bluuebunny/crossref_metadata_2025 huggingface dataset:
Laboratory energetics of larvae of Sericostoma personatum (Trichoptera)
Authors: Iversen Torben Moth
Published: July 2006

The energetics of the shredder Sericostoma personatum Spence were studied in the laboratory at 3,8, 13 and 18°C using conditioned leaves of Fagus sylvatica L. as food. Ingestion (I), growth (G) and respiration (R) were dependent on larval size and temperature. Estimated assimilation (G + R) varied between 4.2–5.7%. Gross growth efficiency (G/I × 100) varied between 0.4–3.4% and was dependent on temperature. Growth rates estimated from field and laboratory data were in the same order of magnitude.

The low assimilation is discussed in relation to the life cycle pattern of the species and its ecological role in the stream community.
Reproduction of the bank vole, Clethrionomys glareolus, in northern and southern Sweden during several seasons and in different phases of the vole population cycle
Authors: Nyholm N. Erik I. , Meurling Patrick
Published: July 2006

The breeding biology of the bank vole was studied in northern and southern populations in Sweden in the years 1973–76. Trapped specimens supplied organ weights and histological data, which were utilized to describe the breeding season, number and size of litters, reproductive losses, spermatogenesis, and sexual maturation. In the north the populations are cyclic. During the increase phase of the cycle the breeding season was long, litter sizes and gonad weights were large, and there was maturation of yearlings in the summer. During the peak phase reproduction was impaired in all these respects. In southern Sweden there was no cyclicity, and the reproductive events varied less, but in 1976 the litters were larger than usual and the season was much extended.

In the south the voles born during the early part of the season regularly became sexually mature during their first summer. The differences in reproductive biology are related to population dynamics and discussed in terms of different hypotheses concerning vole population cyclicity.
A modified drop‐net method for sampling mobile epifauna on marine shallow sandy bottoms
Authors: Evans Sverker , Tallmark Bo
Published: July 2006

The seasonal variations in numbers and biomass of the mobile epifauna of a shallow, sandy bay in Gullmar Fjord (Sweden) was investigated during 1976–1977 using the drop‐net technique. Juvenile plaice, Pleuronectes platessa L., sand goby, Pomatoschistus minutus (Pallas), and brown shrimp Crangon crangon L. are the dominant epifaunal species. A net enclosing an area of 100 m2 was used, and the organisms captured were collected with a small trawl. Three stations with a water depth≤ 1 m were regularly sampled with a total number of 73 drops. Maximum abundance was for plaice in June (6 ind m‐2), for the shrimp in July‐August (61 ind m‐2), and for sand goby in September (2 ind m‐2). Standing stocks (dry wt) were 0.2, 1.5 and 0.2 g m‐2 respectively. Production estimates were based on seasonal changes in size frequency and information on specific growth rates. The production rate was for plaice (0‐group) 0.3 g m‐2 yr‐1, for the shrimp 1.5, and for sand goby 0.2 g m‐2 yr‐1. Reliable estimates of the absolute abundance can be derived from the mean catch per unit area only when the efficiency of the fishing gear is known. After 6 hauls with the trawl in the drop‐net enclosure more than 85% of the shrimps were caught and after the fifteenth haul less than 1% were still left. The fishing efficiency of a push‐net in relation to the drop‐net was for the shrimp 50%, for plaice 35% and for sand goby 17%.
Micro‐stratigraphy of sediment laminations deposited in a chemically stratifying eutrophic lake during the years 1913–1976
Authors: Simola Heikki
Published: July 2006

A sequence of laminated sediment, 30 cm long, deposited in the deepest part of an eutrophic lake, Lovojärvi, in southern Finland, was analyzed microscopically. Seasonal changes in sedimentation were found to be well retained, due to the absence of bottom animals and the rather high sedimentation rate. Delimitation of the annual layers was based primarily on the repeated cyclic pattern observed in the stratigraphy of the planktonic diatoms. The annual character of these diatom cycles was established through their agreement with information obtained during three earlier one‐year studies on the plaktonic diatom community. In the lower part of the sequence studied the laminated structure appeared quite regular, the annual layers being composed of pairs of a whitish, diatom‐rich “summer” layer, and a dark brown, more organic “cold season” layer, but in the upper part the laminations were more variable, due to allochthonous inputs caused by human activity in the drainage area. Several thick clay layers which could be dated back to known constructional events on the lake shore aided the interpretation of this sequence, within which prominent alterations in the planktonic diatom flora were also observed. The gradual increase in the proportions of acidophilous diatoms during the past decades was interpreted as indicating a slight lowering in the trophic status of the lake, primarily due to the termination of flax soaking, which had been going on by the lake shore for centuries.
Damage to marram grass Ammophila arenaria by larvae of Meromyza pratorum (Diptera)
Authors: Huiskes A. H. L.
Published: July 2006

Larvae of Meromyza pratorum Meigen (Diptera, Chloropidae) were found to affect tillers of Ammophila arenaria (L.) Link in the dunes of Newborough Warren. Anglesey, U.K. The highest percentages of affected tillers were found in September. There were clear differences between the proportions of affected tillers in the various successional stages of the dunes. It was found that the proportion of affected tillers was reduced by a fertilizer treatment but slightly increased by removing associated species.
Daily and seasonal activity patterns of the muskrat Ondatra zibethicus as revealed by radiotelemetry
Authors: MacArthur Robert A.
Published: July 2006

Activity patterns of the muskratOndatra zibethicusL. were examined during summer and winter in Delta Marsh, Manitoba, Canada (50°11′N, 98°23′W). Animals exhibited intermittent activity throughout the day with a mean periodicity close to 6 h in both seasons. The 24‐h activity pattern in summer was typically bimodal with major peaks occurring between sunset and sunrise. Muskrats were more diurnal in winter when maximal levels of activity occurred in late afternoon and early evening (1500–2000). Pronounced inter‐ and intra‐individual variability in daily activity ensured continuous, or nearly continuous occupation of winter shelters by a variable number of muskrats, and thus enchanced microclimate stability. Daily variation in activity and weather were weakly correlated both summer and winter. Of the environmental variables tested, only photoperiod and wind speed in summer, and photoperiod and air temperature in winter correlated significantly with total time spent in lodge or burrow per day.
Differences in seasonal activity pattern and breeding time of Patrobus atrorufus (Carabidae) in central Norway
Authors: Refseth Dagfinn
Published: July 2006

Seasonal activity patterns of Patrobus atrorufus (Ström) were studies by the use of pitfall traps. The samples were taken from three habitats at different altitudes, situated in an alder forest, a spruce forest, and a subalpine birch forest, respectively. With increasing altitude the breeding time of the species and the corresponding peak of activity shifted from autumn towards spring. This change in the breeding pattern was found mainly to be caused by climatic factors, thus the species seems able to accomplish considerable alterations in the life history as an adaptive mechanism.
Invertebrate colonisation of the gravel substratum of an experimental recirculating channel
Authors: Ladle M. , Welton J. S. , Bass J. A. B.
Published: July 2006

The development of an invertebrate community in a large scale, experimental stream system is described. Colonisation was chiefly by means of ovipositing adult insects with lesser components introduced with water and stones. A succession of taxa was recorded with large peaks of numbers in the spring and the autumn, comparable to those observed in studies on natural streams. Diversity of the fauna increased quickly at first and then more slowly, possibly because of the reduced availability of ovipositing adults later in the year. Even in the absence of drift and migration, recruitment of insect larvae, which naturally favour gravel substrata in running water, can be rapid and will produce a varied community in which Chironomidae and Ephemeroptera play an important role.
Colonization by Pinus sylvestris of a former middle‐geolittoral habitat on the Umeälven river in northern Sweden, following river regulation for hydro‐electric power
Authors: Grelsson Gunnel , Nilsson Christer
Published: July 2006

The colonization by Scots pine of a former middle‐geolittoral habitat on the Umeälven river, northern Sweden, laid almost completely dry in 1958, was compared with that of a similar habitat, subject to natural changes in water‐level, on the Vindelälven river. The geographical position, altitude, exposition, slope and type of vegetation were similar at both sites. The percentage cover of field and bottom layers of the middle geolittoral are considered to have decreased after the fall in water‐level of the Umeälven river. The pines were dated by making annual ring counts. During the period 1962–67 a significant increase in pine colonization took place at the Umeälven site above the new, regulated, high‐water level. The tree densities (pines m‐2) in 1978 on middle geolittoral sites of the Umeälven and Vindelälven rivers were 4.9 and 1.4, respectively.
Biological nitrogen fixation in coniferous forest watershed areas in Central Sweden
Authors: Rosén Kaj , Lindberg Torbjörn
Published: July 2006

An investigation on biological nitrogen fixation in the forest floor was carried out in five watershed areas in Central Sweden during the summers 1978 and 1979. Five different types of bottom layers with underlying soil horizons were investigated for nitrogen fixation. An inventory on the occurrence of potential nitrogen fixing lichens and alder trees was also carried out.

Low fixation rates were determined in mesic‐soil mosses, F/H,layers and mineral soil. Though two orders of magnitude higher than in mesic‐soil mosses, the nitrogen fixation in the investigated Sphagnum mosses must be considered as low, probably due to absence of blue‐green algal associations. The contribution to total nitrogen fixation by lichens is low, but Alnus incana may play an important role. The estimated biological nitrogen fixation calculated as a weighted mean over the five watersheds is in the order of 0.5 kg N ha‐1 yr‐1.
Phytoplankton assemblages and their periodicity in stratifying lake systems
Authors: Reynolds Colin S.
Published: July 2006

A subjective analysis of the seasonal periodicity of phytoplankton populations in several natural lakes and experimental lake systems (Lund Tubes) has shown that the direction and patterns of change are both general and predictable. The paper distinguishes between autogenic successional changes, consistent with increasing community complexity and segregation, and allogenic changes resulting from turbulent disruption of the stratified system. The periodicity of the assemblages recognized is resolved through the interaction of two major variables – nutrient availability and column stability. A simple possibility matrix is proposed which can account for the observed changes in community structure. The principal pathways in eutrophic lakes (diatoms → Volcocales → Nostocales → dinoflagellates or Microcystis, with reversions through 'summer diatom’assemblages) and in mesotrophic lakes (diatoms →Chrysophyte/Sphaerocystis→ dinoflagellates, with reversions through 'summer diatom‐desmid’assemblages) are generally consistent with the growth and survival strategies of the principal algal species concerned.
Life cycles, microdistribution and production dynamics of six species of net‐spinning caddisflies in a large southeastern (U.S.A.) river
Authors: Cudney Mark D. , Wallace J. Bruce
Published: July 2006

Hydropsyche incommoda. H. rossi, Cheumalopsyche pasella, Mocronema Carolina. Chimarra moslyi, and Neureclipsis crepuscularis were studied on woody substrates (snags) in the lower Savannah River. Distribution of most species biomass was positively correlated with attached macrophytes on snags at medium (25–50 cm s‐1) current velocities. All species were bivoltine at the study site with the exception of M. Carolina which was univoltine. Annual and cohort production estimates (Hynes and removal‐summation methods) were obtained for each species at three velocity ranges. Total annual caddisfly production calculated by the Hynes method was 12.6, 41.4, and 22.7 g (ash free dry wt m‐2 of snag surface area at low, medium and high velocities, respectively; 9.6, 34.4, and 19.9 g with removal‐summation; and, 11.5, 36.1 and 21.1 g when the Hynes method was applied to discrete cohorts. Higher cohort production was attained by the overwintering generation because of higher terminal instar body weights. Dissolved organic carbon comprised most of the total organic load transported by the river; however, abundant paniculate organic food was also apparently available for filler feeders. Organic and inorganic seston concentrations were highest in winter months and lowest in autumn. Over 90 percent of the seston (by weight) was <105 μm. It is suggested that the variation in catchnet mesh size, coupled with spatial heterogeneity of the snag habitat, allows the caddisflies to partition space, which is apparently the limited resource.
Habitats, life histories, migration and dispersal by flight of two water‐beetles Helophorus brevipalpis and H. strigifrons (Hydrophilidae)
Authors: Landin Jan
Published: July 2006

Populations of two Helophorus species from a Swedish lake were sampled during the ice‐free periods of two years. Dispersing beetles were (rapped in light‐reflecting glass traps. Both species are univoltine and breed in the spring. The populations of adult H. brevipalpis are largest during the summer when great numbers emerge and migrate. Very few H. strigifrons adults emerge before spring. Its adult populations are largest in the spring, and small numbers of mature individuals fly with mature H. brevipalpis specimens. This is discussed in relation to their habitat utilization: H. sirigifrons inhabits permanent waters only and is dimorphic for flight musculature. H. brevipalpis inhabits both permanent and ephemeral waters and is always equipped with a functioning flight apparatus. H. brevipalpis is an effective colonizer of ephemeral waters due to its large dispersal capacity and to the fact that the habitat of juveniles differs from that of adults.

Age, sexual maturation and feeding in flying and non‐flying groups are compared. Food is seldom found in the gut of fliers of either species. In the spring flying H. brevipalpis females have larger oocytes than non‐flying ones; flying H. strigifrons females have smaller oocytes than non‐fliers. It is possible that the summer migrations of H. brevipalpis favour outbreeding since fliers are sexually immature; spring fliers, being sexually mature, are more efficient as colonizers.
The ecological requirements of Hierochloë odorata in Nova Scotia
Authors: Goldsmith F. Barrie , Murphy Susan L.
Published: July 2006

Hierochloë odorata (L.) Beauv. is restricted to the upper zone of salt marshes and rarely becomes dominant.

In the field, the species was found not to have strict N, P, K requirements. It grew in a range of pH values from 4.3 to 7.9, tolerated salinities up to 500 mhos and favoured soils with a moisture content from 25 to 30%. It grew in situations with a mean water table between 14 and 28 cm below the surface. Natural shading in the field was found to increase the heights of plants by about 30%. The application of fertilizer in the field increased the height of sweet grass but also stimulated the growth of associated species. In the greenhouse, the effects of different soils and fertilizers on plant growth were assessed. Inorganic fertilizer (12:18:12) application produced more leaves and tillers than organic fertilizer (6:2:0).

Sweet grass grows in a zone of reduced competition between the dune species and the salt‐marsh species. Near the salt‐marsh, the species may be limited by high salt concentration. The low levels of competition offered by cultivation and the responsiveness of the species to fertilizer suggests that cultivation of Hierochloë odorata may be successful.
Daily flight activity of moths in the continuous daylight of the arctic summer
Authors: Dreisig Hans
Published: July 2006

The daily onset of flight and the lime of activity of moths were studied at an arctic and a subarctic locality in midsummer under natural light conditions but with all other factors kept constant. The daily variation of light intensity is much smaller than at temperate latitudes, and the illumination is continuously at levels that normally inhibit the activity of moths. In spite of this, the investigated species showed a distinct daily periodicity with the activity occurring at about the same time of day as in the same or related species from lower latitudes. It is suggested that this is the result of a process of acclimatization to high light intensities.

A number of species show a diurnal activity pattern, and it is suggested that this is connected with their high temperature requirements. In the field, Anarta zetterstedti Staud. thermoregulates by settling frequently on dark rocks which can reach high temperatures when the sun is shining. This species can not fly unless its body temperature is above 30°C and it prefers an ambient temperature of about 36°C.
An analysis of an adult Trichoptera community in the Laurentian highlands of Quebec
Authors: Roy D. , Harper P. P.
Published: July 2006

The adult Trichoptera communities of a small watershed in the Québec Laurentian Hills were studied during two years with emergence and light traps.

Some 180 species and more than 164500 specimens were collected, belonging mainly to the families Hydropsychidae, Polycentropodidae and Leptoceridae; the Limnephilidae with 41 species were the most diverse family.

A comparison of catches in emergence and light traps revealed the importance of species from distant or specialized habitats in the composition of local communities. Two series of light trap catches show little similarity (Sanders index) although the traps were only some 60 m apart; this is in accordance with the suspected limited range of efficiency of light traps.

The Shannon‐Wiener diversity index, the Simpson dominance index as well as the Lloyd and Ghelardi equitability index have been used to describe community structure; our four data series have also been shown to conform to the log‐normal frequency distribution of Preston.

The sex‐ratios of the abundant species are given. In most light trap series and in half the emergence trap series, the ratio differs significantly from 50:50; there is however no overall dominance of one sex. Differences exist between the ratios obtained for the same species in the two types of traps and probably reflect sexual differences in behaviour at light.
Adaptation to an acid environment in Chironomus riparius (Diptera, Chironomidae) from Smoking Hills, NWT, Canada
Authors: Jernelöv Arne , Nagell Björn , Svenson Anders
Published: July 2006

The Smoking Hills in the North West Territories, Canada have burnt for centuries causing long term acidification of ponds in the vicinity. Chironomus riparius, a red chironomid larva dominated the bottom fauna in the ponds. It was investigated if it was the buffering capacity of the hemolymph rather than the oxygen binding capacity of its hemoglobin that gave these larvae a selective advantage and explained their high abundance. Canadian C. riparius larvae were compared with larvae of the same species from Sweden and with larvae of Chironomus plumosus and C. anthracinus also from Sweden. The Canadian strain of C. riparius survived 7 d exposure to pH 3.5 much better than the others. Titration curves on the hemolymph showed that the Canadian larvae had the highest buffering capacity. Within the pH range 6.0–7.0 it was 17–18 meq pH−1 1−1 as compared with 13–15 meq pH−1 1−1 for the others. The hemoglobin content of the Canadian larvae was found to be twice as high as that of the same species from Sweden.
Resource utilization by bumblebee queens, workers and males in a subarctic area
Authors: Ranta Esa , Lundberg Hans
Published: July 2006

We studied the seasonal dynamics of food niche width and annual niche relations of queens, workers and males of six abundant bumblebee species living on a slope of a subarctic hill in North Sweden. The basic data consist of analyses of pollen contents in nectar loads of individual foragers. At any given time of the season individual foragers utilized frequently more than one flower species during each trip, concentrating, however, most of their efforts on one species only. These “major” species varied between individuals thus widening the foraging niche of the species. No obvious differences were observed in niche widths of the sexes and castes of the species (neither day‐to‐day nor annual observations). Queens had highest niche overlaps and males the lowest ones. Sexes and castes were separated into groups by their foraging patterns. Differences in proboscis lengths are not obvious niche separating factors at the study area. The environmental uncertainty (in time and space) may occasionally lead to excess of resources, which, in turn, may open possibilities of wide utilization of available flower species, thus rendering close fit between proboscis length and corolla tube depths of the foraged flowers unnecessary.
Microcommunities of algae on a Sphagnum mat
Authors: Hooper Celia A.
Published: July 2006

The algal epiphytes of three species of Sphagnum from the mat edge of an acid bog were quantitatively sampled over three months. On the basis of differences in total algal abundance, algal diversity, and the growth of certain algal species and species groups, two significantly different algal communities were recognized. While these communities were only centimeters apart, they differed in physical, biological and nutrient parameters, with lower, moister plots having more algae, higher algal diversity, and lower concentrations of phosphate, ammonium, and silicate ions.
Rotifer communities of ponds supplied with post‐waste water
Authors: Klekot Liliana , Klimowicz Henryk
Published: July 2006

The studies concern the changes in communities of rotifers in a model system of 4 through‐flow ponds linked in a row and constantly supplied with waste‐water after mechanical‐biological treatment. Studies were carried out from the spring of 1977 to the spring of 1978 – i.e. during the first year the ponds were used.

Twenty‐four species of rotifers, forming three cenotic communities differing in number of species, dominance structure and abundance, were found. Gradually increasing similarity of communities with the distance from the source of post‐waste water reflects the increasing stability of physico‐chemical and biological conditions in the examined model ecosystem.

Maximum biocenotic stability was observed in the last pond with the highest specific differentiation, and also considerable share of oligo‐ and β‐mesosaprobionts, the highest frequency of species and slight differences in abundance between the dominant and accompanying species.

The role of trophic factor in formation of rotifer communities in the successive links of the presented model pond system is pointed out.
Effects of heavy metal pollution on the microflora of pine needles
Authors: Bewley R. J. F.
Published: July 2006

A leaf washing method was used to compare the numbers and species composition of the phylloplane microflora of corsican pine saplings (a) uncontaminated, (b) exposed to zinc, lead and cadmium pollution from a smelter and (c) artificially dosed with zinc, lead and cadmium oxides to simulate the emissions from the smelter without the complicating effects of other pollutants. There was little difference in total numbers of most groups of micro‐organisms isolated from each site, although both sets of metal‐contaminated saplings generally supported a higher percentage of metal tolerant isolates than the uncontaminated plants. Artificially dosed plants also supported greater numbers of Aureobasidium pullulans and orange and pink chromogenic bacteria. These particular organisms were also among the most metal‐tolerant fungi and bacteria in vitro.
Extraordinary prolongation of the life cycle in a freshwater planktonic copepod
Authors: Elgmork Kåre
Published: July 2006

The limnetic copepod Cyclops scutifer Sars shows an extraordinarily prolonged life cycle in a temperate lake near Oslo, Norway. Developmental sequences become one, two, and three years old, and there are circumstantial evidence of a four year old fraction. Prolongation of the cycle is mainly caused by two consecutive periods of diapause, the first as small copepodids during the second winter, the other as large copepodids during the third winter. There is a marked concentration of diapausing individuals in a small area of the bottom at the deepest part of the lake. There is evidence that this concentration is caused by a horizontal migration to areas with optimal oxygen conditions. The adaptive value of a prolongation of the life cycle is assumed to be an increase in the reproductive potential caused by a spreading out of the reproductive period by three year classes succeeding each other throughout the summer.
The chemistry and flux of throughfall and stemflow in subalpine balsam fir forests
Authors: Olson Richard K. , Reiners William A. , Cronan Christopher S. , Lang Gerald E.
Published: July 2006

The fluxes of water and chemicals in throughfall and stemflow of three subalpine balsam fir forests of New Hampshire, USA were measured. The three fir stands were highly dissimilar in structural characteristics, serving as a test of the importance of stand structure on these fluxes. The sum of throughfall and stemflow water exceeded incident precipitation by more than 18 to 29%. This difference was attributed to the unmeasured input of cloud droplets impacted on canopy surfaces. The principal effect of stand structure was a positive relationship between stand density and stemflow. The flux of NH+4, Na+, SO=4 and Cl− in stemflow was also significantly higher in the most dense stand. The fir canopy effects on capture and chemical alterations of elements were compared with analogous behavior of a nearby deciduous forest. There were several major contrasts, the most striking of which was a flux/canopy pool ratio (leachability index) in the hardwood canopy ranging from two to 32 times higher than in the fir canopy.
Environmental and vegetational variation across a snow accumulation area in montane tundra in central Alaska
Authors: Miller Philip C.
Published: July 2006

Several environmental factors were measured in a transect across a snow accumulation area in order to indicate (1) possible controls of arctic vegetation patterns; (2) water, carbon, and nutrient budgets of different vegetation types; and (3) relationships of Eriophorum vaginatum tussock tundra to other vegetation types. The results indicate that the vegetation zones are largely associated with different levels of nitrogen and phosphorus availability rather than length of the snowfree season, water availability, and soil pH. Nitrogen uptake was highest in the forb‐grass and lower deciduous shrub zones and lowest in the lichen‐heath. Phosphorus uptake was highest in the lower deciduous shrub zone and lowest in the lichen‐heath. On the basis of several floristic and environmental factors tussock tundra has the lowest affinities to the lower deciduous shrub zone.
Vertical distribution of organic matter in eight vegetation types near Eagle Summit, Alaska
Authors: Miller Philip C. , Mangan Robert , Kummerow Jochen
Published: July 2006

The amount and distribution of organic matter was measured in different categories in six montane tundra vegetation types in a snow accumulation area and in tussock and intertussock areas in Eriophorum vaginatum tussock tundra in central Alaska. In root properties, the tussock and intertussock areas were more similar to the fellfield zone than to the vegetation zones below the snow accumulation area. Root density apparently increased as soil nutrients decreased, but this increase may be caused by higher soil moisture and higher root relative water content. The tussock tundra has accumulated more dead soil organic matter than any of the montane zones.
Soil cellulase, chitinase, and protease activity in Eriophorum vaginatum tussock tundra at Eagle Summit, Alaska
Authors: Linkins A. E. , Neal J. L.
Published: July 2006

Cellulase, chitinase, and protease activities were examined in Eriophorum vaginatum tussocks at Eagle Summit, Alaska. Changes in the activities were recorded for tussocks of differing relative plant composition. Highest total activity was found in tussocks with at least 50% (relative surface) cover by mycorrhizal colonized shrubs. Total enzyme activity declined in tussocks as the variety of plants decreased. The lowest enzyme activity was found in the moss dominated tussock. Changes in the nature of cellulose hydrolysis suggested that decomposition may be primarily regulated by litter composition in some cases and soil environment in others.
Seasonal dynamics and standing crops of biomass and nutrients in a subarctic tundra vegetation
Authors: Stoner Wayne A. , Miller Patsy , Miller Philip C.
Published: July 2006

Standing crops of biomass and nutrients were measured in Eriophorum vaginatum tussock tundra and on a north‐facing slope, called the camp site, with similar species composition during the summer of 1976 at Eagle Creek, Alaska. These data were then compared to similar data collected at Meade River, Alaska in 1975. Four species are compared: Ledum palustre, Salix pulchra, Betula nana, and Eriophorum vaginatum. The density of aboveground individuals was greater at the tussock site than at the camp site. The total late season above‐ and belowground standing crop of organic matter and of biomass was greater at the camp site. The nitrogen and calcium contents of new leaves usually increased during the season while phosphorus and potassium contents decreased. Most of the nutrients were in the mosses and lichen compartments rather than in vascular plants.
Growth and tillering patterns within tussocks of Eriophorum vaginatum
Authors: Fetcher Ned , Shaver Gaius R.
Published: July 2006

Growth patterns were investigated for Eriophorum vaginatum tussocks from disturbed and undisturbed tussock tundra at two sites in Alaska. Total basal area of tussocks decreased with increased cryoturbation but mean basal area per tussock did not. Flowering was observed in tussocks of significantly smaller size on disturbed compared to undisturbed tundra. For tussocks with < 10% cover by shrubs and moss, number of tillers per tussock was linearly related to tussock diameter in most disturbed and undisturbed sites. Exceptions occurred in an area that had been bladed with a bulldozer 7 yr before our survey where tiller number increased as the square of diameter and in an area with much frost activity where tiller number was not emulated with diameter. The ratio of daughter tillers to adult tillers decreased with diameter in disturbed tundra, whereas the trend was less pronounced in undisturbed tundra.

Microsuccession in undisturbed tussock tundra was investigated by sampling tussocks with different amounts of shrub and moss cover for number of daughter tillers per adult tiller, weight per tiller, percent nitrogen, and percent phosphorus. Small tussocks without cover by other species and large, partially covered tussocks were not significantly different by any measures, but tussocks that were almost completely buried had significantly (p < 0.05) lower values of tillering index, weight per tiller, and percent phosphorus.
Interactions between zooplankton and fish in a fertilized lake
Authors: Langeland Arnfinn
Published: July 2006

The effects of fish predation on the zooplankton community in an oligotrophic lake, Langvatn, near Trondheim in Central Norway, were investigated during a six‐year period (1973–1978), together with the added effects of changes produced by adding artificial fertilizer in 1975 and 1976. The improved nutrient conditions in 1975 resulted in a rapid increase in biomass and production of the largest herbivore zooplankton species and of the fish population. A change in the behaviour and food habits of the arctic char was recorded; they became more pelagic and fed mainly on zooplankton. An increased survival rate of 0‐group and biomass of planktivorous fish in 1975 enhanced the degree of fish predation on the zooplankton during subsequent years (1976–1978). As a consequence of fish predation, the composition of the zooplankton changed, from a mainly large‐sized to a mainly small‐sized community, dominated by Bosmina longirostris and rotifers. Since fish predation is size‐selective and visibility‐dependent, it induced a decrease in mean size and in body length at onset of maturity of the cladoceran populations and probably also weakened their ability to produce resting eggs.
The effect of a lake fertilization on the stability and material utilization of a limnetic ecosystem
Authors: Reinertsen Helge , Langeland Arnfinn
Published: July 2006

The interaction between the phytoplankton, zooplankton and fish populations and certain abiotic environmental factors, was investigated in an oligotrophic Norwegian lake during a 5‐yr period (1974–1978). The effects of adding artificial fertilizer in 1975 and 1976 were also studied. When cladoceran dominated, the zooplankton community was able to maintain a more or less constant phytoplankton biomass and a rather low phytoplankton production even when nutrient levels were raised. In years when rotifers were dominant, algal biomass and productivity increased, despite the amount of added nutrients being lower. The regression for the relationship between daily phytoplankton P/B and daily herbivore zooplankton P/B indicated that these trophic levels were highly interdependent. A change, from large‐sized to smaller herbivorous zooplankton, due to fish predation, also led to an increase in phytoplankton turnover. The investigations show that planktivorous fish may be the key factor which determines the stability of limnetic systems and controls the material transfer from the algae to the higher trophic level.
The structure of carrion fly communities: the size and the type of carrion
Authors: Kuusela Seppo , Hanski Ilkka
Published: July 2006

Species composition and abundance relations of flies attracted to and bred from different sizes (20‐100 g) and types of carrion (small mammal, cow liver, bird, and fish) were studied experimentally in natural breeding conditions in South Finland. Large pieces of carrion did not attract significantly more individuals or species than did small ones, but there was a positive correlation between size of carrion and numbers of flies bred, apparently because of competition. Altogether 10 species emerged from 50 cultures, and on average 2.78 ± 1.22 (SD) species emerged from one culture. The number of co‐occurrences among the emerging flies indicated random colonization. Variation in species composition between like pieces of carrion was not less than variation between carcasses of different size or type; hence, size and type of carrion are not important determinants of community structure within the size and type ranges used.

Lucilia illustris (Meig.) was the predominant species, comprising 50% of flies trapped and 85% of flies bred. The difference indicates changing species composition in the community. Two sets of cultures were left open for egg‐laying for 2 and 7 d. Competition was less Intensive in the former cultures, which produced 4.0 individuals per gram of carrion, contrasting with only 1.4 individuals per gram in the latter cultures. Competition delayed development in all species, but least in L. illustris, which suggests that fast developing species are at a competitive advantage. In agreement with this, abundance was positively correlated with the rate of development.
Fluctuations in some small rodent populations in Norway 1971–1979
Authors: Christiansen Erik
Published: July 2006

Small rodent populations were monitored by autumn snap trapping in 22 localities of Norway during the years 1971–979. A total of 105528 trap days yielded 7987 small mammals, out of which the bank vole Clethrionomys glareolus and the short‐tailed vole Microtus agrestis made up 52.3 and 29.0%, respectively. Third in abundance was the wood mouse Apodemus sylvaticus.

Both M. agrestis and C. glareolus fluctuated fairly regularly, with general peak years of abundance in 1973 and 1977. Other Microtidae, such as M. oeconomus, C. rutilus and Lemmus lemmus apparently also exhibited cyclic fluctuations. In Arvicola terrestris, Apodemus, and in Sorex shrews, regular fluctuations could not be demonstrated, although the abundance varied considerably.

The body weights of sub‐adult C. glareolus cycled in accordance with the fluctuations in abundance; the highest weights being recorded in peak years. In M. agrestis, this correlation was less obvious.
The lizards Lacerta agilis and L. vivipara as hosts to larvae and nymphs of the tick Ixodes ricinus
Authors: Bauwens D. , Strijbosch H. , Stumpel A. H. P.
Published: July 2006

In this paper we provide quantitative information on the occurrence of larvae and nymphs of the tick Ixodes ricinus in populations of the lizards Lacerta agilis and L. vivipara. Levels of infestation were rather low, at least when compared with those of small mammals and sheep. Hence we suppose that lizards feed only a minor fraction of the total tick population.

Differences in tick loads among lizard subpopulations are probably attributable to difference in body size and mobility among the host groups.

Ticks exhibit a markedly clumped distribution on the lizards. This distribution pattern fits with the negative binomial distribution. The overdispersed distribution of tick larvae in the field and aspects of the lizards' behaviour are considered as factors which contribute to the observed infestation patterns.

Tick larvae were active throughout summer, with peak levels occurring during June‐July. Nymphs were most numerous during May‐June but almost absent during the summer months. Almost always ticks were attached near the lizards' forelimbs. Possible mortality resulting from tick infestation does not contribute significantly to the overall lizard mortality. Hence, these ectoparasites seem to have but a minor impact on the lizard populations.
The spatial and temporal distribution of an epiphytic algal community in a shallow prairie‐parkland lake – Alberta, Canada
Authors: Jenkerson C. G. , Hickman M.
Published: July 2006

In Hastings Lake (longitudes 113°15′ and 53°50′N), a shallow eutrophic lake, the spatial and temporal changes in species composition. diversitv. standing crops, and primary productivity of the epiphytic algae attached to Phragmnes australis and Scirpus validus were investigated in relation to the physico‐chemical environment. Of the dominant species, cyanophycean algae (Lyngbya diguetii and Calothrix sp.) developed best in the 25 cm region below the water surface, while the chlorophycean alga, Stigeoclonium nanum and the diatoms (Cocconeis placentula, Gomphonema parvulum and Rhoicosphenia curvata) did so in the 50 cm and 75 cm regions, respectively. Certain dominant species persisted throughout, interrupted by “shock periods” which created spring, summer, and autumn peaks. Species diversity indices increased with depth, and generally decreased spring through winter. Standing crop maxima occurred within the top 25 cm of the host stems, and showed spring and larger autumn peaks before declining to low. yet significant winter levels. Productivity, too, was greatest in the top 25 cm region, and again peaked in the spring and autumn. Cross incubation studies elucidated vertical and seasonal relationships among productivity, photosynthetic index, and efficiency, and productivity efficiency. An interplay of “sun and shade” adapted populations within the community was found. The epiphytic algae displayed but a muted seasonal response to physico‐chemical fluctuations: however, there was an association with overall nutrient changes as determined by meq HCO3−I−1.
The effects of water temperature, ionic content and total dissolved solids on Nephelopsis obscura and Erpobdella punctata (Hirudinoidea, Erpobdellidae)
Authors: Linton L. R. , Davies Ronald W. , Wrona Frederick J.
Published: July 2006

Using a three‐way factorial experimental design the effects of water temperature, ionic content and total dissolved solids on the reproductive rates of Nephelopsis obscura and Erpobdella punctata were examined. For both species temperature showed the greatest influence on cocoon production and ionic content of the water the least. Water type had no significant influence on the rate of cocoon production in either E. punctata or N. obscura but E. punctata cocoon production was reduced in dilute media. E. punctata laid a larger proportion of deformed cocoons with fewer eggs and embryos than N. obscura which laid a significantly higher proportion of deformed cocoons in soft than in hard water. N. obscura was estimated to produce 1.8 times the number of offspring of E. punctata. Thus the numerical dominance shown by N. obscura in Western Canada could be explained in terms of the differentially higher reproductive rate of N. obscura with respect to the three tested independent variables.
The life history of Glyphopsyche irrorata (Trichoptera, Limnephilidae): A caddisfly that overwinters as an adult
Authors: Berté Stephen B. , Pritchard Gordon
Published: July 2006

Glyphopsyche irrorata has adapted to live in ponds with fluctuating water levels and ponds exhibiting winter drought by passing the winter as an adult in the terrestrial environment.

Larvae, which hatch in May and pupate in late August, are detritivorous shredders. Males and females emerge in September, with a sex ratio of one and commence mating in the autumn. The entire population has mated by May at which time females oviposit in the water. Adult males and females are present in equal numbers in the spring and have similar longevities approaching a maximum of 8 to 9 months.
Distribution, abundance and species associations of earthworms (Lumbricidae) in a reclaimed peat soil in Ireland
Authors: Baker Geoff H.
Published: July 2006

Fifteen species of earthworm were collected from a reclaimed fen peat soil used for rough hay in County Offaly, Ireland. The most common species were Aporrectodea tuberculata, Allolobophora chlorotica, Eisenia rosea and Octolasion tyrtaeum. A. tuberculata, A. chlorotica and E. rosea formed a significant association. The total numbers of earthworms collected by hand‐sorting reached a maximum of 197.1 m−2. Compared with hand‐sorting, formalin‐expulsion was an inefficient sampling method for most species. Soil moisture varied within the study area. Total densities and biomasses of the earthworms were greater where the soil was drier. A. tuberculata, A. turgida, Satchellius mammale and the pink form of A. chlorotica were more common in the dry soils whilst O. tyrtaeum, Lumbricus rubellus and the green form of A. chlorotica were more common in the wet soils.
Invertebrate activity under snow in deciduous woods
Authors: Merriam Gray , Wegner John , Caldwell Douglas
Published: July 2006

Pitfall traps caught large numbers of representatives of 44 families of invertebrates just before snow fall and under the snow. Some groups of ectotherms were most active in late autumn and late winter, the activity of some increased throughout the winter and some showed no major change although subnivean temperatures were usually near 0°C. The most commonly trapped groups were: phalangids, collembolans, diplopods, coleopterans, dipterans, arachnids, gastropods and chilopods.
Influence of woodlot floor topography on microbial decomposer distribution
Authors: Dwyer L. M. , Ivarson K. C.
Published: July 2006

The distribution of microbial populations that decomposed sugar, cellulose and lignin‐related substrates was examined in a beech Fagus grandifolia Ehrh. and maple Acer saccharum Marsh. dominated woodlot developed on glacial till. The topography of the woodlot, characterized by rises, depressions and more extensive level areas about 1 m in diameter with a 0.5 m vertical maximum, produced a mosaic of decomposer habitats designated as high, level and low sites.

In general, populations of sugar, cellulose and lignin decomposing organisms (based on ten estimates made from April to October) were two to four times higher in litter and soil samples from low sites than those from high sites. Sugar decomposing bacteria in litter were most abundant at all topographic sites. 135 × 106 g−1 dry litter at high sites, 396 × 106 g−1 at level sites and 456 × 106 g−1 at low sites; lignolytic fungi were least abundant, 391 × 102 g−1 dry litter at high sites. 700 × 106 g−1 at level sites and 954 × 102 g−1 at low sites. Numbers of microbial decomposers in the topographic sites were correlated with organic matter content. Distribution of fungal genera did not appear to be related to topographic site. Most populations examined showed two numerical peaks, one in late May or June and one in late September or October. It is suspected that these peaks were influenced by the coincident timing of favourable physical conditions and priming by soluble nutrients leached from litter.
Chemical composition of reindeer forage plants in Svalbard and Norway
Authors: Staaland Hans , Brattbakk Ingvar , Ekern Karen , Kildemo Kjetil
Published: July 2006

Several of the most important reindeer forage plants in Svalbard were analysed for content of minerals (Na, K, P, Ca, Mg, S, Cl, Fe, Cu, Mn, Zn, Mo and Co) and for content of ash, crude protein, crude fiber, ether extracts and nitrogen free extracts. Some forage plants were also examined in in vitro digestibility trials. The results were compared with results from similar analyses of alpine mountain plants from southern Norway. Also freshly voided fecal samples were analysed for the same components as the forage plants.

The Svalbard vegetation had a higher content of Na, Ca, Mg, Cl, Fe and Co, than similar plants from Southern Norway. The content of other elements examined seemed to be more equal in Norway and on Svalbard. Within the Svalbard area plants growing in limestone areas had the highest content of calcium and magnesium. Also plants growing on manured soil below bird cliffs appeared to have high nutritional value. It is furthermore concluded that the closeness to the sea as well as the occurrence of several plants with high mineral content, gave the Svalbard reindeer the possibility to further improve their mineral balance compared with continental reindeer. Also the dietary shift from lichens as a major dietary component in Norway, to mosses on Svalbard, may increase mineral intake, but may also have an inferior effect on digestibility.

Although balance experiments and carcass analyses of minerals in Svalbard reindeer are missing, it is concluded that Svalbard reindeer apparently had adequate intake of most mineral elements. In spite of low standing biomass of reindeer forage plants, the quality of the vegetation seemed to compare favourably with continental reindeer pasture.