bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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
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.
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.
Seasonal occurrence of Ixodes ricinus (Acari) in vegetation and on small mammals in southern Sweden
Authors: Nilsson Anders 
Published: July 2006

Seasonal activity of Ixodes ricinus L. was studied with two different sampling methods at three localities in southern Sweden: blanket dragging in vegetation and collection from small mammal hosts (mainly larvae in the latter case). The blanket method yielded all development stages. The seasonal pattern ‐ bimodal, with one peak in spring and another in autumn – was clearer for larvae collected on small mammals. The nymphs had a similar seasonal activity pattern as the larvae, but nymphal activity usually started somewhat earlier in spring. Adults had three activity peaks – spring, summer and autumn – in the vegetation.The autumn peak seems similar to that found in other European countries, but the timing of the spring peak differs. Weather, influencing development rates, seems to be the main agent behind these differences, since ambient weather (above a certain threshold) cannot explain the patterns. Abundance and activity of hosts (different hosts for different developmental stages) probably also plays a certain role.
Thermal preference in the pool frog Rana lessonae: impact on the reproductive behaviour of a northern fringe population
Authors: Sjögren Per , Elmberg Johan , Berglind Sven‐Åke 
Published: July 2006

A documented warmth preference in the pool frog Rana lessonae is also expressed in the reproductive behaviour of a northern fringe population (60°N). During the breeding period of 31 days, individually marked frogs were observed during chorus. Male choruses were formed in the warmest parts of the pond, but moved between three areas. At night, these areas maintained the highest water temperatures in the pond, especially at low temperatures prevailing in the beginning of the breeding period. Oviposition occurred in the current chorus areas, and 86% took place during the first two weeks of the breeding period. That the choruses and oviposition changed locations within the favourable breeding areas can be explained by a pronounced thermal preference in the frogs, and winds moving the warm surface water in different directions.The water temperature required to initiate oviposition was 16°C, which is similar to those reported from related more southern populations. The thermal preference expressed in the breeding behaviour of both sexes and the tendency for early oviposition may be behavioural responses to environmental constraints on reproduction in the short season at 6O°N.
Temporal and spatial patterns in the production of pollen, ovules and seeds in pseudogamous blackberries (Rubus subgenus Rubus)
Authors: Nybom Hilde 
Published: July 2006

Significant variation in the number of stamens and ovules per flower, the stamen/ovule ratio, and the number of seeds per berry was found among seven blackberry species, each represented by one clone, and to a much lesser extent among inflorescences within species. Inflorescence size and architecture were found to have no major influence on these reproductive parameters.The position of a flower within the inflorescence strongly influences its onset of anthesis, which in turn is closely correlated with these reproductive parameters. Ovule number decreases with time, although in some species it increases again at the end of the flowering season. Number of seeds decreases more or less linearly with time, although there is an unexpectedly high number of the earliest berries of the triploid species, which is probably the result of interspecific pollination. Pollen production estimated in one species decreases with time, per theca, per flower and per ovule, whereas the percentage of good pollen grains remains unaltered.
Ecology of the invading moss species Orthodontium lineare in Sweden: Spatial distribution and population structure
Authors: Hedenäs Lars , Herben Tomáš , Rydin Håkan , Söderström Lars 
Published: July 2006

The moss species Orthodontium lineare, originally from the southern hemisphere, has been spreading in Europe during this century. We have monitored the distribution patterns of the species in Sweden.The age distribution differed between localities due to variation in the proportion of colonies in old age classes. We attributed this to differences in colony mortality. Although O. lineare had a high spore output in most localities, the colonies showed a clumped pattern, indicating strong neighbourhood effects in the colonization of new spots within the locality.The regional distribution was uneven and markedly southwestern. The distribution was related to regional and local availability of suitable habitats (decaying wood in not‐too‐dense forests), and to a lesser extent to climatic variables.Spore transport and establishment are suggested to be the limiting factors for colonization of suitable habitats of O. lineare.
Egg development, nymphal growth and life cycle strategies in Plecoptera
Authors: Lillehamnur Albert , Brittain John E. , Saltveit Svein Jakob , Nielsen Per S. 
Published: July 2006

Interspecific and intraspecific differences in egg development, nymphal growth and the life cycles of Fennoscandian stoneflies are examined in relation to zoogeographical aspects and evolutionary trends. Data on other European and North American species are also considered.Egg development shows considerable diversity, the main categories being ovovivipary, egg development with diapause and non‐diapause development. Egg development in species in the non‐diapause category can be classified as eurythermal, cold stenothermal or warm stenothermal. Temperature has a marked effect on nymphal growth of some species but not others. The distribution of several species can be explained by their temperature relationships, either in the egg or nymphal stage. Several species modify their life cycle to fit local climatic conditions. In some species, such as Leuctra hippopus, environmental selection has been so strong that they have probably recently evolved into subspecies and/or species in northern Europe.Morphological and ecological variations in the Plecoptera have facilitated their colonization of the variety of freshwater biotopes that occur in Fennoscandia.
Bioenergetics of cross‐ice movements by Microtus pennsylvanicus, Peromyscus leucopus and Blarina brevicauda
Authors: Lomolino Mark V. 
Published: July 2006

Laboratory and field experiments were conducted to investigate bioenergetics of winter dispersal and to compare winter (cross‐ice) dispersal abilities of three small mammals: Microtus pennsylvanicus, Peromyscus leucopus and Blarina brevicauda. Total metabolic rates increased with running activity and decreased as ambient temperatures increased for all species. Thermal conductance was significantly higher for running than for resting Microtus and Peromyscus, but decreased significantly with activity for Blarina.Winter dispersal abilities, calculated from treadmill experiments, increased with ambient temperature and with body size of the species. The superior dispersal ability of Microtus in comparison with Peromyscus results from the former's ability to utilize more energy reserves during running. The comparatively low winter dispersal ability of Blarina, which was less than a third of the two rodent species, resulted from its high weight specific cost of transport at winter temperatures and its relatively low energy stores and/or energy utilization during running.
Nutrient and water flux in a small arctic watershed: an overview
Authors: Oechel Walter C. 
Published: July 2006

The “Response, Resistance, Resilience to, and Recovery from Disturbance in Arctic Ecosystems” (R4D) program initially concentrated on impacts of altered water and nutrient inputs on tussock tundra vegetation. The intensive site is at Imnavait Creek (68°C 37′ N, 149° 17′ E), near Toolik Lake. Alaska in the foothills of the Brooks Range, approximately 200 km south of Prudhoe Bay. Tussock tundra was selected for initial study because it has an extensive distribution in the Alaskan Arctic (80% of the arctic region), the majority of the pipeline corridor north of the Brooks Range passes through tussock tundra, and disturbances of arctic tundra are expected to occur in the future. Also important is that 18% of the circumpolar arctic primary productivity and 47% of the circumpolar arctic stored carbon are in tussock tundra.Water and nutrient additions were performed because they frequently accompany disturbance and development in the Arctic. Emphasis was placed on determining responses of physical, physiological, and ecosystem processes to environmental change in such a way that extrapolations to other areas would be facilitated. The hills near Imnavait Creek are covered by glacial till of the Sagavanirktok River glaciation. with a deep organic layer on the less exposed hill slopes and valleys. The vegetation is dominated by Eriophorum vaginatum L., Betula nana L., Vaccirtium uliginosum L, Vaccinium viiis‐idaea L., Ledum palustre L., Salix pulcbra L., and Sphagnum spp. Winds were rarely calm but seldom exceed 17 m s−1, generally from the east‐southeast to the south‐southwest (66%). Precipitation in 1986 was 344 mm, about half of which was snowfall. Mean temperature in 1986 was −8.1°C, with an absolute minimum of −43°C. Mean July temperature was between 9.8 and 13.7°C. Nutrients are more mobile than previously thought, moving an estimated 10 m downslope in the first growing season. It underscores the importance of the winter environment to biological and hydrological processes. Greater water flow results in increased plant growth rates, leaf area, and biomass.Effects of changes in nutrient and water supply on photosynthesis were minimal. Where increases in productivity took place, they occurred more likely as a result of changes in allocation patterns, including an initial redirection of carbohydrate stores to new leaf development, than from increases in photosynthetic rates.The work reported here indicates that the downslope transmission of nutrient and water flow effects caused by altered drainage and nutrient supply may result in a larger area of impact than previously thought.
Fine scale patterning of species distributions in a saxicolous lichen community at Jonas Rockslide, Canadian Rocky Mountains
Authors: John Elizabeth A. 
Published: July 2006

Distinct patterns of species distribution upon individual rockfaces are found n a saxicolous lichen community growing on a rockslide in the Canadian Rockies. A grid system was used for sampling individual rockfaces and the likelihood of finding a species on particular parts of the rockface was analysed. Use of chemicals in the field and collection of apothecia allowed specific identification of individual lichen thalli. Lichens were divisible into three groups: those which are distributed apparently at random over the rockfaces, those which are more likely to occur on upper, outer and southerly portions of the rockfaces and those which are found more often on lower, inner and northerly portions of the rockfaces. The upper rockface surfaces are often snow‐free in winter while the lower rockface group experiences deeper and more persistent snow cover. Simple microclimatic measurements suggest that temperature also differs across the surface of a rockface.It is hypothesised that lichen distributions are at least in part explained by ecophysiological adaptations to their particular microhabitat, while it is recognised that competition may also play a role in community organisation.
Ontogenetic shifts in habitat use and activity in a stream‐dwelling isopod
Authors: Holomuzki Joseph R. , Short Terry M. 
Published: July 2006

We examined ontogenetic changes in diel patterns of habitat use and activity of the lotic isopod Lirceus fontinalis in relation to differences in predation risk from green sunfish, Lepomis cyanellus. Juveniles are ≤5 mm total length (TL), individuals 6‐9 mm TL are mature females (c. 90%) and immature males, and mature males are ≥10 mm TL. Isopods of all sizes were far more dense in Cladophora, a filamentous green algae, than in open silt/sand substrates in fish pools. Densities of each size did not increase in open areas at night in fish pools when risk of predation presumably decreases. Few individuals of any size class occurred in open silt/sand areas in fish pools. However, habitat use did not depend on fish presence. Densities and relative abundances of all sizes were similar between algal and open habitats in fishless pools both day and night, except for mature males which were more abundant in open areas during daylight. All sizes of isopods were significantly more dense in fishless versus fish pools, and density of a size class was influenced by fish presence. Densities of size classes were typically juveniles > individuals 6‐9 mm TL > mature males. Green sunfish are size selective feeders on isopods, thus demography of isopods within pools may be partially influenced by the size structure of the fish population.Isopods reduced their activity, as measured by captures in benthic traps, in the presence of caged green sunfish only at night. This behavior coupled with relatively high activity levels during daylight regardless of fish presence suggests other predators or factors may influence diel activity. Mature males were overrepresented in traps relative to their occurrence in fish runs, indicating high activity levels. Mature males were also more active than gravid and nongravid females and juveniles in the presence of fish in laboratory aquaria. Number of male encounters with nongravid females depended on activity level.