bluuebunny/crossref_metadata_2025 huggingface dataset:
Reproductive effort in cotton grass tussock tundra
Authors: Chester Ann L. , Shaver G. R.
Published: July 2006

Eriophorum vaginatum ssp. spissum is a dominant plant species of undisturbed cotton grass tussock tundra in Alaska. It also quickly invades and dominates recently disturbed sites. The hypothesis tested in this research was that the success of E. vaginatum on disturbed sites might be achieved through a higher allocation of biomass to reproductive structures relative to other tundra species. Reproductive allocation of tundra plants in general also was compared with plants of the temperate zone. The results indicate that E. vaginatum is about average among the common tundra species in terms of total reproductive allocation, allocation to seeds, and the proportion of total reproductive allocation that is accounted for by viable seeds. Tundra species, on a relative basis, allocate less biomass to all reproductive structures than temperate species but not necessarily less biomass to the output of viable seeds.
Seedling dynamics of some cotton grass tussock tundra species during the natural revegetation of small disturbed areas
Authors: Chester Ann L. , Shaver Gaius R.
Published: July 2006

The dynamics of seedling establishment, and growth of native cotton grass‐tussock tundra species were studied during the natural revegetation of small bare areas excavated in tussock tundra. The seedlings of Eriophorum vaginatum spp. spissum and Carex bigelowii, two sedge species, established most successfully. Few seedlings of nonsedge species emerged with the small disturbances. Most seedling emergence occurred early in the first growing season following the excavation of the bare areas. The density of emerged seedlings was higher in bare areas excavated in the autumn preceding the observations, rather than in bare areas excavated at the start of the first season of observation. After two growing seasons, survival of seedlings was not affected by the time the seedling emerged within the growing season. Eriophorum vaginatum was the most abundant species because it: (1) had the highest seedling emergence rates, particularly early in the growing season: (2) produced more tillers per seedlings; and (3) had a higher growth rate per seedling than C. bigelowii.
Seedling density and seedling survival in Alaskan cotton grass tussock tundra
Authors: McGraw J. B. , Shaver G. R.
Published: July 2006

Previous workers have suggested that reproduction by seedling establishment is less important in the maintenance of tundra vegetation than in temperate areas, but few quantitative data are available. Seedling densities were studied at 11 tundra sites in or near disturbed and undisturbed cotton grass tussock tundra in Alaska, and numerous seedlings were found. Examination of seedling age structures suggests that at least Ledum palustre and probably also Empetrum nigrum do replace themselves by seed in undisturbed tundra. Seedling densities vary greatly depending on the substrate available for establishment.
Effect of water potential on seed germination
Authors: Oberbauer Steve , Miller Philip C.
Published: July 2006

The response of seed germination to substrate water potential was determined for several plant species of the arctic tundra. Seeds were collected from Cape Thompson and Eagle Summit, Alaska and germinated on dialysis membranes over water solutions of polyethylene glycol with osmotic potentials of 0 to −6 bars. Germination did not occur with potentials below −3 bars, except for three fellfield species. Germination was delayed at lower osmotic potentials. Because the response of most species was similar, substrate water potential is probably not a factor affecting the establishment of most tundra plant species from seeds.
The Lake Langvatn fertilization experiment: Introduction
Authors: Langeland Arnfinn
Published: July 2006

The limnology of Langvatn situated in Trøndelag county in Central Norway, has been studied for five years (1974–1978). In two years, 1975 and 1976, the lake was fertilized with a general fertilizer to change feeding conditions for the fish food organisms. Reasons for the choice of the lake are described together with a brief description of the lake itself, its catchment area, location, geological origin and the effect of human influence.
The effect of nutrient addition on the phytoplankton community of an oligotrophic lake
Authors: Reinertsen Helge
Published: July 2006

This investigation was performed during a 5‐yr period (1974–1978) in the oligotrophic Lake Langvatn, Central Norway. In 1975 and 1976 the lake was enriched with a commercial fertilizer, In 1975 increase in phytoplankton biomass was first recorded more than three weeks after the fertilization started, despite a near fivefold increase in the primary production after fertilizer application. The mean seasonal biomass increased from c. 3500 mg wet weight m−2 in 1974 to 4400 mg in 1975. In 1976 the biomass increased to near 9600 mg −2 and the seasonal primary production to 49.0 g C m−2 (22.2 g C in 1975), despite a reduction in the nutrients added. Chrysophytes constituted the largest share of the seasonal algal biomass in all years, but in fertilization periods cryptophytes dominated in 1975 and diatoms, chlorophytes and cryptophytes in 1976. The highest biomass turnover rate was recorded during a period of cryptophyte dominance. The different biomass and production development in the fertilization years may be explained by a change in the consumer level.
Interactions between phytoplankton and zooplankton in a fertilized lake
Authors: Langeland Arnfinn , Reinertsen Helge
Published: July 2006

The limnology of an oligotrophic lake, Langvatn, situated in Trøndelag county in Central Norway, has been studied for five years (1974–1978). In two years, 1975 and 1976, the lake was fertilized with a general fertilizer to change feeding conditions for the zooplankton. Mean phytoplankton biomass in the epilimnion and primary production for the years (1974–1978) were 417, 618, 1370, 607 and 779 mg m−3 and 10.6, 22.2, 49.0, 26.8 and 17.7 g C m−2 yr−1, respectively. Cladocerans were the dominant herbivore group in 1974 and 1975 and Rotifera in the next three years. The main difference in the interaction between phytoplankton and zooplankton occurred when cladoceran dominance gave way to rotifer dominance. Heavy phytoplankton grazing by cladocerans in 1974 and 1975 stabilized the biomass and maintained it at a low level, which also resulted in a relatively low primary production. The rotifer‐dominated community during the years 1976–1978 did not possess the ability to maintain a stable level of algal biomass. Primary production was also relatively high during these years.
Profundal chironomid populations during a fertilization experiment in Langvatn, Norway
Authors: Aagaard Kaare
Published: July 2006

Populations of Heterotrissocladius subpilosus and Phaenopsectra (Sergentia) coracina were studied from 1974 to 1978 in Langvatn, South‐Trøndelag, Norway. During 1975 and 1976 the lake was fertilized respectively by 1600 kg and 1000 kg fertilizer, (20% N, 4,8% P).

Fertilization had a positive effect on primary production and zooplankton. The effect on the two chironomid species, which both need more than one year for development, was ambiguous. However, there was a positive relationship between the density of H. subpilosus larvae and the primary production.

The number of P. (S.) coracina larvae steadily increased during the investigated period. Production estimates gave values in the range 0.6–1.5 g w.w. m−2 yr−1 for H. subpilosus and ca 2.3 g w.w. m−2 yr−1 for P. (S.) coracina.
The geology of Kaldvelladalen
Authors: Andersen A. B. , Rueslåtten H. G.
Published: July 2006

Langvatn lake is a large waterfilled kettle hole in glaciofluvial deposits developed during the last deglaciation. The main outflow from the lake occurs by percolation through the permeable sediments at the shoreline.

The sedimentary rocks and sediments (calcite bearing) within the watershed influence the quality of the lake waters.
Residue levels of organochlorine and mercury compounds in unhatched eggs and the relationships to breeding success in white‐tailed sea eagles Haliaeetus albicilla in Sweden
Authors: Helander Björn , Olsson Mats , Reutergårdh Lars
Published: July 2006

Eighty‐five unhatched eggs from 68 white‐tailed sea eagle clutches were collected during 1965–1978 along the Baltic coast and in Lapland. The eggs were analysed individually for residue levels of DDT and its metabolites, PCB and mercury. Pooled samples were analysed for levels of dieldrin and hexachlorobenzene (HCB). The variations in residue levels within and between clutches were studied before the material was grouped for investigations of relationships between reproduction and contamination.

Levels of DDE, PCB and mercury were significantly higher in the Baltic as compared to the Lapland material. In the Baltic, the reproductive success on a clutch basis and on a nest basis was significantly and negatively correlated to the egg residue levels of DDE and PCB; no correlation was found with mercury. Critical ranges were estimated to 500–600 mg kg1of DDE and/or 800–900 mg kg−1of PCB (lipid basis). The levels of dieldrin and HCB in the pooled samples were not considered important to reproduction. In a comparative study including six sea eagle and six bald eagle populations, productivity showed the strongest correlation with DDE.
Organic matter and phytomass on three north Swedish tundra sites, and some connections with adjacent tundra areas
Authors: Jonasson Sven
Published: July 2006

The amount of organic matter and phytomass is estimated on three types of shrub tundras in northern Sweden. The organic matter ranges from 23600 kg ha−1 on a dry dwarf birch tundra rich in dwarf shrubs, to 59600 kg ha−1 on a moist moss‐rich dwarf birch‐willow tundra. The phytomass reaches a peak of 14700 kg ha−1 on a mesic dwarf birch tundra, compared with 9230 and 8660 kg/ha−1 on the dry and moist sites. The belowground share of the phytomass decreases from 68% on the dry site to 54 and 47% on the mesic and moist tundras. Some adaptive advantages of belowground storage as well as of different life‐ and growthforms in different vegetational regions and local environments are discussed. Broad scale regional connections with tundra vegetation in other parts of Scandinavia and the Soviet Union are proposed, based on similarities in phytomass, distribution of plant groups, life‐ and growthforms. It is shown that the north Swedish tundra has many features in common with the subarctic shrub tundra in the USSR.
Loss‐on‐ignition and carbon content in a beech forest soil profile
Authors: Christensen Bent Tolstrup , Malmros Per Åkesson
Published: July 2006

The use of loss‐on‐ignition (LOI) and carbon content (C‐content) in estimating soil organic matter is examined. To evaluate the assumptions behind the use of these methods, the conversion factor (LOI/C‐content) is examined as a function of depth and spatial variability.

Due to increasing variability with depth no general relationship between LOI and C‐content can be established for horizons below 60 cm. For horizons above 60 cm it is demonstrated, that more than one conversion factor is needed.

The application of a regression equation to correct for inorganic losses is shown to be problematical. This is due to the variability in inorganic losses and the varying C‐content of the organic matter.
Growth and condition of three introduced reindeer herds on South Georgia: the effects of diet and density
Authors: Leader‐Williams N. , Ricketts C.
Published: July 2006

The patterns of growth and seasonal changes in body weight and fat reserves of three herds of introduced reindeer on the sub‐Antarctic island of South Georgia were investigated. Two of the herds, derived from the same stock, were at different densities but the higher density herd was on the better range. In this herd there was a significant growth advantage to the male reindeer, but not to females. The third herd, of a different stock, was also at a lower density on a range which had become overgrazed. The two lower‐density herds showed the same annual changes in body weight and only slight differences in the fluctuation of their fat reserves. In addition, body weights in both these herds fluctuated to the same degree as those of a barren‐ground caribou in the Northern Hemisphere but fluctuations in the fat reserves of South Georgia reindeer were considerably more severe. The results suggest that the South Georgia reindeer herds are limited by forage availability.
On the ecology of littoral Oligochaeta of an oligotrophic Finnish lake
Authors: Särkkä Jukka
Published: July 2006

In material sampled from 0.5–6 m on two sampling dates and three subareas the dominant Oligochaeta were Limnodrilus hoffmeisteri Claparède and Peloscolex ferox (Eisen), both composing more than 30% of the abundances of oligochaetes present. The numbers of Oligochaeta were mostly higher in August than in May. Regional differences could be found although the lake seems to be very homogenous. Temporal and vertical variations were detectable in separate subareas. The oligochaete biomass was maximal at 2 m depth. In soft bottom sediments the oligochaetes composed 15.9% of macrobenthos biomass and 12.2% of numbers, but on the stony bottom only 1.9% of numbers. The ratio of Oligochaeta/Chironomidae was similar to those in profundals of oligotrophic lakes. Correlation coefficients between species and two measures of niche overlap were in partial agreement. A temporal niche seems to occur: when the chironomid larvae decrease during the summer, the oligochaetes increase.
Effects of selective grazing by cattle on the reproduction of Plantago maritima
Authors: Jerling Lenn , Andersson Marja
Published: July 2006

The grazing areas of cattle in a Baltic sea‐shore meadow changed during the summer. The effects of this on the demography of Plantago maritima was studied. This species is distributed over most parts of the area and suffers differently from grazing in different areas. It was found that the losses of flowers due to grazing, was severe and that the density peak of Plantago maritima coincides with the least grazing intensity. Flower‐spikes established in different time‐periods are disproportionally represented as seed‐dispersers and this may be of importance in regeneration since early and late flowers bear seeds of different size.
The climate of a Danish beech wood, Hestehaven, eastern Jutland
Authors: Rasmussen Søren , Nielsen Mogens Klitgaard , Hansen Jens P. N.
Published: July 2006

The wind profile in the IBP beech stand and the vertical temperature distribution in the same beech stand and in a neighbouring clearing were investigated. In addition the temperature and humidity conditions in the trunk space of the beech stand and in the clearing were compared. The precipitation components were investigated during two periods.

Because of the topography and the small extent of the wood the wind profile depends strongly on the wind direction. Maximum temperatures were found to occur in the upper part of the canopy during in‐leaf periods. During leafless periods the temperature distribution indicates the presence of two distinct levels of energy exchange, Advection of airmasses from the adjoining bay strongly influences the climate of the wood. Because of the density of trees and the narrow fanshaped canopies, yearly throughfalls amount to 55–60% of the total precipitation, while stemflows amount to as much as 12%.
Phytoplankton production in relation to physico‐chemical conditions in a small, oligotrophic subarctic lake in South Greenland
Authors: Mæhl Peter
Published: July 2006

Phytoplankton production and physico‐chemical parameters were measured during the summers of 1976 and 1977 in Lake 95 at 60°52′N, 46°01′W (area 8 ha, z 6.9 m). The duration of lake stratification during summer was weather dependent. Concentrations of total‐CO2 ranged from 2.04 mg l−1 (surface) to 4.02 mg l−1 (bottom during stratification). Nutrient concentrations were generally low, and systematic seasonal variation could not be detected with certainty. Vertical distribution of primary production typically showed a distinct maximum followed by a decline with depth. The low production, both per unit area (max. 60 mg C m−2 d−1) and per unit volume (max, 14.3 mg C m−3 d−1), and the annual production of 4.7 g C m−2 classified the lake as extremely oligotrophic.
Life histories, microdistribution and drift of two mayfly (Ephemeroptera) species in the Pembina River, Alberta, Canada
Authors: Ciborowski Jan J. H. , Clifford Hugh F.
Published: July 2006

Ephemerella inermis Eaton is a univoltine species that emerges in July. Eggs hatch in August and larvae grow rapidly in autumn and spring, but not during winter. Baetis tricaudatus Dodds produces three cohorts per year. Emergence periods occur in early June, July and early September. Only one cohort overwinters as larvae.

Microdistribution of both species is controlled largely by the discharge pattern of the river. During 1978, a year of frequent floods, animals were equally distributed among slow and fast water portions of the river. Nocturnal drift densities of both species were much greater in slow than in fast water areas. During 1979, a year of relatively stable flow, benthic larval densities were significantly greater in fast water than in slow water.

Early instar E. inermis larvae are most abundant in nearshore areas, but move to deeper water in late autumn. Baetis tricaudatus larvae are seldom numerous in near‐shore areas.

Densities of both species were positively associated with concentrations of detritus and of other invertebrates, but only when relationships were considered in areas of similar current velocity independently of season.
A two‐year study of leaf litter decomposition as related to macroclimatic factors and microarthropod abundance in the southern Appalachians
Authors: Seastedt T. R. , Crossley D. A. , Meentemeyer V. , Waide J. B.
Published: July 2006

Chestnut oak Quercus prinus L. litter in the southern Appalachian Mountains of the United States decomposes slowly during winter and more rapidly in other seasons. This pattern differed from other studies of litter decomposition in more northern environments where decomposition rates were relatively constant throughout the year or more rapid beneath a winter snow cover. The pattern observed can be approximated by using monthly actual evapotranspiration estimates as a correction factor for the decomposition constant, k, in the commonly‐used negative exponential decomposition model.

Mean microarthropod densities increased from a seasonally weighted estimate of 18.2 ind. g−1 litter during the first year of decomposition to 73.6 ind. g−1 litter during the second year. In spite of this increase, no difference in the rate of weight loss of the litter was observed between the first and second year of the study.
Prey abundance and reproductive success of the golden eagle Aquila chrysaetos in Sweden
Authors: Tjemberg Martin
Published: July 2006

Reproductive output of the golden eagle Aquila chrysaetos (L.), was studied in two areas within the species distribution in northern Sweden during 1975–1980. Reproductive success was compared with the abundance (based on hunting bag statistics) of small game prey species and with the microtine cycles. The proportion of golden eagle pairs with successful breeding and the number of young produced per occupied territory varied greatly between years (21–85% and 0.27–1.24, respectively). In the northern study area I found a significant correlation between the proportion of pairs with successful breeding versus total hunting bag of small game species. There were also significant correlations between vole density and breeding success one year later. This was not the case in the southern study area, mainly due to a good reproductive year for golden eagles in 1977 when small game species were scarce. The good reproductive output in 1977 may be explained by favourable weather conditions that spring. Whether breeding occurs or not is probably determined by prey abundance early in spring just before the golden eagle female lays her eggs.
The effects of water temperature, ionic content and total dissolved solids on Nephelopsis obscura and Erpobdella punctata (Hirudinoidea, Erpobdellidae)
Authors: Linton L. R. , Davies Ronald W. , Wrona Frederick J.
Published: July 2006

Using a three‐way factorial experimental design the effects of water temperature, ionic content (water type) and total dissolved solids on the mortality rates of Nephelopsis obscura and Erpobdella punctata were examined. A strong interaction between temperature and water type and temperature and total dissolved solids was observed on the mortality of E. punctata. Other than differences in mortality due to reproductive condition, N. obscura showed uniformly low mortality not significantly affected by temperature, water type or total dissolved solids. Thus the numerical dominance shown by N. obscura in Alberta and Western Canada could be explained by the differentially higher mortality of E. punctata with respect to the three tested independent variables.
Food of the white‐tailed eagle Haliaeetus albicilla in Greenland
Authors: Wille Frank , Kampp Kaj
Published: July 2006

Six nests of white‐tailed eagles in the southernmost Greenland were watched during the nestling period and food items recorded photographically by remote controlled cameras. The species composition of the food was representative even for the adult eagles' diet. Fish made up a major part of 90%, various bird species and arctic fox pups the remaining 10%. The total intake of an eaglet amounted lo 50 kg from hatching to fledging. The daily requirements of fledglings, some 800 g fish food, are equal to previously reported values for older birds. The rate of food consumption of eaglets is constant through most of the nestling period.
Changes in Danish farmland habitats and their populations of breeding birds
Authors: Møller Anders Pape
Published: July 2006

Habitat changes and the breeding bird populations were studied at Kraghede, N Jutland the years 1970–1980. Generally, agricultural practice was intensified leading to an increase in the area used permanently for growing barley, and the abandonment of grasslands and meadows. Animal husbandry decreased, until it was restricted to a small number of farms.

These habitat changes were the largest ones to occur in the Danish landscape for some 150–200 yr and had a significant influence on the breeding birds. Species confined to the meadows, such as the lapwing Vanellus vanellus, meadow pipit Anthus pratensis and others, decreased by 50–80% or even more. Species associated with the grassland when feeding, like the swallow Hirundo rustica, starling Sturnns vulgaris and magpie Pica pica, all had lower population levels at the end of the 1970's compared to those at the beginning of the decade.
Seasonal responses of lentic midge assemblages to environmental gradients
Authors: Thorp James H. , Chesser Ronald K.
Published: July 2006

We examined biotic and abiotic factors associated with density and diversity of larval midges (Diptera: Chironomidae) in the littoral zone of Par Pond, an 1100 ha cooling reservoir located near Aiken, South Carolina, USA. A total of 144 core samples were removed from 12 areas during each of 3 sample periods. Principal component analysis. Mantel analysis, and various univariate statistical tests were used to detect seasonal differences in (1) associations among areas and genera of Chironomidae, and (2) responses of midges to a multi‐faceted environmental gradient. Water temperature, which in this case was a function of both season and thermal effluents, was the factor most strongly associated with relative changes in density and diversity within the chironomid assemblages. Plant biomass and/or plant diversity were significant factors correlated with midge density and diversity. Both particle size and organic content of the substratum, which varied little across stations, were relatively unimportant factors. Despite the presence of a multifaceted environmental gradient, the composition and relationships within the midge assemblages were remarkably similar across areas although total abundance and diversity varied.

On the basis of their similarity in structure and function, we classify the midge assemblages within the reservoir as members of the same community. However, in response to dissimilar or unequal selective forces (principally the area‐specific effects of thermal effluents), these assemblages appear to behave environmentally as multiple units rather than as a single component of the benthic community in Par Pond.
Mortality in Svalbard reindeer
Authors: Reimers Eigil
Published: July 2006

Mortality rates in Svalbard reindeer followed the “U”‐shaped pattern, with higher mortality rate among calves and old animals than in middle aged individuals. Assuming a stable population size, the mortality data predict a 16.2% annual mortality and recruitment rate among 6 months and older animals, and a male:female sex ratio of 48.5:51.5 among 1‐yr old and older. Both predictions are supported by field data. Female mortality rate increased and differed from the male rate in the age interval 2‐4 yr, while the male rate increased sharply and differed permanently from the female rate in the age interval above 6 yr. First and last breeding are thought to cause the increased mortality among 2–4 and 11–13 yr‐old females. Increased involvement in rutting activities with age associated with lower grazing activity and depletion of fat reserves probably cause the increasing mortality rate among the 6+ yr males. Maximum life span was 17 yr in females and 12 yr in males. Apart from the unknown but possibly high neonatal calf‐mortality, only few animals died during summer or during the rut in autumn. Death among calves, yearlings and most of the females occurred before antler‐shedding in May‐June. Most of the 2‐yr and older males died after antler shedding, which occurs from December among the oldest and during April‐May among the younger males. Hence, the major part of the mortality takes place in spring. The lack of visible subcutaneous and femur fat in most carcasses indicated starvation as the major mortality cause.
Abundance and trophic structure of pine forest nematodes in relation to soil layers and ground cover
Authors: Magnusson Christer
Published: July 2006

In a 15‐20 yr old forest of Scots pine, the total number of nematodes under the dominating cover grass Deschampsia flexuosa, reached 4.0–4.7 × 106 ind. m−2 stone free soil, corresponding to densities of 8770–9090 and 3500–3790 ind. 100 ml−1 in FH and mineral soil, respectively. Root/fungal feeding nematodes formed 53–59% of the total nematode fauna. The majority in this group was potential mycophages. Obligate root feeders formed only 11–17% of the total number of nematodes. Soil layers and ground cover affected the abundance of trophic groups. Bacterial feeders, potential mycophages and miscellaneous feeders reached their maximal abundance in the FH‐layer. Obligate root feeders tended to reach higher densities in the mineral soil. Higher abundance values of most trophic groups were found under forest grass. The species Calamagrostis arundinacea had a striking positive effect on the relative and absolute abundance of obligate root feeders. This group may be most numerous in early stages of forest development.
Abundance, distribution and feeding relations of root/fungal feeding nematodes in a Scots pine forest
Authors: Magnusson Christer
Published: July 2006

In a 15–20 yr old forest of Pinus sylvestris, Tylenchus spp., Paratylemchus spp? and Malenchus tantulus were the most abundant stylet‐bearing nematodes. Soil layers and ground cover affected the abundance. Mycophagy was observed for Tylenchus sp., M. tantulus, Aphelenchoides sp. and Tylencholaimus stecki. Feeding on roots of the forest grass, Deschampsia flexuosa was recorded for W. tantulus, Paratylenchus spp? and Rotylenchus sp. The latter fed also on pine roots. Connections occurred between feeding habits and field distribution. The facultative feeding habit of M. tantulus probably allowed this species to reach higher numbers under D. flexuosa. The importance, in the field, of the grass Calamagrostis arundinacea for Paratylenchus spp? was confirmed by laboratory experiments. As pine was a non‐host, these nematodes were probably grass feeders. Paratylenchus spp? dominated the obligate root feeders with forest grass being a key‐factor for the group abundance. Suspected high densities of Paratylenchus spp? on clearings should not affect the growth of pine seedlings and although Rotylenchus sp. to some extent reduced seedling growth its pathogenic status on P. sylvestris was doubtful.
Summertime activity pattern of the longtail vole in Alaska
Authors: Van Horne Beatrice
Published: July 2006

Activity of the longtail vole Microtus longicaudus, was monitored in a 25‐m2 outdoor enclosure by recording movements of individuals in and out of an artificial nest box. Diurnal activity occurred in irregular bouts, while nocturnal activity was relatively continuous. Diurnal activity was 63% of nocturnal activity. There was a distinct 2‐h period prior to and including sunrise, in which the level of activity was lower than that during normal nocturnal and diurnal periods. The activity level immediately prior to sunset was similar to the diurnal level and was followed by an increase just after sunset.
Foraging behaviour of the middle spotted woodpecker Dendrocopos medius in Sweden
Authors: Pettersson Börje
Published: July 2006

During winter and spring the oak Quercus robur, was the tree species most utilized by middle spoiled woodpeckers. In March, saptrees, mainly maples Acer platanoides, were preferred for a short period. In winter the birds foraged in the crowns of oaks but in spring they preferred lower stem parts. Dead branches were utilized more in winter than in spring. The birds mostly used a gleaning and probing technique, which may render the species more senstitive to severe weather conditions than other woodpecker species. Arthropods collected from trees were mostly spiders, beetles, thrips or springtails. The nestlings were mainly fed on scale insects and larvae of moths and sawflies. The oak habitat specialization is believed to be caused by competition for food with other gleaning forest birds. Food shortage might possibly occur during periods of bad weather, causing increased mortality.
Nutrient content and dynamics in north Swedish shrub tundra areas
Authors: Jonasson Sven
Published: July 2006

Forbs and leaves of deciduous shrubs had high concentrations of Ca, Mg, K, P, and N. Deciduous dwarf shrubs had intermediate concentrations but higher than evergreen dwarf shrubs. Monocots, cryptogams, woody and belowground tissues had low concentrations.

Plant nutrient concentrations and nutrient content in soil organic matter increased from dry towards moist tundra areas.

The residence time of nutrients was considerably less than ten years in surface litter, but several decades or centuries in total organic matter. The longest residence time was found in the moist part of the tundra.

N, K, and P in Betula nana leaves were translocated to a great extent prior to leaf fall, whereas Mg and particularly Ca were only slightly translocated. As on other tundra areas shortage of nutrients probably limits plant growth. In that case short supply of N and F seems most probable due to retention in litter and soil organic matter.
Successional trends in the energetics of forest bird communities
Authors: Glowaciński Zbigniew , Weiner January
Published: July 2006

Thirty forest bird communities were studied with regard to the changes in structural indices (number of species, density, biomass, species diversity H′) and in energetics (energy flow A, production P, ecological efficiency P/A) in temporal and spatial gradients. All these characteristics increase during temporal succession; in natural deciduous forest there is a two‐peak pattern of the increase, with the maximum in 15–20 yr old forest (“time ecotone”; A = 692.9 Megajoules ha−1 season−1, H′= 4.2 bits), In artificially managed pine forest these indices rise monotonically, reaching a maximum in sub‐climax (A = 426.2 MJ ha−1 season−1, H′= 4.2 bits). In a deciduous forest a tendency exists to decrease the ecological efficiency (from 8% to 2%), while in a coniferous stand this variable remains low (2%) and almost constant during succession. In a spatial gradient, the highest values of energy flow and species diversity occur in forest stands with moderate soil/water regime and of ecotonal character (A = 851.2 MJ ha−1 season−1, H′= 4.5 bits). All mature forest bird communities show similar values of diversity (4.2–4.5 bits) and ecological efficiency (appr. 2%), though they differ in the rate of energy flow. The relation of these findings to the current concepts of ecological succession are discussed.
Rate of establishment and seasonal immersion of Spartina in Mariager Fjord, Denmark
Authors: Christiansen Christian , Møller Jens Tyge
Published: July 2006

Spartina (Sp. × townsendii H. & J. Groves and Sp. anglica Hubbard) was introduced in Mariager Fjord in 1948. The present study of a 154 ha sample area is based partly on topographic mapping and partly on photogrammetric plotting. The total area covered with vegetation was almost constant 1.0 × 105 m2 from 1945 to 1959. Spartina was planted in the study area in 1959, and spread rapidly. In 1978 the vegetation covered an area of 2.1 × 105 m2. It is suggested that this very high rate of establishment could be due to seasonal fluctuations in water levels. As the sea level is often low in spring, the sample area can be dry for up to 9 d at a stretch. This allows the roots to become anchored in the sand.
Processing and macroinvertebrate colonization of detritus in an Alaskan subarctic stream
Authors: Cowan Cathy A. , Oswood Mark W. , Buttimore Carol A. , Flanagan Patrick W.
Published: July 2006

Monument Creek, a second‐order Alaskan subarctic stream, experiences a severe thermal regime, with water temperatures of 0°C for six months. Leaching, long‐term decomposition and macroinvertebrate colonization of 5 g leaf packs were studied using leaves of the major riparian tree species, alder Alnus tenuifolia Nutt., birch Betula papyrifera Marsh. and willow Salix alaxensis (Anderss.) Cov. subsp. alaxensis and Salix arbucolides Anders. var. glabra Anderss. The processing rates of birch (k = 0.0080) and willow (k = 0.0063) were moderate while alder was processed very rapidly (k = 0.0513). Leaching rates did not differ significantly among the three leaf species, and accounted for 10–15% of total weight loss. Densities and biovolume of colonizing insects increased from fall to winter. Shredders dominated insect biovolume by midwinter, but were a small fraction of total biovolume in leaf packs that had frozen over winter and were sampled following spring thaw. This may be a function of low food quality in spring and/or the timing of shredder life histories. Limited allochthonous input and constriction of the stream channel due to freezing, with resultant high shredder densities, may explain the relatively rapid detritus processing rates in Monument Creek, despite cold stream temperatures.
Production of epipelic algae before and during lake fertilization in a subarctic lake
Authors: Björk‐Ramberg Susanna
Published: July 2006

Epipelic production was studied over three years in Lake Gunillajaure, a small, subarctic lake in northern Sweden. In 1977 the lake was in its natural state and in 1978 and 1979 it was continuously fertilized with phosphorus and nitrogen. The fertilizations in 1978 and 1979 did not increase the annual epipelic production measured with 14C technique. Also the seasonal production pattern was the same during the three years. The variation in production with depth was similar all three years with mean values of 85 mg C m‐2 d‐1 at 2 m and 1 mg C m‐2 d‐1 at 11 m. Light penetration and water temperature were found to be the most important environmental factors affecting epipelic production. A long turnover time, between I months and 14 yr at different depths, of the probably well adapted epipelic community is suggested to be an explanation to the absence of a response to the fertilization.
Growth and size of Triturus vulgaris and T. cristatus (Amphibia) in different parts of Norway
Authors: Dolmen Dag
Published: July 2006

The growth and size of the newts,Triturus vulgaris(L.) andT. cristatus(Laurenti) in different parts of Norway (+ Jämtland, Sweden) were studied. Age was estimated from skeletal growth marks, size‐frequency histograms and, for the males, from the number of testis lobes.

On average, the T.vulgarisLarvae in central Norway and Jämtland are smaller than those in southeastern Norway, although in good localities, at the same altitude, they are of approximately the same size and complete their development already within 2½–3 months. Larvae living in eutrophic habitats are larger than those in oligotrophic‐dystrophic habitats. In bog habitats at similar times of year theT. cristatuslarvae from central Norway are about the same size as those from similar habitats in southwestern and southeastern Norway, but somewhat smaller than those from eutrophic ponds in the Oslofjord area.

No significant differences in the mean size of adultT. vulgarisfrom southeastern Norway and from central Norway were found. The maximum lengths attained were recorded from central Norway, however. In eutrophic habitatsT. vulgarisadults BK usually larger than those in oligotrophic/dystrophic habitats.

In southeastern Norway, where growth is rapid,T. vulgarismay become sexually mature when 2+ yr‐old, in central Norway usually a year later, in Jämtland. on average, still later, and in their northernmost locality (Vefsn) they probably do not breed until 5+ or 6+ yr‐old.

On average,T. cristatusadults from southeastern Norway are slightly larger than those from central Norway, and may become mature at 2+ yr‐old. compared with 4 + yr‐old, at the earliest, in the latter area. The differences in the growth rates of both larvae and metamorphosed stages, of both species, most probably represent a response to climatic differences, although biotope quality is also an important factor.
Community structure of carrion flies along an island gradient
Authors: Kuusela Seppo
Published: July 2006

species richness, abundance relations, exploitation efficiencies, and population dynamics were examined within four carrion fly communities from a small isolated island in the Baltic to the large island of Åland. A total of 23 species and 11408 Specimens were collected.

Species richness (studied by rarefaction) of potential carrion flies was lowest on the small isolated island, but the smallest number of species emerged from the second largest island. Lucilia illustris Meig, was the most numerous species at every site, comprising 46–56% of the potential breeders and 71–91% of the emerging flies. Exploitation efficiency, measured by the numbers of individuals emerging per gram of carrion, was highest on the smallest island, but faunal similarity and ordination analyses suggest that competition was more intense on the larger islands.
Distribution and population dynamics of Collembola in relation to soil moisture
Authors: Verhoef H. A. , van Selm A. J.
Published: July 2006

The significance of variations in soil moisture for the distribution and abundance of the four collembolan species Tomocerus minor, Orchesella cincta. Lepidocyrtus lignorum and Entomnbrya nivalis has been studied in a pine forest. During a relatively dry summer, the distribution and abundance of these species were examined on two sites with an initially different soil water content and depth of the titter/humus layer. The distribution of the species investigated could be described with the negative binomial distribution. During the sampling period. Lloyd's “index of patchiness”, x̄/x̄ for T. minor and E. nivalis was subject to changes. For T. minor this was probably related to soil water content.

The densities of T. minor and O. cincta were higher in the wet site than in the drier site. At the beginning and at the end of the sampling period the drought tolerant E. nivalis reached equal densities in both sites. The density fluctuations of the four species appeared to be totally different during the sampling period: the drought sensitive species T. minor decreased strongly, L. lignorum remained constant and the drought tolerant species O. cincta and E. nivalis increased strongly. These latter two species were able to survive the dry periods and to attain high densities by reproduction. The results agree with laboratory data on distribution and survival in relation to humidity.
Areal distribution of a Neodiprion sertifer (Hym., Diprionidae) outbreak on Scots pine as related to stand condition
Authors: Larsson Stig , Tenow Olle
Published: July 2006

Analyses of a recent N. sertifer outbreak in southern Sweden were made during on‐going attack, comprising a regional and local mapping of defoliation severity, as well as a study of intensity of larval consumption, abundance of cocoons and parasitation of larvae in relation to fertilizer application. It was found that (1) the outbreak was preceded by summer and autumn droughts, (2) it was limited to infertile soils, (3) pine stands aged 20–40 yr suffered most, (4) it was less severe in trees benefiting from a reduced inter‐tree competition, as measured from tree‐ring growth, and (5) less severe in a fertilized stand. The findings support the hypothesis on a fundamental effect of stand nutritive state on changes in number of the sawfly.
Enchytraeids, lumbricids and soil arthropods in a northern deciduous woodland – a quantitative study
Authors: Axelsson Björn , Lohm Ulrik , Persson Tryggve
Published: July 2006

Soil/litter inhabiting annelids and arthropods were studied for one year in a mesic deciduous woodland, Andersby ängsbackar, one of the most northerly areas in Sweden to possess unbroken oak/hazel vegetation. Lumbricidae, Enchytraeidae, Collembola, Acari, Coleoptera, Diptera and Araneae were important faunal groups with regard to abundance, biomass and respiratory metabolism. Annual mean biomass (8 g dw m−2) and respiration (450 kJ m −2 yr−1) of the joint annelid and arthropod community were dominated by lumbricids (76 and 50%, respectively). The biomass and respiration of the annelids and arthropods at Andersby were lower than in some other oak forests in northwestern Europe, probably because of lower soil temperature, lower litter supply and because some lumbricid and diplopod species were at their northern border of distribution.

Of the annual respiration, saprovores, fungivores, carnivores and root‐feeders contributed 65, 19, 14 and 1.5%, respectively. The saprovore percentage was lower at Andersby than at other mull sites compared, probably as an effect of the northern climate, which might favour microbial saprovory. The fungivore and carnivore percentages were higher, which might be due to the presence of a litter layer throughout the year.
Microdistribution and water loss resistances of selected bryophytes in an Alaskan Eriophorum tussock tundra
Authors: Alpert Peter , Oechel Walter C.
Published: July 2006

Bryophyte species distributions were analyzed with respect to microtopography at an alpine tundra site in central Alaska which is dominated by tussocks of Eriophorum vaginatum. Bryophyte distributions were found to be significantly correlated with slope but not with azimuth. Different types of tussocks and hollows and mats between tussocks also supported different bryophyte floras. Water loss resistances of three species of moss did not account for differences in their distributions.
Role of benthic insect feces in a Rocky Mountain stream: fecal production and support of consumer growth
Authors: Shepard Richard B. , Minshall G. Wayne
Published: July 2006

The feces of stream insects may be a major component of fine particulate organic matter (FPOM) available to collector organisms. In Mink Creek, Idaho, winter defecation rates for 9 species ranged from 86 mg dry feces (g dry body wt)−1 d−1(Ephemerella spinifera) to 154 mg g−1 d−1(Paraleptophlebia heteronea). Detailed studies of 3 species in summer revealed that rates were much greater than in winter and exhibited high between‐individual variation (e.g., 695 ± 184.8 mg (g body wt)−1 d−1 for Baetis tricaudatus). By combining measured and literature values, it is estimated that the benthic insect community egests approximately 3.4 kg feces m−2 yr−1. This value lies within the range of FPOM estimated to be derived from degradation of leaf litter input (0.7–9.9 kg m−2 yr−1, depending upon assimilation efficiency of the organisms).

Short‐term winter growth experiments showed that, with two exceptions, collectors fed on fecal detritus will grow as well as on other food resources; relative growth rates depend upon the species. Because fecal detritus is abundant throughout the year, and is treated by many species as a source of food, it could be a major mechanism by which seasonal fluctuation in availability of allochthonous litter input is minimized and homeostasis of structure and function maintained.
Fish production in the Jarama River, Central Spain
Authors: Lobon‐Cervia J. , Penczak T.
Published: July 2006

Fish production was estimated at three sites on the Jarama River, a small, typical upland river in Central Spain. Population estimates were made by the successive removal method of electrofishing. The same six species were recorded at each of the sites: Chondrostoma polylepis, Barbus barbus bocagei, Leuciscus cephalus pyraenaicus, Salmo trutta m. fario, Gobio gobio and Cobitis paludicola, with the first three species always dominant. Density, biomass, production (assuming that No is the total number of eggs spawned), and available production were, respectively: 13502‐85776 ind. ha−1, 178.6–221.3 kg ha−1, 221.7–583.6 kg ha−1 yr−1, 118.1–271.9 kg ha−1 yr−1. Production estimates based on mortality curves were 7.9–19.5% (mean: 13.7) lower than those based on estimated from the number of eggs laid. Production per unit of area was highest at the widest and deepest site. Brown trout production contributed only 2–4% of the total production for all sites.
Respiration and energetics of the bumblebee Bombus terrestris queen
Authors: Silvola Jouko
Published: July 2006

Carbon dioxide production by the Bombus terrestris queen was measured at different temperatures (10–30°C) and during different activities of the bumblebee. During flight the CO2 production averaged 50 ml g−1 (fresh weight) h−1 and was only slightly affected by temperature. During rest (with a readiness to fly) and incubation the respiration rate clearly increased with decreasing temperature (5–40 and 13–56 ml g−1 h−1, respectively), whilst during torpor it increased with temperature (0.1–1.7 ml g−1 h−1 at temperatures from 10 to 30°C).

The expenditure of energy as calculated from the continuous respiration measurements agreed well with the amount of energy obtained from food (discrepancy 6–19%). The energy budget of an incubating queen was correctly predicted using the measured respiratory functions, prevailing temperatures, and the behaviour of the queen. The number of flower visits needed to fulfil the daily energy requirements of an incubating queen is discussed.