Effekter av gödsling i äldre tallbestånd på renbetesväxter i fält- och bottenskikt

Sammanfattning: Reindeer husbandry and Forestry are both area related industries and will in big extent use the same lands. Conflicts often arise because of that the industries have different interests. Many of the activities done by the forestry influences the reindeer husbandry in an undesirable way, simultaneously as the reindeer husbandry activities can have negative consequences for the forestry. One such forestry activity is fertilization. It was during the 1960´s forest fertilization began to be practiced and the reason was that the increase in growth that the fertilization gave could be able to cover for the future shortage in wood many feared. During the 1970´s when the fertilizing activities were most intensive about 200 000 ha was fertilized annually. The uncertainty about which consequences N-fertilization would have on the ecosystems gave a decrease in fertilizing activities, and in the beginning of the 21th century only 30 000 ha was fertilized every year. Much research has been concentrated to questions concerning fertilizing and the knowledge about the production effects and the consequences on the environment has improved. This in combination with the great demand of wood and high woodprices has again made it interesting to fertilize the forest, to make it possible to take out larger volumes from the forests. The aim of this study was to evaluate the consequences intensive forest fertilization in older pine stands have on species in field- and bottom layer, mainly the species that is of importance for the reindeer and the reindeer husbandry. The study was carried out in an area 10 km SE of Åsele where SCA Forest Products since 1982 is pursuing an experiment concerning intensive forest fertilizing in older pine stands (Pinus sylvestris). The intention with the original experiment was to study how different fertilizing intervals influence growth plus to investigate whether an intensive fertilizing program can evoke shortage in boron and/or other micronutrients. When the experiment was constructed the stand contained 75 years old pines with a site index of T18 (H100), 990 stems/ha, a basal area of 14 m2/ha and a volume of 105 m3/ha. The experimental plots that had been fertilized every second year (treatment 2-4) differed most regarded to the tree layers characteristics. The basal areas were among the highest for both living and dead trees. Occurrence of a lower tree layer was only visible in these experimental plots and also the crown density was the highest in the experimental plots that had been fertilized most intensive (2-4). In total, seven species were observed in the field layer: lingonberry, blueberry, heather, crowberry, common hair-grass (Deschampsia flexuosa), fire weed (Epilobium augustifolium) and raspberry. For none of the seven species it was possible to find any statistic significant differences between the different treatments. When fertilized plots was compared with unfertilized the occurrence of lingonberry was significantly lower in the fertilized experimental areas (3,3 % compared to 5,8 %). Feather mosses, litter, reindeer lichens, Dicranum scoparium and hair-mosses made up the bottomlayer. In the bottom layer the difference in occurrence of reindeer lichens and litter between the experimental areas was statistically significant. When fertilized plots were compared with unfertilized significant differences was found for feather mosses, litter and reindeer lichens. The fertilized plots had lower cover of feather mosses (61,9 % compared to 92,7 %) and reindeer lichens (0,55 % compared to 3,3 %) but higher cover of litter (34,8 % compared to 2,5 %). The cover of reindeer lichens was thus in general low, even in the control, which probably depend on the fact that the stand had a high canopy closure with large litterfall and low level of light to the ground. Intensive fertilization in older pine stands seems thus to bring negative consequences for the reindeer and the reindeer husbandry. The one from the nourishment point of view so important reindeer lichens were decreased and the lingonberry, who can act as a protective shelter, and with that prevent the formation of an ice layer close to the ground, was also decreased. This means that there is a high probability that the reindeer lichens that may remain will be inaccessible under an icelayer. It should also be noticed that a normal succession bring about a reduction in the cover of the reindeer lichens when a tree stand is growing older and the canopy is closing. In the current stand commercial thinning might be the most important measure to improve the light conditions, reduce the quantity of needle litter and improve the reindeer lichens growth conditions.