bluuebunny/crossref_metadata_2025_split huggingface dataset:
Life cycle variation and habitat longevity in waterlily leaf beetles
Authors: Otto Christian , Wallace J. Bruce 
Published: July 2006

Waterlily leaf beetles inhabiting Nuphur luteum leaves in S. Sweden and Georgia, USA. differed markedly with respect to several life history traits. Developmental time (from oviposition to adult) was about 47 days in Sweden, while it was only 19 days in Georgia. In S. Sweden two generations were reached per year, while the corresponding number in Georgia could be eight. Instantaneous growth rate was three times as high in Georgia as in S. Sweden. Swedish eggs, larvae and imagines were larger than in the Georgian ones. However, clutch size was larger in Georgia, and total estimated fecundity was higher in Georgian females. Mortality rate of immature stages was higher in Georgia. Altogether, the results suggest two different species.Swedish N. luteum leaves were unpalatable to Georgian larvae, and the larvae died from starvation. Longevity of unprotected, grazed Swedish N. luteum leaves was about 28 days, while those protected from grazing lasted for 72 days. In Georgia the corresponding time periods were 13 and >42 days. Thus, it was impossible for beetles to cover all their immature stages on the same leaf, and drowning was presumed to be the main mortality factor. Swedish larvae and imagines were unpalatable to wagtails, and accumulated unpalatable plant chemicals may serve as chemical defences.
Standing biomass and production in water drainages of the foothills of the Philip Smith Mountains, Alaska
Authors: Hastings Steven J. , Luchessa Scott A. , Oechel Walter C. , Tenhunen John D. 
Published: July 2006

In the foothills of the Philip Smith Mountains, Brooks Range, Alaska, tussock tundra is the most widely distributed vegetation, and it occurs on rolling hills and in valleys that were shaped by a sequence of Pleistocene glaciations. In this study, aboveground standing biomass and production were compared in “intertrack tundra” areas that were relatively homogenous with respect to downslope drainage and adjacent “water tracks” that acted to channel water flow to the valley bottom stream. Comparisons of biomass, leaf area index, and specific leaf weight were also made between upper and lower slope positions. Similarities and differences of vegetation structure are examined with respect to graminoid, deciduous shrub, evergreen shrub, herbaceous, and bryophyte components.Water tracks were found to have 1.5–1.7 times the biomass of intertrack tundra, and production (excluding secondary growth) in water tracks was 40% greater than in intertrack tundra. The aboveground biomass for all areas studied and the annual production values were similar to those found in other studies of tussock tundra. While only slight differences in depth of thaw occurred in water tracks and intertrack tundra during June and early July, water tracks thawed more deeply with the onset of summer rains. Warmer temperatures at 40 cm depth in July and August may have increased nutrient availability, whereas greater rooting depth and movement of water may have increased nutrient capture in water tracks as compared with the intertrack areas. Greater biomass and a deeper thaw depth occurred at upper slope locations.
Comparative effects of downslope water and nutrient movement on plant nutrition, photosynthesis, and growth in Alaskan tundra
Authors: Oberbauer S. F. , Hastings S. J. , Beyers J. L. , Oechel W. C. 
Published: July 2006

Changes in water and nutrient movement are common disturbances resulting from human activities in arctic regions. To assess the influence of water and nutrient movement on different plant growth forms, we added water and NPK fertilizer along 10 to 20 m linear transects across small natural drainages on an Alaskan tundra slope. Water was added by continuous‐flow emitters from a drip irrigation system at a rate of 450 L m−1 d−1 during the 1986 growing season and 110 L m−1 d−1 in the 1987 growing season. NPK in the form of Osmocote, a slow release fertilizer, was applied at 0.5 kg per linear meter in early and mid‐season of the 1985 growing season. Tissue N and P contents, light‐saturated photosynthetic rates, and aboveground biomass production were measured at peak season for key species 2 m above and 2 and 6 m below the water and nutrient applications in 1986 and 1987.Mean leaf N and P of the species tested increased slightly 2 m below the water addition sites and dramatically below the fertilizer addition sites. Increases in tissue N and P were also found 6 m below the fertilizer addition points. Leaf photosynthesis tended to increase 2 m below the water and nutrient additions for the species tested. Six meters below the treatment application points, photosynthesis was minimally affected in 1986 but increased in 1987. Increases in leaf area on the irrigation treatments were found only for the evergreen species, Ledum palustre and Vaccinium vitis‐idaea, 2 m below the site of addition. In contrast, fertilizer addition caused large increases in leaf area production for all species tested at 2 m below the treatment, and for some species at 6 m below treatment. The overall effects of the two treatments were similar, but were greater for the fertilizer addition.
Population structure and dynamics of wood mouse Apodemus sylvaticus in Iceland
Authors: Bengtson Sven‐Axel , Nilsson Anders , Rundgren Sten 
Published: July 2006

Five‐year‐studies of two wood mouse populations (Apodemus sylvaticus L.) were carried out outside the village Vík. S. Iceland, and in a birch forest close to the lake Mývatn, N. Iceland. The population at Vík was studied on a 1.10 ha grid on a slope covered with Angelica archangelica L., the seeds of which constituted a major food resource for the mice. Altogether 948 individuals were caught, marked and followed during 1973–1978. No other free‐living small mammals occur in Iceland, and predator pressure is low and considered non‐existent on the Angelica slope. The population density was extremely high; highest autumn density recorded was 150 ind ha−1. Like other Apodemus populations, the one at Vík showed a typical seasonal pattern in numbers: a winter decrease, relatively stable numbers in late summer, and an autumn peak. Breeding started in late April or early May and ended in late September; no winter breeding was observed. Three or four litters were produced, and the last litter(s) of the season greatly contributed to the autumn increase. The output of young per reproductive female throughout the year was negatively correlated with spring density, and autumn peak density with the number of females in August. Also overwinter success and weight changes appeared to be associated with population density (and weather). Survival rates did not vary much between years and seasons and were consistently rather high. Autumn survival of juveniles was positively correlated with mean minimum temperatures. Juvenile survival was, at least at times, negatively affected by the presence of adult males. Trapping outside the main grid did not indicate any marked dispersal, though some immigration to the grid must have occurred, especially in spring and early summer. Among the factors governing the population density and dynamics of wood mouse at Vík we emphasize the absence of interspecific competition and predation, the rich and dependable food resources (mainly Angelica seeds), the mild (though moist and windy) climate, the shelter of dense Angelica stands, the abundance of crevices (e.g. nest‐sites), and the social interactions.The birch forest in northern Iceland was low productive and the wood mouse population differed from the Vík population by exhibiting low density, short breeding season, and high vagility; characteristics we consider to be representative for most Apodemus populations in Iceland.
A model for the conquest of a tree by bark beetles
Authors: Stenseth Nils Chr. 
Published: July 2006

A model for the interaction between attacking bark beetles and a tree is developed and discussed. It is shown that in addition to the more intuitive outcomes where the tree wins or the beetles win, it is also deduced that under certain conditions there may exist a stable coexistence (at least for some period of time) between the beetles and a living tree. Finally, it is demonstrated that the outcome of the tree‐beetle interaction often depends on initial conditions such as the number of colonizing beetles.These results are discussed with reference to empirical findings, as well as to the development of proper population dynamics models for bark beetles in a forest stand, and models developed for assisting forest managers in avoiding bark beetle outbreaks and for minimizing the damage caused by a bark beetle outbreak.
Within‐harem competition among Ips females, an overlooked component of density‐dependent larval mortality
Authors: Kirkendall Lawrence R. 
Published: July 2006

Intraspecific larval competition is commonly believed to be the major component of egg‐to‐adult mortality in bark beetles. Larval mortality is usually shown to be density dependent. In this study I looked specifically at competition among females in the same gallery system, in a sparse but highly female‐biased population of Ips acuminatus breeding in cut pine branches near Kongsberg, southeastern Norway. Supplementary data from a slightly female‐biased population in western Norway and a population with intermediate female bias in W. Germany are also provided.Survivorship from egg to adult or pupa was measured in laboratory experiments, for the area in which larvae from different arms potentially competed relative to survivorship in areas away from competition. Survivorship was significantly correlated with both average interarm distance (r2= 0.76) and food per larva (cm2 per larva: r2= 0.73). There was no evidence that females could detect the presence of other, nearby egg arms: neither egg spacing (on the arm sides nearest each other) nor interarm distance increased when two arms were near each other. Nor did females distribute themselves optimally within harems, though the distribution of egg arms within harems was significantly different from that expected from random settling. analysis of interarm distances and harem sizes in 1984 branches revealed that a minimum of 34% of arm sides could be expected to suffer considerably reduced larval survivorship due to within‐harem competition.Harem size in Ips typographus is reviewed, and data on the distribution of females within harems is presented for Norwegian populations of I. Typographus, Orthotomicus erosus and O. laricis. Evidence from the literature is presented to show that uneven distribution of females between harem sides is not uncommon. I suggest that the findings for Ips acuminatus are applicable to a wide range of harem polygynous scolytids, including I. typographus: the factors influencing density cannot be fully understood without taking into account the distribution of females among males and the distribution of females within harems.
Variable floral phenology: temporal resource heterogeneity and its implication for flower visitors
Authors: Rotenberry John T. 
Published: July 2006

I investigated within‐ and between‐year patterns of flowering phenology of entomophilous plants in an isolated old field in northern Michigan, USA. The number of open flowers was censused at 5‐d intervals from June‐September of 1984–1986, and the data analyzed by detrended correspondence analysis. DCA axis 1 reflected within‐year phenology, was highly correlated with date of censusing, and implied substantial constancy in flowering sequences. However, DCA axis 2 revealed significant between‐year variation in abundances of flowers; years differed significantly in their scores on axis 2, and these differences were driven by variable plant species abundances during late summer. Within‐year patterns showed that the floral community consisted of three more‐or‐less distinct temporal “guilds” of plants, and that the rate of turnover in community composition throughout the season was not uniform. The appearance of these guilds was not synchronous across years.Insects foraging on these species throughout the floral season can expect constancy in the relative timing of blooming, but are exposed to considerable temporal heterogeneity in flower resource abundance both between‐ and within‐years. Opportunities for coevolutionary specialization are therefore likely to be constrained.
The bog climax hypothesis: fossil arthropod and stratigraphic evidence in peat sections from southeast Alaska, USA
Authors: Klinger Lee F. , Elias Scott A. , Behan‐Pelletier Valerie M. , Williams Nancy E. 
Published: July 2006

The hypothesis that bogs are climax (structurally and compositionally stable) communities has been proposed for several large regions including southeast Alaska. A logical consequence of the bog climax is the hypothesis that, where there is infrequent large‐scale physical disturbance, landscape‐level changes from early successional woodland to late successional peatland should have occurred during the Holocene. This hypothesis is tested in southeast Alaska using analyses of fossil arthropods and site stratigraphy, as well as a review of the ecological literature.Results indicate at least three major landscape types have dominated since deglaciation: deciduous woodland (about 9000 to 6000 yr BP), coniferous woodland (about 6000 to 3000 yr BP), and peatland (about 3000 yr BP to present). Other paleoecological and ecological studies from around the region provide evidence for directional changes, both past and present, from woodland to peatland. Furthermore, there is no clear evidence for peatland to woodland transitions in the absence of large‐scale disturbance. These results suggest that the bog climax hypothesis deserves a more careful examination by ecologists studying succession.
Water relations, temperatures, and mineral nutrients in Pedicularis dasyantha (Scrophulariaceae) from Svalbard, Norway
Authors: Gauslaa Yngvar , Odasz Ann Marie 
Published: July 2006

The arctic vascular hemiparasite Pedicularis dasyantha has a lower diffusion resistance for water vapour than any associated species. Excised leaves die within one hour of drought stress under laboratory conditions, in spite of a high succulence. Transpiration rates of P. dasyantha in the field are almost two times higher than in Dryas octopetala, which is the most important host within investigated sites.Diffusion resistances are higher in inflorescences than in leaves, probably because the dense pubescence reduces transpiration rates and raises temperatures in inflorescences to 14°C above air temperature on clear days. Pedicularis dasyantha contains significantly more N, P, and especially K than its host. The high rate of transpiration probably enables the hemiparasite to capture a larger fraction of nutrients supplied by the xylem of its host.
Differences in uptake of persistent pollutants for predators feeding in aquatic and terrestrial habitats
Authors: Larsson Per , Woin Per , Knulst Johan 
Published: July 2006

Persistent pollutants in mustelid species (e.g. otter, mink, marten) were investigated. For a given animal, concentration of PCB and DDT in muscle were correlated with concentrations in its anal gland secretion. The correlation suggests that small samples of secretion could be used for pollutant analysis thereby eliminating the need to sacrifice animals. There was also a correlation between muscle and liver concentrations of these compounds, indicating a partitioning between different organs.Furthermore, we showed that habitat differences between species led to interspecific variation in the uptake of persistent pollutants. Mink, which mainly feed in aquatic environments, contained a higher proportion of p, p‐DDT than marten, which feeds on terrestrial prey. Differences in PCB uptake were also noted between the two predators, though the congener distribution was heavily domined by a few hexa‐ and heptachlorobiphenyls.
Predation on amphibian eggs and tadpoles by common predators in acidified lakes
Authors: Henrikson Britt‐Inger 
Published: July 2006

Eggs and three different stages of premetamorphic tadpoles of moor frog Rana arvalis and common toad Bufo bufo were offered to the following potential predators in acidified lakes: newt Triturus vulgaris, water beetles Rhantus exoletus and Dytiscus lapponicus, dragonfly larvae Leucorrhinia dubia and Aeshna spp., water boatman Notonecta glauca and water bugs, Cymatia bonsdorffi, Glaenocorisa p. propinqua, and Corixa dentipes.The predation pressure on eggs of R. arvalis was low due to thick jelly. The eggs of B. bufo were not attractive to predators with chewing mouth parts due to unpalatability but predators with sucking mouth parts were not repulsed. Tadpoles of R. arvalis were eaten by all predators but tadpoles of B. bufo were unpalatable to most predators. The predators used in the experiments are the new top predators in acidified fishless lakes. They may contribute to the reduction of populations of R. arvalis in acidified areas.
Fecundity of the newts Triturus cristatus, T. marmoratus and their natural hybrids in relation to species coexistence
Authors: Arntzen J. W. , Hedlund Linda 
Published: July 2006

The two larger newt species in Europe, Triturus cristatus and T. marmoratus, have largely exclusive distributions but live in sympatry in a small area in western France, where they also hybridize. Triturus cristatus is increasing in abundance in the area at the expense of T. marmoratus, although this study shows that T. marmoratus has higher relative lifetime reproductive success. Triturus marmoratus lays more eggs than its relative under controlled conditions, and more T. marmoratus eggs in relation to its relative abundance are found in natural breeding sites. The hybrids are even more fecund, but their eggs and embryos have a lower survival rate.The data are compared for age at maturity and species longevity, and estimates of lifetime reproductive success show that T. marmoratus females are more fecund than T. cristatus females. There are no differences between the species in survival of the embryos. It is therefore not clear why T. cristatus is replacing T. marmoratus, but changes in terrestrial habitats due to human activity might be the explanation.
The effect of heather beetle Lochmaea suturalis on vegetation in a wet heath in NE Scotland
Authors: Scandrett Eurig , Gimingham C. H. 
Published: July 2006

An outbreak of heather beetle Lochmaea suturalis on a wet heath in north‐east Scotland was monitored. In many respects, the outbreak was similar to those described in lowland heaths; it started at a particular locus and when the Calluna vulgaris was depleted, spread throughout the heath. Population size then decreased annually due to some undetermined exogenous factor. A contributory factor may be the high incidence (35%) of parasitoid infestation which is density independent and, thus, not controlling.There is no evidence that the hairiness of the var. hirsuta of Calluna has an effect on herbivory by Lochmaea. The distribution of larvae through the canopy is neither influenced by the morphology of Calluna, nor by the associated species, and appears to be at random. This probably represents the distribution of eggs since little lateral migration of the larvae takes place.The response of the vegetation to herbivory is not simple. Associated with decreased cover of Calluna is an increase in Sphagnum plumulosum and Hypnum jutlandicum and reduction in S. compactum and Pleurozium schreberi. Changes seem to depend on initial vegetation and other parameters not measured (e.g. proximity of propagules, microclimate). Regeneration of Calluna does occur, largely by layering; although seedling occurrence increases in some areas, especially in Sphagnum, it seems unlikely that this will make a major contribution to the recovery of Calluna.
Increasing insect abundance by killing deciduous trees: a method of improving the food situation for endangered woodpeckers
Authors: Aulén Gustaf 
Published: July 2006

A total of 135 trees were girdled or notched in a forest area close to the river Dalälven in central Sweden. The purpose was to see whether good microhabitats for wood‐living insects could be created and if so, could be used as food for the endangered white‐backed woodpecker Dendrocopos leucotos. The chosen tree species were three of the most frequent used for foraging by the white‐backed woodpecker, i.e. aspen Populus tremula, birch Betula alba and common alder Alnus glutinosa.The process of dying and decay in the manipulated trees was followed for eight to nine years, and the following variables were studied: tree condition, tree structure, wood‐condition, consistency of bark and cambium, frequency of polypori, foraging marks made by woodpeckers and abundance of insect species of importance as food for woodpeckers. Notched aspen died faster and were more quickly colonized by wood‐living insects than were girdled aspen. Since the notched aspen was also reduced more quickly to low stumps or lost their bark, their value for wood‐living insects was short‐lived. Notched birch died almost as quickly as girdled birch but were populated by slightly fewer insect species. Notching, in general, seemed to create good foraging trees in the short‐term whereas girdling produced trees of a longer‐term value. In order to improve the local food situation for the white‐backed woodpecker, a combination of the two methods is suggested. Nonetheless, both must be seen as emergency measures and cannot compensate for a large‐scale reduction in the abundance of old deciduous trees in the forest.
Bryophytes and decaying wood– a comparison between managed and natural forest
Authors: Andersson Lars I. , Hytteborn Håkan 
Published: July 2006

A comparative study was made of one managed forest and one natural forest regarding the supply of decaying wood on the ground and the occurrence of bryophytes on the wood, especially epixylic specialists.The total substrate surface of wood is larger in the primeval forest. The larger quantity of decaying wood increases the probability of wood occurring in ail decay stages. Logs of Populus tremula occurred only in the natural forest. An important proportion of the wood substrate in the natural forest consisted of logs of large diameter class; these logs were missing in the managed forest. Fiftyfour bryophyte species were found on decaying wood. They were separated into four different groups. Facultative epiphytes first colonized decaying wood, followed by epixylic specialists and finally by competitive epigeics. Opportunistic generalists showed a more irregular pattern of occurrence. The bryophyte flora on decaying wood was most species rich in the natural forest. Sixteen epixylic specialists occurred here, several considered to be threatened by forest management, while only 5 of these species occurred in the managed forest.The higher frequency of epixylic specialists in the natural forest is related to the greater frequency of favourable habitats, specifically: logs of large diameter, decayed wood, Populus tremula and (to a lesser extent) Picea abies.