Search results for "seasonal"
showing 10 items of 484 documents
Seasonality of coastal phytoplankton in the Baltic Sea: Influence of salinity and eutrophication
2005
Abstract In this study long-term (1984–2001) phytoplankton and physico-chemical monitoring data representing different salinity regimes of the Baltic Sea were compiled from HELCOM, national and regional databases. The aim was to define seasonal succession patterns of phytoplankton in seven different areas of the Baltic sea, characterised by different salinity, climate, and trophic conditions and to delineate a set of phytoplankton community indicators that are independent of season and salinity, but indicative of trophic status of different coastal areas. The cluster analysis of the combined data set resulted in eight phytoplankton community types, common for all locations, and characterise…
Behavioural responses of Eurasian treecreepers, Certhia familiaris, to competition with ants
1997
Competition for a specific resource that is essential for the survival of both the competitors may be intense even between very dissimilar taxa. However, the importance of the effects caused by such interspecific competition has seldom been emphasized. These effects can appear as differences in individual foraging behaviour during the breeding season, which can result in critical variation in fitness. In this study we examined the effects of wood ants (Formica rufa group) on the abundance of other invertebrates on tree trunks and on the foraging site selection of breeding Eurasian treecreepers, which use the same habitat as wood ants. Arthropods were scarcer on the trunks with ants present;…
Intercohort competition causes spatial segregation in brown trout in artificial streams
1999
When together in a flume, 13-cm LS (age-1) trout appeared to increase their activity and behaved more aggressively, whereas 10-cm LS (age-0) trout tended to move less and were rarely aggressive in the presence of the larger size class. Both size classes were less mobile and preferred lower water velocities in winter than in summer, and increased their use of instream cover in winter. When both size classes were present, only small trout decreased their use of low water velocities and cover. The results indicate that intercohort competition may cause spatial segregation among size groups of brown trout, especially in winter when trout attempt to minimize their maintenance costs.
Food availability and the male's role in parental care in double-brooded TreecreepersCerthia familiaris
1996
The aim of this work was to examine differences in paternal and maternal care in a double-brooded, monogamous species, the Treecreeper Certhia familiaris, in relation to food availability. As a measure of parental care, we recorded the hourly feeding activity of parents when the nestlings from their first and second breeding attempts were 7 and 12 days old. Feeding frequency of the first brood increased with the age of the nestlings and also with the brood size when 12 days old. While the feeding activities of the females were similar with respect to the first and second broods, the males were less active and failed to provide any food to their nestlings in 15 cases out of 28 second broods.…
Seasonal Variation in Nutrient Status of Foxglove Leaves
2006
The seasonal variation of mineral elements and the relationships among them were studied in natural populations of foxglove (Digitalis obscura). Young and mature leaves were collected in 10 different populations and on four sample dates (May, July, October, and February). Leaf mineral elements [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu)] were determined. The highest concentrations of N, P, and K in young leaf were recorded in May, followed by a decrease in the other months, while in contrast Ca and Fe showed the lowest concentration in May. Mature leaves showed differential seasonal behavior. Besides seaso…
Phenolic Compounds in Needles of Norway Spruce Trees in Relation to Novel Forest Decline I. Studies on Trees from a Site in the Northern Black Forest
1992
Summary Contents of selected phenolic compounds in needles of Norway spruce trees (Picea abies) from the Black Forest were measured using a HPLC-technique elaborated for serial studies in forest decline research. Measurements on needles that were harvested on several dates during two growing seasons gave no hint of seasonal variations in the concentrations of the studied phenolic compounds. Values for picein demonstrate an average decrease in the needles of severely damaged trees compared with the still undamaged ones, but the results are impaired by strong individual variations among the single trees. p-Hydroxyacetophenone was found in only very low amounts showing no constant differences …
Territorial song and song neighbourhoods in the Scarlet Rosefinch Carpodacus erythrinus
2000
Throughout the range of the Scarlet Rosefinch, its territorial song consists of 3–9 (usually 4–5) elements, of which there are 5 different types. The differences lie in the way the pitch of the element changes in time (frequency “slope”) and the width of the frequency band. Within a given type of song, the various elements can be present in almost any combination. Therefore, so many song types can be formed that the songs in even small parts of the species’ area are clearly distinct from one another. Despite this capacity for variation, however, by chance identical songs may be sung in widely separated parts of the area, in some cases by different subspecies. The species has not developed l…
Female choice in the kestrel under different availability of mating options
1992
Abstract Mate choice in relation to its fitness consequences on females was studied in kestrels, Falco tinnunculus , in western Finland. The breeding season is short with rapidly declining prospects of successful breeding, suggesting that females should make their mating decision quickly. On average, males arrived a few days before females, but late males arrived much later than early females. Pairs were usually formed within 2 days of male arrival, and only early males were available to early females. Options for female choice differed considerably in years of different kestrel density. In a good vole year, 1988, females had many males to choose from, but in poor vole years, 1989 and 1990,…
Sedation in allergic rhinitis is caused by the condition and not by antihistamine treatment
1996
Sedation is regarded as a common side-effect of most H1-antihistamines. This view must be accepted, yet can hardly be assessed under treatment of allergic disorders. Since central sedative potency is hard to evaluate, different methods of measurement have been introduced in the four phases of clinical investigation. While tests of high complexity in early trials can detect true central effects, they seem to have the disadvantage of not taking into consideration the important interactions of drugs with the disorder. Therefore, we used a visual analog scale (VAS) as an instrument to demonstrate sedative effects in five clinical studies carried out between 1989 and 1994 with a total number of …
Crop type and altitude are the main drivers of species composition of arable weed vegetation in Tajikistan
2015
Summary The influence of broad-scale environmental factors on the species composition of segetal weed communities in Tajikistan was investigated. The research was conducted throughout the country, analysing plots of root crops as well as cereals from all phytogeographical regions of Tajikistan, with the exception of the eastern Pamir. The study was based on 440 phytosociological relevees sampled between 2009 and 2013 and analysed using direct and indirect ordinations. A set of environmental variables was obtained for each plot: altitude, mean annual precipitation, mean annual temperature, pH, crop type, longitude, latitude and date of sampling (seasonality). Crop type was the major factor d…