bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal dynamics of shoot nutrients in Schoenus ferrugineus (Cyperaceae)
Authors: Ganzert Christian , Pfadenhauer Jörg
Published: July 2006

Seasonal patterns of biomass and standing stock (g m−2) of nitrogen, phosphorus, potassium and calcium were documented in Schoenus ferrugineus L. from an annually mowed calcareous fen in southern Germany. The peak standing crop of nitrogen, phosphorus and potassium occurred in mid‐July. Prior to the end of the growing season, 44% of total potassium, 34% of total phosphorus and 28% of total nitrogen were retranslocated out of the shoots, based on differential nutrient losses between covered and uncovered plots. There is no evidence that any calcium was retranslocated, but 24% of peak calcium and 13% of potassium was leached from standing dead shoots. More than half of the peak phosphorus was found in the overwintering green shootbases. In the light of the low availability of nutrients in the soil, retranslocation of phosphorus in particular is essential, if adequate internal nutrient levels are to be maintained, despite various proposed uptake mechanisms.
Variability in the life‐history patterns of four species of Hydropsyche (Trichoptera: Hydropsychidae) in southern Ontario streams
Authors: Rutherford Jane E. , Mackay Rosemary J.
Published: July 2006

The life‐history patterns of four Hydropsyche species (Trichoptera: Hydropsychidae) found in the Credit and Humber Rivers of southern Ontario were investigated through rearing studies, larval and adult collections, and analyses of densities and mortality of field populations of pupae. Hydropsyche slossonae was univoltine but was probably capable of producing a second generation under favourable conditions at the warmest station at which it occurred. Hydropsyche sparna was partially bivoltine at upstream stations and bivoltine at downstream stations. At downstream stations, the common species were Hydropsyche bronta. which was trivoltine. and Hydropsyche morosa, which was bivoltine. Hydropsyche sparna, H. bronta and H. morosa all exhibited a split‐cohort development, in which not all of the summer‐produced larvae completed development, pupated and emerged before the end of the growing season. Overwintering populations consisted of young larvae that had hatched from eggs laid by adults of the previous generation. Analysis of the temporal changes in the densities of living and dead pupae provided a reliable way to separate overwintering and spring‐ and summer‐produced generations.
The trophic basis of production of the macroinvertebrate community of a southeastern U.S.A. blackwater stream
Authors: Smock Leonard A. , Roeding Cheryl E.
Published: July 2006

The trophic basis of production of the macroinvertebrate communities at three sites on a second‐order, low gradient blackwater stream in southeastern U.S.A. was determined. The sampling sites were located above, within and below a low‐flow swamp system. From 47–64% of macroinvertebrate production was supported by FPOM at the three sites, with dependence on FPOM being greatest at the swamp site. Algae (filamentous species and diatoms) supported 15–31% of production, indicating that algae can be of considerable importance even in fully canopied headwater streams. The production of some collector‐gatherers including Stenonema modestum (55%), Hexagenia munda (58%) and Baetis spp. (78%), was supported predominantly by algae. Algae also supported 61–79% of Hydropsychidae production and 68% of Simuliidae production. Animal material supported 16–26% of macroinvertebrate production at the three sites. CPOM was of minor direct importance to the macroinvertebrate community of this headwater stream, supporting only 1–3% of macroinvertebrate production. Shredders ingested only 1–3 g m−2 y−1 of CPOM, or about 1% of the annual direct leaf fall to this stream. Assuming a 10% assimilation efficiency for CPOM, shredders produced <3 g m−2 y−1 of FPOM through CPOM processing, this being approximately 2 orders of magnitude less than reported for high gradient headwater streams. These results indicate that low‐order coastal plain streams vary somewhat from the River Continuum Concept in that they exhibit little utilization of and dependence on CPOM as a direct energy source. Only the smallest first‐order streams and especially the extensive floodplains may be the functional headwaters of these stream systems.
Density dynamics of bumblebees in subalpine meadows: competition and resource limitation
Authors: Bowers Michael A.
Published: July 2006

Densities of Bombus flavifrons and B. rufocinctus were measured over one summer in 23 and 11 discrete subalpine meadows, respectively. I assessed the relation between observed bee densities and meadow size, elevation, floristics, temperature, and time of day by multiple regression. Multivariate regression solutions for each week of observation accounted for 38 to 61% of the variation in density for B. flavifrons and 47 to 87% for B. rufocinctus. Temperature or time of day consistently accounted for the most variation in density of the two species. In early summer meadow size or elevation also accounted for a large proportion of explained variation in B. flavifrons density; as the summer progressed meadow floristics increasingly contributed to the explanation of variation in both species.

In mid‐ to late summer a statistically significant portion of the variation in densities not explained by habitat characteristics was accounted for by densities of congeners: i.e., densities of B. flavifrons and B. rufocinctus were negatively related in eight meadows where they co‐occurred. In experimental meadows where all Bombus but one of the two target species were removed. B. rufocinctus underwent significant positive density compensation but B. flavifrons did not. To the extent that B. flavifrons appeared to limit the density of B. rufocinctus these statistical and experimental results are consistent with the hypothesis that competition limits local bumblebee densities.
Shrews on small islands: epigenetic variation elucidates population stability
Authors: Hanski Ilkka , Kuitunen Juhani
Published: July 2006

Three large (4 to 8 ha) and 14 small islands (0.3 to 2 ha) in a lake in eastern Finland, all situated less than 0.5 km from the mainland, were surveyed for small mammals. Three species of shrew and two species of vole were resident in July 1982:Sorex araneuson 10,S. caecutienson 2,S. minutuson 5,Microtus agrestison 12 andClethrionomys glareoluson 4 islands. Immigrants were trapped from tiny islets, and the data indicate thatS. caecutiensandM. agrestisare better dispersers thanS. minutusandC. glareolus, respectively.Microtus agrestis, S. araneusandC. glareolusoccurred non‐randomly, on subsets of the larger islands, while the two smallSorexspecies occurred more erratically, possibly because of competition withS. araneus. Juvenile sex ratio was male‐biased on the mainland but female‐biased on large islands, possibly because juvenile males move more and are more likely to emigrate from an island than juvenile females.

Metrical and non‐metrical (epigenetic) cranial traits gave similar patterns of population differentiation inS. araneus. Two of the three large‐island populations have differentiated from the mainland populations and from each other, suggesting that the populations are relatively stable. Small‐island populations, which are often less than 10 individuals in size, showed little differentiation but had more epigenetic traits fixed than large‐island and mainland populations (founder effect). This suggests that the small‐island populations are unstable, have a high extinction rate.
Behaviour and body temperature of hibernating common toads Bufo bufo
Authors: van Gelder J. J. , Olders J. H. J. , Bosch J. W. G. , Starmans P. W.
Published: July 2006

Hibernation behaviour of six common toads Bufo bufo was studied. Transmitters, generating pulses with a temperature dependent repetition rate, implanted in the toad's abdominal cavity, were used to measure the body temperature. Measurements of body temperature and soil temperature at various depths were used to establish the hibernating depth. All toads moved vertically between a few preferred depths and hibernating depth appeared to vary for individual toads. Upward movements mostly were apparent reactions on changes of the soil temperature gradient at the depth of the toad.
The spider communities on peat and upland grasslands In northern England
Authors: Coulson J. C. , Butterfield Jennifer
Published: July 2006

Between midsummer 1976 and November 1977 some 29000 spiders belonging to 168 species were caught in pitfalls on 42 peat and upland grassland sites covering an altitude range of 11–827 m in the north of England. The similarities between the spider faunas of each site have been assessed using a modified form of Sørensen's Index and the sites clustered according to their similarities. The sites divided into two major groups; (1) mineral soils where grasses are dominant or shallow peat soils where Juncus squarrosus is dominant and (2) peat soils where Eriophorum vaginatum and Calluna vulgaris are dominant. It is suggested that this major division is the result of the plant “architecture” rather than the species composition of the vegetation. Direct comparison between paired peat and grassland sites at the same altitudes shows no marked separation in the spider species composition on the two soil types but there are differences in abundance of individual species. The three peat site clusters form an altitudinal sequence which is not the result of the decline in numbers of non‐linyphiid species with increase in altitude as the cluster formation is largely dependent on the linyphiid species which dominate the catches.

Twenty one common species have been used lo identify the communities. Many of these species are often found together and form associations. Typically, a number of associations contribute to each community. Only 19 species contribute more than 4% to the numbers of individuals caught in any one community.

Diversity declines with increase in altitude, as does the number of species caught. The decline in the number of species caught is the effect of a decrease in non‐linyphiid species with increasing altitude. There is no significant decline in the numbers of species of linyphiids with increase in altitude.
Growth and reproduction of Mesidotea entomon (Isopoda) in the northern Bothnian Sea
Authors: Leonardsson Kjell
Published: July 2006

The life cycle of Mesidotea entomon sampled near the shore of Norrbyn in the northern Bothnian Sea, has been investigated. The species, a predacious brackish water isopod, had a three year life cycle. In May – June the juveniles were released from the female marsupium at a size of 3 mm. During the second summer size dimorphism became apparent, where the males were larger than the females. During the third summer and autumn the development of ova started in females. Maturation mostly occurred during late winter. Males matured before, and at larger sizes, than the females, 36.0 and 29.1 mm, respectively. The average fecundity was 153.2 and the females carried the eggs and embryos for several months before the release. Calculation of the survival rate for each year during the life‐span revealed 0.05, 0.66 and 0.43, respectively.
Energetics of the suspension feeding mosquito larva Culex torrentium
Authors: Nilsson Curt
Published: July 2006

During a six‐day period the energetics of the suspension feeding larvae of the mosquito Culex torrentium were studied. An experimental assessment of ingestion, growth and respiration were made at near to field conditions. Assimilation and egestion were calculated and an energy budget for an average larva during the experimental period was established. Gut retention time was measured by marking the gut content with charcoal. Organic carbon in the gut contents, of larvae feeding on natural food, and in the tissues (i.e. to establish growth from 2nd and 4th instar) were measured by an elemental analyser. Oxygen consumption was measured as a decrease in volume of a closed system where the respired carbon dioxide was absorbed by KOH. Only 1.6% of ingested organic carbon was assimilated. The ratio between respiration and growth was 13.8. The high value of the ratio is suggested to occur because of the very active behaviour of the larvae. The results are discussed in relation to the energetics of other aquatic primary consumers (Simuliidae and Trichoptera).
Foraging and diet of the northern bat Eptesicus nilssoni in Sweden
Authors: Rydell Jens
Published: July 2006

Northern bats foraged predominantly in small individual and transient feeding sites usually in open places near trees and over water. Lakes were preferred as foraging habitat as compared to woodlands and farmlands. The pattern of habitat selection did not change drastically during the period of reproduction. The diet was probably unselective, consisting mainly of small dipterans and moths and also caddis flies, lacewings and mayflies (lake area) and dung beetles (farmland). Northern bats consumed insects of 3–30 mm body length, thus taking prey items of a broader size range than other bat species studied.
Feeding by geese on the Filsø Farmland, Denmark, and the effect of grazing on yield structure of spring barley
Authors: Lorenzen Bent , Madsen Jesper
Published: July 2006

From the end of August to early May on average 506400 goose days were spent on the farmland of Filsø, 92% by pink‐footed geese, 7% by greylag geese and 1% by bean geese. 36% of the goose days were spent on stubbles (autumn), 38% on stubbles with undersown seed grass (autumn‐spring), and 21% on new‐sown barley fields (spring).

Geese feeding on spring barley consume kernels left on the surface or in the upper surface layers. In 1982 and 1983 trials were set up to quantify the effect of grazing. The effect on yield and plant structure was measured by comparing ungrazed (exclosures) and grazed plots. Grazing by geese significantly reduced the grain yield (7‐20%), but the reduction was not proportional to goose usage. The maximum reduction in sprout density was observed in 1982 in an area with heavy goose usage; sprout density was reduced by 72%, but the subsequent yield in the same area was only reduced by 8%. Plants on grazed plots compensated for the reduced sprout density by having more tillers with ears and grains of higher weight. The effect of grazing on stubble, seed grass, and winter cereals on Filsø is discussed.
Seasonal changes in vertical distribution, biomass and faecal production of tubificids in the profundal region of a shallow Japanese lake
Authors: Fukuhara Haruo , Ohtaka Akifumi , Isobe Yoshiaki , Sakamoto Mitsuru
Published: July 2006

Two tubificid species Limnodrilus hoffmeisteri and L. claparedeianus formed more than 93% of the total number of oligochaetes in the profundal. Limnodrilus spp. worms were found down to 33 cm in the sediment but in great numbers in the upper zone in June and October. Worms confined to the top 15 cm of sediment accounted for 53‐92% of the total number. There were two annual maxima in population density and biomass, one in late spring (66000 inds m−2, 17 g wet wt m−2) and the other in mid autumn (97000 inds m−2, 176 g wet wt m−2). Two regression lines describing the effect of temperature on faecal production rate were obtained; Log F = 0.0604 T (°C) −0.7660 (below 15°C), Log F = 0.0266 T – 0.2170 (above 15°C). In total 26.8 kg dry wt m−2 of sediment was defecated annually by Limnodrilus spp. The sediment in the 0–10 cm stratum may pass through the guts of the worms 2.3 times a year. Sedimentation rates in profundal region were very low with respect to the faecal production rates of the tubificids.
Ecology of heath communities dominated by Cassiope tetragona at Alexandra Fiord, Ellesmere Island, Canada
Authors: Nams Margorie L. N. , Freedman Bill
Published: July 2006

At a high arctic lowland on Ellesmere Island, heath communities dominated byCassiope tetragonawere widespread, and occurred in a variety of habitats that differred in time of snowmelt, relative site moisture, soil thaw depth, and air and soil temperature. Cover, standing crop, and production were dominated by woody plants, notablyCassiope tetragonaandDryas integrifolia. TheCassiope‐dominated heaths were similar in composition to those at other Canadian high arctic localities, but were less similar to localities in Greenland and Spitzbergen. Compositional relationships amongCassiope‐dominated heaths in different habitats at the study site may be largely determined by two interrelated environmental factors, time of snowmelt and site moisture.

Aboveground vascular plant biomass was concentrated near the ground surface, resulting in simple vertical structure that takes advantage of relatively warm soil and air temperatures in summer, and a protective snow cover in winter. Aboveground vascular plant standing crop was largely comprised of attached dead tissue, and there were equal proportions of above‐ and belowground biomass. Low community production was due to dominance by long‐lived, slow‐growing species, and to short growing seasons and cold temperatures. Overall character ofCassiope‐dominated heaths reflects the conservative, stress tolerant growth strategy of the dominant species,Cassiope tetragona.
Why do European stoats Mustela erminea not follow Bergmann's rule?
Authors: Erlinge Sam
Published: July 2006

Stoat Mustela erminea body size shows remarkably great variation over the species' European range. The pattern of this variation is opposite to that suggested by Bergmann's rule, i.e., stoats in central Europe are significantly larger than those in southern Sweden which, in turn are considerably larger than their conspecifics in northern Sweden. Neither winter temperature nor the length of snow cover shows any consistent correlation with stoat body size variation, and the larger body size of the southern populations could not be related to a widening of the stoat's feeding niche. A positive correlation was found between the frequency distribution, by size, of available prey and stoat body size in the different areas examined. This supports the hypothesis that body size variation in the stoat, especially females, is an adjustment to regional variations in the sizes of their available prey.
Biennal behaviour of Cirsium palustre in ash coppice
Authors: Pons Thijs L. , During Heinjo J.
Published: July 2006

In the first years after coppicing,Cirsium palustreis abundant in Dutch ash coppice woodlands and in the second year, it flowers abundantly. In later years the species is nearly absent. In contrast to its behaviour in meadow and spring communities, the species typically behaves as a true biennial in this system. Despite fairly high mortality, the plants flowering in their second year produce enough seeds to replenish the seed bank. It is suggested that the persistence of the species in this system depends on Its ability to form a longlived seed bank and on a nutrient availability high enough to enable some rosettes to exploit the high photosynthetic photon flux density (PPFD) in the first year after coppicing and thus to reach the critical size needed for flowering in the second year. Rosettes persisting to the third year generally do not flower and ultimately die because shading by the tree canopy has become too severe.
Geographic parthenogenesis in the stream mayfly Eurylophella funeralis in eastern North America
Authors: Sweeney Bernard W. , Vannote Robin L.
Published: July 2006

Unisexual populations were found largely at the periphery of the geographic range of the mayfly Eurylophella funeralis in eastern North America. Bisexual populations generally had a normal sex ratio but at least two populations were observed with only about 2–11% males. Hatch success for unfertilized eggs depended on temperature but in general averaged >61% in unisexual populations and < 14% in bisexual populations. Eggs took about 65 d to hatch at 10°C and 19 d at 25°C; no hatching occurred at 5 or 30°C. Successful oviposition was observed for about 97% and 20% of unmated female adults from unisexual and bisexual populations respectively. The hatch success of unfertilized eggs for three geographically distinct bisexual populations was in versely correlated with the proportion of males in the populations. The genetic structure of bisexual and unisexual populations was very similar. Unisexual populations consists of clones, with as few as four recognizable phenotypes being present at a given location. All offspring had the same phenotype as the mother. Tychoparthenogenesis is suggested as the most reasonable working hypothesis concerning the origin of unisexual populations in E. funeralis.
The effect of bark phenols upon mountain hare barking of winter‐dormant Scots pine
Authors: Rousi Matti , Häggman Juhani , Bryant John P.
Published: July 2006

Due to high numbers of mountain hares in recent winters in northern Finland the barking of winter dormant Scots pines was widespread. The hares fed selectively upon upper crown bark of grafted pines, nitrogen fertilized trees and trees in poor condition. Bark of preferred upper crown branches and physiologically mature scions contained less total phenols than lower parts. However, there were no differences between total phenols concentrations of graft bark preferred by hares and nearby unbarked juvenile phase Scots pine. Neither decrease in resistance after nitrogen fertilization n‐ or stress was correlated with bark total phenolic concentration. Thus, total phenolic concentration is not a reliable predictor of the susceptibility of Scots pine to winter barking by the mountain hare.
Lake outlet blackflies ‐ the dynamics of filter feeders at very high population densities
Authors: Wotton R. S.
Published: July 2006

Larvae of the blackfly Simulium noelleri aggregated at very high population densities (up to 1.2 × 106 individuals m−2) at a lake outlet in Kent, United Kingdom. During 1983 and 1984 their first appearance in these large numbers was in late‐June and they completed three summer generations before the overwintering larval generation appeared in October. It is not known where the larvae overwinter but they recolonized the concrete steps of this outlet in May, together with larvae of the S. ornatum group which, however, were not found after completing one generation at this location.

Female flies from the overwintering generation oviposited en masse during late‐June and the result was a well‐synchronized growth of larvae in the first summer generation. Within this, and other generations, there was A wide range of emergence times for adults; they could emerge early and were then relatively small, or could emerge later and were then relatively large. Females were always larger than males and the emergence of flies was protandrous. A very similar pattern of growth and emergence times was found at a site in Finland.

In all generations, sex ratio was biased to males and the sex ratio in each generation was inversely correlated with population density. This ensured that there were sufficient males emerging, and surviving adult mortality, to guarantee fertilisation of the females which were more expensive to produce.
Growth pattern and distribution of biomass of Calluna vulgaris on an ombrotrophic peat bog
Authors: Wallèn Bo
Published: July 2006

The distribution pattern of Calluna vulgaris on the ombrotrophic peat bog Åkhultmyren, S. Sweden, was investigated.

Calluna occurs primarily on hummocks, with its maximum biomass (ca 250 g m−2 above ground, and ca 300 g m−2 below ground) concentrated on hummock tops. Biomass decreased gradually along the hummock‐hollow gradient to a level of ca 5 cm above the water level. This decreasing biomass was correlated with a decrease in the predominant age of the above ground shoots from 6–8 yr to 3–4 yr old shoots.

Calluna is characterized by extremely slow diameter growth and biomass increment. There was, however, a poor relation between height above water level and stem thickness, assimilating biomass and total shoot weight, respectively.
Unequal catchability of male Bufo bufo within breeding populations
Authors: van Gelder Jan J. , Rijsdijk Gabri
Published: July 2006

For 9 years, three breeding populations of the common toad Bufo bufo were censused during the breeding season. The hypothesis that catchability is equal for breeding males in each population and breeding period was tested. By comparing the lengths of all males captured with those recaptured in the same breeding period, it was shown that large males had a higher catchability than small ones. The ultimate cause of this unequal catchability remains unclear, but several causes can be rejected. Population parameters based on capture and capture – recapture data are highly influenced by this unequal catchability.
Ecology of muskoxen in Jameson Land, northeast Greenland
Authors: Thing H. , Klein D. R. , Jingfors K. , Holt S.
Published: July 2006

Muskoxen Ovibos moschatus in Jameson Land exist at a density of somewhat more than 1 km−2 of useable habitat and select moist meadows and snow bed vegetation for summer grazing and wind‐exposed, dry dwarf shrub heath vegetation in winter. Graminoids dominate the winter diet and willows are the main component of the summer diet. Quality of the winter diet, as measured by the protein to fiber ratio is about one fourth that of the summer diet. During summer muskoxen supplement dietary sodium by using mineral licks. Muskoxen, especially females, retain considerable unused fat reserves through the winter and these are drawn upon during the post‐calving period of lactation. Alternate year breeding is a common occurrence. Calves are frequently not weaned before the end of their first winter. Mean calf mortality is relatively low in the absence of significant predation and annual removal by hunting Inuits approaches the annual increment.
Phenology and resource allocation in a high arctic evergreen dwarf shrub, Cassiope tetragona
Authors: Nams M. L. N. , Freedman B.
Published: July 2006

During the growing season of 1981, we studied phenological patterns of development of vegetative shoots and sexual organs, partitioning of biomass and productivity, and partitioning and concentrations of N, P, K, Ca, and Mg for the evergreen dwarf shrub Cassiope tetragona (Ericaceae) at a high arctic lowland oasis at 79°N on Ellesmere Island, Canada. Short elongation (3.6 mm yr−1) and net production (5% of aboveground phytomass) of Cassiope were small. Vegetative and reproductive development were initialed just after snowmelt. Seasonal patterns of allocation of phytomass and nutrients to current growth were characterized by gradual accumulation of quantity over the growing season. However, concentrations of N, P, and K decreased by ca 50% in current tissues during the growing season, while Ca increased with tissue age. Overwinter storage of nutrients occurred in live aboveground shoots. The large proportion of phytomass that occurred as aboveground, attached dead material, as well as the small net production and belowground standing crop, suggest an allocation pattern more similar to that of high arctic cushion plants, than to other evergreen, ericaceous dwarf shrubs occurring at lower latitudes in the Arctic.
Inter‐ and intra‐specific differences in the effects of anoxia on erpobdellid leeches using static and flow‐through systems
Authors: Davies Ronald W. , Yang T. , Wrona Frederick J.
Published: July 2006

Inter‐ and intra‐specific differences in survivorship of Nephelopsis obscura and Erpobdella punctata under anoxic conditions were examined. Two types of experiments were used. In the closed (static) experiments the leeches faced three stresses – anoxia, build‐up of metabolites and starvation, while in the flow‐through experiments only anoxia was experienced. The results obtained from the two types of experiments indicate that survival times are longer in the flow‐through experiments. Inter‐ and intra‐specific differences in survivorship under anoxic conditions correlate well with the patterns of reproduction observed for field populations of N. obscura and E. punctata.
Relationship between the seed rain and the establishment of vegetation in two areas abandoned after peat harvesting
Authors: Salonen Veikko
Published: July 2006

In this study the number and species composition of diaspores dispersing into two newly abandoned peat harvesting areas in Finland were investigated. In an area abandoned six years earlier a total of 2978 living seeds m−2, representing 18 species, was captured by using water‐filled traps during two summers. In a one‐year‐old succession area the total number of living seeds m−2 was 2241, representing 16 plant species. The soil seed banks were found to be empty of viable seeds. In neither area there appeared to be any relation between number of dispersing seeds and of plant individuals of the same species in the pioneer vegetation. It is suggested that unfavourable conditions on the soil surface for seed germination and seedling growth of most dispersed species are majors factor in determining the structure of the established vegetation.
Within population variation in the demography of Speyeria mormonia (Lepidoptera: Nymphalidae)
Authors: Boggs Carol L.
Published: July 2006

The adult demography of a population of Speyeria mormonia (Lepidoptera: Nymphalidae) near Gothic, Colorado USA was studied for four years. Values of demographic parameters, including survival, dispersal and sex ratio, varied yearly, without major changes in density. Shift in sex ratio with constant population numbers entails variation in effective population size among years. Flight period, catchability, relationship between body size and eclosion date, and significance of correlation between weather and daily survival rates differed between the sexes. Sexual dimorphism in correlation of wheather with survival rate may partially explain the lack of yearly variation in total population size. There was no significant sexual dimorphism in large scale habitat use, or in dispersal, except in 1982.

The demography of this insect is compared to that of related species of Argynnis and heliconiines, from the old world temperate zone and new world tropics, respectively. While some differences are observed which can be ascribed to differences in length of the growing season, many patterns are similar. This implies conservation of demographic traits, even across broad habitat and geographic areas.
Random mating in a boreal population of European common frogs Rana temporaria
Authors: Elmberg Johan
Published: July 2006

A breeding population of European common frogs Rana temporaria was studied during six springs. Male and female body length varied significantly between years. Females averaged 6 mm longer than males. Amplectant males did not differ significantly from non‐amplectant males in body or leg length. No significant correlation was found in body or leg length between males and females in amplectant pairs at any time of the breeding season.
Monophagous leaf‐mining larvae of Stigmella (Lepidoptera: Nepticulidae) on birch: patterns and differentiation in exploitation of the host
Authors: Boomsma J. J. , Timmermans H. , Cörvers C. P. M. , Kabout J.
Published: July 2006

Patterns of larval coexistence, density and mortality of six birch feeding Stigmella leaf‐miners were analysed in four field sites in the Netherlands. Larval feeding was further characterized by quantitative records on phenology, oviposition (per host, per tree and per leaf), larval growth rate and relative use of different mesenchyme layers. As the Stigmella guild on birch in western Europe is known to consist of three phylogenetically distinct species‐groups, the specific feeding syndromes were primarily interpreted in this context. Ecological segregation among species groups tended to be larger than that within these groups. Among group segregation mainly involved differences in phenology, types of birch trees, mesenchyme layers used for feeding and larval body size and growth rate. Within group differentiation primarily concerned the distribution and clumping of eggs and the use of differently sized trees. A preliminary analysis of the frequency of mines per infested leaf produced a rather aggregated pattern, suggesting that only a limited number of the available birch leaves are considered as suitable by ovipositing females.
Habitat characteristics of Capercaillie Tetrao urogallus display grounds in southeastern Norway
Authors: Rulstad Jørund , Wegge Per
Published: July 2006

Habitat composition of 39 capercaillie Tetrao urogallus display grounds was compared with available and unused habitats in two coniferous forest areas in southeastern Norway. Macro‐habitat was described with respect to forest successional stage and topography. Micro‐habitat was described with respect to microtopography, plant association, and forest stand structure. Totally, 28 variables were measured. A pronounced macro‐habitat preference was found for elevated areas with forests older than 60‐70 years. Micro–habitat composition varied considerably. However, a slight but significant preference was found for heterogeneous, open‐spaced understory, and for visibility of more than 30 m. Suitable micro‐habitats were abundant, and distribution of display grounds were mainly limited by macro‐habitat characteristics, i.e. elevated, old forest areas.
Consumption by needle‐eating insects on Scots pine in relation to season and stand age
Authors: Tenow Olle , Larsson Stig
Published: July 2006

Trapping of frass‐drop from needle‐eating insects in three Scots pine stands, 18‐, 55‐and 120‐yr‐old, respectively, in three years, revealed that the consumption rate in the two older stands on average displayed three peaks: in July (consumption by Panolis flammea and a first wave of diprionids), late August/early September (lasiocampid/sphingids, a second wave of diprionids), and September/October (Bupalus piniarius). Annual consumption was the same in these two stands, on average 7 kg dw ha−1. In the young stand, there was no late season peak (due to the absence of B. piniarius,) consumption ceasing one month earlier, at 0.2 kg dw ha−1. Consumption intensity (consumption per needle biomass) corresponded to 0.05%, 0.5% and 1.2% of new needle production, respectively, in the three stands, and increased approximately linearly with the needle biomass of the tree. This increase with size (age) of the tree seems to be due to the multiplicative effect of a larger complexity of the grazer guild and a higher population density of single insect species.
Winter diet, habitat selection and fluctuation of a mountain hare Lepus timidus population in Finnish Forest Lapland
Authors: Pulliainen Erkki , Tunkkari Paavo S.
Published: July 2006

Composition of the winter diet, habitat selection and population fluctuations in the mountain hare Lepus timidus were studied in the Värriötunturi fell area, Eastern Finnish Forest Lapland, during the winters 1968/69–1984/85. The three population lows recorded during this 17‐year period followed each other at intervals of 4 and 8 years. During the lows the hares occurred only in the most favoured (forest‐covered) habitats and in two of them they behaved according to the concept of the refuge theory. The mountain birch Betula pubescens ssp. tortuosa appeared to be the most important, but not the most favoured winter food item. When the population crashed, the proportion of birch in the diet decreased, and was replaced especially by juniper which is one of the secondary food items (and is for this reason often discarded although cut). It is suggested that the quality and/or quantity of the winter food (i.e. winter pastures) are one of the driving forces in the population fluctuation of the mountain hare in this area.
Buried germinative seeds in mature beech forests with different herbaceous vegetation and soil types
Authors: Staaf Håkan , Jonsson Maria , Olsén Lars‐Göran
Published: July 2006

The seed banks in the soils of seven mature beech forests in southern Sweden were examined using the seedling‐emergence method. Seedling emergence in the field was also studied. In the studied forests, covering a wide range of vegetation and soil types, between 1020 and 4500 germinating seeds m−2 were found in the seed bank. Seed abundance showed no apparent relationship with the type of soil or vegetation at the sites, but the highest number of species in the seed bank was found on the mull sites. The species diversity of germinative seeds increased strongly with increasing soil fertility.

Only a minor part (10–35%) of the species in the germinable part of the seed bank were represented in the vegetation. Soil samples from the oligotrophic sites mainly contained graminoids, notably Carex spp., while herbs dominated the seed banks of the rich mull sites. Seeds of e.g. Stellaria nemorum, Oxalis acetosella, Moehringia trinervia, Viola rivinianalreichenbachiana, Melica uniflora, and Milium effusum were especially abundant in the mull soils. Woody species were infrequent on all sites, and no representatives of the early spring flora were noted in the germination tests.

In the mor and moder soils most seeds were recovered from the mineral soil, and they were believed to originate from early stages in the succession of the forest. Several sites had comparatively large seed banks of species that typically occur in disturbed forests, e.g. Juncus effusus and Rubus idaeus, but very few germinating seeds belonged to species restricted to non‐forest habitats. Emerging seedlings in the field were only observed on the mull and moder sites. With few exceptions they belonged to species, which were common both in the seed banks and in the vegetation.
Activity patterns of Capercaillie, Tetrao urogallus, during winter
Authors: Gjerde Ivar , Wegge Per
Published: July 2006

Winter activity patterns of 16 radio‐marked capercaillie, Tetrao urogallus, were studied during 1981–83 at Varaldskogen, SE Norway. Activity was confined to the light hours of the day, closely following the photoperiod. Diel distribution showed a major peak near sunset during every month. A second peak was found in the morning. This peak was comparable to the evening peak in early and late winter, but nearly disappeared in midwinter. Ambient temperature rather than photoperiod seemed to be the important proximate factor responsible for the changes in morning activity. By postponing activity to the afternoon, capercaillie avoids energy expenditure during the coldest morning hours.

Total daily activity (TDA) during the period November‐April averaged about 3 h for both sexes. TDA of cocks was U‐shaped with the lowest values (2.0 h) in December‐January, whereas TDA of hens was fairly stable during November‐March with mean value of 2.7 h, increasing abruptly to 4 h in April. TDA during December‐January is believed to express the time used for feeding in pine trees. The significantly higher TDA of hens (26%) compared with cocks during this period may be explained by a higher relative heat loss of hens (body weights: hens 2.0 kg, cocks 4.3 kg). The increased level of activity during early and late winter among cocks was probably due to display and related territorial behaviour, whereas increased activity of hens during April probably was caused by a shift from feeding in pines to more time‐consuming, selective feeding on the ground
Shelter characteristics of mountain hare resting sites
Authors: Thirgood S. J. , Hewson R.
Published: July 2006

Mountain hares in Scotland live on open tree‐less moorland in a harsh winter environment with frequent high winds and drifting snow. By day they rest in forms in tall heather, seats in shorter heather or snow, or scrapes in snow or peat. All these reduce wind speeds by 84‐90%, but vary in the degree of shelter and concealment. Forms afford the best concealment and shelter and occur as often on flat ground as elsewhere. Seats and scrapes are commoner on sheltered slopes. They command a wide field of view but offer little concealment. During snow‐lie, when forms may be covered, hares move to seats and scrapes, often at the edge of snowfields and gather, sometimes in large groups, on sheltered slopes.
Dynamics of long‐leaved sundew Drosera intermedia populations at two extremes of a hydrological gradient
Authors: De Ridder Filip , Dhondt André A.
Published: July 2006

Densities of Drosera intermedia were low in two studied habitats (10–25 ramets m−1), a path through a wet heath (short inundation in spring, low soil moisture in summer) and a pool edge (longlasting inundation, high soil moisture in summer). The low densities could be explained by the observed low recruitment and high adult mortality.

The low recruitment resulted from: (1) a high first year mortality of the large number of seedlings that emerged each year in the path population, caused by summer drought and cover with algae after heavy rainfall; (2) the absence in two years out of three of seedling emergence at the pool edge, due to the longlasting inundation. In neither population any seedlings survived to flower; (3) low vegetative reproduction rate.

Adult mortality during the growing season was caused by drought, which did not occur at the pool edge. Rapid senescence in autumn, caused by summer drought on the path and by a rapid submersion after heavy rainfall at the pool edge, was associated with a high winter mortality.
Experimental ecology of Dryas octopetala ecotypes. V. Field photosynthesis of reciprocal transplants
Authors: McGraw J. B.
Published: July 2006

The response of photosynthesis to reciprocal transplanting was measured in 1980, 1981, and 1986 in two genetically‐distinct populations of Dryas octopetala, a circumpolar dwarf shrub. Contrary to expectation, photosynthetic rates were lowest in “home” environments and highest in “foreign” sites. Also, “native” plants had lower photosynthetic rates than “alien” plants. A “rapid‐transplant” experiment showed that the observed pattern was not caused by environmental differences between sites at the time of measurement, but rather by the long‐term response of transplants to the environment. These results, in combination with the results of an analysis of the fitness response to transplanting (published elsewhere), caution against assuming that a positive relationship always exists between photosynthetic rate and fitness. Integrated measures of carbon gain may be more appropriate as measures of plant performance.
Downslope fertilizer movement in arctic tussock tundra
Authors: Kummerow J. , Mills J. N. , Ellis B. A. , Hastings S. J. , Kummerow A.
Published: July 2006

Slow release fertilizer pellets (NPK) were spread in June and July 1985, on the frost surface under an 8–20 cm thick layer of thawed tundra in the northern foothills of the Brooks Range, Alaska. The fertilizer was applied at a rate of 3.8 kg N, 1.2 kg P2O5, and 2.4 kg K to two, 10 × 0.75 m tussock bands. These bands were placed parallel to the contour lines in the middle of a uniform 10° slope. The purpose of the experiment was to test the hypothesis that fertilizer moves at a measurable rate downslope, affecting the vegetation in its course. The results support this hypothesis. One year after fertilizer application, plants collected 2 to 6 m downslope from the fertilizer band had significantly larger leaves and significantly higher nitrogen and phosphorus concentrations than those upslope from fertilizer application. It is concluded that nutrient‐releasing tundra perturbations affect the downslope tundra vegetation.
Interspecific and intraspecific variations in egg hatching for British populations of Taeniopteryx nebulosa and Brachyptera risi (Plecoptera: Taeniopterygidae)
Authors: Elliott J. M.
Published: July 2006

Adults were obtained from three populations of Taeniopteryx nebulosa and four populations of Brachyptera risi; their eggs were incubated at seven constant temperatures (range 3.8–22.1°C). There were interspecific, but not intraspecific, differences in adult life‐span, mean number of eggs laid per female, hatching success and egg incubation periods. The optimum temperature for hatching success and the range over which at least 50% of the eggs hatched were lower for T. nebulosa (6.5°C, 2.7–15.0°C) than for B. risi (9.0°C, 5.1–15.8°C). No eggs hatched at 22.1°C. The relationship between incubation period (d days) and water temperature (T°C) was given by; d = 326.4 T−1.015 for T. nebulosa, d = 824.0 T−0.739 for B. risi. Both equations successfully predicted incubation periods for eggs placed in a stream.

Hatching success and incubation periods were similar to those already published for a Norwegian population of T. nebulosa. The lack of significant intraspecific variation suggests that the genotypes associated with the variables examined in this study have remained remarkably stable in these two species in spite of the geographical isolation of their different populations.
Biomass, productivity and relative rate of photosynthesis of Sphagnum at different water levels on a South Swedish peat bog
Authors: Wallén B. , Falkengren‐Grerup U. , Malmer N.
Published: July 2006

The distribution pattern of Sphagnum species on bogs follows a hummock‐hollow gradient. S. Sect. Acutifolia (that is in this study S. fuscum and S. rubellum combined) dominates hummock tops, ca 20 cm above the maximum water level with a green biomass of 50 g m−2, S. magellancium dominates at a lower level, about 5 cm above the water level with a green biomass of 75 g m−2 and S. cuspidatum dominates in the wettest hollows with a green biomass of about 50 g m−2.

In situ measurements of length growth of S. Sect. Acutifolia and S. magellanicum using a 14CO2‐labelling technique during three consecutive years, revealed an unexpectedly high between‐year variation in length growth of 7‐23 mm yr−1, and 16‐22 mm yr−1, respectively. Consequently the dominating producer in the transition between hummock and hollow changes from year to year, probably depending on climatic conditions.

In vitro experiments on the effects of different water levels of 2, 5, 10 and 20 cm below the moss surface, on photosynthetic activity of S. Sect. Acutifolia and S. magellanicum, measured by a second 14CO2‐technique, indicate optimal conditions for S. magellanicum at 10 cm above water level, and for S. Sect, Acutifolia at 20 cm above water level.

Differences in capillary water transport capability between the species are more important than the sensitivity of photosynthesis to water stress in explaining field patterns of productivity and distribution.
Reproductive success, mortality and sexual size dimorphism in the adder, Vipera berus
Authors: Madsen Thomas
Published: July 2006

From 1981 to 1986 an isolated adder population was studied in the extreme south of Sweden. During this period 48 adult males and 44 adult females were marked. Male adders did not grow as large as the females. Large males had a significantly higher annual mating success and were engaged in more combats than smaller males. The mean length of recaptured males was significantly lower than that of those not recaptured, indicating a higher motality of larger males. Females brood size was positively correlated with body size. In females there was no difference in mean length of recaptured vs not recaptured individuals. The adder is one of the few snake species with male combat where males are smaller than females. I suggest that this is due to stronger selective advantages for large body size in females than in males.