bluuebunny/crossref_metadata_2025_split huggingface dataset:
Population dynamics of the coprophilous moss Tayloria tenuis in a Pyrenean forest
Authors: Lloret Francisco 
Published: July 2006

Three populations of Tayloria tenuis (Splachnaceae) growing on three isolated cattle droppings in coniferous forests of the Eastern Pyrenees were sampled by permanent grids through three years. Each population was initially in a different stage of the dung colonization process. At first, T. tenuis developed a conspicuous protonema on the dropping surface. After one or two years, the moss completed development and fruited abundantly. Eventually, the populations were covered by larger pleurocarpous mosses, which were common on the forest soil.There were important differences between the two stages of development of the T. tenuis gametophyte: the protonema stage exhibited high mortality but rapidly covered nearly all the free surface of the dropping. Afterwards, the gametophore stage established more permanently.Pleurocarpous mosses growing over Tayloria tenuis gametophores produced changes in the vegetative and reproductive pattern of this species. Tayloria tenuis disappeared gradually from the places covered by pleurocarps, although these larger species exhibited high rates of mortality at a micro‐scale level.
Flower herbivory and seed predation in Silene vulgaris (Caryophyllaceae): effects of pollination and phenology
Authors: Pettersson Mats W. 
Published: July 2006

Pollination and seed predation were studied in Silene vulgaris populations during two seasons, one with much lower pollinator abundance than the other. Among the pollinators, noctuid moths of the genus Hadena also acted as seed predators. Nectar‐foraging female moths oviposited in flowers, and their larvae consumed flowers and seed capsules.Despite a lower percentage of pollinated flowers in the year of low pollinator abundance, similar numbers of flowers set fruit in both years, because fewer flower buds and flowers were eaten by Hadena larvae during the year of low pollinator visitation. The number of seed capsules preyed upon was also lower in the year with low pollinator abundance, resulting in a higher seed set. The positive correlation between the percentage of pollinated flowers and the percentage of seed capsules destroyed was also observed when comparing flowers opening in different parts of the season.Early flowering plant individuals had the same pollination success but suffered higher seed predation than late flowering ones. Selection for maximized pollination success through synchronous flowering, is probably the main reason for the compressed flowering period in 5. vulgaris, but the high level of predation early in the season may further increase the reproductive success of synchronous flowering individuals.
Mechanisms regulating bird predation on a herbivorous Larva guild in boreal coniferous forests
Authors: Atlegrim Ola 
Published: July 2006

Bird predation was previously found to considerably reduce the abundance of the herbivorous insect larva guild feeding on bilberry Vacanium myrtillus within boreal coniferous forests In this follow‐up study, interest was focused on determining whether female pied flycatchers Ficedula hypoleuca tend to use the field layer more frequently than other types of feeding niches In addition, the degree to which the conspicuousness of a larva increases the risk of its being preyed upon by birds was evaluated in order to further understand the mechanisms regulating the bird predation effect Larval predation risks were measured by presenting larvae with contrasting characteristics to seven captured female flycatchersFemale flycatchers hunted more frequently in the tree and field layers than in the air However, the relative degree of utilization of the tree and field layer varied considerably between years, with use of field layer being positively related to the abundance of insect larvae on bilberryLarge larvae did not suffer higher bird predation than small larvae when both size classes were presented to the birds on bilberry Larvae that crawl on leaves and stems during feeding (high degree of exposure) were preyed upon more than larvae that feed between leaves they have spun together (low degree of exposure) No difference in larval predation risk was found between sawflies and geometrids, the two taxa represented in the exposed feeder group However, dark geometrids suffered higher predation than green sawflies and green geometridsMy findings suggest that the herbivorous larva guild constitutes an abundant food resource frequently utilized by small bird predators However, certain members of the guild appeared to be preyed upon more than other members Thus the risk for predation seems to be highest for dark geometnds followed in decreasing order by green geometrids. sawflies pyralids, and tortricids
Dry matter economy and reproduction of a temperate forest spring geophyte, Allium ursinum
Authors: Eggert Andreas 
Published: July 2006

For a natural population of Allium ursinum age states are defined on the basis of morphological criteria Differences in the dry matter economy of these age states illustrate the underlying life historyMost seeds rest several years m dormancy after maturity It takes on average more than 6 yr until juvenile plants attain the dry matter threshold level for the production of an inflorescence Flowering plants divert 41% of their dry matter gain during spring to reproductive parts (7% to the seeds) Since flowering plants show a marked negative annual dry matter balance, c 81% of them are not able to flower again the next yearAt the same expense of carbon reserves the formation of daughter bulbs results in a considerably higher number of new ramets than the production of seeds Nevertheless, the investment in seed production is extraordinarily high in relation to other woodland perennials This might be explained by the lack of an effective dispersal of the daughter bulbs By vegetative propagation dense groups of adult ramets develop, which will finally undergo mutual shading
The reproductive behaviour of a clonal herbaceous plant, the longleaved sundew Drosera intermedia, in different heathland habitats
Authors: De Ridder Filip , Dhondt André A. 
Published: July 2006

The reproductive behaviour of the longleaved sundewDrosera intermediaHayne was studied in three hydrologically differing heathland habitats a pool edge, an old path through the wet heath and a seepage areaSexual reproductive allocation (SRA) (the slope of the regression of sexual biomass on vegetative biomass m a given season) differed strongly between years (related to temperature and precipitation) and habitats Averaged over years, path plants had a higher SRA than plants in the seepage area and at the pool edgeAsexual reproductive allocation, expressed as the size‐dependent probability of reproducing asexually, did not differ between habitats in most yearsThe observations agreed with general life history theory SRA was high in the path habitat where adult survival chances were low and juvenile (= seed, first year seedling) survival was high SRA was lower in the seepage area where adult survival chances were higher and juvenile survival lower At the pool edge, a habitat with high adult mortality and low juvenile establishment, the predicted optimal reproductive behaviour, a high SRA, was not observed due to environmental constraints (inundation)
Influence of weather conditions on pallid swift Apus pallidus breeding success
Authors: Cucco Marco , Malacarne Giorgio , Orecchia Gualtiero , Boano Giovanni 
Published: July 2006

The reproductive ecology of three colonies of pallid swift in a warm continental climate (Piedmont, NW‐Italy) was studied over a ten years period About 60% of the clutches were laid in late May and June, but continued until late August and September, when some females laid a second clutch Clutch size and the mean number of fledged young decreased progressively from spring to autumnLaying dates were influenced by rain and temperature unfavourable weather conditions during May induced most females to postpone egg laying until June Clutch size was not related to the rain or temperature parameters consideredThese observations differ from the findings about the common swift studied in cool temperate areas, where a very short stay in the breeding colonies does not allow a delay in laying, and spring weather conditions therefore have a strong influence on clutch size There are also differences about the effect of weather on chick rearing In warmer climates, typical of our colonies, fledging success is hindered both by too dry or too rainy seasons, even if these situations very rarely occur and the three‐egg clutch is always the most productive In colder climates the breeding success of the common swift depends primarily on the climatic conditions of May. and in bad weather a two‐egg clutch is more productive than a clutch of three In summary, the annual breeding success of the pallid swift appears little influenced by weather changes, due to a lesser impact of adverse conditions in Southern climates and the possibility, for this species, of shifting the laying period in response to a temporary worsening of climatic conditions
Reproduction and growth in bank voles Clethrionomys glareolus: the effect of food‐quality and density manipulations in a laboratory colony
Authors: Kviljo Tor , Anker Ims Rolf , Stenseth Nils Chr. , Bondrup‐Nielsen Søren 
Published: July 2006

Young laboratory raised bank voles Clethrionomys glareolus, originating from a cyclic population at low phase, were experimentally subjected to manipulations of food and density This was done to assess possible effects of the juvenile environment on later breeding success Juveniles were exposed to the expenmental treatments for 40 d previous to pairingThe study revealed that a high population density in itself can increase future breeding success as compared to low density This effect was only found m females There were also indications that high density led to arrested growth in subordinate females
Habitat use of small mustelids in north Fennoscandian tundra: a test of the hypothesis of patchy exploitation ecosystems
Authors: Oksanen Tarja , Oksanen Lauri , Norberg Mats 
Published: July 2006

The habitat use of small mustelids in a tundra area in Norwegian Lapland was studied chiefly by means of snow‐tracking 1986‐89 Stoats showed strong peference to a habitat complex immediately beneath the thrust line of the Scandes, with exceptional abundance of luxuriant habitats, whereas weasel activity was more evenly spread over the lowland tundra Mustelid activity on the high tundra above the thrust line was consistently low Within each subarea. stoat activity was concentrated to the most luxuriant habitats Similar preferences were shown by weasels on the lowland but not in the vicinity of the thurst cliff Daily movements of both species varied from local (c 200 m) to extensive (up to 4 km), no consistent interspecific differences in travel distances could be observedThe results largely conform to the hypothesis of patchy exploitation ecosystems (T Oksanen 1990a), according to which predator activity tends to “spill over’ from luxuriant habitats, capable of supporting predator populations, to adjacent barren ones, due to despotic behavior within and between species and due to opportunistic predation by transient predators However, predator activity in barren habitats during the crash winter could not be explained by these mechanisms alone A third mechanism ‐ breakdown of habitat preferences of predators during crash phases of a cyclic prey population ‐ was thus introduced
Distribution, ecology, mode of reproduction and karyology of freshwater planarians (Platyhelminthes; Turbellaria; Tricladida) in the springs of the central Pyrenees
Authors: Roca Josep R. , Ribas Maria , Baguñà Jaume 
Published: July 2006

The distribution, reproductive modality and karyology of populations of freshwater planarians were studied together with physico‐chemical variables m 149 springs in the central Pyrenees Diversity was limited to four species (Dugesia (Dugesia) subtentaculata, Polycelis felina. Crenobia alpina and Phagocata vitta), already known from streams and lakes Planarians were found rarely (only a third of springs contain them), m low‐moderate abundance, and any single spring did not harbour more than one speciesThe distribution of potential predators and preys among the springs sampled was fairly uniform So. we assume that whereas predation is unlikely to influence triclad distribution, the oligotrophic character of these habitats may explain, through food shortage and ensuing interspecific competition, the presence of a single species in each spring Besides interspecific competition, the distribution of each species can also be influenced by particular abiotic parameters Temperature and current velocity appeared to be the dominant factors, the first separating C alpina from the rest of species, and the second favouring the presence of P felina in a large set of springs These factors also seem to determine planarian distribution in streams and rivers Other environmental factors such as calcium bicarbonated water (for D subtentaculata) and preference for karst systems (for Phagocata vitta) are of importance Some peculiarities of distribution, like the scarcity of C alpina in reophile habitats and the thermal tolerance of Phagocata vitta, may be due both to competition from P felina and to historical factors in the former and to morphological (presence of pigment) and ecological (epigean habits) features m the latter, respectivelyKaryological analyses demonstrated triploidy in all populations of D subtentaculata. a polyploid origin for C alpina and the finding in Phagocata vitta of a new polyploid series leading to the highest chromosome number in turbellarians (14n = 238) Furthermore, the basic chromosome number of C alpina (n = 21) and Phagocata vitta (n = 17) differs from those found in northern European populations (n = 7 in both, respectively) This suggests that under the specific names C alpina and Phagocata vitta more than one species actually occurs, this being a problem for further studiesWhereas polyploidy has often been related to living in cold, harsh habitats, asexual reproduction has been linked to environments where biotic stress is low The preeminence of asexual reproduction (by fissiparity) and polyploid forms in freshwater planarians inhabiting the unproductive, biotically unsaturated springs of the central Pyrenees adds new evidence to strengthen such links
Demography of persistent juveniles in Fraxinus excelsior
Authors: Tapper Per‐Goran 
Published: July 2006

Seedling emergence, survival, growth, and juvenile development of Fraxinus excelsior were followed over 10 yr in permanent plots m a dense Alnus‐Fraxinus woodland in the outer archipelago of Stockholm, Sweden Number of germinated seedlings varied between years, due to variation in total seed crop but was also affected by weather conditions Seedlings and juveniles showed high survivorship 39 2% of the emerged seedlings of the two oldest cohorts were alive in the 9th growth season Mortality was somewhat raised during the first two years, but was age‐independent from the third year The density of the field‐layer and climatic factors were the most important determinants of mortality The juveniles produced 1 2 pairs of leaves per year and had an annual height increment of 7 1 mm, on average, from their second growth season The ontogenetic development, e g the increase m leaf complexity, was correspondingly slow and included regressions to more simple leaves Fraxinus excelsior shows a regenerative strategy involving persistent juveniles The divergence between this and previous studies may be due to the lack of rabbit grazing
Winter filtering, immigrant selection and species composition of insular mammals of Lake Huron
Authors: Lomolino Mark V. 
Published: July 2006

Patterns in species composition of small mammals on islands of northwestern Lake Huron, USA were studied to test the hypothesis that insular community structure was strongly influenced by immigrant selection, l e, selection for the more vagile species Of 17 insectivores and rodents in the mainland pool nine were detected on at least one of the 25 islands studied These species comprised a biased subset of the mainland pool, biased in favor of species with relatively good winter immigration abilities The five true hibernators were absent from all islands studied and the two winter‐inactive species occurred on just two islands Frequency of insular occurrence increased with level of winter activity (hibernator vs winter‐inactive vs winter‐active) and with body size (p < 0.02)The winter filtering effect remains one of the best documented forms of immigrant selection In general however, insular community structure is influenced by the combined effects of selective extinction as well as selective immigration Common insular species are those which combine relatively high immigration abilities with low resource requirements
Dispersal strategies of Danish seashore plants
Authors: Andersen Ulla Vogt 
Published: July 2006

The present research is based on previous surveys of primary succession in Danish seashore communities Dispersal spectra for these communities set up, using diaspore morphology as evidence for mode of dispersal Dispersal spectra of species occurring in different zones and different successional phases are compared, and differences between the dispersal spectra of natural and man‐made communities are investigatedThe dispersal of diaspores to Danish seashore communities occurs at random because it is mostly achieved by abiotic agents or human beings Wind is the prevalent dispersal vector, even though wind dispersal is not as common in Danish seashore communities as It IS in open, disturbed, treeless vegetation throughout the world Dispersal by water is most common among seashore plants that occur in the outer zones As the succession progresses, it is found that plants with no special device or censer dispersal are more frequent in the intermediary stages, while dispersal by ants, adhesion, and in the digestive tract of animals increases later in the succession No significant difference between dispersal spectra of the natural and man‐made communities was found
Growth and survival strategy of the Antarctic mite Alaskozetes antarcticus
Authors: Convey Peter 
Published: July 2006

Growth and mortality rates of three juvenile instars and adults of the oribatid miteAlaskozetes antarcticuswere measured over a twelve month period using field enclosures m Its maritime Antarctic habitat A pattern was found of rapid growth during the short summer period (0 2‐0 4 μg dry weight increment per day) followed by gradual weight loss overwinter Most individuals completed one instar per year, reaching a premoult resting phase by late summer, with the moult being delayed and relatively synchronised early the next summer A small proportion of proto‐ and deutonymphs completed two moults within one summer period After the final moult adults overwintered again before commencing oviposition, suggesting that the life cycle (egg‐egg) will take at least five years Mortality was not biased towards any instar or time of year Highest individual growth rates were obtained at a constant temperature of 7°C in the laboratory However expenmentai increase of mean field temperature from 2 7 to 4 3°C by use of a plastic cloche led to decreased growth, although no change in moulting frequency or mortality rate Laboratory survival was greatest at 2°C and decreased with increasing temperatureAlaskozetes antarcticusmay be descnbed as ‘a’ (adversity) selected, showing an exceptionally long life cycle of five to six years and extensive physiological investment in survival adaptations Moult synchronisation in early summer, involving entering winter in the inactive premoult phase, will increase overwinter survival by reducing the chance of inoculative freezing from gut contents, and may be advantageous in maximising the time available for feeding during the subsequent summer, or ensuring proximity of the sexes after the final moult
Vertical seed dispersal by earthworms: a quantitative approach
Authors: Willems J. H. , Huijsmans K. G. A. 
Published: July 2006

Earthworms are supposed to play an important role in the dynamics of the soil seed bank, however, experimental evidence and quantitative data are scarce To evaluate the impact of the earthworm species Lumbricus terrains L on the vertical transport of seeds in the soil, laboratory experiments have been earned out Moreover, the worm casts produced and their seed content have been quantified in two chalk grassland sites during one yearThe experiment on seed transport has been earned out in cylinders with controlled numbers of worms and seeds at different depths in stenlized soil Seeds used in this experiment proved to be eaten by the earthworms in preceding palatability tests A significant translocation of the seeds in the cylinders with earthworms was recorded after an eight‐week period In spring earthworm activity was mainly found m the upper soil layers in the cylinders, whereas in summer the activity was spread over a larger vertical distance The amount of worm casts collected on permanently marked plots in two different chalk grasslands was very high a minimal quantity of c 750 g nr2 of worm casts were produced yearly The number of germinative seeds brought to the soil surface by worm casts was at least 60‐100 nr2 each year This means that earthworm activity has a substantial impact on the soil seed bank dynamics and hence on the possibility of plant recruitment in this species‐nch ecosystem
Decomposition and nutrient dynamics of oak Quercus spp. logs after five years of decomposition
Authors: Schowalter T. D. , Zhang Y. L. , Sabin T. E. 
Published: July 2006

Decomposition of oak Quercus spp. logs (25 35 cm diameter, 3 m long) was compared among log substrates in Oregon, Minnesota. Kansas and North Carolina during the first five years on the ground. Decomposition of whole logs (weighted by substrate) averaged 0.069 yr‐1 (±0.16 SD). but followed a 2‐exponential model (k = 0.12 yr‐1 year 1 and k = 0.06 yr ‐1 years 2 5), reflecting qualitative differences among log substrates (outer and inner bark, sapwood and heartwood). Rapid loss from bark substrates contributed to the initial rapid decay rate. Sapwood decay rate averaged 0.15 yr‐1 and dominated the second log decay rate. Heartwood lost only 6% mass during the first five years, for an overall decay rate of 0.012 yr‐1 that likely will represent a longer‐term third exponential decay rate.Carbon loss amounted to ca 5 kg yr‐1 per 170 kg log. Nutrient concentrations generally declined during the first five years, but nitrogen, sulfur, and sodium accumulated in sapwood and heartwood during this period. Sulfur content increased in all substrates and doubled in whole logs during this 5‐yr period. Complex patterns of nutrient content suggest patterns of microbial colonization and nutrient utilization. Polynomial models were developed to describe rates of carbon and nutrient flux in log substrates.
Production of Atlantic salmon (Salmo salar) in fresh water and at sea at hgh and low densities
Authors: Chadwick E. M. P. , Randall R. G. 
Published: July 2006

AbstractA basic management objective is to identify the production capacity of Atlantic salmon in both freshwater and marine environments. Production in the biological sense is the total elaboration of fish biomass over time, and it is a function of fish abundance, growth and survival. In this article, we consider the factors that affect production at low and high stock levels. Using data from New Brunswick (Miramichi and Restigouche Rivers) and Newfoundland (Western Arm Brook), we consider freshwater and marine production of salmon at low and high stock levels. For all life stages, freshwater and marine production are related to initial biomass of the year‐class: thus, it is important to maintain adequate egg deposition. Production at high stock levels is stock‐dependent and mortality is extremely variable, particularly in the marine environment.