bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure in seven bumblebee communities in eastern Finland in relation to resource availability
Authors: Ranta Esa , Tiainen Mauri
Published: July 2006

The structure of seven local bumblebee communities was studied in eastern Finland. The number of species in the study sites varied from 5 to 10, 11 being the number in the species pool. Most of the species (queens) had proboscis lengths of 8–11 mm. When floral resources were analysed on the basis of corolla tube depths, a group was found between 4 and 8 mm. In terms of flower utilization, species with similar proboscises had higher pairwise niche overlaps than species differing by their proboscis lengths.

Spacing between neighbouring species along the proboscis length dimension was not more uniform in the realized communities than what was expected on the basis of random draws from the local species pool. The results were the same for all species observed in the communities and for the abundant species only (frequency >5%), although competition among species in the latter group is expected to be more intense.

When the structure of bumblebee communities and of floral resources was expressed in terms of diversity of proboscis lengths and corolla tube depths, respectively, a positive correlation was found. Data suggest that species with similar proboscis tend to co‐occur on fields with availability of appropriate corolla tubes.
Phosphate absorption and root respiration of different plant growth forms from northern Alaska
Authors: Chapin F. Stuart , Tryon Peter R.
Published: July 2006

Rate of phosphate absorption measured on field‐collected, excised roots of eight species from a tundra site and a taiga forest was more strongly correlated with growth form traits than with type of community. In the taiga forest phosphate absorption rate ranged tenfold among species and was higher in graminoids than in shrubs. In both sites deciduous shrubs tended to have higher rates than evergreens. Phosphate absorption rate was not strongly reduced at low temperature in any species examined and there was a temperature optimum of about 20°C in Eriophorum vaginatum. Phosphate absorption rates were higher in lateral than primary roots, although both root types had substantial respiration rates. At one tundra site, calculations suggest that roots of E. vaginatum require 30–40 d to absorb a quantity of phosphorus equivalent to that required to synthesize the root and another 5–6 d to provide the net phosphorus requirements for the remainder of the plant.
Resource partitioning between unionid mussels in a Swedish lake outlet
Authors: Brönmark Christer , Malmqvist Björn
Published: July 2006

Partitioning of food and space resources of two dominating unionid mussel species, Anodonta piscinalis and Unio pictorum, was investigated in a South Swedish lake outlet. Differences in diurnal activities were not considered to be a mechanism for niche segregation. The two species ingested particles of almost identical size distribution indicating a high overlap in food. Mussel distribution was correlated to environmental variables including substrate properties, water depth, current velocity, and distance from the lake, the latter being a relative measure of food quality and quantity, U. pictorum dominated near the lake and in the centre of the river while A. piscinalis had its peak density ca. 500 m below the lake and was relatively more abundant along the river margins. At maximum mussel densities, which were found near the lake, a separation in space was more obvious than downstream, implying possible interspecific interactions.
The carabid communities on peat and upland grasslands in northern England
Authors: Butterfield Jennifer , Coulson J. C.
Published: July 2006

During a two year period 13498 individuals of 66 species of carabids were taken from 44 sites on peat and upland grasslands over an altitude range of 11‐847 m in the north of England. The similarities between the carabid faunas of each site have been assessed using a modified form of the Sørensen's Index and the sites clustered according to their similarities. Five carabid communities on peat and three on mineral soils have been identified and the more abundant species have been used to characterise them. Peat Community I occurs on dry heath and is characterised by peat associated species such as Trichocellus cognatus and Bradycellus ruficollis together with widespread open habitat species such as Pterostichus madidus, Notiophilus aquaticus, Calathus melanocephalus and Nebria salina. Peat Community II is found on areas where dry heath and deep wet peat are adjacent and is characterised by the species already mentioned together with typical wet habitat species such as Pterostichus diligens, P. nigrita, Patrobus assimilis. Agonum fuliginosum. Peat Community III is found on blanket bog and is characterised by the wet habitat species in the absence of the species present on the dry heath. Peat Community IV found on the lowland oligotrophic mires is characterised by the small number of species present and the addition of Pterostichus niger and Agonum ericeti to the few wet habitat species present. Peat Community V, on the scarp slope of Dun Fell, consists of the wet habitat species of Peat Community III together with Pterostichus madidus. Nebria salina, Notiophilus aquaticus and Calathus melanocephalus.

Grassland Community I, on the fell tops, is characterised by the presence of Nebria gyllenhali, Notiophilus germinyi and Patrobus assimitis. Grassland Community II and III are less clearly defined but Grassland Community II may be present on wetter sites than III and is characterised by the presence of Pterostichus nigrita, P. diligens and P. strennus together with Notiophilus biguttatus. N. aquaticus, Pterosfichus madidus and Patrobus afrorufus. Grassland Community III consists of the latter group of species together with Nebria salina, Calathus melanocephalus and Notiophilus aestuans. The number of grassland sites studied was small and there may be further communities on the upland grasslands.
Alteration of salt marsh plant community composition by grazing snow geese
Authors: Smith Thomas J.
Published: July 2006

A notable omission from wetlands ecology has been the study of the influence of herbivores on vegetation. Reported here are the effects of grazing by snow geese Anser caerulescens altantica on the vegetation of salt marshes along the mid‐Atlantic coast of the United States, Exclosures were used to compare total and species percent cover between grazed and ungrazed areas in three marshes (Salt Flats, South Pond, and Bodie Island) with differing vegetation communities from 1978 to 1980.

Spartina alterniflora was reduced by ⅔ in grazed versus ungrazed areas of Salt Flats, S. S. patens was reduced by ½ in grazed portions of South Pond but recovered when grazing ceased. In grazed portions of Bodie Island total plant cover was reduced by 16%. Scirpus robustus and S. patens reacted in opposite ways to grazing pressure with S. robustus increasing and S. patens decreasing, Elocharis was found only in grazed areas of Bodie Island. Echinochloa crusgali appeared in grazed portions of this marsh in 1978 but decreased in abundance during subsequent years. Scirpus americanus was unaffected by grazing, maintaining a nearly constant percent cover in grazed and ungrazed areas at Bodie Island.

Differences in responses to grazing are discussed in terms of each species' growth and reproductive strategies as tempered by the physical and biological environment within each marsh.
Habitat use by lemmings near Barrow, Alaska
Authors: Batzli Geurge O. , Pitelka Frank A. , Cameron Guy N.
Published: July 2006

Brown lemmings reach much higher densities than collared lemmings near Barrow, Alaska, and captures from 19 summers of snap trapping confirm previous reports that brown lemmings prefer lower, wetter habitats than do collared lemmings. Data also support the hypothesis that brown lemmings concentrate in higher habitats during early summer when melt water floods lower habitats, then shift to lower habitats where preferred food is more available as the waters recede. This pattern appears similar to seasonal shifts in habitat use reported for Norwegian lemmings. Two hypotheses were not supported by our data: (1) Unlike Norwegian lemmings, brown lemmings did not expand their use of suboptimal habitats at higher population densities. Rather, absolute densities changed in concert so that the relative densities among habitats remained unchanged. (2) Preferential use of polygon troughs during winter, as indicated by patterns of winter grazing, was not simply a function of snow depth. Instead it appeared to be related to shoot density of preferred foods. Nearly all patterns of habitat use seemed to be linked to food availability. Other factors, such as protection from predators by vegetative cover in summer and increased insulation from deeper snow in winter, did not appear to influence the distribution of lemmings as strongly.
Seasonal variation in the lateral distribution of mayfly nymphs in a boreal river
Authors: Olsson Tommy I.
Published: July 2006

Seasonal variations in the lateral distribution of mayfly nymphs were investigated in the North Swedish river Vindelälven; a river with large seasonal differences in water level, current velocity and ice conditions, A total of 22 mayfly species about equally divided between summer and winter species were found along a single transect. At low water level in late summer and autumn most species were distributed over the whole transect. In winter the populations occupying the littoral moved into deeper water, so avoiding the ice. Only very small mortalities were detected in the ice. Prior to the spring flood most characteristically still water species moved to the shallow uppermost littoral while lotic species and the burrowing Ephemera vulgata L. did not show the same aggregation near the shore. It is suggested that these lateral movements allow the nymphs to avoid adverse environmental conditions and to exploit food resources over the whole transect.
Digestibility and retension of food components in caged mountain hares Lepus timidus during the winter
Authors: Pehrson Åke
Published: July 2006

Adult mountain hares in outdoor cages were studied in order to evaluate the consumption and the digestibility of natural winter foods. Food, feces and urine were analysed for nitrogen, phosphorus, calcium, potassium, magnesium and sodium, and food and feces for fiber as well. The metabolism of the different nutrients are presented in this paper.

When energy equilibrium was maintained hares assimilated as an average 21.6 g dry matter per kg body weight and day (29.5 g kg0‐75). The fiber fraction showed a low digestibility ranging from 10 to 30% between different food species.

At energy equilibrium nitrogen equilibrium was usually also achieved; the hares then digested approximately 0.20–0.25. g nitrogen per kg body weight and day (0.27–0.34 kg ‐0.75). The apparent nitrogen digestibility was low, usually below 40%.

The demand for calcium, potassium and magnesium seemed to be well covered via the food. Phosphorus on the other hand was absorbed in small amounts only, which may sometimes have been insufficient. A negative sodium balance occurred when the hares were fed heather or the finest twigs of birch. Due to the low concentrations in the food this could create problems in the supply of sodium.
Population dynamics of three planktonic diatoms in lake Constance
Authors: Sommer Ulrich
Published: July 2006

A population dynamics analysis for planktonic diatoms is presented that allows estimates of the net rate of increase (k), the death rate (δ), the sedimentation rate (σ) and, in absence of grazing, the growth rate (μ). It requires counts of live and dead cells suspended in the euphotic part of the water column and accumulated in sedimentation traps. The application of the model is demonstrated for the three dominant summe diatom species in Lake Constance. Asterionella formosa Hass, Fragilaria crotonensis Kitton and Stephanodiscus binderanus Krieger. Only during the first two weeks of the summer bloom of diatoms the loss rates were unimportant in comparison to the growth rates. Thereafter diatom population dynamics was strongly influenced by sedimentation and mortality, which sometimes led to a decrease in population density even when cell division continued at high rates. There were two periods of extraordinarily high death rates, which were associated in the case of A. formosa with silicon depletion and in the case of F crotensis with fungal parasitism.
The impact of some environmental factors on the establishment of Plantago maritima seedlings and juveniles along a distributional gradient
Authors: Jerling Lenn
Published: July 2006

The establishment of Plantago maritima seedlings and juveniles along a distributional gradient was investigated with pantograph technique. Mortality was closely dependent on vegetational characters such as cover, height of vegetation and amount of litter. Superimposed on these factors was mortality due to flooding. The density dependent mortality of seedlings was also investigated. The number of surrounding seedlings seemed to be of vital importance for survival, i.e. self thinning occurred most likely as a result of competition for light. The establishment and survival of seedlings cannot fully explain the distribution of adults.
Effects of forest regeneration on the structure of bird communities in northern Finland
Authors: Hello Pekka
Published: July 2006

Breeding bird communities in five stages of secondary forest succession were studied in northeastern Finland in 1980–82. Three groups of communities were distinguished: open land, brush phase and forest communities, dominated by Motacilla alba and Oenanthe oenanthe, Phylloscopus trochilus and Anthus trivialis, Phylloscopus trochilus and Fringilla montifringilla, respectively.

Pair density, number of species, biomass of adult birds and species diversity increased in the course of succession, none of these, however, monotonously. Average bird weight showed a decreasing trend although the variation was considerable. The degree of specialization in communities (measured by ratios derived from numbers of species, genera and families) increased in the course of succession with the exception that the initial stage had relatively high values. Species nesting and feeding in trees and shrubs increased in numbers during forest regeneration whereas species nesting and feeding on the ground showed the opposite trend. The proportions of hole‐nesting and sedentary species increased with increasing forest age.

The initial stages of forest succession in the north are occupied by specialized open habitat species breeding originally on open bogs and shores. These communities thus clearly differ from those predicted from the general theory of succession, which postulates that the pioneer stages of succession are dominated by habitat generalists and that these communities should have relatively low values of community diversity.
Distribution, activity, life‐history and standing crop of Julidae (Diplopoda, Myriapoda) in the Central High Alps (Tyrol, Austria)*
Authors: Meyer Erwin
Published: July 2006

The research area includes subalpine meadows, alder communities, dwarf‐shrub heaths, lichen heaths and highalpine meadows (1960 m–3090 m a.s.l.). The material consists of 4419 Julidae (31.6% adult) collected by extraction of litter samples (66.4%), in pitfall traps (26.3%) and by handsampling (7.3%).

Cylindroiulus meinerti (Verhoeff) only occurred below 2000 m; Leptoiulus saltuvagus (Verhoeff) was mainly found at Alnus viridis sites; Leptoiulus simplex (Verhoeff) had its main distribution in the lichen heath (2200‐2300 m); Ommatoiulus sabulosus (L.) was found most frequently in the subalpine meadow and Leptoiulus alemannicus (Verhoeff) occurred up to 2800 m without any altitudinal concentration.

Adults of L. saltuvagus showed only one distinct activity peak in September, those of L. simplex were diplochronous (June/September) and O. sabulosus summer stenochronous (July).

L. saltuvagus reached maturity in stage IX (only males), X or XI after four or five Years. In their first year of growth the members of a generation reached the third or fourth stage, in the second year the sixth or seventh, in the third year the eighth or ninth. Females could carry full‐sized eggs in the autumn of the fourth year in the tenth stage or in the fifth year in stage eleven. Apparently eggs may be laid in spring of the fifth or sixth year. Overwintering density of L saltuvagus in alder litter was found to be 215.6 ± 38.7 inds m−2, the mean biomass 1.16 g m−2(max. 1.88 g m−2). Mean annual production during the growth period of 4‐5 months was in the order of 0.85 g m−2 (max. 1.36 g m−2).
Dynamics and structure of a Velia caprai (Heteroptera) population in a South Swedish stream
Authors: Brönmark Christer , Malmqvist Björn , Otto Christian
Published: July 2006

Population density was estimated monthly by means of direct counts for 16 consecutive months. Capture‐recapture experiments revealed that 9–22% of the population was observed by this technique. Most nymphs appeared in June, and the presence of nymphs in September suggests a second generation. There was a strong positive correlation between summer surface drift and mean annual population density for five out of six sections studied. In July‐August the sex ratio was near equal, while in September females began to dominate. The bias towards females was strong until new imagines emerged in July. From September a marked weight dimorphism was observed between the sexes. Food limitation, and skewed sex and weight ratios implied intersexual competition in this population. Brown trout possibly affected the population density in one section with less shelter. Wing dimorphism was observed in July and August. Macropterous individuals represented a low percentage (<17%) and were only observed in sections with high densities.
Factors influencing breeding site choice by the pioneering amphibian Bufo calamita
Authors: Banks Brian , Beebee Trevor J. C.
Published: July 2006

We have investigated environmental factors influencing the choice of breeding pools by Bufo calamita in two different habitat types in Britain, using a number of methods including the construction of artificial pools and the translocation of spawn laid by competitively superior anuran species. On heathland, major determinants were aspects of pond chemistry especially pH, Na and SO4. On coastal dunes other criteria were important, notably maximum water temperatures achieved the day prior to spawning. These in turn related to the precise shape and size of the pond. In addition, natterjacks were able to discriminate against ponds which already contained large numbers of competitor species Rana temporaria and Bufo bufo larvae. Possible mechanisms underlying site choice by B. calamita are discussed.
Goshawk predation during winter, spring and summer in a boreal forest area of central Sweden
Authors: Widén Per
Published: July 2006

Predation by goshawks was studied in a central Swedish boreal forest area. Data were collected in winter (January–February) 1977‐81 by tracking radio‐tagged goshawks, and in the breeding season (April–July) by collecting prey remains at the nest. In the breeding season birds dominated the prey, amounting to 86% of prey number and 91% of prey biomass. Wood pigeon Columba palumbus, black grouse Tetrao tetrix, hooded crow Corvus corone cornix and jay Garrulus glandarius accounted for more than 50% of the prey animals, whereas capercaillie Tetrao urogallus and black grouse accounted for more than 50% of prey biomass. There was no functional response to black grouse density fluctuations. Every year goshawks killed significantly more females than males of both capercaillie and black grouse, due to high vulnerability of the grouse hens while laying and incubating. It was estimated that during spring and early summer goshawk predation removed 25% of the female, and 14% of the male black grouse population. In winter squirrel was the dominating prey, both in terms of number (79%) and weight (56%). The proportion of squirrel in the diet was equally high both in winters of low and high squirrel density. The high proportion of squirrel in the winterdiet, as compared to the breeding season, is believed to be due to squirrels having to accept an increased predation risk in winter, in order to feed efficiently enough.
Effects of pH and aluminium on embryonic and early larval stages of Swedish brown frogs Rana arvalis, R. temporaria and R. dalmatina
Authors: Andrén Claes , Henrikson Lennart , Olsson Mats , Nilson Göran
Published: July 2006

The effects of pH and aluminium on embryonic and early larval stages of Swedish brown frogs Rana arvalis, R. temporaria and R. dalmatina were tested in laboratory bioassays. In all three species egg mortality and time needed for embryonic development to hatching increased when pH declined, but no significant effects were found on embryonic development when aluminium level was elevated. In R. arvalis and R. temporaria larval mortality was affected by both pH and aluminium. In both species the frequency of occurrence of larval deformities increased in acid water, and there was a synergistic effect of pH and aluminium. In R. arvalis swimming behaviour was disturbed by high levels of aluminium at pH 5. In all three species the frequency of stressed larvae increased when pH was depressed and aluminium concentration elevated, and there was a synergistic effect when both were combined. The three species differed significantly in egg mortality, time needed for embryonic development, larval mortality, larval deformities and larval stress al low pH and high aluminium levels. R. arvalis showed the highest acid tolerance and R. dalmatina was the most sensitive to low pH.
Two‐ and three‐year life cycles in the planktonic copepod Cyclops scutifer in two high mountain lakes
Authors: Elgmork Kåre , Eie Jon Arne
Published: July 2006

The life cycles of Cyclops scutifer Sars (Copepoda, Crustacea) in two high mountain lakes in Norway, Gjende and Bessvatn in Jotunheimen, are presented. The population in Gjende has an exclusive 2‐yr life cycle and that in Bessvatn a 3‐yr cycle which is exceptionally long both among freshwater and marine zooplankton. Bessvatn is situated about 400 m higher than Gjende, and the heat preservation is lower with longer periods of ice cover and lower primary production explaining the difference in cycle length. The prolongation of the life cycle is due mainly to retardation of the developmental rate during the long periods of winter stagnation with water temperatures mostly below 2°C. The retardation is especially evident in the nauplii and in the copepodid instars III, IV, and V. Neither population diapauses. Reproduction takes place only in late summer and no adults survive the winter.
Inter‐ and intraspecific variation in the resistance of winter‐dormant birch (Betula spp.) against browsing by the mountain hare
Authors: Rousi Matti , Tahvanainen Jorma , Uotila Ilari
Published: July 2006

The palatability of saplings of several different species, geographic origins and F2‐families of Betula spp. to the mountain hare was tested in feeding trials with captive and free‐ranging animals. Significant variation in the palatability was detected among species and among conspecifics representing different origins and families. The results show that the combination of genetic and environmental factors determines the resistance of individual plants to mammals. Saplings that were stressed by severe competition from surrounding weeds were more resistant than saplings of the same age grown under optimal conditions. One‐yr‐old seedlings were more resistant than 7‐yr‐old saplings of the same origin. Some of the exotic species tested were extremely resistant, whereas others were highly palatable. The most resistant species and origins came from Asia and Alaska.
Habitat selection, reproduction and survival of two small carabid species on arable land: a comparison between Trechus secalis and Bembidion lampros
Authors: Wallin Henrik
Published: July 2006

In central Sweden, teneral adults of the strictly larval‐overwintering carabid beetle Trechus secalis Paykull started emerging during mid‐June and bred in midsummer (July). In contrast, the strictly adult‐overwintering carabid Bembidion lampros Herbst bred in early summer (June), and the new‐generation emerged in late summer (August). Both species appeared to be univoltine and had a short period of sexual activity (2–3 months). Their main oviposition periods did not overlap, and gravid B. lampros contained a higher mean number of eggs than did gravid T. secalis. Conversely, T. secalis had a longer oviposition period than B. lampros. Prereproductive B. lampros accumulated in high densities along field edges prior to hibernation. The cereal fields appeared to be optimal for reproduction and larval development of both species. Trechus secalis also reproduced in adjacent uncultivated habitats, whereas B. lampros did not. Trechus secalis larvae were completely subterranean, whereas B. lampros larvae were partly surface active. The adaptive significance of their reproductive tactics and habitat preferences as adults and the suitability of cereal fields as habitats for reproduction and survival of populations are discussed.
Mass attack of trees by Ips typographus induced by sex‐specific pheromone: a model of attack dynamics
Authors: Schlyter Fredrik , Anderbrant Olle
Published: July 2006

A model of attack dynamics on a single tree under mass attack by the spruce bark beetle Ips typographus is developed from earlier studies of pheromone production and response of the flying population to the pheromone signal. The model is explored for different numbers and sex‐ratios of pioneer beetles and responding beetles. Both numbers of pioneers and responders were important for the dynamics, while the sex‐ratio of pioneers was less important. A decreased proportion of males among the responding beetles was important for the result of the model. In the early stage of the attack the model predictions of both numbers and sex‐ratio of beetles landing were similar to examples from naturally mass‐attacked trees, although the attack proceeded more slowly than in the field. Several aspects of the attack dynamics, such as density‐regulation of the number of attacks on the tree, as observed in the field, were not predicted by the model. Gaps in the knowledge of the chemical ecology of the tree‐insect relation, such as qualitative change in odours from the tree, spacing mechanisms on the bark surface, and mortality due to host resistence, are pointed out with help of the model.
Changes in total nitrogen, protein, amino acids and NH+4 in tissues of bilberry, Vaccinium myrtillus, during the growing season
Authors: Lähdesmäki Pekka , Pakonen Tuulikki , Saari Esko , Laine Kari , Tasanen Leena , Havas Paavo
Published: July 2006

Free amino acids and related compounds together with total nitrogen, total protein and soluble small‐molecular nitrogen were analyzed quantitatively in monthly tissue samples from bilberry, Vaccinium myrtillus, from 15 May to 24 September 1985, in Oulu, northern Finland. Pronounced accumulation (at the millimolar level) of soluble low‐molecular‐weight nitrogen in the form of free amino acids was observed at the end of September. Arginine in particular accumulated in the rhizomes and older branches. Protein levels remained relatively constant. Mobilization of amino acids from winter storage into the growing tissues (buds) was evident in May.
The effects of size, age and a cost of early breeding on reproduction in female mountain hares
Authors: Iason Glenn R.
Published: July 2006

Both age and size may influence female reproductive performance in mammals, and successful early reproduction may lead to reduced success at later attempts. The effects of age, size and early reproduction on distribution of reproductive effort throughout a single breeding season was examined in female mountains hares Lepus timidus L. Hind foot length was used as an index of body size, because, unlike body weight, it did not fluctuate with reproductive status. Fifty‐six female carcasses were collected from March to October 1984, and their litters were assigned to one of three chronologically equal‘litter periods’(1–3) of equal length. Whereas number of ova shed was always independent of age, large females shed more ova than did smaller females in litter periods 1 and 2. Prenatal mortality of ova and embryos was highest during litter period 1, when it was independent of age and size. Although prenatal mortality remained high in first year females in litter period 2, there was an overall decline through to the final litter period when it was negligible. Total number of young produced through the season increased with skeletal size in old females (age > 1), but not significantly in first year females. It is concluded that large size, rather than age, favours early reproduction in mountain hares. Every additional offspring produced in litter periods 1 and 2 reduced that female's production in period 3. After correcting for this cost of early reproduction the number of young produced in the final litter period also increased with maternal size.
Ecomorphological relationships in a group of insectivorous birds of temperate forests in winter
Authors: Carrascal Luis M. , Moreno Eulalia , Tellería José L.
Published: July 2006

We examined the relationships between morphology and foraging behaviour in a group of insectivorous birds wintering in temperate mixed forests in northern Iberia. Using principal components analysis we reduced 11 biometric variables to three major morphological components and 20 foraging categories to four major ecological factors. The relative length of the tarsometatarsus and bill morphology were the most important morphological variables predicting foraging ecology. Birds exploiting distal parts of trees and foliage were generally smaller and had relatively longer tarsometatarsi than those foraging on trunks. Foraging on the ground and branches of medium diameter was associated with bill thickness. Ecomorphological patterns were discernible at the level of substrate use and foraging methods, but bear no relation to selection of tree species or foraging height. Morphology correctly predicted niche breadth and interspecific overlap. In Parus spp. interspecific differences in bill shape could explain 63% of the interspecific segregation according to substrate use (R2= 0.63, p <0.01).
Seed and tuber banks of aquatic macrophytes in the Askö area, northern Baltic proper
Authors: Kautsky Lena
Published: July 2006

Sediment samples from 5 stations in the northern Baltic proper, 6.5 o/oo S, were collected in April 1987 and the emergence of seedlings was recorded over 120 days in a greenhouse at 20°C. Total seedling densities varied from 0 to 3328 m‐2: and of seven species, Zannichellia palustris and Chara spp. were the most abundant among seedlings and sporelings, respectively. Several common macrophytes in the area were rare as seedlings and no seedlings were recorded for the most abundant angiosperms, Potamogeton pectinatus, Potamogeton perfoliatus and Ranunculus baudotii. Except for the few annual species, reproduction by seeds contributed little to the dynamics of the vegetation in the area and no correlation was found between vegetation composition and the seed bank. For perennial species the winter survival of vegetative propagules is the most important factor for vegetation dynamics.
Combined effects of varying water content and CO2 concentration on photosynthesis in Spagnum fuscum
Authors: Silvola Jouko
Published: July 2006

The photosynthesis of Spagnum fuscum (Schimp.) Klinggr. at different water contents and CO2 concentrations was measured in the laboratory. The optimal water content for photosynthesis near the current atmospheric CO2 concentration is 600–800% (percentage of dry weight). The decrease in photosynthesis is very steep towards lower water contents and less steep towards higher water contents. The optimal water content range moves higher and becomes wider with increasing CO2 concentration. At 3000 ppm there is no longer any decrease in photosynthesis with increasing water content. The water content of S. fuscum has a considerable effect on the response of photosynthesis to CO2 concentration. In a moss saturated with water, photosynthesis increases gradually until 8000 ppm CO2, but this saturation concentration becomes lower with decreasing water content, being c. 1500 ppm at a water content of 700–800%. An increase in CO2 concentration over 300 ppm will raise photosynthesis very little in dry moss with a water content of only 300–400%.
Structure and succession of ant assemblages in a north European sand dune area
Authors: Gallé L.
Published: July 2006

Ant assemblages of a successional dune area (Tvärminne, south Finland) were analysed at three levels: the distribution of species among habitats, the distribution of colonies within habitats and the spatio‐temporal distribution of individuals. The distribution of ant species among habitat patches representing different stages of succession is correlated with the composition of the epigeic fauna, the number and condition of dead twigs on the ground and the vegetation architecture. The composition of ant assemblages seems relatively independent of the plant species composition, and there are uncoordinated successional steps between the vegetation and ant communities.

In the early successional stages interference competition is weak and insignificant, as indicated by the random spatial arrangement of colonies, the absence of postcompetitive niche segregation and the low encounter rates of ant workers on the ground and at baits. In the aggressive behavioural hierarchy, Formica cinerea is a submissive species as compared with either Formica sanguinea or Lasius alienus.
Factors affecting the distribution pattern of bats in Uppland, central Sweden
Authors: de Jong Johnny , Ahlén Ingemar
Published: July 2006

Bats were surveyed and insects were trapped in several different habitats to test the hypothesis that insect abundance and types are the most important factors affecting the regional distribution of bats. A bat community of ten species dominated by Eptesicus nilssoni and Pipistrellus pipistrellus was analysed. The results show that the general pattern of bat distribution in different habitats, and the seasonal changes in habitat utilization, could be explained in terms of the abundance of swarming insects, mainly chironomids. Deciduous woodland near water provided essential habitat in early summer for each bat species. Later on, in July, all species spread out to many different habitats. In autumn street‐lamps were an important factor affecting bat distribution.
Long day stimulation of dry matter production in Poa alpina along a latitudinal gradient in Norway
Authors: Solhaug Knut Asbjørn
Published: July 2006

Photoperiod extension with weak include from 8 to 24 h stimulated relative growth rate (RGR) of Poa alpina up to 20%. The response was greatest in young plants at low temperatures. The leaf area ratio (LAR) increased by about 50% which more than compensated for a reduction in net assimilation rate (NAR) by about 20%. The effect of daylength extension on RGR was similar for an arctic ecotype of P. alpina from Svalbard, an alpine ecotype from southern Norway and a borealtemperate ecotype from southern Norway. The main changes in the growth parameters occurred over the 13 to 17 h photoperiod range in P. alpina from both Svalbard and Rondane, although plants at Svalbard are exposed to midnight sun throughout their growing season. The ecotype of P. alpina from southern Norway had fewer tillers and allocated less dry matter to the roots than the two other ecotypes.
Oviposition date and pattern of embryogenesis in the grasshopper Chorthippus brunneus (Orthoptera, Acrididae)
Authors: Cherrill Andrew , Begon Michael
Published: July 2006

The morphological development of eggs of the grasshopper Chorthippus brunneus, laid during successive periods through a single season, was closely monitored in the field at a site in NW England. Eggs within the same clutch developed synchronously. However, there were significant differences between clutches laid at the same time, reflecting spatial variation in microclimate (and possibly maternal effects and/or genetic differences). Eggs laid early in the season entered diapause and hatched relatively synchronously in the following spring. Eggs laid later failed to reach the diapause‐stage before winter, but hatched, albeit late and with greater variance. Diapause was averted in these eggs. Plasticity in the nature of diapause has been documented from laboratory studies of many insect species (including C. brunneus,) but this study directly relates the incidence of such developmental plasticity to oviposition date and seasonal temperature cycles in the field. The adaptive significance of diapause aversion and the evolutionary consequences for female reproductive behaviour are considered.
Habitat associations of carabid beetles in fields and forests on the Åland Islands, SW Finland
Authors: Niemela Jari , Halme Eero
Published: July 2006

Carabid beetles (Coleoptera, Carabidae) were collected by using pitfall traps in 68 sites on the Åland Islands, SW Finland The sites were divided into four environmental types 1) cultivated fields and grazed pastures. 2) recently abandoned fields, 3) abandoned, overgrown cultivations, and 4) forests A total of 4901 carabids belonging to 77 species were caught Twenty of the most abundant species were classified into four distributional types according to their occurrence among the various environmental types 1) generalists (five species), 2) field species (five species), 3) species of open habitat (seven species), and 4) forest species (three species) Associations with environmental types were strictest among field species and forest species However, most of the species were found in low numbers outside each preferred environmental type The number of species and species diversity was highest in fields and pastures and lowest in forests, which agrees with previously detected patterns on the mainland Finland Pairwise similarity of the carabid assemblages among the environmental types was highest between the two types of abandoned cultivations The spatial distribution of two carabid species, Pterostichus melanarius and P niger, were examined in detail to ascertain whether any interspecific interaction could help explain their different island‐mainland distribution observed in previous studies
Fast life in cold water: Diamesa incallida (Chironomidae)
Authors: Nolte Ulrike , Hoffmann Thomas
Published: July 2006

Development times of Diamesa incallida and its numbers of generations per vear were studied using in situ reanngs in conjunction with continuous collection of egg masses from the field The evidence suggested that the crenophilous D incallida laid eggs throughout the year and produced eight to ten generations per year, depending on water temperature (76°C to 80°C) This is the first proof for a muitivoltine Diamesinae as well as for continuous egg laying behaviour by a non–troprcal chironomid The comparatively large mature larvae (96 mm, 710 μ.g a f d weight) and the numerous generations per year indicate that D incallida is a highly productive component of crenal communities The importance of rearing chironomids over a sufficient number of generations is emphasized as a basis for the reliable interpretation of field data
Seed banks in Danish deciduous forests: species composition, seed influx and distribution pattern in soil
Authors: Kjellsson Gösta
Published: July 2006

Samples of soil from six forest stands of different age and composition were collected, and the seedlings emerging during germination experiments were recorded Total seed bank densities varied between 2230 and 15,630 seeds m−2 The seed bank size was positively correlated with the yearly seed influx, which constituted from 400 to 2720 seeds m−2Juncus effusus dominated the seed banks with generally 2000 to 3300 seeds m−2, to exceptionally 10820 seeds m−2 Seeds of Rubus idaeus, Betula pubescens and Carex spp were also abundant in the soil Similar numbers of species were present in the seed banks and vegetation, but only 7‐48% were species in common Anemochorous species were more frequent in soil than above‐ground, while zoochorous species were rare in soil but abundant in the vegetation A measure of the occurrence of seeds in relation to soil depth was designed Seeds of species with short‐term survival in soil (e g Anemone nemorosa, Epilobium angustifolium, Oxalis acetosella and Stellaria holostea) were confined to the top soil, while many well known long‐term survivors (e g Carex piluhfera, Poa annua, Rubus idaeus and Stellaria media) were found predominantly deep in the soil The horizontal distribution of seeds of herbaceous species forming short‐term seed banks was largely random, while seeds of herbs capable of long‐term survival in soil were significantly aggregated Except for one old and species‐poor site, the dormant flora indicated generally high levels of disturbance in the past
Element concentrations in mosses and surface waters of western Canadian mires relative to precipitation chemistry and hydrology
Authors: Maimer Nils , Horton Diana G. , Vitt Dale H.
Published: July 2006

Concentrations of N, P, S, Na, K, Mg, Ca, Mn, Fe, Cu, Cd, Zn, Pb, Al, and AIA (acid insoluble ash) m mosses (three Sphagnum species and Tomenthypnum nitens, all hummock species) from a variety of mires, both ombrotrophic and minerotrophic, in the coastal western and central parts of Canada are considered in relation to surface water pH and concentrations of Na+, K+, Mg2+, Ca2+, Cl−, and SO42‐ Distinct west‐east concentration gradients were present for most elements in both mosses and water, but there were correlations between surface water and moss concentrations only for Ca and Mg

On ombrotrophic sites and sites characterized by poor fen vegetation, wet deposition is the main source of elements in the surface water On rich fen sites, additional Ca and Mg from surrounding soils change the elemental proportions We conclude that hydrochemically the limit between poor and rich fen sites is more decisive than between bog and fen The increase in Ca may give brown mosses a competitive advantage over Sphagnum

Moss concentrations of Na and Mg are the only ones decreasing inland The constancy or inland increase of moss elemental concentrations may depend on either an increasing atmospheric supply (e g Pb), differences in moss growth rates (especially N, P, and K) or site conditions related to the water regime (e g Fe and Al)
Population fluctuations and habitat selection in the Eurasian red squirrel Sciurus vulgaris
Authors: Andrén Henrik , Lemnell Per‐Arne
Published: July 2006

The population fluctuations of Eurasian red squirrel Sciurus vulgaris during ten winters showed a strong relation to Norway spruce Picea abres cone crop one year before Neither, Scots pme Pinus sylvestris cone crop nor mean temperature in December and January had an additional significant effect on the fluctuations The one‐year time‐lag between the good spruce cone crop and mcreased red squirrel density suggests that the rich food supply first mcrease the winter survival and then the reproductive success

The highest density‐index of red squirrels was found m old forest dominated by Norway spruce (mean density‐index 34 km−2) This habitat was also occupied in all 10 winters Other habitats with lower densities were occupied in fewer winters The vanation in density‐index was also highest in this habitat indicating that the dispersion of red squirrel individuals in different habitats follow the food supply
Species composition and within archipelago co‐occurrence patterns in the Canary Islands
Authors: Fernández‐Palacios José María , Andersson Christian
Published: July 2006

The distribution of trees and shrubs, ferns, land birds, beetles, and butterflies on the Canary Islands were analysed according to the null hypothesis approach Deviations from the expected number of species were found in the species groups trees and shrubs and Tenebrionid beetles This was interpreted as the result of deterministic processes influencing the colonisation of the archipelago In an other analysis the relationship between species similarity and geographical distance between the islands was investigated It showed that species similarity between the island decreased with distance The decrease was steepest for Tenebrionid beetles and trees and shrubs so it was concluded that their dispersal ability was lower than in the other species groups
Numbers, geographic distribution and habitat utilization of waders (Charadrii) in spring on the shores of Iceland
Authors: Gudmundsson Gudmundur A. , Gardarsson Arnthor
Published: July 2006

The occurrence of waders m spring (breeding as well as migrating species) in the intertidal zone was studied along the shores of Iceland Ground surveys were made at a total of 115 sites on the west coast in May 1986 and 1987 Repeated counts in the same season were conducted at 76 sites visited m both early and late May 1987 Furthermore, an aerial census covering most of the Icelandic coastline was carried out in May 1990 (76% of the total coastal length of 6650 km and 92% of the total intertidal area of 445 km2 were covered from the air) Altogether 345 000 waders were recorded, including 270 000 knot Cahdrts canutus Geographic distribution was uneven, as is the distribution of intertidal areas, with over 85% of all waders occurring on the west coast where >80% of suitable intertidal habitats are found A majority of the knot population, possibly about half of the turnstone Arenaria interpres population and probably only a minority of the sanderling C alba population wintering in the Palearctic and breeding in Greenland/Canada use Iceland as a staging post on their spring passage The local breeding populations of waders and the High Arctic wader populations on passage have rather well separated time schedules for their utilization of intertidal habitats in Iceland Between them the three above‐mentioned species of passage migrants show considerable differences m geographic distribution and habitat utilization during the spring staging period m Iceland
Reproductive strategies in two arctic Pedicularis species (Scrophulariaceae)
Authors: Eriksen B. , Molau U. , Svensson M.
Published: July 2006

A study of a number of reproductive traits in two sympatric species of Pedicularis in northern Swedish Lapland, the subarctic‐alpine P lapponica and the artic P hursuta, revealed that the life‐history strategies of the two species differ profoundly High fruit set and low seed abortion rate, as m P hursuta, is common in arctic plants in late‐thawing habitats and represents a case of extreme adversity selection rather than an indication of a ruderal life‐history strategy Pedicularis lapponica, on the other hand, is a typical K‐strategist (or stress‐tolerator) requiring a longer period of growth for optimal reproduction Occuring at both low and high altitudes in the area, P lapponica tends to increase in self‐compatibility with altitude, which is interpreted as an adaptation to lower pollinator visitation frequency in arctic environments The variation in length of the protruding part of the style in P lapponica is shown to be correlated with exposure to light Predispersal seed predation is severe m P lapponica at low altitudes, where the capsules are attacked by fly and moth larvae At high altitudes, a minor proportion of the capsules of P lapponica experience predation and only from flies, while P hursuta is completely unpredated