bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of food plants on food utilization by Orthosia gothica (Lepidoptera, Noctuidae) larvae
Authors: Hesjedal Kåre
Published: July 2006

Malus domestica, Salix caprea L. and Betula pubescens Ehrh. are host plants for Orthosia gothica L. The influence of the three plant species on time of larval development, mortality, and weight gain, and of adult fecundity, was studied. M. domestica was the most suitable food plant for the O. gothica larvae, and there was a positive correlation between the live weights of the females and their fecundity. The consumption, digestion and respiration of O. gothica larvae reared on foliage of S. caprea and B. pubescens were compared. Larvae fed on S. caprea had a shorter time of development, a higher weight gain, and a lower mortality, consumption, digestion and respiration compared with larvae reared on B. pubescens. Larvae reared on B. pubescens used a greater part of metabolism for maintenance than those on S. caprea. The different effects of the two food plants on the larvae were due to nutritional and/or physical conditions.
Composition and viability of the seed bank along a successional gradient on a Baltic sea shore meadow
Authors: Jerling Lenn
Published: July 2006

The seed‐bank in a Baltic sea‐shore meadow was studied and soil samples were taken regularly along a 60‐m transect. The transect reflected a successional gradient. The seed bank had its highest density around the mean water level for August, which was about 10 cm above the yearly mean water level. It was totally dominated by seeds of Juncus gerardii. The depth distribution was investigated. Only at two of ten sampling points (i.e. around mean water level of August) could a significant peak in the second cm from the top be observed, otherwise the distribution was quite even. A comparison between present vegetation and the seed bank revealed a strong difference.
Factors affecting food utilization by a leaf shredding aquatic insect: leaf species and conditioning time
Authors: Golladay S. W. , Webster J. R. , Benfield E. F.
Published: July 2006

Gravimetric feeding studies were used to examine the feeding strategy of Pteronarcys proteus (Plecoptera) using unconditioned, 1 month conditioned, and 2 month conditioned deciduous leaves of four species (white oak, red maple, black locust, dogwood). Assimilation efficiencies of Pteronarcys nymphs feeding on unconditioned and conditioned leaf material ranged from 13.4 to 21.9% AFDW of leaf material indicating that Pteronarcys was able to digest and assimilate leaf material. Assimilation efficiencies did not change as leaf material conditioned which suggests that assimilation efficiency does not accurately reflect changes in detrital food quality. However, as leaves conditioned, the ingestion rate of Pteronarcys nymphs accelerated. Rates at which dogwood and locust leaves were ingested peaked after 1 month, then declined with a second month of conditioning. Rates at which maple and oak leaves were ingested increased significantly with 2 months of conditioning. Assimilation rates of Pteronarcys nymphs varied in a pattern similar to ingestion rates. This reflects the importance of ingestion rate in the feeding response of Pteronarcys.
Germination response to salt in Festuca rubra in a population from a salt marsh
Authors: Bülow‐Olsen Anne
Published: July 2006

Germination of caryopses and seeds of Festuca rubra L. coll. from wet, dry and dune areas in the salt marsh at Skallingen, Jutland, Denmark, was tested in deionized water and diluted sea water. A strong correlation was found between percentage of germination and the topography of the collection sites. Further it was found that salt tolerance for the most salt tolerant populations, growing on low dunes, was provided partly by the husks rather than only being a characteristic of the seed. In less salt tolerant populations from low and dry areas, husks had no influence on germination percentage in 25% sea water.
A limnological investigation of the tarn Syslaktjønn, W Norway
Authors: Lännergren Christer , Øvstedal Dag Olav
Published: July 2006

An investigation covering hydrography, chemistry, vascular and cryptogamic plants, nitrogen fixation, phytoplankton biomass and production, and zooplankton was carried out from April to November 1976 in tarn in W Norway, The volume of the tarn was 18000 m3 and the turnover time about 30 d. Temperature ranged between 3.6 and 23.4°C and pH between 4.8 and 5.5. Nuphar luteum and Carex rostrata were the two dominating vasculars‐with biomasses of 117 and 97 g m−2, respectively The biomass of the bryophytes (Sphagnum spp.) was about 510 g m−2 and the production of the order 0.2–2.1 μg (mg d.w.)−1h−1. Nitrogen fixation in association with Sphagnum spp. was estimated at 25 g yr−1 for the whole tarn. Phytoplankton was dominated by diatoms, green algae and chrysophyceans. The chlorophyll a content ranged from 2 to 20 mg m−3 and the carbon assimilation rates from 0.03 to 20 mg C m−3h−1 at 0–4 m depths. Production in the period was of the magnitude 22 g C m−2. The copepod Eudiaptomus gracilis was the most common netzooplankter. Large numbers of rotationrians were found during summer.
Periphyton, chlorophyll a, and diatoms of the Middle Fork of the Salmon River, Idaho
Authors: Cushing C. E. , Cummins K. W. , Minshall G. W. , Vannote R. L.
Published: July 2006

Periphyton samples were collected at 15 sites in the Middle Fork of the Salmon River drainage basin, Idaho, USA to test certain principles of the River Continuum Concept (RCC) and to characterize the diatom communities. The standing crop of chlorophyll a increased from 2nd to 4th order streams, peaked in the 5th order stream, and declined in higher orders. These data support the RCC predictions except that peak values were reached somewhat earlier, in terms of stream order, because of the lack of shading in these streams. Also, downstream decreases were not completely attributable to increasing turbidity and decreasing benthic productivity, and may be partially related to discharge. The number of scraping invertebrates was positively correlated with the standing crop og periphyton (AFDM, not chlorophyll a); this, too, supports the predictions of the RCC. One hundred forty‐five species of diatoms were identified and the system is characterized by an Achnanthes minutissima – Fragilaria pinnata ‐ Navicula seminulum–Cocconeis placentula community.
Natural age and size of Pinus sylvestris and Picea abies on a mire in the inland part of northern Sweden
Authors: Ågren Jon , Isaksson Lennart , Zackrisson Olle
Published: July 2006

The investigation was carried out on a sparsely forest covered poor fen 350 m a.s.l. in the inland pan of northern Sweden (64°32′N, 18°55′E). On the investigated mire the natural regeneration of pine Pinus sylvestris has been relatively successful from the 1920's up to the beginning of the 1970's. Natural regeneration of spruce Picea abies has taken place throughout the period 1938‐1970, whereafter no establishment at all has occurred. The age and size structures of the pine and spruce stands on the mire vary in pattern according to the particular type of vegetation in which they are growing. Both the climatic amelioration during the first half of the present century and the successional stage of the mire vegetation were found to be important in regard to present‐day age and size structures of the pine and spruce. Root competition and snow conditions arc probably important determinants of the size structure of pine stands in the mire environment.
Abundance and productivity of protozoa in chalk streams
Authors: Baldock B. M. , Baker J. H. , Sleigh M. A.
Published: July 2006

The distribution and abundance of protozoa in two chalk streams were studied. Particular attention was given to the ciliates and amoebae associated with the dominant submerged macrophyte, Ranunculus penicillatus. Highest numbers of protozoa occurred in habitats in the stream where the current velocity was reduced. Mean standing crops of ciliates, flagellates and amoebae were 32.5, 2.9 and 2.0 mg dry wt m−2 of stream bed respectively. Estimates of production and respiration rates by field populations of ciliates and amoebae were made for one type of habitat within the streams. The results are compared with published data on the productivity of protozoa in other habitats and of other invertebrates within the chalk stream ecosystem. The limitations of such productivity estimates are discussed.
Effects of lime and artificial acid rain on the enchytraeid (Oligochaeta) fauna in coniferous forest
Authors: Abrahamsen Gunnar
Published: July 2006

Effects of lime and artificial rain of varying acidity on the enchytraeid fauna were studied in 4 field experiments in coniferous forest. Artificial rain was applied 5 months per year in quantities of 25 or 50 mm per month and with pH values from about 6 to 2. The “rain” was produced by mixing groundwater and sulphuric acid. The greatest total abundance of enchytraeids and the greatest population densities of Cognettia sphagnetorum and Mesenchytraeus pelicensis were found in plots supplied “rain” of pH 6, pH 4 and pH 3. Their abundances were lowered by additional acidification (pH 2.5 and 2) and also by liming. Species like Enchytronia parva and especially Enchytraeus buchholzi and Fredericia parnoniana were mostly stimulated by liming.
Longitudinal patterns of production, food consumption, and seston utilization by net‐spinning caddisflies (Trichoptera) in a southern Appalachian stream (USA)
Authors: Ross Douglas H. , Wallace J. Bruce
Published: July 2006

Larval production of ten species of Hydropsychidae and Philipotamidae was studied at six stations along 6.4 km of a southern Appalachian stream, encompassing stream orders 1–4 and a 600 m elevation change. Species‐specific production estimates ranged from 23–983 mg AFDM m−2 yr−1 These low values are attributed to the paucity of nutrients in these undisturbed headwater streams which reduces detrital food quality, algal growth, and production of smaller invertebrates eaten by hydropsychids. Animal food supported the majority of hydropsychid production (72%); philopotamids relied primarily on fine detritus (80%) and diatoms (15%). The contribution of animal food to caddisfly production decreased downstream, while the relative importance of filamentous algae and diatoms increased. These changes reflect the downstream decline of more carnivorous species, as well as increased primary production which accompanies the shift in lotic community metabolism from heterotrophy towards autotrophy with increasing stream order.

Net‐spinning caddisflies had a minor impact on seston quantity, consuming only 0.0003%‐0.005% of the total seston (including invertebrate drift) passing over a m2 of substrate annually. In contrast, the percentage of invertebrate drift consumed was, on the average, > 400 × higher than total seston consumption. These insects influence seston quality rather than quantity. The percentage of total seston and animal drift consumed declined downstream, indicating that turnover lengths of these materials increase with stream order. Longer turnover lengths or “spirals” result from changes in the physical characteristics of the stream, i.e., increasing discharge and stream power and decreasing numbers of retention devices (i.e., organic debris dams), which increase the downstream transport velocity of seston. Higher transport velocities reduce the rates at which these filter feeding caddisflies can process the organic inputs to a given reach of stream. Small streams (orders 1–3) appear to be most responsible for efficient processing of a stream's energy inputs.
Population dynamics and production of Daphnia galeata (Crustacea, Cladocera) in Lake Esrom
Authors: Petersen Flemming
Published: July 2006

The population dynamics and production of D. galeata Sars were investigated from April 1974 to April 1975. The population density and biomass was maximum in June. Population dynamics indicated that food supply was better in spring and early summer than mid‐summer. Net production was calculated by method of daily addition of biomass for eight size groups. The total net production of biomass for the year of investigation was 26.5 g dw m−2. The P/B yr−1 was 35 8.
Wood decomposition in an abandoned beech and oak coppiced woodland in SE England
Authors: Boddy Lynne , Swift M. J.
Published: July 2006

Stand structure and rates and patterns of wood litterfall, between 23 June 1977 and 27 June 1979, are described for two sites In a coppiced beech Fagus sylvatica L. and oak Quercus petraea (Mattuschka) Liebl. woodland in south‐east England.

Total wood fall (excluding trunks) was estimated at 1264 kg ha−1 and 593 kg ha−1 for the two years of sampling at one site and 776 kg ha−1 during the second year on the other site. The majority of leaf fall occurred in autumn; the maximum twig (wood < 1 cm diameter) and branch (wood ≥ 1 cm diameter) fall, occurred in winter at times generally corresponding with high wind speeds. Many oak twigs, however, abscissed in early November irrespective of wind speed.

Branch characteristics at fall (size, state of decay and bark cover) were documented. The most significant feature observed was that a large amount of decay frequently occurred in branches whilst still in the canopy.
Variations in litter size and reproductive effort within and between some populations of Lacerta vivipara
Authors: Pilorge Thierry , Xavier Francoise , Barbault Robert
Published: July 2006

We studied the relationships between litter size, litter weight, newborn weight, relative clutch mass and the female snout‐vent length in some Lacerta vivipara populations over a period of three years.

Litter size and litter weight were positively correlated with female snout‐vent length in all the populations for all the years, as in most other lizard species. Relative clutch mass generally increased with female size, though correlations appear not to be very tight.

Considering the two best studied populations suggests that montane females invest less in reproduction than lowland ones.

The main reproductive traits of the species appeared highly variable between as well as within the different populations hitherto studied.

We argue that current theory about lizard reproductive strategy requires, first to work out a good estimate of reproductive effort, and second to get more information about the relations between the species and their environmental, biotic and abiotic conditions.
Growth, dynamics, and distribution of a population of the brook lamprey Lampetra planeri in a South Swedish stream
Authors: Malmqvist Björn
Published: July 2006

Size and structure of a South Swedish population of Lampetra planeri larvae were studied during 5 yr. Population size fluctuated considerably within the studied section of stream with a general decline. The fluctuations were positively and strongly correlated (multiple R2= 0.85) with the population density at the beginning of each analysed period, while poorly correlated with such variables as heavy precipitation and temperature. Several factors suggest the entire larval population drifts downstream: fluctuations in the studied stream section, increasing mean size downstream, and incongruity in longitudinal distribution in surveys, performed with a 5‐yr interval. Growth, estimated both in caged larvae and from length frequency data, occurred mainly in autumn. High density in cages reduced the growth rate of larvae.
Effect of habitat, date of laying and density on clutch size of the Great Tit Parus major in northern Finland
Authors: Orell Markku , Ojanen Mikko
Published: July 2006

The sizes of 1034 Great Tit clutches were studied at the Oulu area (c. 65°N, 25°30′E) in northern Finland. The average size was 9.86 eggs in the first clutch and 7.51 in the second in 13 study areas. The decrease in clutch size from the first to the second laying was most pronounced in those females laying the largest first clutches.

Irrespective of habitat, the clutch size was larger in the sparsely populated areas than in the densest area (Taskila). The clutch size decreased according to the season in all the areas, but this was not as pronounced in Taskila as in the other areas.

The annual average size of the first clutches was inversely related to the breeding density and pronouncedly so to the mean dale of laying. The latter was suggested to be an adaptation to the short season in the northern areas.

An analysis of data from 27 study areas in Europe, north of the Mediterranean region, suggests that the clutch size does not vary with latitude or longitude.
Microbial activity during leaf decomposition in an Alaskan subarctic stream
Authors: Buttimore Carol A. , Flanagan Patrick W. , Cowan Cathy A. , Oswood Mark W.
Published: July 2006

Fungal biomass and growth and microbial respiration were studied for two field seasons in a second‐order subarctic stream where water temperature is 0°C for approximately 6 months. Leaf packs (5‐g) of alder Alnus tenuifolia, birch Betula papyrifera and willows Salix alaxensis and Salix arbusculoides immersed in autumn of 1979 and 1980 were sampled until June 1980 and January 1981, respectively. Fungal growth and microbial respiration occurred in submerged detritus at 0°C. Total and FDA‐active hyphal lengths were measured, the active proportion averaging 25% of the total (all leaf species, both years). Generally, microbial respiration peaked in all leaf species after two weeks in the stream. As water approached 0°C, respiration declined by 20–50% depending on leaf species, but often increased later in decomposition (at 0°C). Seasonal trends in microbial respiration and FDA‐active hyphal lengths were not similar although maximal respiration usually occurred as FDA‐active hyphae were growing most rapidly. The calculated leaf weight loss due to microbial respiration was small (7–10%) in all leaf species, compared with total weight loss over 98 d. Scanning electron microscopy provided a visual record of leaf surface microorganisms and apparent leaf cuticle dissolution by fungi and bacteria.
Seasonal dynamics of small vagile predators on a marine shallow soft bottom
Authors: Evans Sverker , Tallmark Bo
Published: July 2006

The seasonal on‐ and offshore migrations of the epibenthic community on a marine shallow soft bottom in Gullmar Fjord (Sweden) was recorded for a period of three years. Quantitative sampling was carried out in shallow water (≤ 1 m depth) using drop‐nets. A new sampling device was also introduced which allowed quantitative sampling in deeper water. The brown shrimp Crangon crangon L., juvenile plaice Pleuronectes platessa L. and the gobiid fish species Pomatoschistus minutus (Pallas) and P. microps (Krøyer) constituted the dominant inhabitants of shallow water, contributing >90% of the total number. The annual production was 2.2–2.9 g m−2 yr−1 dry wt with the brown shrimp as the dominant contributor. The abundance in shallow water fluctuated strongly between the seasons, while a relatively small seasonal variation was recorded in deeper water (2.5–10 m depth). The shallow/deep water abundance ratio for the epibenthic community heavily increased during the summer months, for the brown shrimp the ratio exceeded 200 in July. However, the heavy concentration in shallow water did not correspond to the reduced density of animals in deeper water. The boardering deeper water seemed to serve only as a transition area for animals arriving from or migrating to still deeper areas. Heavy mortality in the shallow nursery due to predation by the small epibenthic carnivores may also explain the low abundance in deeper areas during the autumn migration.
Species richness and succession of aquatic beetles in some kettle‐hole ponds in northern Sweden
Authors: Nilsson Anders N.
Published: July 2006

Ten closely‐located kettle‐hole ponds in northern Sweden were ordered along a vegetational, successional gradient from the present‐day representation of the six vegetational units distinguished. Different rates of vegetational development caused by differences in depths of basins have made possible the long‐term existence of early successional stages. A fact that has offered the possibility of studying most of the vegetational succession of these habitats.

The number of water beetle species inhabiting each pond were correlated to successional stage and area of pond. Mean species numbers decreased from 34 to 14 per pond with increasing maturity of the vegetational succession. This decrease in species richness of water beetles is caused by a decrease in number of habitats or vegetational units present. The increased floral conformity is mainly due to a more stable water‐level caused by lower rates of bottom seepage from the accumulation of organic deposits. Besides the extended zonation of littoral vegetation, a high water‐amplitude is also connected with recurrent nutrient pulses caused by the faster detritus composition during drought periods. Thus the changing water‐levels contribute to a high water beetle diversity through the maintenance of both a high habitat complexity and a high production.

A positive correlation between pond size and number of water beetle species were only found if the fen ponds were excluded. From this it is concluded that the area effect is here a good predictor of species richness only within ponds of a similar successional stage.
Development of woody vegetation in treefall gaps in a beech‐sugar maple forest
Authors: Runkle James R.
Published: July 2006

Treefall gaps sampled for size, age, and woody vegetation in 1977 were resampled in 1981. Large gaps had more and larger stems than did small gaps; however, basal area and number of stems per unit area remained fairly constant over the range of gap sizes encountered. Overall, most species showed little change in their relative importance values in gaps of different sizes or ages. However, the four main canopy species differed in their responses. Acer saccharum Marsh, reached maximum importance in small gaps, Liriodendron tulipifera L. and Fraxinus americana L. in large ones. As gaps aged, Fraxinus decreased in importance while Fagus grandifolia Ehrh. gained in importance for all gap sizes. For about half the gaps studied, some new adjacent disturbance had occurred between 1977 and 1981.
N2(C2H2)‐fixation in early stages of a primary succession on a reclaimed salt marsh
Authors: Holter Vibeke
Published: July 2006

Nitrogen fixation activity was determined for Lotus tenuis. Medicago lupulina and Trifolium pratense. The three species grew in clones in grassland in an area reclaimed from brackish water in the 1940s. The N2[C2H2]‐fixation was measured in soil cores throughout 1974 and 1975. From cores taken in dense and uniform stands of the species, the yearly N2[C2H2]‐fixation at maximum cover was estimated. L. tenuis fixed about 4 g N m−2 yr−1 (area with max. cover 130%), i.e. 30–56% of its requirement. Both M. lupulina and T. pratense fixed about 7 g N m−2 yr−1 (maximum cover 37% and 80%) i.e. 67% of their N‐requirement. Average N2[C2H2]‐fixation for the whole area was 0.4 g N m−2 yr−1, considerably less than the N‐addition through rainfall.
Processing of willow leaves in two Alberta Rocky Mountain streams
Authors: Mutch Robert A. , Davies Ronald W.
Published: July 2006

Nylon bags of 3.5 mm and 0.25 mm mesh were used lo investigate the processing of Salix drummondiana Barratt leaves in two second order Alberta Rocky Mountain Creeks, Twin Creek and Cabin Creek. Micro‐organism processing and macroinvertebrate shredding of the leaves were significantly greater in Twin Creek where it was estimated that macroinvertebrate shredding was responsible for 45% of the weight loss. The decay coefficient (k = 0.0209) for the leaves in Twin Creek, the more typical Rocky Mountain stream, was similar to that reported for the fastest decaying leaves in warmer streams. The predominant shredder among the leaves in the mesh bags, Zapada columbiana (Classen) (Plecoptera, Nemouridae) was also the most abundant macroinvertebrate in the benthos of Twin Creek. In Cabin Creek the predominant organism in the benthos, Oreogeton sp. was poorly represented in the leaves. Low orthophosphate concentration of the water and precipitation of calcium carbonate onto the leaves may have inhibited the biotic processing of leaves in Cabin Creek.
Energy transfer and female condition in nursing harp seals Phoca groenlandica
Authors: Stewart R. E. A. , Lavigne D. M.
Published: July 2006

Lactating female harp seals, most with their pups, were collected on the “whelping” ice in the Gulf of St. Lawrence in 1976 and from 1978 to 1980. During lactation females lost weight at an average rate of 3.17±0.52 (SEb) kg d−1, for a total energy loss of approximately 250000 kcal. Pups grew at a mean rate of 2.78±0.19 kg d−1 for a gain in production energy of about 194000 kcal. Compared to 1976, adult females sampled in 1978 to 1980 had lower energy reserves at the onset of lactation. Coincidentally there has been a decrease in newborn lengths and girths. Although compensatory growth in weight appears to occur, between‐year differences in newborn lengths persist to weaning. Various reproductive strategies of female harp seals faced with reduced energy stores are discussed.
Wolf‐avoidance strategies of moose
Authors: Stephens Philip W. , Peterson Rolf O.
Published: July 2006

Two possible anti‐predator strategies of prey were suggested by the distribution of moose at Isle Royale, a 544 km2island with numerous offshore islets. Aerial surveys in winter indicated that moose density on small islets (<1.5 km2) averaged 415% greater than on the main island, with about 11% of the calf population existing on the small islets which comprise less than 2% of the total land area. On small islets and shorelines, protection from wolves (in the form of escape terrain) is provided by nearby water in summer and coniferous cover in winter. Calves on islands appear to have a higher survival rate. In summer, cow moose with calves were seen more commonly in camps with human activity (and no wolves) than away from camps, suggesting that people provided a refuge from wolf predation for this unhunted moose population. These subtle patterns of habitat selection by moose are attributed to the intensive natural selection pressure of wolf predation.
Dynamics of Plantago maritima along a distributional gradient: A demographic study
Authors: Jerling Lenn , Liljelund Lars‐Erik
Published: July 2006

The dynamics of a Plantago maritima population was studied along a distributional gradient on a sea shore meadow during four years. The dynamics of the population varied along the gradient. In the lower parts there was a high flux with high mortality due to flooding but also a higher reproductive effort and good establishment. In the upper parts the flux was slower with lower reproductive effort and lower seedling success but instead longer lifespans. Population growth in these upper areas was primarily restricted by competition for light which prevented flowering and lowered the seedling success. Both cover values and the number of species decreased seawards and consequently the strength of competition. Simultaneously the risk of flooding increased. Thus the density peak was found at the intersect of these two variables. The plants showed differences in behaviour along the gradient in reproductive effort, growth rate, phenology etc. Whether this variation was phenotypical or genotypical is not known.
Influence of velocity and food availability on catchnet dimensions of Neureclipsis bimaculata (Trichoptera: Polycentropodidae)
Authors: Petersen Robert C. , Petersen Lena B.‐M. , Wallace J. Bruce
Published: July 2006

Larvae of Neureclipsis bimaculata (Trichoptera: Polycentropodidae) construct elaborate catchnets in lotic habitats to trap small drifting invertebrate prey. Three populations located at two oligotrophic and one eutrophic site were studied in southern Sweden. Measurements were made of larval weight, net size, seston quality and quantity, and stream velocity.

Neureclipsis larvae alter their net dimensions in response to both velocity and seston concentration. This was determined by comparing net structure and seston at the three locations. Larvae from the eutrophic, high quality seston site attain a significantly (P < 0.001) heavier instar V dry weight, spin a smaller catchnet, filter a volume of water dependent on body size, and slightly alter their catchnet dimensions with velocity. Larvae from the two oligothrophic sites are significantly smaller than those from the eutrophic site, spin a larger net at comparable velocities, filter a larger volume of water at comparable weights, and alter net dimensions with velocity.

Estimates of silk production indicate that the net cost is minimized by spinning a very fine silken strand and by adding silk over a period of time. The cost while large is offset by a large capture rate of prey.

The structure of Neureclipsis nets appears to be the result of a trade‐off between maximizing food capture and minimizing hydraulic stress on the net.
The age distribution of a Cirsium palustre population in a spring area in Jutland, Denmark
Authors: Ballegaard T. K. , Warncke E.
Published: July 2006

In European floras Cirsium palustre (L.) Scop. usually is classified as a biennial and monocarpic species. The value of this classification was examined in a population growing in a spring area in Jutland, Denmark. It was possible to describe five ontogenetic states, i.e. life‐states, in the population, the seed state excluded. Each Kate normally lasted for one growing season. Therefore the flowering state was generally not reached until in the fifth growing season. Observation on mortality revealed that seedlings were exposed to an extremely high death risk. However, in the other vegetative life states the death risk was rather low and constant.
Behaviour of West Greenland caribou during a population decline
Authors: Roby Daniel D. , Thing Henning
Published: July 2006

The major decline of the West Greenland caribou herd during the 1970s prompted a study in 1977–78 of caribou behaviour in relation to environmental factors associated with the decline. Quantification of caribou activity revealed behavioural responses to critically low standing crops of preferred winter forage. Caribou on poor winter range were mostly inactive with low feeding intensities and abnormal diurnal activity patterns. In addition, these animals exhibited very restricted movements, frequently occurred alone or in small groups, and were unable to maintain normal social bonds. In contrast, where fruticose lichen winter forage was available, caribou did not display these behavioural traits. After the initiation of new vegetative growth, feeding intensity increased and social tendency returned. Comparison with behavioural data from other Rangifer populations suggests that the observed responses to low forage quality are not restricted to Greenland but are a normal response of barren‐ground caribou to winter ranges poor in lichen forage.
The importance of bacterial utilization of released phytoplankton photosynthate in two humic forest lakes in southern Finland
Authors: Jones Roger I. , Salonen Kalevi
Published: July 2006

Bacterial utilization of photosynthetically fixed dissolved organic carbon (PDOC) released from natural phytoplankton assemblages was studied in two small, extremely humic, forest lakes in southern Finland. Bacterial activity (measured as uptake of 14C‐glucose) and phytoplankton photosynthesis (measured as light uptake of 14CO2) could be most effectively separated using Nuclepore filters of pore size 1–2 μm. Released PDOC was 10–67% of total phytoplankton carbon fixation during in situ experiments, and represented about 0.1% of total DOC. Net uptake of PDOC by bacteria was found to be about 20% during 24 hour laboratory incubations, although about 40% of PDOC present at the start of an experiment could be utilized by bacteria during a 24 hour period. PDOC does not provide a quantitatively important substrate supply for bacterial respiration in humic forest lakes.
The life‐cycles of four amphipod species in the Kattegat
Authors: Leineweber Peter
Published: July 2006

Populations of four species of Gammaridae (Crustacea, Amphipoda) were sampled over 15 months in the south‐western Kattegat at Sangstrup Klint (Denmark). Chaetogammarus marinus, C. stoerensis and Gammarus oceanicus had annual life‐cycles, while G. salinus most likely had two generations per year. Mature C. marinus females were found from March to July, mature C. stoerensis females from March to June, mature G. oceanicus females from December to early June and mature G. salinus females from late November to late July. The theoretical maximum number of clutches were estimated at five for C. marinus, five plus for C. stoerensis, and six for G. oceanicus and both winter and summer reproducing G. salinus. Spring was the period of main recruitment in all populations, with additional recruitment during summer in G. salinus.

The geographical patterns of the reproductive strategies are discussed in relation to environmental factors and interspecific competition.
Clutch size and breeding success in relation to nest‐box size in Tengmalm's owl Aegolius funereus
Authors: Korpimäki Erkki
Published: July 2006

Clutch size and breeding success was related to nest‐box size in 215 nests of Tengmalm's owl in the Kauhava region, western Finland in 1966–82. In vole peak years, but not in other years, mean clutch size was positively correlated with the bottom area of the nest‐box, increasing on average by 0.005 eggs cm−2. In successful nests there were fewer nestlings in small and medium‐sized than in large boxes. Breeding was most successful in thick‐walled boxes with a small entrance diameter. The optimal box for Tengmalm's owl has the following dimensions: bottom area 20 × 20 cm, entrance diameter 8 cm, and wall thickness at least 3 cm.

Hypotheses suggested to explain the “area effect” based on breeding data of hole‐nesting passerines do not hold good for Tengmalm's owl. Since there were more stored prey animals in medium‐sized and large boxes than in small boxes, I suggest that the “area effect” is related to food availability, which may determine how sensitive the species is to different bottom areas of the boxes, at least in areas with cyclic food (e.g. northern Europe).
Reproduction of the white‐tailed sea eagle Haliaeetus albicilla in Sweden
Authors: Helander Björn
Published: July 2006

Sixty‐eight white‐tailed sea eagle territories were studied on the Swedish Baltic coast in 1964–1982 and 22 territories in Swedish Lapland in 1976–1982. Older data were assembled for comparison. The breeding frequency of adult pairs was high in both study areas (ca. 90%). Median egg‐laying dates were 17 March (Baltic) and 7 April (Lapland). Average clutch size and egg volume did not differ between samples from the Baltic taken between 1856 and 1982. Average clutch size was significantly smaller in Lapland (1.6 eggs) than on the Baltic coast (2.1 eggs). Clutch size in Lapland was positively related to carrion availability during March. Nestling survival was significantly lower in Lapland, due to starvation in broods of more than one young. Brood loss was significantly more frequent in Lapland. At the Baltic, nest success decreased from 75 to 22%, and brood size from 1.8 to 1.2, from the early 1950's to the mid 1960's. Nest success in 1976‐1982 was significantly lower at the Baltic (26%) than in Lapland (45%), with a much larger proportion of consistently failing pairs. The proportion of eggs laid that resulted in fledged young was estimated at 16% at the Baltic and 39% in Lapland. It is concluded that egg production and nestling survival were suppressed by limited food supply and nest success by human interference in Lapland, and that the reproductive impairment of the Baltic population was due primarily to contamination with toxic substances, mainly DDE.
Effect of ground water regime on development and distribution of Fritillaria meleagris
Authors: Zhang Liquan , Hytteborn Håkan
Published: July 2006

This paper deals with a change in abundance of a population of Fritillaria meleagris L. The results of the investigation were compared with those of a study performed about 40 yr ago. The comparison showed both a change in the vegetation and in the abundance of the fritillary along a topographical gradient. The study reported here was a transplant experiment carried out in order to evaluate the hypothesis that regulation of the water levels of an adjacent lake was the main reason for the change. The transplantations showed that the performance of the fritillary was negatively affected by the high ground water levels and inundations of the site where the fritillary earlier was most abundant.
Sex‐related differences in the diet of the mink Mustela vison
Authors: Birks J. D. S. , Dunstone N.
Published: July 2006

The diets of free‐ranging male and female mink were sampled by analysing faeces collected from radio‐tagged individuals. Significant sex differences were apparent in the predation upon three of the five principal prey groups. The larger males preyed much more heavily upon lagomorphs, the largest prey taken, while females preyed more upon fish and crustaceans than did males. These differences were consistent in each season except the autumn (September to November), when males preyed more heavily upon fish and crustacea than did females. Due to their large size, adult lagomorphs are felt to be relatively unavailable to female mink. Male mink are apparently large enough to specialize on lagomorphs, and male mink niche breadth was consistently lower than that of females. Dietary overlap approximated to 40% in all seasons except summer (68%), when female predation upon lagomorphs reached a peak. This reduction in intraspecific feeding competition was felt to be a valuable side‐effect of body‐size dimorphism.
Breeding and movements of goshawks in boreal forests in Sweden
Authors: Widén Per
Published: July 2006

Goshawks were studied in their boreal forest breeding habitat in central Sweden from 1977 to 1982. Nests were regularly spaced, with a nearest neighbour distance of 6.3 km. corresponding to a density of about 3 pairs 100 km−2. Of initiated breedings. 68% were successful. There was no difference in breeding performance between years. Average brood size was 2.7. Sex ratio among first captures of adults was even, but males were recaptured more often than females. Nearly all juveniles left the area in winter. Among radio‐tagged adults 20% of the males, and 50% of the females moved out of the area. When moving, both adults and juveniles moved into agricultural areas, the juveniles generally covering longer distances. From autumn to spring, body condition of females improved, whereas that of the males deteriorated. It is argued that the males' stronger tendency to stay in winter is due to the advantage of possessing a territory in early spring. Females, on the other hand, can move to areas with as good food conditions as possible.
Growth analysis of presmolt Atlantic salmon Salmo salar at three sections of a small Norwegian stream
Authors: Lund Roar A. , Heggberget Tor G.
Published: July 2006

The growth of Atlantic salmon parr was investigated at three different sections of the small stream Levangerelva and its tributary during the period October 1978 to October 1979.

Mean growth varied significantly between the sampling sites studied. The growth was found to be density dependent at all the sampling stations. Faster growth in the tributary was considered to be related to warm water draining from the epilimnion of a lake situated 2 km above the sampling site and a greater supply of alloctonous food from the alder wood covering parts of the stream banks. Differences in nitrogen and phosphorus content, conductivity, pH, total hardness and humus content of the stream water did not show any relation to growth variations in the different parts of the stream.
Microhabitats of stream invertebrates on two submersed macrophytes with contrasting leaf morphology
Authors: Tokeshi Mutsonori , Pinder L. C. V.
Published: July 2006

Larvae of Chironomidae, Simuliidae and Trichoptera exhibited various patterns of micro‐distribution on the submersed macrophytes Potamogeton×zizii, with broad leaves, and P. pectinatus, with thread‐like leaves. Seven common species of chironomid, six belonging to the subfamily Orthocladiinae and one to the Chironominae, showed four distinguishable patterns of distribution. The density of Simulium larvae was much greater towards the apices of the stems on both plants. Among three species of Trichoptera studied, the predatory Rhyacophila dorsalis had a pattern of distribution which was strongly related to prey density, particularly that of Simulium, on P. ×zizii, but not on P. pectinatus. P. ×zizii supported proportionately more free‐ranging scrapers, such as the chironomid Thienemanniella vittata. than did P. pectinatus while the reverse was true for filter‐feeders. These patterns are discussed in relation to habitat structure and behavioural characteristics.
The chironomid fauna of North Norwegian lakes, with a discussion on methods of community classification
Authors: Aagaard Kaare
Published: July 2006

The chironomid communities of fifty lakes in northern Norway are presented and briefly described. A limnological classification of the communities is given, together with remarks on the methods used.

The interrelationships are given of the chironomid communities and such lake‐water parameters as the minimum oxygen content, Secchi disc values, conductivity, total hardness and calcium content, total nitrogen, total phosphorus, chlorophyll a, and estimated fish yield. The best predictive and monitoring value of the chironomid communities, as classified by the above system, was obtained for the organic parameters. Compared with other indices used for estimating fish yields, the present method is as reliable as the better ones.
Feeding and sexual dimorphism in adult midges (Diptera: Chironomidae)
Authors: Burtt E. T. , Perry R. J. O. , McLachlan A. J.
Published: July 2006

Adult chironomids feed readily on materials containing sucrose and glucose, and the addition of dyes is an easy way of demonstrating that food passes through the gut. Male and female flies are shown to make very different use of the food they take in. Males show no change in longevity but extend their flight time for an average of 160% over unfed males. Females, by contrast, show no detectable increase in flight time, but increase longevity by about 40%. Sexual dimorphism in the use of food seems appropriate to the roles of the sexes. We infer that males improve their swarming performance while females may benefit from increased longevity both in gaining time to find suitable mates and in the distance dispersed after mating. Males, and to a less extent females, are found on aphid infested trees near fresh water, and the suggested biological value of feeding is in sustaining the swarming flight especially for the males. Trichoptera adults are found feeding on aphid infested trees and the earlier findings that adult Trichoptera feed are confirmed.
Longitudinal zonation and food of larval chironomids (Insecta: Diptera) along the course of a river in temperate Canada
Authors: Ward Angela F. , Williams D. Dudley
Published: July 2006

The chironomid larvae of the Rouge River, Ontario, Canada, showed a longitudinal zonation which may have been influenced by water temperature and substrate composition. Species of Orthocladiinae predominated in the cooler headwaters while species of Chironomini dominated the comparatively warmer water near the estuary. In the middle section the chironomid assemblage was of a more mixed nature.

Differences occurred in both food availability and feeding between sites along the river. Within genera, there were differences in the proportions of major food items between the larval guts and the available food material sampled from the same area. In most cases (e.g. Cryptochironomus, Polypedilum and Orthocladius) larvae selected detritus over diatoms. Some genera (e.g. Microtendipes) changed the proportions of food items ingested seasonally, while others (e.g. Psectrocladius) exhibited a more stable diet throughout the year. Second instar larvae appeared to seasonally adjust their diet most often (e.g. Cricotopus. Tanytarsus and Eukiefferiella), however these changes were not just in the types of food eaten, but also in the proportions of food types consumed. Larvae of all genera continued feeding throughout the cold water conditions (<5°C) of winter. Incidence of predation was very low, for example <10% in the Tanypodinae. In the laboratory, species of Chironomini ingested and assimulated, to varying degress, isolated populations of diatoms, detritus and bacteria.
Utilisation of different ages of heather on three Scottish moors by red grouse, mountain hares, sheep and red deer
Authors: Savory C. John
Published: July 2006

Utilisation of heather at three Scottish moors, by red grouse, mountain hares, sheep and red deer, was measured by collecting their faecal droppings regularly from plots on heather patches of different ages. Rates of heather growth differed between moors, and preferences of the four species, all grazers of heather, were related more closely to its height than to its age. Thus hares spent most time on ground with heather less than 15 cm high, sheep less than 20 cm, grouse preferred heather 10–30 cm high and deer spent most time on heather over 25 cm high.

Differences between outer, middle and inner plots on patches at one of the moors in dicated that grouse are reluctant to move far from cover into areas of newly burned ground, and reluctant to move far into patches of tall, dense heather, when these are next to shorter material. Hares preferred the middle of patches on newly burned ground and very young heather.

At two of the moors, but not the third, there was evidence that heavy grazing by hares in winter reduced the amount of young heather available to hares and grouse in spring. This potential reduction in the quality of the spring diet of grouse is discussed In relation to previously reported associations between numbers of hares and grouse at those two moors.
Foraging by moose on two species of birch when these occur in different proportions
Authors: Danell Kjell , Ericson Lars
Published: July 2006

The two tree‐like birch species Betula pendula and B. pubescens are of medium preference to moose during winter in northern Sweden. Because these birches are abundant in many biotopes, they form a major part of the moose diet. The two birches are very similar in appearance and often occur in mixed stands. Twenty‐one birch stands where B. pendula formed from 2 to 97% of the birches were investigated to determine how the relative composition of the stands affected browsing of the two species by moose. In stands composed of 60% or less of B. pendula, there was a preference for this species when regarding 1.5–3.0 m high birches, which carry the largest amount of available browse per tree. At higher proportions B. pendula was still preferred, but use was closer to availability. However, in all stands there were significantly more moose bites per tree of B. pendula than of B. pubescens. In four birch stands browsing on 1.0–1.5 m high birches was also investigated. For this height class there was still a preference for B. pendula, but the difference between the two species was less pronounced than for the 1.5–3.0 m height class.
Reproduction and spacing behaviour of females in a peak density population of Clethrionomys glareolus
Authors: Bondrup‐Nielsen Søren , Ims Rolf Anker
Published: July 2006

A peak density population of Clethrionomys glareolus was studied by snap‐trapping to determine by experimentation whether spacing behaviour regulated the breeding density. On control plots onset of reproduction was asynchronous, litter size of overwintered females decreased significantly during the summer and no year‐born animals matured during the reproductive period. A removal experiment in the early summer resulted in sexual maturation of year‐born females. A second removal in late summer indicated an inhibition of maturation in year‐born females despite continued intense reproduction of overwintered females. We conclude that spacing behaviour regulated maturation of females early in the summer but other factors, such as food quality, limited maturation in late summer.