bluuebunny/crossref_metadata_2025 huggingface dataset:
Phyto‐ and necromass above and below ground in a fen
Authors: Sjörs Hugo
Published: July 2006

Few investigations deal with the subterranean phytomass in fens (minerotrophic peatlands), their results differing widely. This study was carried out in a “rich fen” in central Sweden, and involved excavation of peat monoliths, depth‐sectioning and hand‐sorting as to species, type of organ, and living or dead condition. The below‐ground living phytomass was large, over 4 kg m−2 in each of two sample plots, being no <97–96% in the dominants, Carex limosa and C. lasiocarpa, 89% on average in Menyanthes trifoliata, and c. 93% for all species. Carex limosa had its rhizome maximum slightly higher than C. lasiocarpa, but a greater part of its roots penetrated deeper. For Menyanthes, also net annual production above and below ground was estimated. The subterranean phytomass decreased with depth, but living roots were found even at 42 cm. The recognizable necromass did not decrease with depth. These recent constituents would render a very unequal age to the peat. The imbalance between the small green aerial phytomass and the much greater subterranean phytomass was emphasized. It could be related to a relatively very great translocation of photosynthates from above to below ground, and/or to longevity of below‐ground organs, the latter at least in Menyanthes.
Stomach content analysis of minke whales Balaenoptera acutorostrata from the Lofoten and Vesterålen areas, Norway
Authors: Lydersen Christian , Weslawski Jan Marcin , øritsland Nils Are
Published: July 2006

Stomach contents from 15 minke whales Balaenoptera acutorostrata collected in the Lofoten and Vesterålen areas of Norway, August 1988, were analysed. All stomachs contained identifiable remains and constituted of fish only. Herring Clupea harengus was the dominant prey species found in all whale stomachs and constituted 92% of the total prey volume. Cod Gadus morhua was the second most abundant prey. In addition pollock Pollachius virens, haddock Melanogrammus aeglefinus, and great silver smelt Argentina silus were found in single whale stomachs. All fish species found in the whale stomachs in our investigations are of commercial importance, and the sizes of the herrings and cods in minke whale stomachs are of interest for commercial exploitation.
Changes in forest soils and vegetation in Søgne, southern Norway, during a 20 year period
Authors: Bjørnstad Ottar Nordal
Published: July 2006

An investigation of the edaphic conditions and the vegetation of 21 fixed plots in Søgne municipality, Vest‐Agder, South Norway was carried out in 1967‐69 and 1987. Loss on ignition, pH, total nitrogen, total exchangeable bases, base saturation, exchangeable hydrogen, sodium, potassium, magnesium, calcium and manganese was analysed. The species composition of vascular plants was investigated. The total cover of the bottom layer was scored.

The soil pH had decreased in the more basic soils but had increased in the more acidic soils. The organic content had increased and base saturation had decreased in most samples. Na+ had increased in more than half of the plots, Ca2+ and Mg2+ had not changed, and K+ and Mn2+ had decreased in most plots. Salt depositions from the neighbouring North Sea and leaching from the soil accounted for these changes. In many of the parameters opposite changes were found in the poorer soils compared to the richer soils. In the field layer Deschampsia flexuosa, Convallaria majalis had increased, and Oxalis acetocella, Galium odoratum had decreased. The cover of cryptogams had decreased in most of the plots.
Distribution history and present status of the raccoon dog in Finland
Authors: Helle Eero , Kauhala Kaarina
Published: July 2006

The raccoon dog Nyctereutes procyonoides Gray was introduced from the Far East in several areas of the USSR, mainly the European part, in 1929–55. The first raccoon dogs were seen in Finland in the latter half of the 1930s, and by the mid‐1950s, the frontier of the first regular observations had reached the most southeasterly parts of the country. Since then, the raccoon dog dispersed through southern and central Finland at an average annual rate of 20 km. The rate of population increase, as well as present density, has been highest in southern and southeastern Finland, and lowest in the northern parts of the distribution area. The northern limit of the distribution lies nowadays in southern Lapland, only a little further north than two decades earlier, when most of southern and central Finland was already inhabited.

The length of the growing season seems to explain most of the variation in the population density between the provinces. The longer the growing season, the better the raccoon dog manages; in southern Finland where the summers are longer, the juveniles have enough time to grow and gather fat reserves before hibernation. Therefore, many of them survive the winter and even breed in the following spring. In the north, in contrast, juvenile mortality is high during the first winter because of the short summer. The food availability, the yield of wild berries and the abundance of small rodents, is mostly responsible for the annual variation in the population density. Near the northern limit of the distribution, climate may also cause some of the annual variation in population density.
Effect of light and nutrients on biomass allocation in Calamagrostis canadensis
Authors: Allan Powelson R. , Lieffers V. J.
Published: July 2006

The effects of light intensity and nutrient availability on the biomass allocation of Calamagrostis canadensis were studied under both greenhouse and field conditions In the greenhouse, seedlings from forest and wetland populations were grown in sand‐peat mixtures, under three light intensities and three fertilizer levels Total above and below ground growth increased with light intensity and nutrient availability, nutrient availability, however, only altered plant growth when light intensity was above moderate levels Numbers of rhizomes were greatest under low and moderate nutrient regimes but high light was also needed for maximum numbers of rhizomes In the field, tillers and rhizomes were examined under open, 40% and 85% canopy cover Tiller and rhizome weight and diameter of rhizomes decreased with canopy closure However, proportional allocation of biomass to rhizomes was greatest and percentage total non‐structural carbohydrates of rhizomes was lowest under a 40% canopy
Ontogenetic changes in the micro‐habitat preferences of Decticus verrucivorus (Orthoptera: Tettigoniidae) at the edge of its range
Authors: Cherrill A. J. , Brown V. K.
Published: July 2006

The large ground‐dwelling bush cricket Decucus verrucivorus is widespread in continental Europe, but declining at the northern edge of its range This paper defines the species' habitat requirements in northern Europe by describing the distribution of each of the seven nymphal instars and adults in relation to vegetation structure within a chalk grassland in southern England First instars were strongly associated with short, sparse turf, reflecting the oviposition behaviour of females Subsequent early instars were also found in short, open turf, but at the fifth moult a distinct shift in distribution to dense grass tussocks occurred Late instars and adults were strongly associated with these structures, probably to avoid vertebrate predators Mean temperatures within tussocks were lower than in short turf, but these highly mobile stages actively thermoregulate by basking on the sides of tussocks In contrast, areas of short turf may be crucial for the development of the smaller and less mobile early instars and eggs It is concluded that a fine mosaic of closely‐grazed turf, dense tussocks and intermediate structures must be created and/or maintained at the species northern‐most sites, if its present distribution is not to contract
Satellite tracking of ringed seals Phoca hispida off northwest Greenland
Authors: Heide‐Jørgensen Mads Peter , Stewart Brent S. , Leatherwood Stephen
Published: July 2006

We monitored movements and haul‐out patterns of four ringed seals Phoca hispida, off Northwest Greenland between 5 June and 31 October 1988 using the Argos Data Collection and Location System When the seals were hauled out on fast ice their locations were accurately determined, but when they were at sea, few accurate locations were obtained, evidently because these seals spent little time at the surface between dives The seals remained within the fjord where they were tagged, and hauled out often to early July Thereafter, as fast‐ice disappeared, they dispersed widely and spent less time hauled out Time of day had no significant effect on haul‐out patterns Haul‐out periods declined significantly from June to August and increased in September‐October Satellite contact with one seal was lost after 16 d while the seal was still in the fjord in late June One seal travelled over 200 km southwest and was located 4 July in offshore waters of Smith Sound 30 d after instrumentation Another seal moved southeast along the Greenland coast where contact was lost after 49 d on 23 July The fourth seal moved north along the Greenland coast, hauled out regularly on ice, and returned south along the coast in late September and October after 181 d of contact with the satellite
Changes in the land mollusc fauna and soil chemistry in an inland district in southern Sweden
Authors: Wareborn Ingvar
Published: July 2006

The land mollusc fauna and some abiotic soil variables were investigated at 20 forest sites SW of Vaxjo, southern Sweden, in 1964‐66 and again in 1987‐88 to evaluate possible effects of soil acidification, base cation leaching and nitrogen deposition The number of snail individuals decreased on average by 60% in herb‐rich deciduous forests and by 80% in spruce and herb‐poor oak forestsNesovitrea petronella, N hammonis, Euconulus fulvus, Vertigo substriata, Cochlicopa lubricaandClausilia bidentatawere most affected The calcium content in litter and surface layer of soil had decreased on average by 31%

The snail number decrease is negatively correlated to base saturation In the lower range of calcium content the change is in good accordance with a significant regression line of abundance on calcium from 1964–66

The snail abundance is positively correlated to base saturation, to soil moisture and probably also to nitrogen content

The soil chemistry and the snail fauna of the coniferous forest sites are so severely affected that a continued acidification and base cation leaching might lead to extinction of the snail fauna in this kind of forest Problems, possibilities and use of results from retrospective studies on the soil fauna are discussed
Stream continuum and metabolic rate in the larvae of five species of Hydropsyche (Trichoptera)
Authors: Roux C. , Tachet H. , Bournaud M. , Cellot B.
Published: July 2006

The effects of temperature on the metabolic rate of five species of Hydropsyche larvae belonging either to the rhithron (Hydropsyche dinarica, H pellucidula and H siltalat) or to the potamon (H contubernalis and H modesta) have been studied The total amplitude of the metabolic rate between 5 and 25°C is higher in the larvae inhabiting the potamon than those of rhithron (particularly in H siltalat and H dinarica) The shapes of the metabolism temperature curves (M/T curves) of H contubernalis and H modesta differ from each other, although they live in the same habitat and are closely related A comparison with some species of Gammarus suggests a relationship between metabolic rate and the variability of environmental conditions
The demography of a clonal herbaceous perennial plant, the longleaved sundew Drosera intermedia, in different heathland habitats
Authors: De Ridder Filip , Dhondt André A.
Published: July 2006

Eight populations of longleaved sundew Drosera intermedia Hayne ramets were studied in three hydrologically and phytosociologically differing heathland habitats over a 4 yr period a pool edge, an old path through the wet heath, a seepage area At the extreme sites, with high levels of water table fluctuations (pool edge and dry path), both survival and recruitment were low, resulting in small populations The pool edge populations went extinct At the less extreme sites (wet paths and seepage area), populations were stable, but ramet and genet turnover was higher at the path sites than in the seepage area Demographic variation between populations was explained by differences in adult survival and sexual recruitment (asexual recruitment did not differ clearly), which, in turn, were related to specific biotic and abiotic factors Likely adult mortality causes were summer drought (all habitats), winter frost (path habitat), cover with a crust of iron bacteria after heavy summer rainfall (seepage area) and shading by Sphagnum and algae (pool edge) Low seedhng recruitment was caused by a low germination succes (pool, seepage area) and seedling survival (seepage area, dry path)
Demographic responses of arctic hares Lepus arcticus placed on two predominantly forested islands in Newfoundland
Authors: Small Robert J. , Keith Lloyd B. , Barta Robert M.
Published: July 2006

During January‐April 1989. we monitored survival, reproduction, and body condition of 19 radio‐collared arctic haresLepus areticusintroduced to two predominantly (80%) forested islands. Merchant (66 1 ha) and Burke (82 6 ha), in Placentia Bay, Newfoundland By late April, bone‐marrow fat (42 7%) and kidney fat indices were lower than found in populations on the mountain barrens of western Newfoundland However, most island hares gained weight overwinter, and litter sizes (mean. 4 2 in utero) and testis weights (mean, 8 3 g) were as large or larger than recorded from other introduced and natural populations in Newfoundland The distribution of telemetry locations, tracks and feeding sites indicated that hares frequented the scattered barrens (totalling c 30 ha) on both islands in greater proportion than available These results suggest that, in the absence of snowshoe hares and mammalian predators, forested regions interspersed with small patches of barrens can sustain arctic hares
The response of invertebrate assemblies to grazing
Authors: Gibson C. W. D. , Brown V. K. , Losito L. , McGavin G. C.
Published: July 2006

Invertebrate communities were monitored in a controlled sheep grazing experiment on ex‐arable land on limestone and in nearby older calcicolous grasslands Results for vacuum sampling of Heteroptera and herbivorous Coleoptera are presented and compared with the responses of spiders, leafhoppers and leaf‐miners

Invertebrate groups differed in their responses to grazing and grassland age in terms of species diversity, abundance, variability over time and the development of a specific fauna on short turf Leaf‐miner assemblies were most strongly determined by the effects of grazing on plant species composition, while spiders' responses could largely be explained by the effects of grazing on plant architecture Spider species simply accumulated over time, whilst leaf‐miners were the most labile group Spiders, leaf‐miners and leafhoppers all contained some common species restricted to old grasslands, whilst herbivorous Coleoptera and Heteroptera did not

No single group demonstrated the full range of invertebrate responses Spiders, leafhoppers and leaf‐miners each showed useful features as “indicator groups'”, but more than one group should be chosen for study in the context of particular research projects
Latitudinal and elevational variation in fruiting phenology among western European bird‐dispersed plants
Authors: Fuentes Marcelino
Published: July 2006

I try to test the prediction that bird‐dispersed plants should produce fruits when fruit‐eating birds are most abundant by reviewing some phenological data of fleshy fruit production in western Europe The prediction that fruit ripening dates in populations of the same species should occur later at lower latitudes and elevations, to coincide with the maximum abundance of fruit‐eating birds, is not supported by the data The patterns of seasonal variation in the total number and biomass of fruits, but not in the proportion of species in fruit, in communities at different latitudes and elevations do coincide with patterns of seasonal abundances of avian frugivores 1 suggest that this coincidence is due to the greater relative abundance (and contribution to total fruit production) in each locality of species that fruit at times of the year when birds are most abundant These species may have achieved a demographic advantage by getting more seeds dispersed than species that ripen fruits in other seasons
The effects of different dissolved oxygen regimes on the growth of a freshwater leech
Authors: Davies Ronald W. , Monita D. M. A. , Dratnal E. , Linton L. R.
Published: July 2006

The growth rates of two size classes of Nephelopsis obscura, a freshwater predatory leech, were determined at five different dissolved oxygen regimes (three constant 10%, 100%, 300%. and two diel cyclical 10‐100% and 100‐300%) at 15°C Both small and large N obscura showed highest growth rates in the diel 100‐300% regime and the lowest in the constant 10% or diel 10‐100% regimes These differences in growth rate affect the predicted time to reach the minimum size for reproduction, e g 42 8 d m constant 10% and 315dm diel 100‐300% regimes for small and 67 9 d and 8 8 d respectively for large N obscura These differences determine whether individuals surviving winter reach maturity and produce cocoons in the spring or the autumn and whether individuals hatched in the spring can reach mature size the same summer
Plant colonization of bare peat surface ‐ relative importance of seed availability and soil
Authors: Salonen Veikko , Setala Heikki
Published: July 2006

A field survey on two former peat harvesting sites of similar successional age revealed a marked difference in species composition and a 30‐fold difference in biomass of the established vegetation Based on this observation, a field experiment in which the substrate was changed between sites was conducted to examine whether the differences in revegetation were mainly a consequence of differences in seed supply or in substrate quality After three growing seasons, a many hundred‐fold difference in plant biomass existed between the transplanted and control plots with the same substrate, but only a small difference between the plots with a different substrate within the site Biological activity in the substrate of the slowly revegetating site (site 1) increased when transported to the more rapidly revegetating site (site 2), while the opposite was true when substrate from site 2 was transported to site 1 The sites differed in the rate of N mineralization, and particularly in nitrification Despite the differences in substrate quality between the two sites, seed supply appeared to be the major factor controlling colonization The impact of the soil factors on plant establishment was, however, considered to be large enough to act as an additional controlling factor
Long‐term microtine dynamics in north Fennoscandian tundra: the vole cycle and the lemming chaos
Authors: Oksanen Lauri , Oksanen Tarja
Published: July 2006

Densities of microtine rodents in two habitat complexes in the tundra of Finnmarks‐vidda, Norwegian Lapland, were studied during 1977‐89 by means of snap trapping (Small Quadrat Method) Predator populations were studied by mapping breeding raptors and by snow‐tracking small mustelids During 1977‐85, snow‐trackmg was conducted only during peak and decline years, whereas during 1986‐89, snow‐tracking was conducted every winter (November‐December) and live‐trapping (in August) was used as an additional method

Lowland vole populations had regular density fluctuations with peaks in 1978‐79. 1982‐84 and 1987‐88 Highland vole populations fluctuated less regularly and at lower over‐all densities Highland lemming populations had two outbreaks, in 1978 and 1988, ending in abrupt winter crashes In the lowland, outbreak levels were reached only in 1978 All microtine declines in relatively productive lowland habitats were accompanied by intense activity of small mustelids. whereas avian predators were common only in 1983 Lowland declines also showed clear between‐habitat asynchrony they started in areas with an exceptional abundance of productive habitats and then spread to more barren areas These lowland data are consistent with the hypothesis of a mustelid‐microtine limit cycle, although also several other hypotheses remain unrefuted The highland lemming data suggest a simple exploiter‐victim interaction between lemmings and the vegetation
Changes in use of lake habitat by experimentally segregated populations of cutthroat trout and Dolly Varden char
Authors: Andrew Joyce H. , Jonsson Nina , Jonsson Bror , Hindar Kjetil , Northcote Thomas G.
Published: July 2006

The role of competition in a lacustrine community of two salmonid species, cutthroat trout Oncorhynchus clarki and Dolly Varden char Salvelinus malma, was studied in three coastal British Columbia lakes Habitat use by the species alone (allopatric) and in coexistence with each other (sympatric) was investigated by gill netting at 0‐40 m depth contours (surface to bottom) so that several habitats (littoral, epipelagic. pelagic, epibenthic) were sampled From June to October, trout used mainly littoral and epipelagic habitats in sympatry and allopatry Char used all habitats in allopatry. and deep habitats (pelagic, epibenthic) not frequented by trout in sympatry The two species were thus spatially segregated with depth in sympatry Diel (day, night) and seasonal changes (spring, summer, autumn) in habitat use were not pronounced The shift in habitat use by experimentally allopatric char but not trout suggests that the effects of competition between sympatric trout and char for habitat resources are greater on the char
Mycorrhizal colonization and macronutrient status of cliff‐edge Thuja occidentalis and Acer saccharum
Authors: Matthes‐Sears Uta , Neeser Christoph , Larson Douglas W.
Published: July 2006

This work was done to determine if suppressed growth of stunted old‐growth Thuja occidentalis along Niagara Escarpment cliff edges was associated with low concentrations of tissue macronutrients and/or the absence of mycorrhizae, and if the restriction of Acer saccharum from cliff edges could be due to similar limitations Mycorrhizal colonization rates and foliar concentrations of N, P, K, Ca, and Mg were compared between the cliff face, cliff edge, deciduous forest and a swamp for T occidentalis, and between the cliff edge and deciduous forest for A saccharum There were statistically significant differences in tissue nutrient concentrations and mycorrhizal colonization between species but not among habitats This suggests that the stunted growth of T occidentalis on the cliff face, and the absence of A saccharum from the cliff edge are not due to limitations imposed by macronutrients or lack of mycorrhizae
Effects of freshwater availability on the summer distribution of otters Lutra lutra in the southwest coast of Portugal
Authors: Rui Beja Pedro
Published: July 2006

The availability of freshwater has been suggested to strongly influence the distribution of coastal otters Lutra lutra The test this hypothesis, a study was undertaken on the relationships between otter distribution and freshwater availability in a coast where freshwater is a very scarce resource during the summer In this area otters occur mostly in a few small coastal streams but feed largely in the sea Twentynine streams were surveyed in the summer of 1990, and the presence/absence of otter signs was related to nine habitat variables Freshwater availability was found to be the most important factor influencing the occurrence of otters in summer It is suggested that otters favour large streams with good vegetation cover, for these are the most likely to maintain frestwater during the dry periods The distribution of otter signs m streams was also analysed, and it was found that signs tend to concentrate particularly near the mouth of the streams This habitat analysis has some conservation implications, indicating that the decrease of freshwater availability or quality of streams can make these unsuitable for otters, severely decreasing the areas suitable for the species in the southwest coast of Portugal
Terrestrial paternal care and short breeding seasons: reproductive phenology of the midwife toads Alytes obstetricans and A. cisternasii
Authors: Márquez Rafael
Published: July 2006

The reproductive phenology of two Iberian populations of midwife toads Alytes obstetricans and A cistemasii were studied in 1988 and 1989 in two different habitats where chmatological conditions restricted reproductive activity to a few months per year All the observed mating activity of A cisternasii occurred in less than a week while A obstetricans ma tings were observed for over a month A cisternasii matmg activity was explosive and correlated with rainfall No clear trends were observed m the timing of egg mass releases with male size, egg mass size, and proportion of egg mass hatched In both populations males did not complete more than one cycle of egg mass tending per season The duration of terrestnal egg development was estimated to be of 32 d for A obstetricans Alytes cistemasii showed greater flexibility on the duration of egg development, egg masses being released 23 d after the matings m 1988 and 30 d after in 1989 This flexibility is an example of the adaptive significance of terrestrial paternal care when water availabihty is unpredictable
Quantitative analysis of sexual dimorphism and sex ratio in Hyphydrus ovatus (Coleoptera: Dytiscidae)
Authors: Juliano Steven A.
Published: July 2006

Sexual dimorphism in size, shape, and mass relative to length, and sex ratios are quantified for populations of Hyphydrus ovatus. a dytiscid beetle Males of H ovatus are not only longer than females, but also significantly larger in elytron length, thorax width, head width, leg length, total width, total depth, and abdominal segment length Two local populations differ slightly but significantly in total depth and abdominal segment length, but sexual dimorphism in size is similar for the two populations Hyphydrus ovatus are also sexually dimorphic in shape, with males having relatively broader heads and thoraxes than females The two populations differed slightly but significantly in relative abdominal segment length, but as with size, sexual dimorphism in shape is similar for the two populations Males are relatively heavier than females, although the slope of the log mass vs log length relationship is the same for the two sexes Sex ratios in field samples vary significantly over the summer, with percent females declining from c 50% to c 15% Sex ratios are significantly below 50% females m two of five monthly samples and in the total pooled set of samples Sexual dimorphism in size, shape, and relative mass, combined with male‐biased sex ratios suggest that larger size of male H ovatus is a product of sexual selection
Induced defence reaction in Scots pine following stem attacks by Tomicus piniperda
Authors: Långström Bo , Hellqvist Claes , Ericsson Anders , Gref Rolf
Published: July 2006

The induced defence reaction of Scots pine Pinus sylvestris to stem attacks by the common pine shoot beetle, Tomicus piniperda (Col, Scolytidae), was studied by inducing natural attacks on young Scots pine trees of different vigour Pruned trees were more heavily attacked by T piniperda than unpruned ones Vigorous trees successfully contained the attacking beetles within resinous lesions, whereas less vigorous trees failed to defend themselves The content of resin acids increased dramatically in the lesions on all trees, and the resin acid composition differed somewhat between some treatments Starch accumulation in the inner bark of the main stem was lower in pruned trees than in unpruned ones, and starch reserves were depleted in the most heavily attacked trees All but one of the unpruned trees survived the attack, whereas most of the severely pruned ones died following attack by beetles at densities exceeding c 300 egg galleries m−2
The diet of coastal breeding hooded crows corvus corone comix
Authors: Berrow S. D. , Kelly T. C. , Myers A. A.
Published: July 2006

Three methods of analysis were used to determine the diet of territorial hooded crows at Lough Hyne Marine Reserve, Co Cork, Ireland The regular collection of prey Items from these sites at Lough Hyne was integrated with pellet and stomach analysis to determine diet Intertidal organisms occurred in over 80% of pellets and 43% of stomachs and occupied over 77% of the total wet weight of foods identified in pellets All prey items recovered from drop sites originated from the intertidal habitat, involved either large‐sized species or larger individuals of smaller‐sized species, and were only dropped during October to February Twenty‐five intertidal species were identified but only a few of these species contributed to the bulk of the diet Hooded crows were shown to consume a wide range of intertidal species throughout the year, though the species composition in the diet was seasonally influenced Depletion and weight loss of intertidal molluscs through the winter was shown to have a minimal effect on selection suggesting that prey switching was driven by the birds nutritional requirements
Shorebird predation may cause discrete generations in an amphipod prey
Authors: Matthews S. L. , Boates J. S. , Walde S. J.
Published: July 2006

We examine the possible impact of intense, periodic predation by the semipalmated sandpiper Calidris pusilla, on the life history patterns of its amphipod prey, Co‐rophium volutator We compare populations from two mudflats, one of which is visited by shorebirds on their annual migration south, and one which physically appears very similar but is not visited by the birds The Corophium population exposed to intense predation had two distinct peaks in density within the season, corresponding to two generations, and the two cohorts had constrained size distributions, and relatively synchronized timing of reproduction On the mudflat not visited by sandpipers, densities increased m spring and then remained constant through summer Reproduction was continuous The mid‐summer decline in amphipod density on the mudflat used by sandpipers could not be attributed directly to sandpiper predation as had been previously argued We interpret the decline as the result of a synchronized natural die‐off after reproduction Selective predation on large amphipods may contribute to the second peak in density by increasing juvenile survivorship due to the removal of competing adults Size‐selective predation by sandpipers causes the overwintering cohort to have a restricted size range m the autumn, and this synchrony persists through to the reproductive period of the following spring We do not exclude the possibility that these differences in life history have been influenced in an evolutionary sense by the long history of intense periodic predation
Insect herbivory on water mint: you can't get there from here?
Authors: Warren Philip H.
Published: July 2006

Aquatic plants are thought to have fewer herbivore species than their terrestinal counterparts, and possibly to suffer less herbivory I examined herbivory on water mint Mentha aquatica growing in and out of water and tested possible processes determining the observed pattern of leaf damage Plants growing on land had much more herbivore damage than those growing in water The most common herbivore of Mentha at the site (a chrysomelid beetle) showed no p reference for leaves from terrestrial plants over those from aquatic plants Caging aquatic plants to exclude moorhens suggested that these predators were not having a strong effect in removing insect herbivores (though this conclusion is tentative due to low insect numbers) Transplanting aquatic plants to a terrestrial location, while keeping their roots in water, resulted in marked increases in herbivore damage, relative to control aquatic plants The results suggest that the water barrier may prevent effective exploitation of emergent aquatic plants by terrestrial herbivores This may have consequences for observed patterns of herbivore richness on such plants, plant fitness, and a more speculative suggestion, for the mode of reproduction in aquatic plants
Fish species‐environment and abundance relationships in a Great Plains river system
Authors: Taylor Christopher M. , Winston Matthew R. , Matthews William J.
Published: July 2006

Fish assemblages in the upper Red River system of southwestern Oklahoma (USA) were predictable along measured environmental gradients Conductivity was the most important variable predicting structure of fish assemblages followed by stream size, alkalinity woody debris and water clarity Classification of abundance data identified four groups each of species and sites Species groups were separated on a habitat template indicating similar environmental responses within groups However, site groups showed considerable overlap on the template Correlations among species environmental preferences were significantly associated with correlations of species abundances Likewise, site correlations on the basis of measured environmental variables and on the basis of species abundances were significantly similar

We tested abundance and distribution data for agreement with the hierarchical model of Kolasa Several testable predictions of the model described our data well specialist species outnumbered generalist species and were less abundant on average, than generalist species Average abundance of species was highly correlated with their ecological ranges and species were clumped along both ecological range and abundance axes
Reproductive ecology of the boreal riparian guild of Drosophila
Authors: Aspi J. , Lumme J. , Hoikkala A. , Heikkinen E.
Published: July 2006

The reproductive ecology of four sympatric Drosophila virths group species (Diptera Drosophilidae) was studied in the field to trace the factors maintaining species isolation There was a high probability of meeting a heterospecific individual belonging to the same species group on the basis of adult spatial occurrence Direct field observations revealed that the males court also females of the foreign species but interspecific courtships do not lead to mating The main mating period among these species lasted only several weeks and the timing of mating periods differed markedlv in the three most common species Reproductive character displacement between species may explain the observed differences in the timing of the mating periods but they could have arisen in the context of other selective pressures than the prevention of interspecific courtships and matings
Response of a raptor community to shrinking area and degradation of tropical rain forest in the south western Ghâts (India)
Authors: Thiollay Jean‐Marc
Published: July 2006

The influence of irregular or incomplete fragmentation and increasing degradation of natural rain forest on diurnal raptor community was studied in the northern part of the western Ghâts in southwestern India A census of mainly territorial breeding pairs on 400 ha sample quadrats was associated with a measure of the percent cover of the main habitat types and a degree of forest fragmentation including irregular patch shape and habitat heterogeneity

Four groups of 3‐4 species were defined according to their decreasing tolerance to forest fragmentation and disturbance, from mostly open grassland species to interior forest specialists Habitat selection, density and sensitivity to landscape structure were investigated The community composition and dynamic of each habitat were the sum of these specific reactions The distribution of species along the succession of increasing fragmentation and forest degradation was thus found to be non random, but did not follow a nested subset pattern The density of forest species declined with forest patch size possibly because of the irregular patch shape, the increased edge effects and the consequent increase of linear distance for a bird to cover within its territory However, sensitivity to habitat structure and disturbance was found to be even higher than sensitivity to area per se The need to conserve the largest patches of little disturbed forest is emphasized, as well as the conservation value of woodlots‐open habitat mosaics that are suitable for a different set of species
Artificial nest predation and habitat fragmentation: different trends in bird and mammal predators
Authors: Nour Nadia , Matthysen Erik , Dhondt André A.
Published: July 2006

Predation on artificial nests was studied in Belgian deciduous forest fragments between 1 and 200 ha Predation rates were compared to fragment size, distance from the forest edge, time period (three replicates), and nest type (ground and tree) Logistic regression analysis showed that overall nest predation did not vary with distance from the edge, forest size, and time period Birds represented over 70% of all predator attacks but their importance decreased in larger areas and away from the forest edge where mammals were responsible for much of the nest predation It is concluded that the effect of habitat fragmentation depends on the composition of the local predator community
Plant population patterns in a glacier foreland succession: pioneer herbs and later‐colonizing shrubs
Authors: Whittaker Robert J.
Published: July 2006

Glacier forelands provide valuable sites for the study of patterns and processes of primary succession The Storbreen glacier foreland, south‐central Norway, has previously been the subject of a suite of community‐level approaches Here the focus is population‐level studies of six key pioneer plants Arabis alpina, Deschampsia alpina, Oxyria digyna, Poa alpina, Saxifraga cespitosa and Trisetum spicatum and four heath shrubs Betula nana, Empetrum hermaphroditum, Phyllodoce caerulea and Salix complex (Salix glauca and S lanata) Size‐frequency distributions are used as indicators of population phenomena

The optimal conditions for growth and fecundity of Arabis alpina and Saxifraga cespitosa appear to be almost immediately upon deglaciation (< 7 yr), although both achieve their maximum cover on slightly older terrain A similar pattern was noted for the grasses, although their optima come at slightly later times Population phenomena in Oxyria digyna could not be related to terrain age, indicating a differing role of this species within the succession

Among the shrubs a number of demographic and behavioural patterns are identifiable as successional features, and other patterns are explicable in relation to changing histories of disturbance and site moisture relationships Establishment and build‐up in Empetrum hermaphroditum and Salix complex do not appear to be environmentally constrained, in contrast to Betula nana and Phvllodoce caerulea Betula nana is the slowest species to colonize, but occasional early colonists appear healthy and fecund, pointing to a strong environmental sieve at the point of establishment The population patterns varied considerably among the shrub species, the most striking common feature being in mode of establishment Establishment of ramets by vegetative means occurs increasingly on older ground within the foreland (maximum terrain age 230 yr) but only in sites of the mature heath outside the foreland is it the characteristic mode of establishment In exception to this pattern, vegetative establishment of Phyllodoce caerulea is very rare in all conditions studied Discussion focuses upon the importance of population phenomena, seed dispersal and life‐history characteristics in successional change It is concluded that processes involved in species turnover include both allogenic and autogenic elements and that although the two classes are difficult to separate in practice, autogenic factors become more significant whilst species‐environment relations become tighter in later phases of vegetation development
Sphagnum mosses as a microhabitat for invertebrates in acidified lakes and the colour adaptation and substrate preference in Leucorrhinia dubia (Odonata, Anisoptera)
Authors: Henrikson Britt‐Inger
Published: July 2006

The increase of peat mosses. Sphagnum spp, in acidified lakes leads to a changed microhabitat structure for benthic invertebrates The importance of this change was investigated for some benthic invertebrates Comparisons between quantitative samples of Sphagnum and debris within the acidified Lake Stora Hastevatten, in the Lake Gårdsjon catchment of SW Sweden, showed significantly higher abundances of Chironomidae, Ceratopogonidae, Odonata, Trichoptera, Cladocera and Argyroneta aquatica (Araneae) in Sphagnum For Chironomidae and Cladocera the differences were tenfold

Special reference was made to the libellulid Leucorrhinia dubia which is common in acid lakes In a laboratory test, late instar larvae of L dubia were shown to be able to change colour to correspond to the brown and green colour of Sphagnum This result was completed with a field test where larvae of L dubia were significantly more common in Sphagnum of the same colour as the larvae The ability to change colour may have an adaptive value when coexisting with visual predators Small larvae, 4‐5 mm, were significantly more prevalent in Sphagnum and they also showed significant preference for this substrate in the laboratory test For medium‐sized larvae, 12‐14 mm, a tendency to prefer Sphagnum was found in the laboratory test

Larvae of L dubia were shown to be more successful as predators on Asellus aquaticus in Sphagnum substrate than in debris in the laboratory test

Laboratory predation tests with Notonecta glauca, Corixa dentipes, Acilius sulcatus, Hyphydrus ovatus and L dubia showed that they could all feed on larvae of L dubia The complex habitat structure of Sphagnum is probably the reason for the high abundance of invertebrates since it may serve as both shelter against predation and as foraging sites It is probably important as a key habitat for young instars of, for example, L dubia In lakes with large Sphagnum mats, L dubia can coexist with fish

The expansion of Sphagnum due to acidification will probably benefit many acid‐tolerant invertebrate species
Temporal and spatial variation of coastal zooplankton in the Baltic Sea
Authors: Johansson Sif , Hansson Sture , Araya‐Nuñez Orfelina
Published: July 2006

When analysing temporal variation monthly mean abundances of zooplankton sampled at a eoastal station in the northern Baltic Sea between 1976 and 1988 showed the lowest between‐year variation in the summers The coefficients of variation were estimated at 50% for rotifers in June. 70% for cladocerans in August and between 30 and 50% for different copepodite stages in August Moreover in the summers, all dominating zooplankton groups were abundant Estimates of yearly biomass or production of zooplankton must, however, be based on frequent sampling during the whole year because of large differences between months in zooplankton composition and abundance

In 1989. spatial variation was analyzed by sampling zooplankton on three occasions along a 9 8 km transect with 15 stations, 700 m apart All taxonomic/life‐stage groupings of zooplankton were heterogeneously distributed Geostatistical analysis did not give a definite answer to what the minimum distance between stations should be to obtain independent samples but indicated that 700 to 1400 m would be sufficient in most cases For most of the zooplankton groupings the coefficients of variation in the sampled area were estimated at 20‐40% on all sampling occasions
Vegetation communities and plant distributions and their relationships with parent materials in the forest‐tundra of northwestern Canada
Authors: Timoney Kevin P. , La Roi George H. , Zoltai Stephen C. , Robinson Anne L.
Published: July 2006

Vegetation data from 95 sites and chemical and textural data for parent materials from 98 sites in subarctic northwestern Canada were analyzed by ordination, classification, and statistical techniques A discontinuity in plant species occurrence, vegetation communities, and parent materials takes place near the southeast/northwest boundary north of Great Slave Lake Till parent materials in the forest‐tundra show regional differences in nutrient concentration and texture that correlate with the local bedrock Northwestern tills, as a group, are markedly richer in nutrients and finer‐textured than Shield tills, with much higher levels of cation exchange capacity, nitrogen, potassium, calcium, magnesium, hydrogen, and organic carbon, and more silt and clay than Shield tills Plant species occurrence and vegetation community composition show strong relationships with soil pH, moisture, texture, and latitude The northwest is characterized by calciphilic white spruce. Dryas, legume, and bryophyte communities, and high species diversity, on basic loamy Cryosols The southeast is characterized by acidophiles and widespread generalist black spruce, ericad, and lichen communities, and low species diversity, on acidic loamy sand and sandy loam Brunisols
Accumulation and release of organic matter in ombrotrophic bog hummocks ‐ processes and regional variation
Authors: Malmer Nils , Wallén Bo
Published: July 2006

Dry bulk density (BD) and concentrations of N and C in the organic matter have been studied in the top layers (0‐40 cm) of Sphagnum‐dominated hummocks on ombrotrophic bogs selected to form three gradients from hyperoceanic to weakly oceanic conditions in areas of different latitude in NW Europe and North America In such hummocks N is conserved during the decay process and can therefore be used as an innate marker to calculate mass balances and the rate of the decay process and also to establish an approximate time scale

The variation in BD and N by depth in the living moss layer is explained by the growth pattern of the mosses and the litter formed at the bottom of the layer (the litter depositon level, LDL) becomes depleted in N Further down in the litter and peat layers the variation in BD and N is explained by the decomposition and the subsequent losses of C and disintergration of the matrix of the organic matter in the acrotelm

Below the LDL the concentration of N increases with depth down to the decay decrease level (DDL) as does BD down to the compaction decline level (CDL) a few cm below the DDL In both cases the increase can be described by an exponential function of the cumulative amount of N and cumulative weigth of organic matter respectively The increase in BD dependes more on the matrix of organic matter losing resistance than on the load of the overlying peat The DDL is regarded as the limit between the two functional layers which are the acrotelm and catotelm Below the DDL and CDL the irregular variation in N and BD indicates that the processes of decay and compression have become interrupted at various stages

The annual transfer of organic matter to the litter layer at the LDL is about ten times greater on the bogs in the hyperoceanic temperate regions, than in the sub‐arctic region However, the depth of the DDL and amount of organic matter contained above it does not correlate with the degree of oceanity The age of the organic matter at DDL (range 40‐ >400 yr) is less in the hyperoceanic areas than in the less oceanic areas at the same latitude However higher decay rates on the bogs in the hvperoceanic areas offset the higher transfer of organic matter at the LDL As a result the final accumulation of slowly decaying organic material in the catotelm does not correlate with the degree of oceanity but might instead depend more on the hydrology of the bog