bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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 1964–66The snail abundance is positively correlated to base saturation, to soil moisture and probably also to nitrogen contentThe 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
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‐minersInvertebrate 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 notNo 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
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 methodLowland 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
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 similarWe 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
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 heterogeneityFour 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
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 phenomenaThe 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 successionAmong 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 tenfoldSpecial 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 testLarvae of L dubia were shown to be more successful as predators on Asellus aquaticus in Sphagnum substrate than in debris in the laboratory testLaboratory 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 fishThe 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 abundanceIn 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
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 scaleThe 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 acrotelmBelow 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 stagesThe 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
Naïve birds and noble savages ‐ a review of man‐caused prehistoric extinctions of island birds
Authors: Milberg Per , Tyrberg Tommy 
Published: July 2006

Many bird species were extirpated or became extinct when prehistoric man reached oceanic islands We list > 200 species of extinct island birds only recorded as sub‐fossils and which probably vanished due to prehistoric man In addition we list c 160 cases where an extant species has been found as subfossil on islands where it no longer occurs Several species today considered endemic to single islands of island groups had a much wider distribution in the past Biogeographic analyses of insular avifaunas are almost meaningless it the extensive prehistoric extinctions are not taken into accountMost extinct species belong to Anatidae Rallidae and Drcpanididae while local extirpations are numerous among doves and seabirds Smaller birds are rare mainly due to sampling bias and taphonomic factors The bird populations were depleted mainly by overhunting predation by introduced vertebrates and alteration of the original vegetationPrehistoric humans on islands although dependent on limited animal resources regularly failed to exploit these in a sustainable way Several cases where human populations disappeared from islands in the Pacific may have been due to over‐exploitation of native animalsPrehistoric man reached most tropical and temperate islands and most of the few remaining island faunas have been severely depleted in historic times The prehistoric extinctions emphasize the extreme vulnerability and value of the very few pristine island faunas that still remain
Factors affecting species number and density of dabbling duck guilds in North Europe
Authors: Elmberg Johan , Nummi Petri , Poysa Hannu , Sjoberg Kjell 
Published: July 2006

We addressed how species number and pair density in guilds of co‐existing species is related to habitat structure, and to the abundance and diversity of food resources using the assemblage of seven species of dabbling ducks (genus Anas) breeding in 60 lakes distributed over six regions in temperate north EuropePartial correlation and multiple regression revealed that species richness was best predicted by habitat structural diversity as indexed by a principal component analysis based on 18 vegetation and lake characteristics, and by the abundance of aquatic and emergent prey We found no effect of lake size or prey size diversity on species richness Pair density was correlated with the percentage of shoreline with horsetails (Equisetum), by habitat structural diversity and by the abundance of emergent invertebrate prey Neither prey size diversity nor abundance of aquatic prey correlated with pair density Species richness and pair density in North European duck guilds vary both with habitat structure and prey availability
The distribution of Salix species in Fennoscandia ‐ a numerical analysis
Authors: Myklestad Åse 
Published: July 2006

This paper aims to detect, describe, and interpret the major distributional patterns of species within the genus Salix in Fennoscandia, and to compare these results with a European‐scale analysis of Salix distributional patternsThe occurrences of the 24 native Salix species in the 558.50 km grid squares that comprise Fennoscandia, were recorded on the basis of distnbutional maps in Atlas Florae Europaeae Distnbutional patterns were summarised numencally by means of two‐way indicator species analysis and detrended correspondence analysis, and were related numerically to 42 climatic, geographical, topographical, geological, land‐use and edaphic variables by means of canonical correspondence analysis The possible importance of the relationships between species distributions and the environment was tested statisticallyRegional climate, the most important components being related to summer temperatures, largely accounts for the regional distributional patterns within Salix in Fennoscandia This result agrees with the European‐scale results for Salix, and suggests that these two scales may belong to the same domainThe regionalisation based on Salix is similar to earlier phytogeographical regionalisations of Fennoscandia, suggesting that the climatic factors proposed as being important for Salix distributions may also be important for regional vegetation patterns at the scale of Fennoscandia