Natural abundances of nitrogen isotopes, δ15N, indicate that, in the same habitat, Alaskan Picea glauca and P. mariana use a different soil nitrogen compartment from the evergreen shrub Vaccinium vitis-idaea or the deciduous grass Calamagrostis canadensis. The very low δ15N values (-7.7 ‰) suggest that (1) Picea mainly uses inorganic nitrogen (probably mainly ammonium) or organic N in fresh litter, (2) Vaccinium (-4.3 ‰) with its ericoid mycorrhizae uses more stable organic matter, and (3) Calamagrostis (+0.9 ‰) exploits deeper soil horizons with higher δ15N values of soil N. We conclude that species limited by the same nutrient may coexist by drawing on different pools of soil N in a nutrient-deficient environment. The differences among life-forms decrease with increasing N availability. The different levels of δ15N are associated with different nitrogen concentrations in leaves, Picea having a lower N concentration (0.62 mmol g-1) than Vaccinium (0.98 mmol g-1) or Calamagrostis (1.33 mmol g-1). An extended vector analysis by Timmer and Armstrong (1987) suggests that N is the most limiting element for Picea in this habitat, causing needle yellowing at N concentrations below 0.5 mmol g-1 or N contents below 2 mmol needle-1. Increasing N supply had an exponential effect on twig and needle growth. Phosphorus, potassium and magnesium are at marginal supply, but no interaction between ammonium supply and needle Mg concentration could be detected. Calcium is in adequate supply on both calcareous and acidic soils. The results are compared with European conditions of excessive N supply from anthropogenic N depositions.

Nitrogen nutrition and isotope differences among life forms at the northern treeline of Alaska.

https://archive-ouverte.unige.ch/unige:17919/ATTACHMENT01

Localization and effects of cadmium in leaves of a cadmium-tolerant willow (Salix viminalis L.). Part II Microlocalization and cellular effects of cadmium

Chronic illness as a result of low-level exposure to synthetic pyrethroid insecticides: a review of the debate.

https://archive-ouverte.unige.ch/unige:17920/ATTACHMENT01

Localization and effects of cadmium in leaves of a cadmium-tolerant willow (Salix viminalis L.) I. Macrolocalization and phytotoxic effects of cadmium

The relative contribution of visual and chemical components in the orientation ofLasius niger andIridomyrmex humilis (Argentine ant) workers during mass recruitment to newly discovered food sources is analyzed over short time intervals. While both species orient in response to the trail pheromone, a large number ofL. niger foragers rapidly switch to a more individual orientation, based on their memory of environmental cues.I. humilis workers, on the other hand, predominantly use collective chemical cues. The effect of the number of reinforcements on visual learning and its interference with chemical communication show that olfactory cues always prevail in the Argentine ant. InL. niger, the proportion of ants orienting to visual cues is independent of the trail concentration. Detailed observations of the trail-laying behavior of individually marked foragers show that nearly all theI. humilis workers initially lay a trail, whereas only half theL. niger foragers do so. This proportion decreases considerably with the number of trips performed byL. niger workers, while remaining constant for the Argentine ants. These results are interpreted with respect to the species' behavioral ecology.

/pdf/memory-and-chemical-communication-in-the-orientation-of-two-fyylclwyvt.pdf

Memory and chemical communication in the orientation of two mass recruiting ant species

Hartmann, G., & Nienhaus, F., & Butin, H. (1988): Farbatlas Waldschäden/Diagnose von Baumkrankheiten. — Stuttgart (Verlag Eugen Ulmer); 256 S., 418 Farbfotos; kart. 32.00 DM

PASSERA, L. (1984): L'organisation sociale des fourmis [Die soziale Organisation der Ameisen]. - Toulouse (Éditions Privat [Université Paul Sabatier]); 360 S., 95 Abb., 26 S. Lit.; brosch. -

Mehlhorn, H., & Piekarski, G.: Grundriß der Parasitenkunde/Parasiten des Menschen und der Nutztiere. — Stuttgart (Gustav Fischer Verlag); 1981 X + 268 S., 81 Abb., 19 Tab., 7 S. Lit.; brosch. 24,80 DM

KRIEG, A.: Bacillus thuringiensis, ein mikrobielles Insektizid. Grundlagen und Anwendung. ‐ Berlin + Hamburg (Parey Verlag); 1986 191 S., 16 Abb., in Iab., 12 S. Lit.; kart. 58.00 DM.‐.

Jäger‐Mischke, I., & Wollny, V. (1988): Pyrethrum und Pyrethroide/Ein Beitrag zur Naturstoffdiskussion. — Werkstattreihe Nr. 50 des Öko‐Instituts Freiburg (Freiburg i. Br.); brosch. IV + 118 S

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