| 1. |
- Angerbjörn, Anders
(författare)
-
Gigantism in Island Populations of Wood Mice (Apodemus) in Europe
- 1986
-
Ingår i: Oikos. - 0030-1299 .- 1600-0706. ; 47:1, s. 47-56
-
Tidskriftsartikel (refereegranskat)abstract
- Many rodents have large body sizes on islands, and there are many hypotheses that try to explain this observed pattern. Using body size data on Apodemus in Europe as an example, I try to evaluate the main hypotheses. These can be divided in four different categories. 1) Hypotheses assuming climatic differences between islands and mainland: no trend in body size on islands in the Mediterranean, in Britain or in the Baltic area is observed. 2) Hypotheses based on island size: no trend is observed in the data analysed. 3) Hypotheses based on distance to mainland: no general effect is found, although there is an effect in the British material. 4) Hypotheses based on faunistic differences: consistent relationships are found in all areas. A. sylvaticus shows larger body size when lacking competition from A. flavicollis or Clethrionomys glareolus or when predation is absent. A. flavicollis is larger when predators are lacking, and smaller when no competitors are present. This is in agreement with character displacement theory
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Bååth, Erland, et al.
(författare)
-
Impact of microbial-feeding animals on total soil activity and nitrogen dynamics - a soil microcosm experiment
- 1981
-
Ingår i: Oikos. - 1600-0706. ; 37:3, s. 257-264
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedThe long-term impact of microbial-feeding animals on microbial populations was studied in microcosms containing pine seedlings growing in a gamma sterilized humus-sand mixture. Organism communities of diverse complexity were introduced into the microcosms. The two main experimental series contained microorganisms only and microorganisms and microorganism-feeding nematodes, respectively. After 18 months the following analyses were made: soil chemical characteristics, weight and nitrogen content of the seedlings, soil respiration, abundance, biomass, and in some cases, species composition of the different soil organism populations. During the incubation, leaching of nitrogen from the microcosms was measured continuously. The rate of nitrogen leaching from the microcosms increased during the first 6 months. During the remaining 12 months the leaching stabilized at a low rate. Initially, the series with microbial-feeding nematodes had a lower rate of nitrogen loss through leaching compared to the series with only microorganisms added. Towards the end of the experiment the situation was reversed. The pine seedlings showed a very poor growth in all series with no significant differences between the treatments. In the microcosms, bacteria appeared to be the most important microorganism group; fungi, algae and yeasts were present in low amounts. The presence of bacterial feeding nematodes reduced the number of bacteria but did not reduce the soil respiration rate. A significant correlation was obtained between the numbers of nematodes and the respiration rate of the microcosms, which is interpreted as an increased bacterial production rate due to the presence of bacterial-feeding animals.
|
|
| 7. |
- Clarholm, M., et al.
(författare)
-
Biological aspects of nitrogen mineralization in humus from a pine forest podsol incubated under different moisture and temperature conditions
- 1981
-
Ingår i: Oikos. - 1600-0706. ; 37:2, s. 137-145
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedFluctuations of soil organism abundance, soil respiration and inorganic nitrogen werestudied in a laboratory experiment on material taken from the humus layer of a Scotspine forest and incubated under different moisture and temperature regimes. Theexperiment was run for 28 wk with samplings every 7 wk. At 28 wk, increases in"total movable N" (inorganic N + biomass N) were observed in samples incubated athigh temperature and/or high moisture content. Most of the N was found in biomassexcept in incubations at the highest temperatures and moistures. Under those conditions,high abundance of nematodes occurred together with drastically increasedamounts of inorganic N. Low values of inorganic N were recorded under conditionscommon in the field. No obvious relations could be detected between standing cropsof bacteria and temperature, moisture or respiration. The number of bacterial-feedingnematodes seemed to be a possible measure of previous bacterial productioncontributing more information than the standing crop measurements of the bacteria,which varied little despite the direct evidence of substantial bacterial production insome incubation conditions.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Jonsson, I., et al.
(författare)
-
Photography and temperature measurements from a remotely piloted vehicle
- 1980
-
Ingår i: Oikos. - : JSTOR. - 1600-0706 .- 0030-1299. ; 35:1, s. 120-125
-
Tidskriftsartikel (refereegranskat)abstract
- Radio-controlled model planes are useful when carrying out photography, especially from low altitudes, and meteorological soundings (air temperatures in boundary layers). Soundings were carried out with a system which stored the measured data on board the plane pending evaluation after the flight. The payload of the plane was a camera and equipment for measuring temperature and air pressure (altitude). Data were stored so that the signals from the temperature and pressure sensors (thermistor and micro aneroid respectively) lit a combination of light-emitting diodes (BCD code) that corresponded to the actual temperature and pressure (altitude). At the instant of measurement, this combination was photographed togther with the ground surface. the camera manoeuvred by means of servo-function. The position of the plane at the instant of measurement was determined on the basis of pressure values and air photographs. Photography from model planes is not a new method. However, previous results have in general been inadequate because, for safety's sake, cheap and consequently less advanced cameras were used. The determination of temperature and other soundings from such aircraft has been little tried hitherto. Photography and sounding from model planes can be of interest in ecological, physical-geographical and meteorological contexts. The method lends itself best to a rapid and handy documentation from the air of a water or land area, e.g. a severely polluted area, or a wind-eroded ground surface, or to the sounding or sampling of aif qualities such as pollution in the smoke plumes of stacks and other types of discharge, of radioactivity in the air over leaking plants, of temperature and humidity conditions in urban boundary layers and of eolian dust in the air over wind-exposed erosion surfaces in arid areas. Radio-controlled model planes could possibly also be used for dissemination of e.g. silver iodide in order to artificially release precipitation and for pollination of forest.
|
|
