bluuebunny/crossref_metadata_2025 huggingface dataset:
Species composition and biomass of an epipelic algal community in a subarctic lake before and during lake fertilization
Authors: Björk‐Ramberg Susanna
Published: July 2006

The species composition, biomass (measured as algal volumes) and chlorophyll concentration of epipelic algae was studies before (1977) and during (1978–1979) fertilization with phosphorus and nitrogen of Lake Gunillajaure, a small subarctic lake in northern Sweden.

The epipelic biomass, dominated by Cyanophyceae and Bacillariophyceae, was high (5.6–20.1 cm3 m−2) at all depths in the lake with the highest values in the hypolimnion (8–13.7 m). Calculated over mean depth it was 20 times higher than that of the phytoplankton. There was no significant increase in biomass during fertilization and neither did the species composition change. The chlorophyll concentration on the other hand were significantly higher in late 1978 and in 1979 which was probably an effect of the declining light climate caused by a large phytoplankton development in the lake. Constant seasonal biomass and species composition indicate a perennial epipelic community in this lake.
Primary productivity and biomass of epiphytes on Phragmites australis in a eutrophic Danish lake
Authors: Rjber Hans H. , Sørensen John P. , Schierup Hans‐Henrik
Published: July 2006

A field incubator based on a closed flow system was applied for primary productivity measurements in situ. The seasonal development of epiphytes showed a pronounced productivity maximum in May (610 mg C m−2Phragmites stand d−1) and a maximum chlorophyll a content of 414 mg m−2Phragmites stand. Substratum limitation was indicated during the spring maximum. Primary productivity and biomass decreased to low values in late summer, mainly due to shading from the aerial shoots. Significant quantitative heterogeneities in epiphyte biomass occurred over a few decimeter of Phragmites stem. Productivity and biomass were higher on old stems than on new ones throughout the growth period. The annual epiphyte production (23,7 g C m−2Phragmites stand) was mainly a result of the spring maximum. The fact that 64% was produced on old stems emphasizes the importance of the highly variable degree to which these may be destroyed. The host plant phenology appears from this investigation to be a key factor affecting epiphyte growth in the emergent vegetation determined by (1) the amount of available substratum and (2) the light penetration through the canopy.
Island biogeography of Corsican birds: some trends
Authors: Martin Jean‐Louis
Published: July 2006

The species composition, species richness, and the general characteristics of the Corsican bird fauna are compared to those of similar French mainland areas. Species richness on Corsica is approximately 30% lower than on similar‐sized reference areas on the mainland. A comparative study of the species composition Indicates that species impoverishment is not evenly distributed among different species groups. These groups were defined on three levels: taxonomical, biogeographical, and ecological. The sea bird fauna appears not to be impoverished. Freshwater and anthropophileous bird species groups show only little impoverishment, which is to be related to their good dispersal ability as a consequence of the discontinuous distribution of their habitats even on the mainland. The mainland forest species group is one of the most impoverished, but mainland forest species having colonised Corsica show important habitat expansion and increased densities on the island. The sedentarity of these species and particular features of the Corsican environment are proposed as explanations.
Wood decomposition in an abandoned beech and oak coppiced woodland in SE England
Authors: Swift M. J. , Boddy Lynne , Healey I. N.
Published: July 2006

The results of three surveys of wood decomposing on the forest floor of two sites in an abandoned beech and oak coppiced woodland, between 1968–1979, are described.

Total wood stainding crop on the forest floor was estimated as 311 g m−2on one site and 311–440 g m−2on the other site.

Between 1969‐71 almost 1000 branches were sampled and of these 60% showed signs of past or present animal activity, Diptera were the major taxonomic category with Tipulidae being the most prevalent class;Tipula flavolineatawas detected in 39% of the branches. The second most prevalent species wasCylindroiulus punctatus(Diplopoda) followed byOniscus asellus(Isopoda), the OligochaetesLumbricus terrestrisandLumbricus rubellus, Lithobius variegatus(Chilopoda),Cylindronotussp. (Coleoptera).

Branches invaded by animals were generally more decayed than uninvaded branches on the forest floor which in turn were more decayed than branches at fall.
Wood decomposition in an abandoned beech and oak coppiced woodland in SE England
Authors: Boddy Lynne , Swift M. J.
Published: July 2006

The rate of litter decomposition is often expressed as a constant decay rate (k; g g−1yr−1) or as the time required for a certain percentage (often 95% and estimated as 3/k) of it to decompose (termed turnover time). Estimates of k may be obtained by determining the weight loss of litter in the field and also by assuming a steady state and obtaining the ratio of litter input: standing crop. Both methods were used to estimate decay rate and turnover times for beech and oak branches and twigs decomposing on the forest floor and these were critically evaluated.

Considerable variation, ranging between 1.8–144.5 yr, was found between the 95% turnover time estimates of various size components of the two species, obtained from woodfall and standing crop data. Likewise variation in decay rate of 2–2.5 cm diameter beech branches, estimated from field experiments, was large both between and within groups of branches categorised according to initial state of decay and presence or absence of bark. The mean annual decay rate for the various categories ranged between k = 0.165‐0.452 g g−1yr−1. Branches without bark generally decomposed more slowly than those with bark. Beech twig (<0.5 cm diameter) decomposition rates, from field experiments, ranged between k = 0.149‐0.220 g g−1yr−1and variation was relatively low compared with that of branches. No significant differences (P<0.05)were detected between twig decomposition rates obtained from experiments initiated at different seasons although there was a slight decline in decay rate in winter months. Twig and branch decomposition rates fell within the range found in the few other comparable studies.
Activity periods and energetic reserves of the brown lemming in northern Alaska
Authors: Peterson Roy M. , Batzli George O.
Published: July 2006

Radiotelemetry provided data on the activity periods of brown lemmings Lemmus sibiricus in northern Alaska. Activity inside the burrow and inactivity outside the burrow usually occurred in short episodes (<3 min), whereas periods of activity outside the burrow and inactivity inside the burrow were more prolonged and appeared to be associated with foraging (outside) and sleeping (inside). Energetic reserves for lemmings entering a burrow consisted of body fat and undigested gut contents, which allowed minimal survival times of 8.6 ± 2.3 h (mean ± 1 S.E.). Nevertheless, lemmings usually left their burrows within 40 min of entering, at which time their stomachs would be at least two‐thirds empty. Activity patterns of lemmings appear to change in response to predators, weather and nutritional requirements. We argue that lemmings seek to minimize the time spent foraging rather than to maximize the net energy gain while foraging.
Life cycle, growth and production in estuarine populations of the polychaetes Nereis virens and N. diversicolor
Authors: Kristensen Erik
Published: July 2006

Life cycle, growth, mortality and production of the polychaetes Nereis virens and N. diversicolor were studied in Norsminde Fjord, Denmark. When 3 yr old, N. virens showed synchronous spawning induced at new moon in April when water temperature was 10–12°C. Nereis diversicolor showed a prolonged spawning during early spring and summer at an age of 12–18 months. Average weight‐specific growth rate for N. virens and N. diversicolor were O.0062 and 0.0050 d−1, respectively; showing a reduced rate with age. Annual mortalities of 76–77% and 98%, respectively, reduced N. virens to 1.2–1.4% and N. diversicolor to 1.2–2.3% of the initial population at the time of spawning. Annual production of N. virens and N. diversicolor was 23.73 and 27.17 g AFDW m−2, tantamount to an annual turnover (P/B) of 2.52 and 2.60, respectively.
Life cycles of Gammarus oceanicus and G. salinus (Amphipoda) in the Oslofjord, Norway
Authors: Skadsheim Arnfinn
Published: July 2006

In the Oslofjord the amphipods Gammarus oceanicus Segerstråle, 1947 and G. salinus Spooner, 1947 were estimated to live for a maximum of 15 months. All specimens which survived during winter died in spring, mainly in May. A G. oceanicus population living on a freshwater influenced shore contained smaller specimens, had a lower proportion of the female population in breeding condition and probably produced fewer broods than a population living on a fully marine shore. The differences are discussed in relation to environmental factors and the distribution of G. salinus. Gammarus oceanicus possibly was breeding from December to May, some females even in June, resulting in an estimated maximum of three broods from December to May. Gammarus salinus showed two breeding periods, the first from December to May, a few of these females even bred in June, while new females bred from June to October, giving estimated maxima of respectively three (December to May) and five broods. Gammarus salinus females entered a reproductive resting stage in September‐October. The sex ratio was mostly female dominated. A shift to male dominance was noted in one population and was related to possible infections. Information from the literature on longevity and breeding periods was compiled and compared to the Oslofjord data.
Transplantation experiments with saplings of Betula pubescens ssp. tortuosa near the tree‐limit in Central Sweden
Authors: Kullman Leif
Published: July 2006

Saplings of mountain birchBetula pubescensEhrh. ssp.tortuosa(Ledeb.) Nyman, three years old, were transplanted into three contrasting habitats, viz. moderate and extreme snow‐bed and windswept crest. The experimental sites were situated just below the present local tree‐limit of birch. During 1978–1983 mortality and height increment were monitored. High initial mortality was succeeded by lower mortality at all three sites. The height increment was significantly higher in moderate snow‐bed compared with the two extreme habitats (winswept crest and extreme snow‐bed). The main conclusions are that after the first seedling stage the mountain birch survives broad climatic variation. However, normal completion of the life‐cycle is only possible within more narrow limits. A minimum amount of the snow‐free preriod is needed, e.g. to satisfy the requirements of nitrogen nutrition. The results Stress the opportunistic nature of the mountain birch which gives it a selective advantage in the extremely unpredictable climate in mountainous areas in Scandinavia. The reproductive strategy of mountain birch apparently includes having a bank of persistent saplings.
The effects of patchy food availability on nest‐site selection and movement patterns of reproductively active female meadow voles Microtus pennsylvanicus
Authors: Sherman Lori J.
Published: July 2006

Radiotelemetry was used to study the movements of female meadow voles Microtus pennsylvanicus Ord through the reproductive cycle. The study was conducted on a commercial field of crownvetch Coronilla varia L., a plant which provides excellent cover but contains a toxin making it unsuitable as forage. In this habitat, food is limited to small patches of grass and other non‐crownvetch species dispersed throughout the fields. Four measures of movement (activity radius, distance moved per hour, nest radius, and area covered) showed significant reductions at parturition. Females maintained low levels of movement throughout the first week of nursing as they concentrated activity around the brood nest. After seven days of lactation, they began to spend less time at the nest. A slight increase in median activity radius occurred through the last six days of gestation.

Brood nests were constructed in a portion of the home range that contained a relatively high concentration of food. Chi‐square tests revealed a significant positive association of females with non‐crownvetch plants during the first six days of lactation but no association with non‐crownvetch was found before parturition. Females chose nest locations in which, prior to parturition, they had spent little or no time presumably because nutritious plants were less grazed there.
Predation on brown hare and ring‐necked pheasant populations in southern Sweden
Authors: Erlinge Sam , Frylestam Bo , Göransson Görgen , Högstedt Göran , Liberg Olof , Loman Jon , Nilsson Ingvar N. , Schantz Torbjörn von , Sylvén Magnus
Published: July 2006

Predation on brown hares and pheasants in relation to their production was examined in an open field area in southern Sweden. Biomass and numbers of hares and pheasants eaten by the predators were calculated from data on food habits, food requirements, and numbers of the mammalian and avian predators present (11 species). At the same time estimates of numbers and production of hares and pheasants were obtained. At least 40% of the estimated annual production of hares and almost 60% of subadult‐adult pheasants in autumn were consumed by the predators. Estimated numbers of hares and pheasants taken by the predators greatly exceeded shooting and road mortality. Foxes and cats were the predominant predators on hares (about 90% of total hare consumption). Foxes accounted for about two‐thirds of predation on pheasants; cats and goshawks were of secondary importance. Pheasant nests were preyed upon by hooded crows and also by badgers. Hares and pheasants contributed only about 3 and 1%, respectively, of the food of the predators.
Polar deserts, their plant cover and plant production in the Canadian High Arctic
Authors: Bliss L. C. , Svoboda J. , Bliss D. I.
Published: July 2006

A total of 41 stands was sampled for species composition and 29 of these stands for plant standing crop and net annual production at 7 sites on 6 arctic islands. Fourteen additional sites on 10 islands were studied in less detail.

Through polar ordination, three groupings were recognized: polar barrens with an average species richness of 6, a phytomass of 24 g m−2, and a net annual production of 0.8 g m−2. Comparable data for the cushion plant and snowflush communities were 9, 120, 3 and 13 species, 400 g m−2, phytomass and 41 g m−2net production respectively. Cryptogams are minor except within showflush communities.

The soils show no horizon development, arc alkaline, and are very tow in organic matter, nitrogen, and phosphorus. It is believed that the combination of limited soil moisture in mid‐summer and very low nutrient levels are the primary reason for such low plant cover and plant production in these predominantly polar barren landscapes. Geologic substrate with an abundance of frost‐shattered rock and topographic position are factors that control the limited availability of water.
Plant communities and plant production in the western Queen Elizabeth Islands
Authors: Bliss L. C. , Svoboda J.
Published: July 2006

A study of soils, plant communities, and net annual plant production was conducted with 41 stands at 3 sites on 3 arctic islands. Twelve additional sites were studied in less detail on Ellef Ringnes, King Christian and Melville islands and on four other islands. Through polar ordination five groupings were recognized. Alopecurus and Puccinellia barrens on sand to silty soils and on silty soils, high in sodium salts respectively. Species richness averaged 2.6 ± 2.0 and total plant cover 6.8 ± 2.7%. The Phippsia barrens occur on sheet eroded surfaces and in gulleys with deep winter snow. Species richness was 9.8 ± 5.0 and total plant cover 14.8 ± 9.6%. The graminoid steppes on sandy soils averaged 7.6 ± 2.4 species and total plant cover 40.0 ± 2.8%. Eight stands were dominated by moss‐graminoids, mostly on loam soils. Species richness was 24.9 ± 3.4 and total plant cover 77.7 ± 16.1%. Plant producion was 8.0 g m−2 in a Puccinellia barren and 9.4 g m−2 in a Luzula confusa graminoid steppe. Net annual production ranged from 18.8 to 58.7 in 6 other stands. The 13 stands within the cryptogam‐herb community complex occur on sandy loam to clay‐loam soils. Species richness averaged 26.3 ± 6.2 and total plant cover 61.2 ± 24.7%.

Mosses and lichens play a significant role in the establishment and maintenance of communities with a greater species richness and plant production of vascular plant species. The ability of mosses to hold moisture and the presence of limited bluegreen algae that fix nitrogen appear essential to the maintenance of greater species richness, plant cover and plant production compared with the barren polar deserts that are often nearby.
Vertical distribution of primary production and phytoplankton in two small lakes with different humus concentration in southern Finland
Authors: Arvola L.
Published: July 2006

Vertical distribution of primary production and phytoplankton was studied in a polyhumic brownwater lake and in an oligo‐mesohumic lake. During summer both lakes were thermally, chemically and biologically stratified. In the brownwater lake primary production was restricted to the uppermost layer of 1–1.5 m of epilimnion. In the oligo‐mesohumic lake noticeable primary production was detected down to depths of 2–3 m. The ice‐free period primary production was about 20% higher in the oligo‐mesohumic lake, though occasionally the surface production was 2–3 times higher in the brownwater lake. Epilimnetic total phosphorus and total nitrogen concentrations were higher in the brownwater lake, while nitrate‐nitrite, ammonium and phosphate concentrations were very low in both lakes.

Phytoplankton was confined to the uppermost productive layer in the brownwater lake. In the oligo‐mesohumic lake phytoplankton was distributed more evenly, though the mean maximum biomass was at the depth of 3–4 m. Below the oxic water layer biomass decreased abruptly in both lakes. In the oligo‐mesohumic lake chlorophyll concentration was extremely high (max. 320 mg chl a m−3) in the anoxic hypolimnion, due to green sulphus bacteria.

Flagellated chlorophytes and thrysophytes dominated in the brownwater lake; in spring Chlamydomonas species, followed by Mallomonas caudata. In the oligo‐mesohumic lake small coccal green algae, such as Oocystis, Scenedesmus and Westella‐like species, dominated in mid‐summer, and chrysophytes and cryptomonads in autumn.
Fecundity and mortality in populations of Salicornia europaea agg. at Skallingen, Denmark
Authors: Jensen A. , Jefferies R. L.
Published: July 2006

Seedlings of the annual, Salicornia europaea (sensu stricto), germinated in the outer marsh sand flats at Skallingen in early May, and the relative growth rates of root and shoot were high during the establishment phase. Mortality of plants, which was not density‐dependent, was greater than 70% in most plots from early May to early October, as a result of wave action, desiccation and the presence of algal mats.

Salicornia ramosissima was present in the outer and inner marshes mixed with Puccinellia maritima. Seedling densities of this annual were high, and in early May growth rates were lower than those for Salicornia europaea. Overall mortality of plants from early May to early October was density‐independent. Mortality of S. ramosissima in the inner marsh was only 50% from May to October, whereas the mortality of S. ramosissima in the outer marsh was 95% in the same period.

Different levels of seed production per plant, which reflected differences in plant architecture, were evident between the two micro‐species.

Reciprocal transplants from the inner marsh failed to survive on the outer marsh sand‐flat. Mean seed production per plant in plants transplanted from the outer marsh sand‐flat to the inner marsh was only 10% of the value of the control populations. The distances of seed dispersal were different in the outer and inner marsh. Low recruitment occurred in areas cleared of Salicornia plants in the inner marsh, unlike the situation in the outer marsh sand‐flat where tides dispersed seed.
Community structure of birds in agricultural areas in summer and winter in Denmark
Authors: Møller Anders Pape
Published: July 2006

The spatial distribution of bird species was studied by grid mapping in 273 (250 × 250 m) squares in an open rural area in Denmark in summer and in winter. Species frequencies (fraction of squares with species present) followed a logarithmic linear distribution when arranged by their rank. Species frequency probably reflects relative abundance as the two variables were highly positively correlated. The number of species increased with the number of vegetation layers, ground water level, and habitat diversity. The distributional segregation of species was similar in summer and in winter, even though the winter assemblage only comprised 62% of the species present in summer. The number of species per square in winter was positively correlated with the number of species in summer; the fraction of species wintering in various habitats increased with the number of vegetation layers and the presence of human habitation. Species that flocked had a low similarity between their summer and winter distributions. Among pairs of potential competitors the smaller species either changed distribution locally or emigrated from the area in winter. The number of habitat types was reduced from 5 in summer to 4 in winter, and the number of species assemblages decreased from 5 in summer to 3 in winter. Birds were absent from 52% of the squares in winter.
Growth, maturation and survival of frogs Rana temporaria L.
Authors: Gibbons M. M. , McCarthy T. K.
Published: July 2006

A total of 1560 breeding frogs were collected in three consecutive years at sites in the west of Ireland. Alt were weighed and measured and the ages of 702 individuals were determined by skeletochronology. The length‐weight relationship differed between gravid females, spent females and males, with the gravid females showing the largest weight gain for any increase in length. The majority of males bred for the first time at two years, but most females delayed maturity until they were a year older. While the two‐year olds were of similar size, the females subsequently grew at a faster rate and achieved larger maximal sizes than the males. However, both sexes exhibited a decelerating growth rate with age. There was no apparent difference between the sexes in post‐maturation survival, which was estimated to be about 50% annually. The oldest frogs were seven years old.
Winter breeding in three rodent species, the bank vole Clethrionomys glareolus, the yellow‐necked mouse Apodemus flavicollis and the wood mouse Apodemus sylvaticus in southern Sweden
Authors: Eriksson M.
Published: July 2006

Winter breeding, as judged from heavy reproductive organs in both males and females, was observed in bank voles, yellow‐necked mice and wood mice in south Sweden during the winter of 1976–1977. The breeding was probably a result of unusually favourable feeding conditions created by an extremely rich beech mast crop.
Effects of water and mineral nutrient supply on a deciduous and an evergreen dwarf shrub: Vaccinium uliginosum L. and V. vitisidaea L.
Authors: Karlsson P. Staffan
Published: July 2006

The effects of irrigation and fertilization on nutrient content, shoot growth and photosynthetic rate of the deciduous Vaccinium uliginosum L. and the evergreen V. vitis‐idaea L. were studied in a field experiment at Abisko, Swedish Lapland. V. vitis‐idaea responded to fertilization with a greater increase in leaf nitrogen, phosphorus and potassium concentrations, as well as with a relatively greater change in shoot growth than V. uliginosum. Also to irrigation did V. vitis‐idaea respond more strongly. Decreased leaf longevity was indicated in both irrigated and fertilized plants of V. vitis‐idaea. It is concluded that no general response pattern for evergreen and deciduous plants can be expected to emerge unless one also takes other plant characteristics, and also site characteristics, into consideration.
Photosynthetic characteristics and leaf carbon economy of a deciduous and an evergreen dwarf shrub: Vaccinium uliginosum L. and V. vitis‐idaea L.
Authors: Karlsson P. Staffan
Published: July 2006

The seasonal course of photosynthetic rate, and light and temperature relations were studied in the dwarf shrubs Vaccinium uliginosum L., deciduous, and Vaccinium vitisidaea L., evergreen, at a subarctic site in northern Sweden, Using the photosynthetic characteristics and meteorological data from the site, the seasonal and life‐span carbon dioxide gain was estimated.

The photosynthetic capacity of V. uliginosum was at a maximum one month after the start of leaf expansion and declined rapidly in the beginning of September. The old V. vitis‐idaea leaves needed about 2 wk to recover full photosynthetic capacity after snow‐melt; the current‐year V. vitis‐idaea leaves needed the same time after bud‐break to reach full capacity. The leaves of V. vitis‐idaea showed no seasonal trend in photosynthetic capacity after the first two wk of recovery, but their capacity decreased by one third after the first winter and by approximately 10% yr−1 over the following two yr. The seasonal variation in the photosynthetic response to temperature was more marked in V. uliginosum than in V. vitis‐idaea. Light saturation occurred at approximately 3000 μmol m−2 s−1 in V. uliginosum and at 60 μmol m−2 s−1 in one‐year‐old V. vitis‐idaea leaves. The leaves of both species had a positive carbon balance at photon flux densities above 5 μmol m−2 s−1.

The calculated seasonal CO2 gain was 21 g CO2 g−1 leaf in V. uliginosum and 6–8 g CO2 g−1 in V. vitis‐idaea leaves. Life‐span CO2 gain for leaves of V. vitis‐idaea was the same as in V. uliginosum, viz. 21 g CO2 g−1. One fifth of the CO2 gain of V. vitis‐idaea was assimilated during periods when V. uliginosum was leafless.
The effect of microhabitats on the leaf litter decomposition and on the distribution of soil animals
Authors: Szlavecz Katalin
Published: July 2006

Earthworm burrows as microhabitats for other soil fauna were studied in a hornbeam‐oak mixed forest in Hungary. Comparative chemical analysis and feeding experiments were carried out to find out whether the leaves in the burrows of large‐bodied earthworms are more decomposed than those from the surrounding areas. The total organic matter content, the C/N ratio, the stability coefficient and the percentage of tannins and lipids indicate that the chemical breakdown of the litter material is more advanced in the burrows than on the other parts of the forest floor especially in autumn. No consistent differences were observed in the amounts of other organic components. Feeding experiments showed that three species of the fauna preferred the leaves pulled into the burrows to those from the surrounding areas and the preference was greater in autumn than in spring.

It is suggested that the high density of some soil animals in the burrows in autumn is due to the more palatable food there; in summer the microclimate of the burrows is favoured, whereas spring can be considered as a transition period.
Littoral chironomid communities in an arctic Alaskan lake
Authors: Hershey Anne Evelyn
Published: July 2006

The soft‐sediment littoral zone of arctic Toolik Lake (68°N) is composed of patches of macrophytes and bare sediments, which support distinct communities of chironomid larvae. Macrophytes were typically dominated by Stictochironomus rosenschoeldi (Zett.) but also had persistent populations of Heterotrissocladius maeaeri Brund., Paratanytarsus spp., Ablabesmyia sp., as well as several other less common taxa. Bare sediments were dominated by H. maeaeri, Parakiefferiella sp., and Zalutschia zalutschicola Lip. S. rosenschoeldi was common in bare sediments hut far less so than in macrophytes. Few taxa were restricted to either habitat. Life cycle lengths, estimated for some species, ranged from 1 to 4 yr. Analysis of indicator species suggested that Toolik is oligotrophic to ultra‐oligotrophic, which is consistent with the available primary production estimate for Toolik Lake. Littoral chironomid communities, in addition to profundal communities, may be useful in lake typology.
Different reproductive success at low salinity determines the estuarine distribution of two Palaemon prawn species
Authors: Berglund Anders
Published: July 2006

The two prawn species Palaemon adspersus Rathke and P. elegans Rathke differ in their distribution patterns in estuaries: P. adspersus occurs at lower salinities and also extends further into the Baltic than P. elegans. Yet, at low salinities adult survival does not differ between the two species. Reproductive success was, however, substantially reduced in P. elegans at low salinity, but not in P. adspersus. Berried P. elegans females from the Swedish west coast hatched significantly fewer clutches at 10%‰ than did P. adspersus females from the same locality. Furthermore, larval survival in P. elegans was significantly lower at 5 and 7.5‰ than in P. adspersus. At higher salinities (10 and 24.5‰) no interspecific differences in larval survival were found, except in one experiment where P. elegans larvae had a lower mortality. It is concluded that the different estuarine distributions of the two palaemonid prawn species result from these interspecific differences in reproductive success at low salinity.
Relative importance of habitat area, isolation and quality for the occurrence of middle spotted woodpecker Dendrocopos medius (L.) in Sweden
Authors: Pettersson Börje
Published: July 2006

In a stepwise regression analysis, oak habitat area and habitat isolation were the most important parameters explaining numbers, density, regularity, and probability of presence in two successive years of middle spotted woodpeckers. No estimate of habitat quality contributed significantly to the equations. A 50% regularity of occurrence during the study period was found in oak areas of 75 ha. It is suggested that, for a small population, habitat fragmentation that gives rise to partially isolated subpopulations will make the population more vulnerable. The large area required by Swedish middle spotted woodpeckers compared with Central European ones, is believed to be a result either of an ‘extinction disequilibrium’ or of poorer habitats in the periphery of the distribution area of the species.
Observations on autotoxic effects on seed germination and seedling growth in Cirsium palustre from a spring area in Jutland, Denmark
Authors: Ballegaard T. K. , Warncke K.
Published: July 2006

Ethanol extracts from fresh leaves of Cirsium palustre (L.) Scop. were tested for inhibitory effects on the germination of own seeds, and dried leaves were ground and incorporated in soil to determine if growth of own seedlings was affected. Leaf extracts strongly inhibited seed germination, and leaf residues seedling growth. Inhibition was apparently not mediated by effects on pH or by nutrient deficiency.
Lichen communities and the associated fauna on a rocky sea shore on Bornholm in the Baltic
Authors: Søchting Ulrik , Gjelstrup Peter
Published: July 2006

Thirty‐three sampling sites representing 11 lichen dominated plant communities on maritime rocks on Bornholm were analysed with respect to composition of the vegetation, number of animals present and gross taxonomic composition of the fauna. The specific fauna of one moss and seven lichen species was examined.

The lichen communities studied were largely the same as those found in similar studies in NW Europe, except for the recognition of a distinct Ramalina cuspidata community. The highest average number of animals per area was found in the Schistidium maritimum and the Ramalina siliquosa communities, whereas the highest average number of animals g−1 dry plant biomass was recorded in the Parmelia saxatilis community. Among the species examined Anaptychia fusca contained the highest average number of animals g−1 dry thallus and Ramalina cuspidata the lowest number, 114 and 7, respectively. Collemboles appeared to dominate in the moss Schistidium maritimum and in foliose lichens, whereas mites dominated in crustose and fruticose lichens.
Resource partitioning of roach Rutilus rutilus and bleak Alburnus alburnus in two eutrophic lakes in SE Norway
Authors: Vøllestad Leif Asbjørn
Published: July 2006

In this paper I investigate the resource partitioning of roach Rutilus rutilus and bleak Alburnus alburnus in two eutrophic lakes in SE Norway. Zooplankton was the preferred food item for both species during summer, whereas blue‐green algae dominated the diet in September/October. There was no diet overlap in May, with the roach feeding mainly on detritus and the bleak feeding on surface insects. During summer the diet overlap increased, reaching high values in autumn. Habitat overlap was close to unity in spring and early summer. Coinciding with increasing diet overlap during summer and autumn the overlap in habitat decreased.
Are Chaoborus larvae more abundant in acidified than in non‐acidified lakes in Central Canada?
Authors: Yan N. D. , Nero R. W. , Keller W. , Lasenby D. C.
Published: July 2006

Eriksson et al (1980) hypothesized that the abundance of certain macroinvertebrate predators, such as larvae of the phantom midge Chaoborus, should increase in acidified lakes because of the elimination of fish. To examine the influence of pH and presence of fish on Chaoborus abundance, we surveyed Chaoborus populations in 33 lakes in Ontario, Canada which ranged in pH from 4.5 to 7.4. Chaoborus larvae were not more abundant in the acidified lakes that were devoid of fish than in the remaining lakes. Therefore, we concluded that pH and presence of fish are not prime determinants of total Chaoborus abundance in Canadian Shield lakes. We hypothesized that significant increases in Chaoborus abundance should only be anticipated when fish populations are eliminated by acidification of relatively nutrient rich lakes.
Life history of the moose Alces alces: relationship between growth and reproduction
Authors: Sæther Bernt‐Erik , Haagenrud Hans
Published: July 2006

We studied the relationship between increase in body weight and reproductive performance in different populations of Norwegian moose to evaluate costs associated with early onset of reproduction, viz. whether early onset of reproduction was correlated with low adult body weight or reduced adult fecundity.

The mean carcass weight of non‐ovulating yearlings was significantly lower than for ovulating yearlings. However, those 2.5 yr old females that conceived as yearlings were lighter than non‐reproducing females of the same age. Thus, to begin to reproduce as a yearling was assumed to be expensive because it reduces the possibilities for further growth. The cost associated with reproduction was further illustrated by the fact that the difference in mean carcass weight from age 2.5 to 3.5 yr of females that produced calves in both years, was less for the females from regions with lowest mean yearling weights, i.e. regions with probably the lowest resource availability.

In populations with high mean yearling carcass weights, the proportion of cows with calf and the number of calves per pregnant female in the early reproductive phase (2.5 or 3.5 yr old) were higher than in populations in which the mean yearling weights were low. There was a negative correlation between growth rate in the population after 1.5 yr of age and the mean yearling carcass weight. Thus, low yearling weight was associated with a prolonged period of growth and thereby a reduced reproductive output during the first year of the female's life.

For old females (≥ 9.5 yr old) the number of calves produced per pregnant female was highest in populations where yearling carcass weights were highest. Furthermore, mean yearling weight and the mean adult female weight were positively correlated in those regions. This relationship suggests that within this species early onset of reproduction is not related to retarded reproduction or lower weight later in life. We suggest that the moose has been selected for an early onset of reproduction.
Incubation rhythm in the great snipe Gallinago media
Authors: Løfaldli Lars
Published: July 2006

The incubation rhythm of four female great snipe was monitored with telemetric equipment. The mean daily incubation constancy was 90.3 ± 2.0 (SD) per cent, and the mean daily time off the nest amounted to 139.8 ± 28.8 min. The number of recesses per day averaged 8.7 ± 1.9, with a mean duration of 15.7 ± 6.1 min. Generally, the birds incubated for long bouts during the night, and left the nest frequently during the daylight hours.

Recesses were concentrated in the warmest part of the day in cool periods, but were more evenly distributed throughout the day in warmer periods. Recess duration decreased with decreasing temperature. These adjustments minimize egg cooling when the bird is off the nest, and thus allow the incubating bird more time to feed without lowering the mean egg temperature.

Calculations of the cooling rates of eggs indicate that the bird minimizes incubation energy expenditure as far as possible, but without letting the eggs cool beyond the temperature of no embryonic development.
Associations between corticolous microarthropod communities and epiphytic cover on bark
Authors: André H. M.
Published: July 2006

The discontinuous bark cover formed by epiphytic lichens and algae provides a mosaic of microhabitats for the fauna. Multivariate analyses applied to 1800 samples collected in Belgian Lorraine (southern Belgium) during each of the four seasons has made it possible to distinguish five major classes of arthropod microcommunities. Two of them are confined to special habitats or places at certain seasons, viz.

a Pseudochermes fraxini (Homoptera) community found on Fraxinus during the summer, and “trophically” different from others;

a Vertagopus arborea (Collembola) community observed in foliose lichens in St. Mard mainly in winter.

The three other classes are directly related to the epiphytic cover, viz.

a Dometorina plantivaga (Oribatida) community found in crustose epiphytes;

an Eueremaeus oblongus/Trichoribates trimaculatus (Oribatida) community sheltered by foliose lichens;

an Entomobrya nivalis (Collembola)/Cerobasis guestfalicus (Psocoptera) community observed in fruticose lichens.

The ecological meaning of those microcommunities (mosaic and stratification patterns, seasonal variation, succession) is discussed. The results support the hypothesis that corticolous microcoenoses are associated with the epiphyte type and that their composition is greatly affected by the vegetation stratification pattern on bark.
The population dynamics of the crested newt Triturus cristatus at a pond in southern England
Authors: Verrell Paul , Halliday Tim
Published: July 2006

The population dynamics of a population of crested newts Triturus cristatus were studied in 1983 at a pond in southern England, Three length classes of individuals were distinguished. Adult newts between 67 and 84 mm snout‐vent length migrated to the pond in spring, on days when the temperature approached 5°C. Males tended to arrive earlier than females and to remain in the pond for longer. A second period of immigration of smaller adults, between 57 and 70 mm in length, took place in the autumn; these newts overwintered in the water and may have been about to breed for the first time. Juvenile newts measuring between 40 and 51 mm in length also visited the pond during the spring and summer. Immigrant male and juvenile crested newts were significantly higher in weight than emigrants: there was no significant difference between the weights of immigrating and emigrating females.
Frugivory of transient and wintering European robins Erithacus rubecula in a Mediterranean region and its relationship with ornithochory
Authors: Debussche M. , Isenmann P.
Published: July 2006

Stomach contents of 209 dead and droppings of 57 mist‐netted migrating or wintering European robins Erithacus rubecula in a Mediterranean area in southern France showed the following seasonal trends: (1) a dominance of invertebrates in early autumn, (2) a dominance of fruits in mid‐autumn, (3) acorns being important in midwinter, and (4) a strong dominance of invertebrates at the end of winter and in early spring.

The fruits of 23 plant species had been consumed. The most widespread and abundant ones were also the most commonly taken (Rubia peregrina at the regional level and Viburnum tinus at a local one). The size of these fruits ranged from 4 to 12 mm. mostly between 6 and 8 mm. Owing to the amount of fruits consumed and the numbers of birds involved, the European robin is one of the few main dispersers of the numerous fleshy‐fruited plant species of the Mediterranean area. Nevertheless, a correct evaluation of its role is only possible within the dense network existing between these plant species and all their dispersers (mainly birds but also mammals).
Effect of lake acidity and morphometry on the distribution of aquatic birds in southern Quebec
Authors: DesGranges J.‐L. , Darveau M.
Published: July 2006

More than half the lakes in the deciduous and boreal forest regions of southern Quebec harbour at least one aquatic bird species during the nesting period. Although the number of nesting pairs per lake is generally small, those pairs are most commonly seen on lakes with a surface area of more than 15 ha, a winter pH lower than that of normal rain (i.e. < 5.6), an irregular shore configuration marked by abundant riparian vegetation, and islands.

In a correspondence analysis, the first axis, representing lake acidity, explains 68% of the total variance. The common goldeneyeBucephala clangula, which is frequently seen on the most acidic lakes, and the American black duckAnas rubripes, which tends to avoid acidic lakes, show the largest contributions to that axis. The second axis describes an altitude/surface area gradient and brings the cumulative percentage of explained total variance to 94%; the great blue heronArdea herodiasand the common loonGavia immerprimarily use large, low‐altitude lakes, whereas the ringnecked duckAythya collarisand the American black duck are often found on the smaller, higher‐altitude lakes. Those results are discussed as they relate to the feeding requirements of the various species of bird and the biology of their main prey. The ecological segregation of the three waterfowl species is attributed to interspecific competition.
Diel activity patterns of South Scandinavian high mountain ground beetles (Coleoptera, Carabidae)
Authors: Ottesen Preben S.
Published: July 2006

Fourteen species of carabids were studied throughout the snowfree season in outdoor arenas above the timberline at Finse, South Norway (60°36′N, 7°30′E). Ten species were nocturnal. Onset of nocturnal activity occurred after termination of twilight with peak activity before midnight, but in June, with less than 1 h of darkness, activity was extended into evening twilight, the peak being around midnight. Linear regressions between ground surface temperature and nocturnal activity predicted zero activity in the range −2.0 to0.8°C, mean −0.5°C, indicating that activity is possible on most nights throughout the snowfree season. Two diurnal species had activity threshold temperatures at 4 and 8°C, respectively, the former with a peak at 16°C and an upper threshold at 28°C.

The proportion of nocturnal species in the study area was significantly greater than in lowland open fields. Large and common species were mainly nocturnal, while small and rare species were mainly diurnal. It is suggested that nocturnalism in the South Scandinavian high mountains is a response to avoid bird predation and desiccation.
Environmental control of the prostrate growth form in two high arctic grasses
Authors: Gruike N. E. , Bliss L. C.
Published: July 2006

In the High Arctic, leaf angles of graminoids are lower than would be expected to optimize absorption of incident solar radiation. Inflorescence, leaf, and culm angle of two prostrate grasses, Phippsia algida and Puccinellia vaginata, were measured in a variety of plant communities with differing microtopographic and microenvironmental conditions (surface relief, soil stability, soil moisture, and soil and air temperature). Growth form was found to be controlled primarily by environmental factors. Both species exhibited a plastic response to an amelioration of physical factors in situ. Leaf angles of both species were higher under conditions of increased soil moisture and temperature, and decreased vapor pressure deficit and windspeed. Adaptation to reduce the severity of the environment apparently holds a greater selective advantage than adaptation to maximize leaf orientation to a low sun angle.
Annual activity and life cycles of carabid beetles in two forest communities
Authors: Loreau Michel
Published: July 2006

The annual activity and life cycles of thirteen species of carabid beetles coexisting in two forests in Belgium were studied by recording above‐ground activity of adult and larval populations, and by examining the reproductive condition of adults in the course of the year. The cycles were far more complex and diversified than suggested by previous works. Besides typical “spring breeders” and “autumn breeders”, species were found

with a continuous reproductive period from spring to autumn,

with several variable breeding periods, part of the population overwintering as adults, part as larvae,

with a breeding period that begins facultatively in autumn and continues the next spring,

with a winter reproduction.

Comparison of life cycles in Scandinavia and In Belgium also shows their variability in relation to climate. More flexible and varied cycles are made possible by the milder winters further south. Existing classifications of life cycles of carabids appear unable to account for such a diversity and variability.
Nutritional ecology of yellow‐bellied marmots in the White Mountains of California
Authors: Carey Hannah V.
Published: July 2006

This study examined the basis of diet preference in a mammalian hibernator, the yellow‐bellied marmot Marmota flaviventris, in the White Mountains of California. Preference indices calculated from dietary data and food plant availability in the habitat indicated that forb species were preferred over graminoids, particularly in the spring and early summer. Chemical analysis of food plant species suggested that marmots preferred forbs over graminoids because of their lower fiber (cellulose) content and higher concentrations of phosphorus, sodium and possibly protein. Inclusion of graminoids in the diets was probably due to their greater availability in the habitat coupled with the need to maximize the rate of nutrient intake during the short (4–5 month) active season. Seasonal changes in diet composition were noted which may reflect, in part, temporal changes in nutrient demands.