Markberedningens, planteringspunktens och behållardjupets inflytande på granminiplantors etablering i fält

Abstract: A new type of forest tree seedling, called mini seedling, has been developed by the University of Dalarna in Garpenberg, Sweden. Compared to traditional containerized seedlings that are grown for 1 – 2 years, mini seedlings are grown for only 10 weeks. The mini seedlings are small, easily planted, cost effective, and reduce the amount of chemicals used in the nursery. Research has shown that mini seedlings tend to have higher overall survival rates than traditional container seedlings. Mini seedlings are rarely attacked by the pine weevil (Hylobius abietis (L.)), but are more sensitive to drought than traditional containerized seedlings. The growing season of 2006 was unusually dry with several weeks without precipitation, resulting in widespread damage to newly planted seedlings. Since container depth and the selection of planting spot may have an impact on resistance to drought two field experiments with different kinds of mini seedlings and scarification methods were carried out in the area of Garpenberg during 2007. The first experiment included three different container depths of mini seedlings planted at the top of mounds and at the terrace of the ridge. The second experiment included two different container volumes of mini seedlings planted after disc trenching and inversal scarification. Both field experiments were conducted to investigate how container depth/volume, planting spot, and scarification method, affects survival rate and establishment during the first planting season. As reference, both field experiments included 1- year old conventional seedlings of Norway spruce (Picea abies L.). The results for the first field experiment showed an overall survival rate of 85 %. All of the reference seedlings were alive, while 5 % were deadly damaged by the pine weevil. Between 5 – 15 % of the mini seedlings were dead, caused by drought or mechanical damage. The results indicate that mini seedlings with shorter container depth were more susceptible to drought. However, no significant difference was found between container depths, and plantation spots when comparing survival rate, and establishment. Overall, mini seedlings were less attacked by the pine weevil, but were more vulnerable to drought, mechanical damage, and grazing. There are no significant results indicating that mini seedlings planted at the top of the ridge grow better than in those planted lower at the terrace. The results for the second field experiment show an overall survival rate of 95 % after one season. Of the reference seedlings, 5 % were dead due to pine weevil, while for mini seedlings, 2 – 15 % was dead, caused by pine weevil, drought, and mechanical damage. The results show no significant difference in survival between container volumes, and scarification methods. Mini seedlings were less attacked by pine weevil compared to conventional seedlings, but were more vulnerable to drought, mechanical damage, and grazing. The hypothesis that an increasing container volume for mini seedlings would lead to an increase in survival and vitality could not be confirmed in this experiment. A reason for this could be that the 2007 growing season was less dry than 2006 and a better water situation may not have created enough stress during 2007 to achieve significant differences between the two different types of seedlings.