbivore dynamics of the availability of good quality regrowth of food‐plants are discussed.
Life history variation in Pisidium (Bivalvia: Pisidiidae)
Authors: Holopainen Ismo J. , Hanski Ilkka
Published: July 2006

Intraspecific variation in the maximum shell length ofPisidiumis small in comparison with variation in the life span of the clams, from 4 mo to 4 yr. The use of shell length as a measure of size is complicated by large intraspecific variation in the weight‐length relationship, a possible reflection of resource availability on the weight of the soft parts. Maximum embryo length is relatively constant (1 mm) in the majority of species but litter size is variable (1 to 40), generally increasing with parent size. The time of egg‐laying is determined by the size of the clam, season, and previous episode of reproduction, while the timing of the release of embryos, depending also on embryonic growth rate, is additionally affected by temperature and oxygen conditions. In brief, the maximum adult and embryo lengths are relatively conservative traits while growth rates vary by an order of magnitude.

Reproductive effort, when measured by the ratio of litter weight to parent weight, may increase or decrease with parent length and age. Both semelparous and iteroparous populations are known in several species. We suggest that if maximum adult length can be reached by the first reproductive season (in a favourable environment) the population is semelparous, otherwise (in an unfavourable environment) the population is iteroparous. Gravid clams in semelparous populations continue to grow, and thus assimilation cannot be meaningfully partitioned into reproduction, somatic growth and maintenance.

Along a depth gradient from 8 to 65 m, maximum and mature shell lengths, embryo length and litter size varies significantly inPisidium conventussubpopulations not distinguishable electrophoretically. Large clams in deep water produce large embryos but small litters, which is contrary to the general trend of increasing litter size with parent length. Low food availability that decreases juvenile growth rate may restrict litter size in this case.
Influences on the density and dispersion of bumble bee nests (Hymenoptera: Apidae)
Authors: Harder Lawrence D.
Published: July 2006

To determine some of the influences on nesting densities of bumble bees I examined the dispersion and occupancy of 35 nests in an old field on Amherst Island, Ontario, Canada and 39 nests found by Cumber (1953) in England. Densities up to 1 nest per 200 m2 were observed. Overall, Cumber's nests were randomly dispersed, but nests on the ground surface were aggregated. Nests of surface‐nesting species were consequently more aggregated than expected at random, whereas surface‐nesting and underground‐nesting species seldom nested near one another. This distribution of nests probably reflects the nesting habits of the rodents that originally constructed the nests, rather than interactions between bees. On Amherst Island, abnormally wet spring weather apparently hampered normal colony development, particularly of underground‐nesting bees based on a low frequency of underground nests, scarcity of workers of two underground‐nesting species compared with the relative abundance of spring queens, and delayed appearance of workers of all species relative to the previous year. The nests of two common species were randomly dispersed, but those of a third species were regularly distributed, suggesting that intraspecific interactions may limit nesting density for this species.
Fecundity, reproductive effort, age‐specific reproductive tactics and intrinsic rate of natural increase of a High Arctic nematode belonging to the genus Chiloplacus
Authors: Procter D. L. C.
Published: July 2006

The reproduction of an undescribed species of the genus Chiloplacus from the Canadian High Arctic was studied at 10°C. The mean number of eggs laid per female was 317.8±89.2, of which 46.8±7.8% hatched, resulting in net reproduction of 148.8 juveniles per female. Beginning as new‐laid eggs the observed maximum age attained was 99 d, and the calculated generation time was 52.6 d. Egg‐laying began 26 d after hatching and the reproductive period spanned 56 d. The intrinsic rate of increase was 0.095, and the first 12 reproductive days contributed 80.587% of the value of r. When r = 0.095 the stable age distribution was calculated to be 91.5% immatures and 8.5% adults. Chiloplacus sp. is intermediate in fecundity for free‐living soil nematodes. lying between the generally highly fecund Rhabditidae on the one hand, and the much less fecund Dorylaimidae on the other. Chiloplacus sp. lays a larger portion of its eggs early in the reproductive period at 10°C than do species from warmer environments, suggesting that reproduction of Chiloplacus sp. is low‐temperature compensated.
The effect of temperature on the egg incubation period of Capnia bifrons (Plecoptera: Capniidae) from Windermere (English Lake District)
Authors: Elliott J. M.
Published: July 2006

Gravid females of Capnia bifrons (Newman) from Windermere (English Lake District) were almost completely ovoviviparous, the eggs hatching within 15 min after oviposition in the water. When kept in the laboratory at constant temperatures between 3.8 and 19.8°C, few females survived to lay eggs at temperatures above 12.1°C. The relationship between air temperature (T°C) and the egg incubation period (Y days between fertilisation and oviposition) was given by the regression equation: Y = 316.4 T−0.9996 (r2= 0.957, p < 0.001). This equation successfully predicted egg incubation periods for gravid females kept in cages in the field.

Comparisons with similar studies on four non‐ovoviviparous species of Plecoptera showed that egg development was rarely more rapid in C. bifrons. It was also shown that the hypothesis of ovoviviparity being an adaptation to combat low water temperatures could be rejected for C. bifrons from Windermere.
Patterns of dispersion, density and dispersal in alpine populations of the land snail Arianta arbustorum (L.) (Helicidae)
Authors: Baur Bruno
Published: July 2006

In studying populations of the land snailArianta arbustorumin the eastern Swiss Alps, juvenile and subadult snails were found to be aggregated all the time, while adults were mostly aggregated during summer, the main mating period. The mean size of aggregations was 25 cm × 25 cm but varied, according to the area a grass tuft covered, while the intensity of aggregations was influenced by weather conditions. Densities of 10–15 subadults and 3–6 adults m−2were found along ditches and streams, 2–25 subadults and 2–20 adults on uncultivated alpine meadows, while on scree‐covered alpine grassland the density of subadults and adults was 0.3–0.5 m−2. The extent of daily movements varied with microclimatic factors and season and depended on the structure of the habitat. The dispersal rate was greatest in June (2.6 m month−1) and least in August (1.1 m month−1). In summer and autumn, active uphill movements were noted, a process which compensates for the loss of altitude by passive downhill displacements. Roiling down on snowfields and being carried away by avalanches and streams were observed.
Seasonal colonisation and effects of salinity and temperature on species richness and abundance of fish of some brackish and estuarine shallow waters in Sweden
Authors: Thorman Staffan
Published: July 2006

In this study two questions concerning the structure and organisation of shallow brackish and estuarine fish assemblages are: (1) Does the species number decline with lower salinity as found for the macrofauna invertebrates? (2) Does the water temperature during the year influence the abundance of fishes along the Swedish coast?

In a west coast estuary salinities were higher but fluctuated more than in the Bothnian Sea. Days with temperatures exceeding 15°C were up to twice as many in the west coast estuary as in the Bothnian Sea. In spring the species number increased, but later on in summer it declined to increase again in autumn, but declined once again as winter approached. Fish density in the west coast estuary increased gradually to a maximum in late summer and then declined, while in the Bothnian Sea there was often a decline during summer. Positive correlations were found between observed minimum salinities and average species number, and between number of days with temperatures exceeding +15°C and both yearly average and maximum fish densities. Juveniles (0+) were present for longer periods in the west coast estuary than in the Bothnian Sea and reproduction of the common species started earlier in the former area. In winter the shallow areas are devoid of fish because of ice and so are re‐colonised each spring. The study demonstrates that water salinity limited the species number, and water temperature the abundance of fish.
Effects of temperature on incubation times and mortality rates of eggs of Dytiscus alaskanus (Coleoptera: Dytiscidae)
Authors: Aiken R. B.
Published: July 2006

Eggs of the predaceous water beetle Dytiscus alaskanus were incubated in the laboratory at 10, 15, 20, 25 and 30°C. All measures of rate of development showed a significant linear regression with temperature. Mortality rates showed no significant regression with temperature. Data for this species were compared with similar data for D. marginalis and results discussed with reference to the climate each experiences.
Ectoparasites on small mammals in Iceland: Origin and population characteristics of a species‐poor insular community
Authors: Bengtson S.‐A. , Brinck‐Lindroth G. , Lundqvist L. , Nilsson A. , Rundgren S.
Published: July 2006

The Icelandic small mammal fauna is depauperated as is the associated ectoparasite fauna. Three small mammal species occur, viz. Apodemus sylvaticus L., Mus musculus L., and Rattus norvegicus Berk. (R. rattus is probably not a regular member). The mice supposedly came to the island by settlers from the 10th century and onwards.

Apodemus and Mus from five localities altogether had seven ectoparasite species, five mites and two fleas. All species occurred on Apodemus whereas Mus was infested by four. Compared with the numbers of ectoparasite species recorded in similar studies in the Nordic countries, there are conspicuously few species in Iceland. Further, Apodemus had an overall higher infestation frequency than Mus (90% and 30%, respectively) and a higher total density of ectoparasites (3.3–20.3 and 0.5 inds/host, respectively). The density figures were high compared with those for mainland Apodemus. Especially the mite Laelaps agilis C. L. Koch and the flea Ctenophthalmus agyrtes (Heller) were common on Icelandic Apodemus. Reduced competition among parasites and/or low predator pressure on small mammals may explain the density figures obtained.

The ectoparasite species compositions on small mammals in Scandinavia and Iceland have many features in common that renders it probable that Apodemus originate from Scandinavia.
The life‐cycle and productivity of Tibifex tubifex (Oligochaeta; Tibificidae) in the Moat‐Feeder Stream, Cardiff, South Wales
Authors: Lazim M. N. , Learner M. A.
Published: July 2006

A population of Tubifex tubifex in an organically rich stream was found to have an annual life‐cycle with a prolonged period of reproductive activity throughout the winter and spring. Cocoons were produced mainly during the late winter and early spring. No cocoons were found during August and September, and there were few mature worms at this time.

The population density ranged between 5420 m−2 in mid‐September and 613000 m −2 in mid‐May. The maximum population biomass (Bmax) recorded was 106 g dry wt m−2 (March) and the minimum was 10 g dry wt m−2 (September). Total annual production (P) was 139 g dry wt m−2 and the average annual biomass (B) was 46 g dry wt m−2 giving an annual P/B ratio of 3.0, and a P/Bmax ratio of 1.3.
Reproductive differentiation in a Saxifraga hirculus population along an environmental gradient on a central Swedish mire
Authors: Ohlson M.
Published: July 2006

The perennial herbaceous mire plant Saxifraga hirculus was studied in different population densities along an environmental gradient on a mire in central Sweden. Tests were made whether the habitat conditions influenced the balance between vegetative growth of runners and seed production. Along a 30 m long transect the gradient was analysed for vegetation, hydrology, temperature and contents of ions in groundwater and surface peat. Three main zones were distinguished, a spring area, a rich fen area and an intermediate fen area. Range in concentration of ions in groundwater along the transect (mg 1−1): Ca 4–59, Mg 0.3–3.5, K 0.1–3.0, Na 1.0–4.1 and Fe 0.4–4.5. Range in pH: 5.8–7.5. Despite the gradient in ion concentration, the element content in S. hirculus was constant along the transect. Population density reached maximum in the rich fen, 52 floral shoots 0.25 m−2. In the spring area, S. hirculus was characterized by few flowers per floral shoot, low height, numerous runners and a large total length of runners. In the rich fen, high seed production was characteristic; in the intermediate fen, production of both runners and seeds were low. The flowering of S. hirculus starts early in the spring area. Consequences of this with regard to genetic variation along the transect are briefly discussed.
Phytoplankton structure in different lake types in central Finland
Authors: Eloranta Pertti
Published: July 2006

Phyloplankton structure and its relation to physical and chemical properties of the water was studied in 58 central Finnish lakes. The biomass ranged from 0.2 to 14.2 g m−3 and the number of taxa per sample ranged from 33 to 152. The lakes were grouped into 5 types according to their trophic state: eutrophic, dyseutrophic, mesotrophic, oligotrophic, and acid oligotrophic lakes. The average biomass in eutrophic lakes was 5.57 g m−3, in dyseutrophic 3.54 g m−3, 1.23 g m−3 in mesotrophic, 0.52 g m−3 in oligotrophic and 0.39 g −3 in acid oligotrophic lakes. The average number of taxa per sample in the corresponding lake types were 109. 1, 79.3, 97.9, 90.9 and 43.8, respectively. The phytoplankton communities in eutrophic lakes were characterized by blue‐green algae (21.2% of total biomass) and green algae (18.7% of total biomass). In dyseutrophic lakes the proportion of green algae was much smaller (7.2% of total biomass) than in eutrophic lakes, whereas the proportion of diatoms and cryptophytes was higher (28.2 and 20.4% of total biomass, respectively). Chrysophytes dominated in the oligotrophic and mesotrophic lakes (27.3–39.9% of total biomass). The contribution of dinoflagellates to the total biomass was highest in the most oligotrophic acidified lakes and in those lakes the relative proportions of blue‐green and green algae were much higher than in the typical oligotrophic lakes. The lakes were also grouped into 8 community types according to the dominating algal group. Cyanophyceae‐ and Chlorophyceae‐types characterized the eutrophic lakes, whereas Chrysophyceae‐Dinopheceae‐type was typical for most oligotrophic lakes. The other 5 types occurred in mesotrophic and oligotrophic lakes but the physical and chemical properties of these lakes did not differ much.
Pitfall trapping within enclosures: a method for estimating the relationship between the abundances of coexisting carabid species (Coleoptera: Carabidae)
Authors: Desender Konjev , Maelfait Jean‐Pierre
Published: July 2006

Pitfall trapping within enclosures is proposed as a method to get a reliable impression of the relationship between the abundances of a number of coexisting carabid species. The investigations were performed during two years in a heavily grazed pasture at Melle (Belgium). On a rather large scale soil samples could be compared with both enclosed and open pitfall catches.

In all cases fenced pitfalls gave ratios between the catches of the different species showing a much better correlation with those from soil samples than the catch ratios from open pitfalls. This method seems especially suitable to compare the relative abundances of a number of carabid species in short term investigations during periods of peak activities.
Clonal constitution and sex ratio in northern populations of balsam poplar Populus balsamifera
Authors: Comtois P. , Simon J. P. , Payette S.
Published: July 2006

Isozyme analyses performed on balsam poplar stands in subarctic northern Québec indicated polyclonal predominance (76%). This suggests that seed sources were adequate for colonization of new habitats. High variance at the clone and the stand levels did not permit, however, the use of morphological traits for clonal partitioning. A non‐random sex distribution related to habitat conditions was found both at the regional and the local scales, although there is an equal male‐female ratio in the study area. Female stands predominate in regions subject to a maritime climate (1:5) and in fertile and humid habitats (1:7).
Succession, dominance and diversity in lichen‐rich pine forest vegetation in Finland
Authors: Oksanen Jari
Published: July 2006

Succession of forest floor vegetation (cryptogam and understorey vascular plant synusiae) is studied. Diversity patterns in northern boreal and hemiboreal to middle boreal lichen‐rich forests are different. Even when the lichen volume, which describes the successional status, is taken into account, the diversity in southern forests is lower. The descriptors of diversity are rather independent of lichen volume in southern forests. When the Stereocaulon‐rich forests are excluded, stronger correlations are observed in the northern forests, but the species number decreases only slightly as the lichen volume increases. Evidently this is due to relatively large sample plots, where suitable patches for minor species are usually available. The decrease is much stronger in Shannon's and Simpson's indices. This is mainly due to a decrease in evenness since, as the lichen volume increases, the dominance of some Cladina species increases. Therefore, these indices are not particularly efficient in describing the richness of the community. Stereocaulon‐rich stands have diversity values which correspond to Cladina‐rich stands with a considerably higher lichen volume, which gives additional evidence for their status as successionally rather mature communities.
Breeding performance of the red‐throated diver Gavia stellata in Shetland
Authors: Gomersall C. H.
Published: July 2006

Breeding red‐throated divers Gavia stellata were studied in Shetland during 1981‐1983. The overall probabilities of nest success were 0.35 in 1981 and 0.25 in 1982, as calculated by the Mayfield method. Productivity was shown to be at least 0.51 chicks fledged per breeding pair in 1981 (n = 100) and 0.36 in 1982 (n = 91), and a review of all field studies for Shetland gave a mean value of 0.45 per year (n = 1104) with no detectable trends in productivity since 1918; this was considered probably sufficient to maintain a stable population. Nests at lochs smaller than one hectare experienced the greatest hatching success. The majority of known breeding lochs wore used in three consecutive years, with a significantly greater re‐use of lochs which had previously supported successful pairs. Breeding success declined with season in 1981 and 1982 largely due to reduced hatching success of late nesters, and a slight seasonal decline in egg volume was found in 1983.
Geographic clines in body weight of Norwegian red deer: a novel explanation of Bergmann's rule?
Authors: Langvatn R. , Albon S. D.
Published: July 2006

Variation in body weight of red deer in Norway was investigated along two climatic gradients: one with increasing latitude, and the other with proximity to the coast. Deer of all sex/age classes were significantly heavier in the northern parts of their range compared with the south and were also significantly heavier at inland localities compared with the coast. Body weights were negatively correlated with temperature and precipitation throughout the years. These clines in body weight apparently support Bergmann's rule, and may reflect selection for large size in cold environments. However, we interpret the results in the light of recent work on plant physiology which indicates higher quality forage at high latitudes, and in cooler and drier climates: conditions which are likely lo enhance growth in the north and inland. Evidence that individual deer which migrate inland, following the snow melt, are heavier is also presented and discussed in terms of an adaptive behaviour that maximises the intake of digestible energy and high quality nutrients.
Egg development and life cycle of Chaetopteryx villosa (Trichoptera)
Authors: Wagner Rüdiger
Published: July 2006

Combined field and laboratory investigations showed that C. villosa was univoltine in the Breitenbach, Germany. Speed and duration of embryogenesis were determined by temperature. Lowest values of accumulated temperature occurred at 6 and 8°C, when the duration of embryogenesis was shortest, and egg mortality was low. Egg masses exposed at upstream field sites needed similar time and accumulated temperatures for embryogenesis to those expected from laboratory experiments. At a downstream site embryogenesis was accelerated, possibly depending on increased daily temperature fluctuations in spring. At all field sites the emergence period of adults lasted from September until December. Size and weight of both sexes were significantly lower at the upstream site, not necessarily as a result of temperature, but possibly caused by differences in nutrition.
Survival of the first stage larva of the metastrongyloid nematode Elaphostrongylus rangiferi under various conditions of temperature and humidity
Authors: Lorentzen Geir , Halvorsen Odd
Published: July 2006

First‐stage larvae of E. rangiferi kept in water at 50°C died within 80 minutes, while at 6° the last larvae died between day 180 and 210. The time it took to reach 1x= 0.5 (half of the larvae dead) at various temperatures between 6° and 50° was well described by the exponential function y = 614.6e−0.15x, giving a value of 615 days to reach 1x= 0.5 at 0°C. There was no clear decrease in the survival of larvae frozen at −20° in faeces and in water, and at −80° in faeces after 360 days. When subjected to repealed freezing and thawing, all larvae died within 77 days. When kept in air at RH = 20% and 22°C, all larvae died within 11 days, while when frozen (−20°C) in air at RH approx. 0%, 1x stayed at approx. 0.5 from day 5 to day 16.
Bark consumption of voles in relation to snow cover, population density and grazing impact
Authors: Hansson Lennart
Published: July 2006

The voles Microtus agrestis and Clethrionomys glareolus consume more bark in north than in south Sweden in spite of lower availability in the former area due to snow‐pressed ground. Field experiments with genetically homogeneous aspen sticks demonstrated that this pattern reflects differences in animal behaviour and not differences in plant palatability. Within a region consumption in snow‐pressed areas was usually less than in subnivean spaces or runways. The amount of bark consumption was generally correlated with population density and amount of grazing impact. Great differences in bark consumption between north Swedish areas with high peak vole populations and south‐central Swedish areas with moderate peak numbers imply that nutrition is of different importance at population declines in different regions. The ability of voles to move into snow‐pressed areas and locate woody sticks in the snow suggests that control of ground cover will not protect tree seedlings at reforestation.
Microhabitat selection and feeding relations of smooth and warty newts, Triturus vulgaris and T. cristatus, at an upland pond in mid‐Wales
Authors: Griffiths R. A. , Mylotte V. J.
Published: July 2006

The utilization of microhabitat and food resources by Triturus vulgaris and T. cristatus was studied in an upland pond in mid‐Wales. From April to June T. vulgaris was more evenly distributed across the pond than T. cristatus, which showed a preference for the middle of the pond and the bottom of the water column. From July to September however, when most T. vulgaris had left the pond, T cristatus was evenly distributed within the water column and a much higher proportion was captured around the shorelines. Both species appear to be generalist predators with diets limited by prey size. Zooplankton were the most important prey for T. vulgaris, while leeches formed the bulk of the diet of T. cristatus. However, T. cristatus did not select larger‐sized zooplankton than T. vulgaris. Large body size therefore enables T. cristatus to consume a wider range of prey sizes than T. vulgaris. Microhabitat niche overlap was greater than feeding niche overlap between the species.
Seasonal crayfish activity as influenced by fluctuating water levels and presence of a fish predator
Authors: Hamrin Stellan F.
Published: July 2006

The diel rhythm of juvenile (0+) Astacus astacus was studied experimentally with constant and dielly fluctuating water levels. In the first case the diel rhythm was mainly crepescular, but with tendencies of a phase shift towards diurnal rhythm during low light conditions. The locomotor activity increased with temperature and with the length of the dark period. In presence of a crepescular predator the crayfish decreased their light period activity.

With fluctuating water levels the activity increased especially when the water level changes occurred during normal resting periods. Crayfish did not show any adaptation to fluctuating water levels by preferring covers constantly situated beneath the surface. The relative effect of the water level fluctuations increased with temperature.

As the main part of the juvenile crayfish population is concentrated to the litoral zone, diel water level regulations are thought to be detrimental to crayfish populations even if the regulation amplitude is small.
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.
Response of Microtus pennsylvanicus to vegetation fertilized with various nutrients, with particular emphasis on sodium and nitrogen concentrations in plant tissues
Authors: Inoye Richard S. , Huntly Nancy J. , Tilman D.
Published: July 2006

Fertilization of 1 × 4m plots of old‐field vegetation in Minnesota, USA, with various compounds resulted in increased plant tissue concentrations of N, P, K, Ca, Mg, Na, and Mn. Microtrus pennsylvanicus showed significantly greater activity, estimated by scat counts, on plots fertilized with sodium sulphate. Data also suggested that increased Microtus activity in response to elevated plant tissue sodium concentration resulted in greater soil nitrogen availability and higher levels of nitrogen in plant tissues.
Micro‐site performance of evergreen and deciduous dwarf shrubs in a subarctic heath in relation to nitrogen status
Authors: Karlsson P. S.
Published: July 2006

The relationship between micro‐site nitrogen status (total soil N conc., total vegetation N, and leaf N conc.) and performance (biomass) for two evergreen and two deciduous dwarf shrubs was studied in a subarctic heath. One deciduous species, Vaccinium uliginosum, dominated on sites having the highest vegetation nitrogen content and highest leaf nitrogen concentrations. The evergreen Empetrum hermaphroditum dominated on sites with a low total vegetation nitrogen content and low leaf nitrogen concentrations. Two other species, V. myrtillus (deciduous) and V. vitis‐idaea (evergreen), showed intermediate patterns that were not clearly separated from either V. uliginosum or Empetrum. Soil nitrogen content showed no significant differences between micro‐sites. Possible physiological reasons for the observed patterns are discussed.
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.
The effect of zooplankton abundance on feeding behaviour and prey size selection in Atlantic salmon, Salmo salar, alevins1
Authors: Browman Howard I. , Marcotte Brian M.
Published: July 2006

In an experiment on the effect of zooplankton density on feeding behaviour and prey size selection in Atlantic salmon (Salmo salar) alevins, total behavioural activity (feeding, social, ambiguous) was positively related to prey abundance up to a density of 350 items 1−1, after which activity peaked. Feeding error (missed attacks and/or rejected ingestions) increased with prey density. The likelihood that an alevin would attack an item upon which it had binocularly fixed (no. bites/no. visual fixes) peaked at densities of 270 items 1−1 and then declined. Feeding success (no. ingestions per bite or per fixation) also peaked and then declined. Changes in success were reflected in total number of items found in the gut. At high prey abundance (608 items 1−1) only 0.5 – 0.9 mm copepods were preferred components of alevin diets. Over all prey densities, preferred sizes of cladocerans and copepods did not overlap. These results may reflect a perceptual constraint (at high zooplankton densities) on alevin feeding behaviour.
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.
Relative success of residents and immigrants in Peromyscus leucopus
Authors: Krohne David T. , Burgin Alex B.
Published: July 2006

The relative success of a sample of 99 immigrant dispersers was studied in a population of Peromyscus leucopus in deciduous forest from 1980 to 1985. Dispersers were identified in two ways; (1) as immigrants to a natural dispersal sink and (2) as individuals that relocated their center of activity more than one home range diameter within a large live‐trapping system. Female immigrants were significantly less likely to be pregnant or lactating than philopatric residents; males showed no significant difference. Reproductive immigrants were more likely than non‐reproductive immigrants to establish residency after dispersal. There was no difference in survivorship of philopatrie residents and those dispersers that successfully immigrated.
The diet of breeding dippers Cinclus cinclus cinclus and their nestlings in southwestern Norway
Authors: Ormerod S. J. , Efteland Svein , Gabrielsen Leif E.
Published: July 2006

The diet of dippers in south west Norway was investigated by faecal analysis during the 1985 breeding season. Overall, the diets of adults and nestlings were similar and consisted mostly of nymphs and larvae of Baetidae (mayflies). Leuctridae/Nemouridae (stoneflies). Hydropsychidae, Limnephilidae and Rhyaeophilidae (caddisflies). However, strong trends were apparent with nestling age: large items such as caddisflies declined in adult diet but increased in nestling diet as the chicks grew. The pattern probably reflected the growing energy demands of the brood in a central‐place. Because some of the items of dietary importance are scarce in acidic streams, we stress the need for research on the influences of acidification on the ecology of Scandinavian dippers.