bluuebunny/crossref_metadata_2025 huggingface dataset:
Population biology of the weasel Mustela nivalis on British game estates
Authors: King Carolyn M.
Published: July 2006

The mean year‐class ratio in 6 samples of weasels (total n = 477) ranged from 59% to 84% young, and mean age from 0.79 to 1.16 yr. There was no difference in age structure between samples from 5 game estates and 1 reserve. Mean annual mortality of weasels of both sexes and all ages was 75‐90%. In 12 pregnant weasels the mean number of embryos, observed from April to June, was 5.6. There was a definite anoestrous season in winter. Records of the number of weasels killed on game estates show that weasels and stoats reacted differently to the first outbreak of myxomatosis in England in 1954; and that weasel populations are capable of enormous sudden increases (usually associated with “mouse years”). These increases are probably due largely to summer litters produced by precocious juveniles, and also to some adults breeding a second time (both possibilities confirmed from ovarian histology on this material). Traditional gamekeeping practice may influence the seasonal pattern of mortality of weasels (highest in spring) but its effects are probably short‐lived.
Aerial census of ringed seals Pusa hispida basking on the ice of the Bothnian Bay, Baltic
Authors: Helle Eero
Published: July 2006

The censuses are based on six surveys (1590 km total) carried out between 13 April and 17 May 1975 and two surveys (560 km) on 13 and 15 May 1978. The material consists of 716 observations in 1975 and 214 observations in 1978, involving 1960 and 572 ringed seal specimens respectively. The transect width was determined in retrospect on the basis of the sighting angle and sighting distance, the latter being estimated and corrected by a factor typical for each separate flight. The mean sighting distances varied from 720 to 1140 m with a range from 160 to 2450 m. On average over 3000 ringed seats were basking on the ice of the Bothnian Bay in 1975 and 1978, promising at least 4000 specimens living in the area in total. Sources of methodological bias, factors affecting the observability of the seals, and the estimation of the total population based on the numbers of basking seals are discussed.
Browse supply in lowland forests of eastern Poland
Authors: Borowski Stanislaw , Dzięciolowski Ryszard
Published: July 2006

Browse supplies in different growth stages of 4 forest associations and forest site types were estimated. Two ecological situations were compared: exclusion from browsing and unrestrained access of ungulate animals. Harvest technique was applied. Three big forest tracts in eastern Poland provided study locations. Results were tested with the use of analysis of variance. The fresh mixed coniferous forest revealed the highest species diversity in the understorey and regeneration zone, while fresh coniferous forest had the lowest.

No obvious influence of animal exclusion upon the number of plant species was found. Altogether, 41 plant species were found in the understorey and regeneration zones. In young plantations shoot weight was higher than in thickets, pole‐sized and timber stands. Shoots clipped in autumn were heavier than those clipped in spring. The browse biomass varied from 400‐600 kg ha‐1in poor communities to 2–3 tonnes ha‐1in the most productive ones. Generally, low (5%) utilization of browse by ungulates was found.
The life cycle of Chironomus anthracinus in Lough Neagh
Authors: Carter Clare E.
Published: July 2006

Chironomus anthracinus generally had a one year life cycle at 8 m depth in Lough Neagh, during the study period. In spring 1975 however only a proportion of the population emerged as usual, the rest remaining a second year in the benthos to emerge in 1976. The mean dry weight of larvae just before emergence was 2.8 mg in 1971 and 2.6 mg in 1974 but only 1.6 mg in 1975, and it seems that larvae must reach a weight of at least 1.0 mg in the early spring to emerge that year. Considering temperature, oxygen saturation and standing crop of phytoplankton as factors influencing the life cycle, mean monthly chlorophyll a (phytoplankton) was weakly correlated with mean monthly increase in weight and % monthly weight increase could be related to temperature.
Aquatic feeding by moose Alces alces in a Canadian lake
Authors: Fraser D. , Arthur D. , Morton J. K. , Thompson B. K.
Published: July 2006

The aquatic feeding behaviour of moose, and the abundance, species, and chemical composition of aquatic plants, were studied in a small Canadian lake which attracted many animals. Feeding was much more common in June than later in the summer, and somewhat more common during the morning and evening than in (he afternoon. Individual adult moose appeared to use the lake intensively during 1‐ to 4‐day visits. Compared to deciduous browse, the aquatic plants had high levels of sodium and iron, less fat, and similar levels of crude protein, crude fibre, sulphate and other minerals. In the preferred feeding areas, compared to other parts of the lake, plants were more abundant, had a different species composition, and were richer in iron and calcium. Recent flooding, a flow of water through the feeding areas, and a bicarbonate‐rich tributary may all have contributed to the lake's attraction for moose.
Epifaunal associates of Fucus serratus at Dale, south‐west Wales
Authors: Seed R. , O'Connor R. J.
Published: July 2006

The macrofauna associated with Fucus serratus at Dale in south‐west Wales contained 30 taxa of which five were common: these comprised four encrusting bryozoans and a hydroid. The bryozoans Flustrellidra hispida and Electra pilosa showed significant variations in abundance according to the size and structure of plants colonised. Electra was most abundant on plants where other bryozoans were least numerous. Colony growth in Electra was proportional to the amount of space provided by individual plant segments whilst growth in competitively superior species appeared to be independent of the size of the plant segments colonised. Dynamena pumila was larger and more abundant on larger segment faces where competition was presumably weaker. Each species showed a specific pattern of zonation along the fronds. The dominant species were generally more abundant on the concave surfaces of the plants. There was some evidence for the tendency for certain taxa to co‐occur but the degree of association between species was weak and probably of limited biological significance. Species diversity varied with plant structure. More species occurred on concave surfaces at all plant levels but the overall pattern of diversity on the two segment faces was similar; diversity was greatest in the shrubbier mid‐frond regions. Differential distribution of the dominant encrusting taxa within this Fucus community results in a considerable degree of niche segregation and ecological isolation.
Diet of the golden eagle Aquila chrysaetos during the breeding season in Sweden
Authors: Tjernberg Martin
Published: July 2006

During a five‐year period, 1975–1979, a total of 2881 prey individuals of 65 prey species were collected at 162 golden eagle nests from northern Sweden and from the island of Gotland. In northern Sweden birds are taken in higher numbers than mammals but calculated as weight the two categories are of equal importance, The main prey during the breeding season are capercaillie, black grouse, willow grouse, ptarmigan, mountain hare and reindeer fawns which together form 91% of the total food biomass. The capercaillie and the black grouse are taken more in the southern part of the coniferous region than in the northern. In contrast, in northern areas, reindeer fawns are more preyed upon than in the South, Ptarmigan and willow grouse are the most commonly captured prey species in mountain areas. The total number of reindeer fawns taken (dead and/or alive) by the Swedish golden eagle population during one summer is estimated at 600 individuals. On Gotland the golden eagles take mammals more often than in its northern distribution area. Rabbit and hedgehog arc the most important species.
Patterns of occurrence of myxomycetes in a spruce forest in South Sweden
Authors: Eliasson Uno
Published: July 2006

A 4‐yr field study was carried out on selected species of myxomycetes. Reticularia jurana, Symphytocarpus flaecidus, Amaurochaete atra, and A. tubulina occur predominantly in May–June. Ceratiomyxa fruticulosa, Stemonitis axifera, S. fusca, S. hyperopta, and Fuligo septica in June–August, and Colloderma oculatum, Trichia botrytis, T. decipiens, and Fuligo muscorum in September–October. Lycogala epidendrum may occur from May to October. Whereas several species seem to be restricted to late autumn, those appearing in spring and early summer are occasionally found also later in the season. Many species with large plasmodia are rare under arid conditions. Complex factors probably influence spore germination, and it is often impossible to explain a sudden abundance of a species merely from temperature and precipitation. Several species show clear substrate preferences. Plasmodia may develop in cavities in wood and then move out to the surface to fructify. Insects are probably important for the dispersal of several species. Invertebrates, among them snails, are predators on plasmodia as well as on fructifications.
Benthic detritus dynamics in a mountain stream
Authors: Short Robert A. , Ward James V.
Published: July 2006

The dynamics of sedimentary detritus was examined over a 17‐month period in a third‐order mountain stream in Colorado. Autumnal and vernal peaks in total detritus standing crop (197 g and 165 g AFDW m−2, respectively) were associated with leaf abscission and ice out. The flushing action of snowmelt runoff rapidly reduced benthic detritus to 14 g AFDW m−2. Detrital size classes differentially contributed to temporal fluctuations in total detritus. The autumnal maximum was largely comprised of coarse particulate organic matter (CPOM), primarily leaf litter. The large increase following ice out was mainly due to fine detritus (FPOM, 0.45–75 μm) which accounted for > 50% of benthic detritus during 9 months of the year. Evidence suggests that changes in standing crop and particle size distribution during the extended period of ice cover (November‐March) resulted from in situ processing rather than transport. Despite major differences in climate, geochemistry and hydrology, the Colorado stream exhibited patterns of detrital dynamics remarkably similar to an eastern deciduous forest stream.
Interaction between Heracleum laciniatum and some other plants
Authors: Myrås Harald , Junttila Olavi
Published: July 2006

The aim of this study was to find out whether the low plant production under a canopy of Heracleum laciniatum Horn was due to competition for water, nutrients or light or to chemical inhibitors produced by H. laciniatum.

The main conclusion is that the low plant production observed under the canopy is due to competition for light. There were also indications that the competition for nutrition was larger in the soil under H. laciniatum than in the meadow outside the stand, but it has not been shown that nutrient supply limits the plant growth under the canopy. There were no indications that competition for water was a limiting factor. Water percolated through pots with H. laciniatum plants slightly inhibited growth of Poa pratensis and Phleum pratense, but had no effect on H. laciniatum. In soil samples collected from mid of June to late October seeds of Phleum pratense germinated better in meadow‐soil than in soil collected under H. laciniatum. Allelopathy is suggested to account for a minor part only of the suppressed plant production under a H. laciniatum canopy.
Seasonal differences between moose and roe deer in ability to digest browse
Authors: Cederlund Göran , Nyström Anders
Published: July 2006

The digestive capacity of free‐living moose Alces alces (L.) and roe deer Capreolus capreolus (L.) for four plant species was studied with in vitro technique. Moose were found to digest all species better than roe deer. Individual variations were also smaller for moose. In moose the level of digestibility was the same both summer and winter, while roe deer shot in winter digested winter samples of bilberry Vaccinium myrtillus L. and to some extent Scots pine Pinus silvestris L. better than did summer roe deer. This was taken as evidence for a seasonal adaptation in the roe deer rumen. Digestibility of the plant material studied showed a strong negative correlation to the fiber content. The results are discussed in relation to winter problems for roe deer and possible food competition between moose and roe deer.
Oxygen and nitrate respiration in a reed swamp sediment from a eutrophic lake
Authors: Andersen Frede Østergaard
Published: July 2006

Seasonal measurements of the oxygen and nitrate uptake by a reed swamp sediment were carried out in a shallow, eutrophic Danish lake, Arreskov Sø. The oxidation of organic carbon in the sediment by aerobic and nitrate respiration was 290 and 188 g C m−2 yr−1 respectively. During winter, nitrate respiration amounted to 94% of the total carbon oxidation, whereas it was zero during summer. On an annual basis nitrate respiration constituted 39% of total respiration. Sediment nitrate uptake was correlated to nitrate concentration. In consequence of this the nitrate uptake rates varied during the year from zero in summer to 55 mg N m−2 d−1 in spring.

Oxygen uptake rates varied from 30 to 250 mg O2 m−2 h−1 during the year, with a maximum uptake in August. The oxygen uptake per year was calculated to 860 g O2 m−2. The oxygen uptake rate was correlated to lake temperature and Kjeldahl nitrogen content of the sediment. The oxygen uptake rate, however, showed no correlation with loss on ignition of the sediment. A Q10‐value of 2.2 was found for lake measurements in the temperature interval of 5–15°C. The corresponding O10‐value in the laboratory was 2.6. A high microbial biomass indicated by the maximum content of Kjeldahl nitrogen and the lowest ratio of loss on ignition on Kjeldahl nitrogen appeared in late August, when the maximum oxygen uptake occurred. The oxygen uptake rate increased during the time interval from sampling to the start of the experiments.
Effects of air pollutants on the wintertime water economy of the Scots pine Pinus silvestris
Authors: Huttunen Satu , Havas Paavo , Laine Kari
Published: July 2006

The changes effected by air‐borne pollutants in the wintertime water economy of the Scots pine were investigated in industrial and urban environments in Oulu (65°N). Pine needles were found to undergo a wintertime water stress, which was more intense in the polluted area than in the less polluted environment. The water stress of the needles was found to be the more severe, the more pollutants had accumulated in the needles. In the needles of the trees growing in the polluted area, transpiration started shortly after they had been brought into laboratory even at midwinter, but the healthy trees were not equally sensitive in their response. When the weight loss of branches was observed in outdoor conditions, it was noted that the branches brought from the polluted area lost weight more rapidly than the branches of the healthy area. Air‐borne pollutants hence constitute an obvious additional risk to the wintering of plants, particularly their water economy.
Effects of microtopography on the summer survival of Plantago maritima seedlings
Authors: Jerling Lenn
Published: July 2006

The survival of Plantago maritima seedlings was studied on a Baltic sea‐shore meadow and related to a topographical gradient and to microtopography. The seedlings showed different survival at different microtopographical levels. These differences could be identified all along the gradient but did not show in the same place in every year. The survival of seedlings was also different in different parts of the gradient. This means that the distribution of safe‐sites flucluates with time. Areas with the highest survival rate of seedlings did not coincide with areas with the highest abundance of adults.
Growth patterns and food habits of Baetis rhodani, Capnia pygmaea and Diura nanseni in a West Norwegian river
Authors: Baekken Torleif
Published: July 2006

As a part of weir‐pond‐ecosystem project, the growth patterns and food habits of Baetis rhodani (Ephemeroptera), Capnia pygmaea (Plecoptera), and Diura nanseni (Plecoptera) were investigated. B. rhodani was bivoltine. The winter generation consisted of three cohorts. C. pygmaea and D. nanseni accomplished their nymphal growth in one year. The predominate food consumed by B. rhodani and C. pygmaea was detritus. Variations in the diet of these detritivores are discussed in relation to microdistribution and possible competition. The most common prey items of the carnivorous D. nanseni were chironomids and nymphs of B. rhodani and C. pygmaea. Prey shortage is suggested to be the reason for small D. nanseni eating detritus.
Comparative primary productivity of algal epiphytes on three species of macrophyte in the littoral zone of Lake Ohrid, Yugoslavia
Authors: Allen Harold L. , Ocevski Boris T.
Published: July 2006

Primary productivity of algal epiphytes on the surfaces of Phragmites, Potamogeton, and Nuphar was measured seasonally from June 1978, through June 1979, in the littoral zone of Lake Ohrid, using 14C methodology. Surface areas of individual macrophytes were determined throughout the study period through the use of a non‐miscible surfactant and a calibration curve of surfactant weight versus known, calculated surface areas.

Mean total surface area available for epiphytic colonization during the study period was 1.032 m2 macrophyte surface per m2 of littoral zone for Phragmites, 0.810 m2 for Potamogeton, and 0.167 m2 for Nuphar. Seasonal rates of mean primary productivity of algal epiphytes on Phragmites from the surface to the light‐compensation depth ranged from 84–1406 mg C m−2 littoral zone d−1; ranges for epiphytes on Potamogeton and Nuphar were 77–586 and 69–268 mg C m−2 littoral zone d−1, respectively. Maximum rates were observed typically during June; minimum rates were observed typically during August to December. Mean daily productivity rates over the 12 month period were for epiphytes on Potamogeton 167.0, on Nuphar 100.4 and on Phragmites 671.2 mg C m−2 littoral zone d−1. Calculated annual production for epiphytes on Nuphar was 36.65, on Potamogeton 60.95 and on Phragmites 245.0 g C m−2 littoral zone yr−1. Epiphytic production data were typically considerably higher than production data obtained for littoral and pelagial planktonic algae and compare favorably with published data for epiphytic and periphytic production in Lawrence Lake, Marion Lake, and Borax Lake.
Dynamics of ectomycorrhizae in Abies amabilis stands: The role of Cenococcum graniforme
Authors: Vogt Kristiina A. , Edmunds Robert L. , Grier Charles C.
Published: July 2006

The growth and development of the predominant mycorrhizal fungus infecting the root systems of subalpine Pacific silver fir was examined seasonally in 23 and 180 yr old stands. All data was obtained by sorting roots from intact soil cores separated into forest floor and mineral soil horizons.

The predominant mycorrhizal fungus infecting the root systems of 23 and 180 yr old Pacific silver fir was Cenococcum graniforme. C. graniforme comprised 36–97% and 40–96% of the total mycorrhizal root tips in the soil profile in the young and old stands, respectively. C. graniforme root biomass reached a maximum in autumn in the young stand, and in winter in the old. Dual mycorrhizal associations were commonly observed on the same root tip during the spring and autumn periods of root elongation in both stands. Over 80% of the C. graniforme roots were located in the forest floor and A‐horizon throughout the study in both stands, Sclerotia were predominantly located in the A‐horizon (38‐70%) in both stands.
Winter bird communities in the Åland archipelago: an island biogeographic point of view
Authors: Haila Yrjö
Published: July 2006

The distribution of wintering land birds was examined in the archipelago of Åland (60°N, 20°E) along two ecological dimensions: (1) the island continuum from small skerries ((0.5 ha) to the mainland of Åland (97000 ha), and (2) the habitat range of the mainland of Åland. In the species‐area relationship, both the exponential and power function models fitted well. The increase of the number of species with island size was interpreted as a consequence of increasing habitat diversity on larger islands. The smallest islands supported only few seed‐eating species utilizing the islands in a fine‐grained fashion; none of these birds belonged to the breeding fauna of the islands. With increasing island size and habitat diversity, insectivores and species tied to the human culture were added. On the mainland of Åland, more than half of the birds were observed near human habitations: bird communities wintering in pine forests were richer than in deciduous forests. Proportion of wintering species was greatest in the breeding communities of pine forests. The proportion of wintering species was presumably regulated by the degree of structural change in the habitat between summer and winter, this change being most drastic in deciduous habitats The species observed could be broadly classified into three feeding categories: opportunists., omnivores and scavengers, dependent on the diverse food items provided by man; food specialists, species éating seeds and berries, ranging widely in the islands and habitats; and insectivorous habitat specialists, inhabiting coniferous habitats, and islands with coniferous (pine) forests. Opportunists, in particular, gel increasing wintering opportunities by the impact of man.
Spatial differentiation of ectoparasites on small mammals
Authors: Nilsson Anders
Published: July 2006

Different ectoparasitic species occur on different areas on the small mammal host: chiggers in the ear muzzle, ticks on the ears and other parts of the head, fleas and lice on the back and most gamasid mites on the posterior part of the host body.

The distribution might be affected by (1) the mechanical interference of the host. Thus attached species such as ticks and chiggers occur in areas where direct predation is limited and small and/or very mobile species are found on other parts of the body. (2) interaction between parasitic species. In areas where species meet, there might be a segregation in time or in space. Species such as Laelaps agilis (C. L. Koch) and Haemogamasus nidi Michael are most frequently found within a restricted area on the host, but differ in their seasonal occurrence. In other combinations of species, such as in fleas, there are marked differentiations in body areas used. These differentiations may be evolutionary fixed or manifested at first when species meet. (3) Abundance, where an increasing abundance enlarge the habitat used.
Trophic variety and abundance of hoverflies (Diptera, Syrphidae) in an English suburban garden
Authors: Owen Jennifer
Published: July 2006

28924 hoverflies of 85 species were caught in a Malaise trap in an English suburban garden during the eight‐year period 1972–79, and three additional species were hand‐netted. Hoverfly larvae fall into five trophic categories all of which were represented by adults in the trap sample. 82.71% of the hoverflies trapped have larvae that feed on aphids, 12.04% feed on decaying organic material, 5.14% eat living plants, 0.09% scavenge in Hymcnoptera nests, and 0.02% are associated with tree sap or rotting wood. The relative frequency of the different trophic groups varied annually and seasonally although the aphid‐feeders were nearly always the most abundant. 22 species are believed to breed in the garden, and a further 29 in the surrounding area; 15 species are regarded as casual and 22 as chance visitors. It is suggested that the high plant diversity and spatial heterogeneity of gardens result in them supporting more species than would be found in a natural area.
Forest floor respiration in a black spruce taiga forest ecosystem in Alaska
Authors: Cowling Joanne E. , MacLean Stephen F.
Published: July 2006

A technique was developed for measuring respiration of virtually undisturbed forest floor samples, and used to follow seasonal changes in two black spruce forest stands in interior Alaska, In the laboratory, soil respiration showed a positive response to increasing temperature: however, respiration measured in the field was negatively correlated with air and soil temperature, but positively correlated with water content of the soil within the range (100–250% of dry weight) normally experienced in the field. Moisture levels above 250% inhibited respiration. Precipitation events usually stimulate forest floor respiration, but prolonged periods of dry and rainy weather lead to limitation of respiration by sub‐ and supraoptimal moisture, respectively. Long‐term confinement of soil has significant effects upon soil arthropod densities, moisture content, temperature, and respiration, and should not be taken to represent the natural conditions of the forest floor.
Age distribution and fertility of populations of the arctic‐alpine species Oxyria digyna
Authors: Humlum Carstem
Published: July 2006

Age distributions and fruit production of populations of Oxyria digyna (L) Hill were studied in Norway and Greenland. The observed age distributions were described by the negative exponential function and by the power function. Three kinds of distributions were observed: steep, flat and bell‐shaped with the corresponding hint production: 33–917, 8–108 and 76–303 fruits per individual. The population with the steep age distributions and high fruit productions were assumed to be increasing. They were found in sites with almost no vegetation (≤10% cover). The populations with the flat age distributions and the low fruit production were assumed to be stable. They were found in sites with a vegetational cover of 50–75%. The populations with the bell‐shaped age distributions and the intermediate fruit productions were assumed to be decreasing. They were found in sites with a closed vegetation (cover ≥100%).
Fin whales in the NE Atlantic; relationships between abundance and distribution
Authors: Árnason Úlfur
Published: July 2006

It has been a widely held opinion that several fin whale populations inhabit the NE Atlantic. In the present communication the existence of one versus several fin whale populations in this area was considered. A survey of catch figures indicated considerable similarities among the various whaling grounds. Thus the figures did not support the belief that the various grounds were inhabited by different populations. The low productivity of the whales and their good mobility in an environment where the effects of physical barriers are limited were among the factors discussed as acting against the origination of separate populations. A model, (“the funnel analogy”), was presented according to which decrease in density would first be expected at the periphery of distribution. The area W of Iceland was suggested to constitute the present distributional core of the fin whale in the NE Atlantic. An account was given of the catch of fin whales in Iceland during the past 32 yr. Catch figures calibrated for Increased catcher efficiencies showed a falling tendency.
Life history and bionomics of Arctopsyche grandis (Trichoptera) in a Central Idaho stream
Authors: Cuffney Thomas F. , Minshall G. Wayne
Published: July 2006

Arctopsyche grandis was studied for two years In a cold stream in central Idaho. Larvae have a one year life cycle consisting of five instars. Three to four instars are present in most months. Growth is rapid in summer with instar I and II passing to IV and V in 30 d or less. Little or no growth occurs during winter. Maximum larval densities were 547 (1977) and 2060 m−2 (1978) of planar rock surface area. Populations fitted a negative exponential survivorship curve with similar exponents (−0.0078, −0.0103) in both years. Larval growth was generally isometric with head capsule width (403–2197 μm) and weight (0.05–16.23 mg AFDW) increasing by a factor of 1.5 between instars. Net dimensions correlated with head capsule width and nets were made by all instars and maintained throughout the year. Larvae fed preferentially on animals and diatoms avoiding vascular plant detritus. No differences were detected in diet among the instars.
Mercury levels in feathers of eagle‐owls Bubo bubo in a captive, a reintroduced and a native wild population in SW Sweden
Authors: Broo Björn , Odsjö Tjelvar
Published: July 2006

Mercury levels in feathers are presented for both captive and wild eagle‐owls from the period 1963‐1976. Levels are compared between wild birds occupying old territories and released birds in newly occupied territories. The wild population in SW Sweden shows decreasing levels in the inland territories, and at present these levels are similar to the natural background level. The coastal owls have significantly higher levels which show no decrease. Low levels prevail in captive eagle‐owls, fed on low‐contaminated food. Birds in newly occupied territories (mainly released birds) have similar mercury levels as native birds. After being released captive birds therefore seem to accumulate mercury rather quickly.
Litterfall in two Canadian deciduous woods: quality, quantity and timing
Authors: Merriam Gray , Dwyer Lianne , Wegner John
Published: July 2006

Litterfall in two deciduous woods in Ontario, Canada, was caught in bag traps and by new screen traps for two years. The beech‐maple wood produced 818 g m−2 (8.2 t ha−1) and the poplar wood produced only 450 g m−2 (4.5 t ha−1). Of these totals, canopy leaves alone made up 386 g m−2 for the beech‐maple wood and 270 g m−2 for the poplar wood leaving 47% and 34%, espectively, for other litter components. Data are presented for seven types of litter in addition to canopy leaves.

Redistribution of litter on the ground causes spatial heterogeneity of substrate and of habitats for decomposers and hence of decomposition.

Temporal distributions of various types of litterfall differ between the two woods in relation to their vegetation structure. The diversity of litter types combines with extensive temporal distribution of litterfall in the beech‐maple woodland to give that wood the potential for nearly continuous decomposition activity. In contrast, the poplar woodland has low diversity of litter and short duration of litterfall.
Inputs and transformation of allochthonous particulate organic matter in a headwater stream
Authors: Iversen Torben Moth , Thorup Jens , Skriver Jens
Published: July 2006

Inputs and outputs of allochthonous particulate organic matter were measured during 15 months in the upper part of a beech forest headwater stream. Inputs were estimated to 716 g m−2 yr−1, and leaves made up 71%. Outputs were estimated to 535 g m−2 yr−1 and consisted mainly of FPOM (92%). Therefore, a significant transformation of CPOM into FPOM took place. The mean FPOM concentration varied between 0.6 and 3.4 mg 1−1, but the daily variations greatly surpassed the seasonal variations. As discharge was rather constant, the observed variations were due to external disturbances, especially precipitation.

A tentative scheme for leaf processing is established from the present data and previous studies in the area, indicating that a significant part takes place in the MPOM pool and that microbial and invertebrate processing make up about 50% each of total intra‐system processing.
Nitrogen fixation by free‐living microorganisms in the soil of a mature oak‐stand in Uppland, Sweden
Authors: Nohrstedt Hans‐Örjan
Published: July 2006

The nitrogenase activity of free‐living microorganisms was investigated in a brown forest soil beneath a mature oak‐Stand outside Uppsala, Central Sweden. The effect of season, air temperature, soil depth and some soil parameters on nitrogenase activity was studied.

Only heterotrophic nitrogenase activity was detected. The main activity occurred in the upper 5 cm of the soil profile. The amount of nitrogen fixed during the growth season was calculated to 0.73 kg ha−1. There was a strong seasonal variation of the nitrogenase activity with the highest level in July, August and September. The activity, when the soil was incubated at 25°C, was significantly correlated with the mean air temperature at the field site.
Regeneration of Scots pine Pinus sylvestris at a natural tree‐line in the Cairngorm Mountains, Scotland
Authors: Miller G. R. , Cummins R. P.
Published: July 2006

The age, density, distribution and reproductive capacity of Scots pine Pinus sylvestris L. were investigated along an altitudinal gradient through the only undisturbed tree‐line remaining in the Cairngorm Mountains. Saplings at 300–410 m a.s.l. were unlikely to develop to reproductive maturity because of repeated browsing by red deer Cervus elaphus L. By contrast, pines were regenerating successfully in scrub at 531–590 m, where the population included individuals of all ages up to 300 yr. Above 590 m, there grew only saplings aged less than 30 yr and these declined in density with increasing altitude up to 730 m.

The climate at 531–590 m was not so severe as to prevent pines from growing to reproductive maturity. However, it may have been severe enough to restrict the activities of large herbivores and so the pine saplings there escaped the heavy browsing suffered by plants at lower altitude. Presumably zones of successfully regenerating pine scrub might occur more widely in the Cairngorms but for a shortage of seed‐bearing trees.
Structure of communities of ground‐living spiders along altitudinal gradients
Authors: Otto Christian , Svensson Björn S.
Published: July 2006

Differences in the altitudinal composition of ground‐living spider communities were studied by pitfall trapping in western Norway. These data plus compilations of information from the literature were used to investigate features in the size composition, temporal appearance and spatial distribution of species. Spiders at the highest altitude had the widest distribution both in terms of geographical and altitudinal range. At the lowest altitude species were more often stenochronous than at higher altitudes. The size composition, reflecting food choice of the spiders, tended to be bimodal with increasing altitude. It is argued that small spiders are segregated mainly along the habitat dimension (searchers), while the larger ones are segregated with respect to diel activity patterns and food choice (pursuers). We suggest that mountain spider faunas in temperate regions at high latitudes mainly consist of widely distributed and easily dispersed species.
Seasonal changes in census efficiency of birds at marshes and fen mires in southern Sweden
Authors: Nilsson Sven G.
Published: July 2006

Sixteen fens and marshes with areas between 10 and 285 ha was censused at least six times in the period 11 April to 10 June. The proportion of the number of resident species observed on a visit increased from the beginning of the census period up to the end of May. Thereafter it decreased. Variability in the census of the number of species was lowest in the end of May and the beginning of June. Throughout the seasons studied there were frequent visits of non‐resident species. The proportion of non‐resident, but not the proportion of resident species, observed on a visit, increased as the number of resident species at a locality increased.

Census efficiencies per ten‐day periods are given for 14 species. Census efficiency of a species correlated positively with the body weight of the species. The highest census efficiency for most species occurred in the period 21 April to 31 May. It is suggested that if two visits are made in that period about 80% (S.D. = 9.8) of the resident species will be observed.
Effects of freshwater outflows on microbial populations in the Tvärminne archipelago, southern Finland
Authors: Väätänen Pentti
Published: July 2006

The effects of freshwater outflows were evaluated in three ways: (1) microbial populations in the outflow area (mainly Tvärminne Storfjärd) were compared with populations outside the area, (2) direct counts were made at three sites to monitor the abundance of bacteria along the seaward course of the outflows, and (3) a survey was made of the distribution of microorganisms in the archipelago. The indices used for the presence of freshwater outflows in the archipelago were low salinity, increased amounts of humic matter, and increased temperatures in the winter.

In the outer archipelago, the effects of the outflows were most evident in the low‐salinity surface layer below the ice and were also distinguishable in spring and late autumn, but were noted only sporadically in the summer. The outflows were traced as far seaward as the border of the sea zone. The outflows transported various types of bacteria, bacterial spores and yeasts, but did not significantly affect the community respiration. Many of the microorganisms flowing with the fresh water in the winter evidently originated from sewage. During the other seasons, the roles of outflows from the firth of Pojoviken and runoff from the land became evident, but their contributions could not be estimated because fresh water and sewage move together. However, most of the bacterial spores seemed to originate from the land.

The archipelago east of Tvärminne Storfjärd proved to be appropriate for inshore brackish‐water investigations being undisturbed by freshwater outflows.
Distribution, life cycle and population dynamics of the aquatic enchytraeid Propappus volki (Oligochaeta) in an English chalkstream
Authors: Bird G. J.
Published: July 2006

Propappus volki was recorded in Dorset chalk streams from gravel substrata where it represented up to 88% of the oligochaete fauna. It was absent from silted sediments associated with marginal and submergent macrophytes. P. volki showed an annual life cycle with a peak of mature individuals in the period April to June, whilst young worms were most abundant after July. The mean monthly biomass in Bere Stream was estimated to be 0.29–0.45 g wet weight m−2 and the highest mean density was 5465 m−2 in April 1979.
Do willow warblers Phylloscopus trochilus of northern origin start their autumn migration at an earlier age than their southern conspecifics?
Authors: Högstedt Göran , Persson Christcr
Published: July 2006

Data on hatching time in the willow warbler for different regions (S Germany, S Sweden and N Sweden) are compared with the median of the corresponding migration diagrams. By doing so it is possible to calculate the age, at which the young of the year start their autumn migration. Our calculated values for the above mentioned regions are 68, 62–66 and 61–62 d, respectively. In our opinion this difference is too small to justify the statement, that northern birds migrate at an earlier age than their southern conspecifics. An alternative explanation is that the German migration diagrams are influenced by the passage of northern migrants, resulting in a later median and an apparently higher age for southern birds.
Bryophyte vegetation and ecology along a topographic gradient in montane tundra in Alaska
Authors: Alpert Peter , Oechel Walter C.
Published: July 2006

Analysis of bryophyte vegetation along a topographic gradient in Alaskan montane rundra reveals definite species distribution patterns. Because the bryophyte species distributions do not always correspond to boundaries between vascular vegetation zones, tundra vegetation types based mainly on vascular plants may be imperfectly suited to description of bryophyte vegetation.
Phenological observations of major plant growth forms and species in montane and Eriophorum vaginatum tussock tundra in central Alaska
Authors: Murray Carole , Miller Philip C.
Published: July 2006

The development stages of several tundra plant species were observed during the summers of 1977 and 1978 in different vegetation zones in a snow accumulation area and in tussock tundra. Leaf maturation and senescence tend towards synchrony regardless of the time of emergence from under the snow. Flowering stages are less synchronous and general than are the vegetation stages within a growth form.
Mycorrhizae, mycorrhizal fungi and fungal biomass in subalpine tundra at Eagle Summit, Alaska
Authors: Miller Orson K.
Published: July 2006

The root systems of 16 dominant higher plants in 6 tundra plant communities were examined for the presence of mycorrhizae. Six are ectomycorrhizal, one strictly ectendomycorrhizal, six endomycorrhizal, and three nonmycorrhizal. The higher fungi which fruited among these plants were identified and related to the plants with appropriate ectomycorrhizal associations. Fungal biomass was measured in each community and the mycorrhizal component discussed and estimated. New records of Alaskan species of higher fungi are presented along with new descriptions of mycorrhizae on two subalpine plants.
Soil oxygen flux measured polarographically in an Alaskan tussock tundra
Authors: Stuart Lee , Miller Philip C.
Published: July 2006

Soil oxygen flux was measured polarographically in undisturbed tussock tundra and in an old vehicle track at Eagle Creek, Alaska. Because some polarograms did not show effective voltage plateaus, the polarographic method was tested for use in the tundra by experimental manipulation of soil water content and microbial oxygen demand. The response of soil oxygen flux was as predicted for artificially waterlogged systems, and the response to increased microbial demand indicated relatively high oxygen availability. Soil oxygen flux ranged from 25.9 ng O2 cm−2 min−1 in Sphagnum mats to 3.9 ng O2 cm−2 min−1 in unvegetated ruts of the vehicle track. Most sites in unvegetated ruts did not have measurable soil oxygen flux. In contrast, oxygen flux beneath Eriophorum vaginatum tussocks growing in the vehicle track averaged 10.7 ng O2 cm−2 min−1.
Evapotranspiration measurements in Eriophorum vaginatum tussock tundra in Alaska
Authors: Stuart Lee , Oberbauer Steve , Miller Philip C.
Published: July 2006

Evapotranspiration was measured periodically from late June through mid‐August 1978 in Eriophorum vaginiatum tussock tundra near Eagle Creek, Alaska. The average evapotranspiration rates from tussock and intertussock areas were 0.8 mm d−1 and 1.3 mm d−1, respectively. Potential evaporation was calculated according to the Penman equation using microclimate data collected at the same time actual evapotranspiration was measured. Actual evapotranspiration was 0.56 ± 0.06 (X± SE, N = 10) of the potential evaporation from moss and 0.43 ± 0.08 (X± SE, N = 10) of the potential evaporation from E. vaginatum tussocks. Seventy three percent of the variability in the ratio of actual evapotranspiration to potential evaporation from tussocks was accounted for by linear regression on net radiation. Eighty nine percent of the variability in the same ratio for mosses was explained by linear regression on the vapor pressure deficit of the air and net radiation.
Photosynthetic and respiratory responses to temperature and light of three Alaskan tundra growth forms
Authors: Limbach W. E. , Oechel Walter C. , Lowell William
Published: July 2006

Photosynthetic and respiratory response of four Alaskan tundra species comprising three growth forms were investigated in the laboratory using an infrared gas analysis system. Vaccinium vitis‐idaea, a dwarf evergreen shrub, demonstrated a low photosynthetic capacity: Pmax= 1 mg CO2 g dry wt−1 h−1; Topt < 10°C. Betula nana, a deciduous shrub, had a high relatively photosynthetic capacity: Pmax= 14 mg CO2 g dry wt−1 h−1; Topt 17°C. Two graminoid (sedge) species, Carex aquatilis and Eriophorum vaginalum, showed different responses. Carex showed a high photosynthetic capacity: Pmax= 20 mg CO2 g dry wt−1 h−1; Topt 22°C. Eriophorum vaginatum demonstrated an intermediate photosynthetic capacity of 4 mg CO2 g dry wt−1 h−1 at saturated light levels. Leaf dark respiration, up to 20°C, was approximately the same for all species. The patterns of root respiration among species was opposite to the trend in photosynthesis. Vaccinium vitis‐idaea had the highest rate of root respiration and B. nana the lowest (C aquatilis was not measured). Correlation between leaf nitrogen content (%) and photosynthetic capacity was high. Hypothesized growth form relationships explained differences in photosynthetic capacity between the deciduous shrub and evergreen shrub, but did little to account for differences between the two sedges. Differences in rooting patterns between species may affect tissue nutrient content, carbon flux rates, and carbon balance.
Nutrient effect on maximum photosynthesis in arctic plants
Authors: Bigger C. Mollie , Oechel Walter C.
Published: July 2006

The effect of a 1976 nitrogen, phosphorus, and nitrogen‐phosphorus‐potassium fertilization at Eagle Creek, Alaska, on photosynthetic rates was investigated in 1978 in eight vascular and three nonvascular plant species. While NPK fertilization increased the growth rate of shoots of most vascular plant species, this treatment depressed photosynthetic rates in all vascular species. Therefore, it appears that nutrient limitation of growth is a direct limitation and not mediated through nutrient effect on carbon uptake rates and levels of available photosynthate. The reason for the reduction in photosynthetic rates with fertilization is not known. It is speculated that increases in growth with fertilization causes a dilution of other nutrients or factors, the effect of which is to depress photosynthesis.

Moss photosynthesis is stimulated with fertilization, High NPK fertilizer levels stimulate photosynthesis more than low NPK fertilizer levels. This may indicate basic differences in the ecology or physiology of the two growth forms. It is not yet known if the growth of mosses in this area is stimulated by NPK fertilization.
The effects of variable nitrogen and phosphorous concentrations on Eriophorum vaginatum tillers grown in nutrient solutions
Authors: Kummerow Jochen , Krause David
Published: July 2006

Eriophorum vaginatum tillers were collected at Eagle Creek, Alaska and cultivated in aerated solutions under controlled environmental conditions. The nutrient solutions contained traces, 1.05 and 21 mg l−1 N (nitrate) and traces, 0.15 and 3.10 mg l−1 P (phosphate), pH was maintained at 5.5. The high N, 21 mg l−1, and P, 3.18 mg l−1, nutrient solution produced significant biomass increases. Functional leaf areas were significantly enhanced by high N and P doses in the solutions. Root surface areas varied considerably between treatments; however, significant differences were not found. The mean root surface area of a tiller reached 126 cm2 (range 35–290 cm2), whereas the functional leaf area was 6.8 cm2 (range 3.3–20.3 cm2). Tillers growing in the highest N + P solutions produced twice the number of daughter tillers as tillers growing in solutions with trace amounts of N and P.
Growth of Alaskan tundra plants in relation to water potential
Authors: Oberbauer Steve , Miller Philip C.
Published: July 2006

The relationship of growth to plant water potential was studied in several arctic tundra species by experimentally altering the water regimes on excised tussocks, by clipping leaf area, and by clipping roots. Most species, including evergreen shrubs, showed greater growth under waterlogged conditions. The reduction of leaf area did not affect plant water potentials or growth. Root pruning decreased both plant water potentials and growth. Growth was suppressed when plant water potentials were −12 to −15 bars.