POLLEN PRODUCTION OF ALNUS-INCANA AT ITS SOUTH NORWEGIAN ALTITUDINAL ECOTONE - PRELIMINARY-OBSERVATIONS

The pollen production (number of pollen grains per catkin) of Alnus in cana is studied along two vertical transects across the altitudinal li mit of the species. Annual variation in pollen quantity, and a conside rable reduction in the number of pollen are found with increasing alti tude. Normal pollen is virtually not produced at the ecotone. It is su ggested that parameters such as the temperature of the preceding summe r, length of the growing season, and soil factors are limiting factors . A test study shows no germination of seed from the ecotone, and redu ced fertility is suggested.