bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seasonal responses of lentic midge assemblages to environmental gradients
Authors: Thorp James H. , Chesser Ronald K. 
Published: July 2006

We examined biotic and abiotic factors associated with density and diversity of larval midges (Diptera: Chironomidae) in the littoral zone of Par Pond, an 1100 ha cooling reservoir located near Aiken, South Carolina, USA. A total of 144 core samples were removed from 12 areas during each of 3 sample periods. Principal component analysis. Mantel analysis, and various univariate statistical tests were used to detect seasonal differences in (1) associations among areas and genera of Chironomidae, and (2) responses of midges to a multi‐faceted environmental gradient. Water temperature, which in this case was a function of both season and thermal effluents, was the factor most strongly associated with relative changes in density and diversity within the chironomid assemblages. Plant biomass and/or plant diversity were significant factors correlated with midge density and diversity. Both particle size and organic content of the substratum, which varied little across stations, were relatively unimportant factors. Despite the presence of a multifaceted environmental gradient, the composition and relationships within the midge assemblages were remarkably similar across areas although total abundance and diversity varied.On the basis of their similarity in structure and function, we classify the midge assemblages within the reservoir as members of the same community. However, in response to dissimilar or unequal selective forces (principally the area‐specific effects of thermal effluents), these assemblages appear to behave environmentally as multiple units rather than as a single component of the benthic community in Par Pond.
Nutrient content and dynamics in north Swedish shrub tundra areas
Authors: Jonasson Sven 
Published: July 2006

Forbs and leaves of deciduous shrubs had high concentrations of Ca, Mg, K, P, and N. Deciduous dwarf shrubs had intermediate concentrations but higher than evergreen dwarf shrubs. Monocots, cryptogams, woody and belowground tissues had low concentrations.Plant nutrient concentrations and nutrient content in soil organic matter increased from dry towards moist tundra areas.The residence time of nutrients was considerably less than ten years in surface litter, but several decades or centuries in total organic matter. The longest residence time was found in the moist part of the tundra.N, K, and P in Betula nana leaves were translocated to a great extent prior to leaf fall, whereas Mg and particularly Ca were only slightly translocated. As on other tundra areas shortage of nutrients probably limits plant growth. In that case short supply of N and F seems most probable due to retention in litter and soil organic matter.
Growth and size of Triturus vulgaris and T. cristatus (Amphibia) in different parts of Norway
Authors: Dolmen Dag 
Published: July 2006

The growth and size of the newts,Triturus vulgaris(L.) andT. cristatus(Laurenti) in different parts of Norway (+ Jämtland, Sweden) were studied. Age was estimated from skeletal growth marks, size‐frequency histograms and, for the males, from the number of testis lobes.On average, the T.vulgarisLarvae in central Norway and Jämtland are smaller than those in southeastern Norway, although in good localities, at the same altitude, they are of approximately the same size and complete their development already within 2½–3 months. Larvae living in eutrophic habitats are larger than those in oligotrophic‐dystrophic habitats. In bog habitats at similar times of year theT. cristatuslarvae from central Norway are about the same size as those from similar habitats in southwestern and southeastern Norway, but somewhat smaller than those from eutrophic ponds in the Oslofjord area.No significant differences in the mean size of adultT. vulgarisfrom southeastern Norway and from central Norway were found. The maximum lengths attained were recorded from central Norway, however. In eutrophic habitatsT. vulgarisadults BK usually larger than those in oligotrophic/dystrophic habitats.In southeastern Norway, where growth is rapid,T. vulgarismay become sexually mature when 2+ yr‐old, in central Norway usually a year later, in Jämtland. on average, still later, and in their northernmost locality (Vefsn) they probably do not breed until 5+ or 6+ yr‐old.On average,T. cristatusadults from southeastern Norway are slightly larger than those from central Norway, and may become mature at 2+ yr‐old. compared with 4 + yr‐old, at the earliest, in the latter area. The differences in the growth rates of both larvae and metamorphosed stages, of both species, most probably represent a response to climatic differences, although biotope quality is also an important factor.
Community structure of carrion flies along an island gradient
Authors: Kuusela Seppo 
Published: July 2006

species richness, abundance relations, exploitation efficiencies, and population dynamics were examined within four carrion fly communities from a small isolated island in the Baltic to the large island of Åland. A total of 23 species and 11408 Specimens were collected.Species richness (studied by rarefaction) of potential carrion flies was lowest on the small isolated island, but the smallest number of species emerged from the second largest island. Lucilia illustris Meig, was the most numerous species at every site, comprising 46–56% of the potential breeders and 71–91% of the emerging flies. Exploitation efficiency, measured by the numbers of individuals emerging per gram of carrion, was highest on the smallest island, but faunal similarity and ordination analyses suggest that competition was more intense on the larger islands.
Distribution and population dynamics of Collembola in relation to soil moisture
Authors: Verhoef H. A. , van Selm A. J. 
Published: July 2006

The significance of variations in soil moisture for the distribution and abundance of the four collembolan species Tomocerus minor, Orchesella cincta. Lepidocyrtus lignorum and Entomnbrya nivalis has been studied in a pine forest. During a relatively dry summer, the distribution and abundance of these species were examined on two sites with an initially different soil water content and depth of the titter/humus layer. The distribution of the species investigated could be described with the negative binomial distribution. During the sampling period. Lloyd's “index of patchiness”, x̄/x̄ for T. minor and E. nivalis was subject to changes. For T. minor this was probably related to soil water content.The densities of T. minor and O. cincta were higher in the wet site than in the drier site. At the beginning and at the end of the sampling period the drought tolerant E. nivalis reached equal densities in both sites. The density fluctuations of the four species appeared to be totally different during the sampling period: the drought sensitive species T. minor decreased strongly, L. lignorum remained constant and the drought tolerant species O. cincta and E. nivalis increased strongly. These latter two species were able to survive the dry periods and to attain high densities by reproduction. The results agree with laboratory data on distribution and survival in relation to humidity.
Enchytraeids, lumbricids and soil arthropods in a northern deciduous woodland – a quantitative study
Authors: Axelsson Björn , Lohm Ulrik , Persson Tryggve 
Published: July 2006

Soil/litter inhabiting annelids and arthropods were studied for one year in a mesic deciduous woodland, Andersby ängsbackar, one of the most northerly areas in Sweden to possess unbroken oak/hazel vegetation. Lumbricidae, Enchytraeidae, Collembola, Acari, Coleoptera, Diptera and Araneae were important faunal groups with regard to abundance, biomass and respiratory metabolism. Annual mean biomass (8 g dw m−2) and respiration (450 kJ m −2 yr−1) of the joint annelid and arthropod community were dominated by lumbricids (76 and 50%, respectively). The biomass and respiration of the annelids and arthropods at Andersby were lower than in some other oak forests in northwestern Europe, probably because of lower soil temperature, lower litter supply and because some lumbricid and diplopod species were at their northern border of distribution.Of the annual respiration, saprovores, fungivores, carnivores and root‐feeders contributed 65, 19, 14 and 1.5%, respectively. The saprovore percentage was lower at Andersby than at other mull sites compared, probably as an effect of the northern climate, which might favour microbial saprovory. The fungivore and carnivore percentages were higher, which might be due to the presence of a litter layer throughout the year.
Role of benthic insect feces in a Rocky Mountain stream: fecal production and support of consumer growth
Authors: Shepard Richard B. , Minshall G. Wayne 
Published: July 2006

The feces of stream insects may be a major component of fine particulate organic matter (FPOM) available to collector organisms. In Mink Creek, Idaho, winter defecation rates for 9 species ranged from 86 mg dry feces (g dry body wt)−1 d−1(Ephemerella spinifera) to 154 mg g−1 d−1(Paraleptophlebia heteronea). Detailed studies of 3 species in summer revealed that rates were much greater than in winter and exhibited high between‐individual variation (e.g., 695 ± 184.8 mg (g body wt)−1 d−1 for Baetis tricaudatus). By combining measured and literature values, it is estimated that the benthic insect community egests approximately 3.4 kg feces m−2 yr−1. This value lies within the range of FPOM estimated to be derived from degradation of leaf litter input (0.7–9.9 kg m−2 yr−1, depending upon assimilation efficiency of the organisms).Short‐term winter growth experiments showed that, with two exceptions, collectors fed on fecal detritus will grow as well as on other food resources; relative growth rates depend upon the species. Because fecal detritus is abundant throughout the year, and is treated by many species as a source of food, it could be a major mechanism by which seasonal fluctuation in availability of allochthonous litter input is minimized and homeostasis of structure and function maintained.
Respiration and energetics of the bumblebee Bombus terrestris queen
Authors: Silvola Jouko 
Published: July 2006

Carbon dioxide production by the Bombus terrestris queen was measured at different temperatures (10–30°C) and during different activities of the bumblebee. During flight the CO2 production averaged 50 ml g−1 (fresh weight) h−1 and was only slightly affected by temperature. During rest (with a readiness to fly) and incubation the respiration rate clearly increased with decreasing temperature (5–40 and 13–56 ml g−1 h−1, respectively), whilst during torpor it increased with temperature (0.1–1.7 ml g−1 h−1 at temperatures from 10 to 30°C).The expenditure of energy as calculated from the continuous respiration measurements agreed well with the amount of energy obtained from food (discrepancy 6–19%). The energy budget of an incubating queen was correctly predicted using the measured respiratory functions, prevailing temperatures, and the behaviour of the queen. The number of flower visits needed to fulfil the daily energy requirements of an incubating queen is discussed.
Species composition and biomass of an epipelic algal community in a subarctic lake before and during lake fertilization
Authors: Björk‐Ramberg Susanna 
Published: July 2006

The species composition, biomass (measured as algal volumes) and chlorophyll concentration of epipelic algae was studies before (1977) and during (1978–1979) fertilization with phosphorus and nitrogen of Lake Gunillajaure, a small subarctic lake in northern Sweden.The epipelic biomass, dominated by Cyanophyceae and Bacillariophyceae, was high (5.6–20.1 cm3 m−2) at all depths in the lake with the highest values in the hypolimnion (8–13.7 m). Calculated over mean depth it was 20 times higher than that of the phytoplankton. There was no significant increase in biomass during fertilization and neither did the species composition change. The chlorophyll concentration on the other hand were significantly higher in late 1978 and in 1979 which was probably an effect of the declining light climate caused by a large phytoplankton development in the lake. Constant seasonal biomass and species composition indicate a perennial epipelic community in this lake.
Wood decomposition in an abandoned beech and oak coppiced woodland in SE England
Authors: Swift M. J. , Boddy Lynne , Healey I. N. 
Published: July 2006

The results of three surveys of wood decomposing on the forest floor of two sites in an abandoned beech and oak coppiced woodland, between 1968–1979, are described.Total wood stainding crop on the forest floor was estimated as 311 g m−2on one site and 311–440 g m−2on the other site.Between 1969‐71 almost 1000 branches were sampled and of these 60% showed signs of past or present animal activity, Diptera were the major taxonomic category with Tipulidae being the most prevalent class;Tipula flavolineatawas detected in 39% of the branches. The second most prevalent species wasCylindroiulus punctatus(Diplopoda) followed byOniscus asellus(Isopoda), the OligochaetesLumbricus terrestrisandLumbricus rubellus, Lithobius variegatus(Chilopoda),Cylindronotussp. (Coleoptera).Branches invaded by animals were generally more decayed than uninvaded branches on the forest floor which in turn were more decayed than branches at fall.
Wood decomposition in an abandoned beech and oak coppiced woodland in SE England
Authors: Boddy Lynne , Swift M. J. 
Published: July 2006

The rate of litter decomposition is often expressed as a constant decay rate (k; g g−1yr−1) or as the time required for a certain percentage (often 95% and estimated as 3/k) of it to decompose (termed turnover time). Estimates of k may be obtained by determining the weight loss of litter in the field and also by assuming a steady state and obtaining the ratio of litter input: standing crop. Both methods were used to estimate decay rate and turnover times for beech and oak branches and twigs decomposing on the forest floor and these were critically evaluated.Considerable variation, ranging between 1.8–144.5 yr, was found between the 95% turnover time estimates of various size components of the two species, obtained from woodfall and standing crop data. Likewise variation in decay rate of 2–2.5 cm diameter beech branches, estimated from field experiments, was large both between and within groups of branches categorised according to initial state of decay and presence or absence of bark. The mean annual decay rate for the various categories ranged between k = 0.165‐0.452 g g−1yr−1. Branches without bark generally decomposed more slowly than those with bark. Beech twig (<0.5 cm diameter) decomposition rates, from field experiments, ranged between k = 0.149‐0.220 g g−1yr−1and variation was relatively low compared with that of branches. No significant differences (P<0.05)were detected between twig decomposition rates obtained from experiments initiated at different seasons although there was a slight decline in decay rate in winter months. Twig and branch decomposition rates fell within the range found in the few other comparable studies.
The effects of patchy food availability on nest‐site selection and movement patterns of reproductively active female meadow voles Microtus pennsylvanicus
Authors: Sherman Lori J. 
Published: July 2006

Radiotelemetry was used to study the movements of female meadow voles Microtus pennsylvanicus Ord through the reproductive cycle. The study was conducted on a commercial field of crownvetch Coronilla varia L., a plant which provides excellent cover but contains a toxin making it unsuitable as forage. In this habitat, food is limited to small patches of grass and other non‐crownvetch species dispersed throughout the fields. Four measures of movement (activity radius, distance moved per hour, nest radius, and area covered) showed significant reductions at parturition. Females maintained low levels of movement throughout the first week of nursing as they concentrated activity around the brood nest. After seven days of lactation, they began to spend less time at the nest. A slight increase in median activity radius occurred through the last six days of gestation.Brood nests were constructed in a portion of the home range that contained a relatively high concentration of food. Chi‐square tests revealed a significant positive association of females with non‐crownvetch plants during the first six days of lactation but no association with non‐crownvetch was found before parturition. Females chose nest locations in which, prior to parturition, they had spent little or no time presumably because nutritious plants were less grazed there.
Polar deserts, their plant cover and plant production in the Canadian High Arctic
Authors: Bliss L. C. , Svoboda J. , Bliss D. I. 
Published: July 2006

A total of 41 stands was sampled for species composition and 29 of these stands for plant standing crop and net annual production at 7 sites on 6 arctic islands. Fourteen additional sites on 10 islands were studied in less detail.Through polar ordination, three groupings were recognized: polar barrens with an average species richness of 6, a phytomass of 24 g m−2, and a net annual production of 0.8 g m−2. Comparable data for the cushion plant and snowflush communities were 9, 120, 3 and 13 species, 400 g m−2, phytomass and 41 g m−2net production respectively. Cryptogams are minor except within showflush communities.The soils show no horizon development, arc alkaline, and are very tow in organic matter, nitrogen, and phosphorus. It is believed that the combination of limited soil moisture in mid‐summer and very low nutrient levels are the primary reason for such low plant cover and plant production in these predominantly polar barren landscapes. Geologic substrate with an abundance of frost‐shattered rock and topographic position are factors that control the limited availability of water.
Plant communities and plant production in the western Queen Elizabeth Islands
Authors: Bliss L. C. , Svoboda J. 
Published: July 2006

A study of soils, plant communities, and net annual plant production was conducted with 41 stands at 3 sites on 3 arctic islands. Twelve additional sites were studied in less detail on Ellef Ringnes, King Christian and Melville islands and on four other islands. Through polar ordination five groupings were recognized. Alopecurus and Puccinellia barrens on sand to silty soils and on silty soils, high in sodium salts respectively. Species richness averaged 2.6 ± 2.0 and total plant cover 6.8 ± 2.7%. The Phippsia barrens occur on sheet eroded surfaces and in gulleys with deep winter snow. Species richness was 9.8 ± 5.0 and total plant cover 14.8 ± 9.6%. The graminoid steppes on sandy soils averaged 7.6 ± 2.4 species and total plant cover 40.0 ± 2.8%. Eight stands were dominated by moss‐graminoids, mostly on loam soils. Species richness was 24.9 ± 3.4 and total plant cover 77.7 ± 16.1%. Plant producion was 8.0 g m−2 in a Puccinellia barren and 9.4 g m−2 in a Luzula confusa graminoid steppe. Net annual production ranged from 18.8 to 58.7 in 6 other stands. The 13 stands within the cryptogam‐herb community complex occur on sandy loam to clay‐loam soils. Species richness averaged 26.3 ± 6.2 and total plant cover 61.2 ± 24.7%.Mosses and lichens play a significant role in the establishment and maintenance of communities with a greater species richness and plant production of vascular plant species. The ability of mosses to hold moisture and the presence of limited bluegreen algae that fix nitrogen appear essential to the maintenance of greater species richness, plant cover and plant production compared with the barren polar deserts that are often nearby.
Vertical distribution of primary production and phytoplankton in two small lakes with different humus concentration in southern Finland
Authors: Arvola L. 
Published: July 2006

Vertical distribution of primary production and phytoplankton was studied in a polyhumic brownwater lake and in an oligo‐mesohumic lake. During summer both lakes were thermally, chemically and biologically stratified. In the brownwater lake primary production was restricted to the uppermost layer of 1–1.5 m of epilimnion. In the oligo‐mesohumic lake noticeable primary production was detected down to depths of 2–3 m. The ice‐free period primary production was about 20% higher in the oligo‐mesohumic lake, though occasionally the surface production was 2–3 times higher in the brownwater lake. Epilimnetic total phosphorus and total nitrogen concentrations were higher in the brownwater lake, while nitrate‐nitrite, ammonium and phosphate concentrations were very low in both lakes.Phytoplankton was confined to the uppermost productive layer in the brownwater lake. In the oligo‐mesohumic lake phytoplankton was distributed more evenly, though the mean maximum biomass was at the depth of 3–4 m. Below the oxic water layer biomass decreased abruptly in both lakes. In the oligo‐mesohumic lake chlorophyll concentration was extremely high (max. 320 mg chl a m−3) in the anoxic hypolimnion, due to green sulphus bacteria.Flagellated chlorophytes and thrysophytes dominated in the brownwater lake; in spring Chlamydomonas species, followed by Mallomonas caudata. In the oligo‐mesohumic lake small coccal green algae, such as Oocystis, Scenedesmus and Westella‐like species, dominated in mid‐summer, and chrysophytes and cryptomonads in autumn.
Fecundity and mortality in populations of Salicornia europaea agg. at Skallingen, Denmark
Authors: Jensen A. , Jefferies R. L. 
Published: July 2006

Seedlings of the annual, Salicornia europaea (sensu stricto), germinated in the outer marsh sand flats at Skallingen in early May, and the relative growth rates of root and shoot were high during the establishment phase. Mortality of plants, which was not density‐dependent, was greater than 70% in most plots from early May to early October, as a result of wave action, desiccation and the presence of algal mats. Salicornia ramosissima was present in the outer and inner marshes mixed with Puccinellia maritima. Seedling densities of this annual were high, and in early May growth rates were lower than those for Salicornia europaea. Overall mortality of plants from early May to early October was density‐independent. Mortality of S. ramosissima in the inner marsh was only 50% from May to October, whereas the mortality of S. ramosissima in the outer marsh was 95% in the same period.Different levels of seed production per plant, which reflected differences in plant architecture, were evident between the two micro‐species.Reciprocal transplants from the inner marsh failed to survive on the outer marsh sand‐flat. Mean seed production per plant in plants transplanted from the outer marsh sand‐flat to the inner marsh was only 10% of the value of the control populations. The distances of seed dispersal were different in the outer and inner marsh. Low recruitment occurred in areas cleared of Salicornia plants in the inner marsh, unlike the situation in the outer marsh sand‐flat where tides dispersed seed.