Överlevnad, tillväxt och skador i planteringar av sitkagran (Picea sitchensis) efter stormen Gudrun

Abstract: Sitka spruce (Picea sitchensis (Bong.) Carr) is just like Norway spruce (Picea abies) a species in thegenus picea. The natural range of Sitka spruce is a narrow strip along the west coast of North America. Itis the most coastal of all picea species, and very dependent on the mild and humid climate along thepacific coast.Sitka spruce has been grown a long time in the countries around the North Sea, particularly in GreatBritain where it currently is the most important species in British forestry. Sitka spruce has not beenplanted in Swedish forests to any large extent before the storm Gudrun in 2005. Several studies indicatethat the production of wood biomass is higher for Sitka spruce compared to Norway spruce. The factorsthat most likely limits the use of Sitka spruce in Sweden is primarily frost, but also drought.An inventory was carried out at 32 sites 4-5 years after planting in the counties of Halland andKronoberg. In circular plots, general site characteristics were registered and total height and length of theleading shoot were measured on all Sitka plants. In addition, an estimation of damages was done. Thesites were divided into two groups, one eastern and one western. An interview was performed with theforest owners in connection with the inventory or by phone. Most of the forest owners responded that ageneral interest and a willingness to try something new was their motivation to plant Sitka spruce. Inaddition, a better economy and higher growth were common arguments. About half of the forest ownerswere satisfied with their plantation and might consider planting Sitka spruce again in the future.The result of the inventory shows that there are big differences in how well the plantations haveperformed, about both survival and growth. Many plantations in the eastern group have developed poorly,with high mortality and surviving plants gave a stunted impression, with lots of damages. In the westerngroup, plantations looked better. Survival was higher and there were stands with good growth that hadbeen thinned or were in need of thinning. The inventory of damages show that frost was the main cause ofdamage in the eastern group, whereas competing vegetation was the main cause in the western group.It was difficult to determine the specific cause for higher mortality in the eastern group. Sitka spruce issensitive to both frost and drought and it is possible that these damages were the actual causes of death.Both frost and drought hit the interior parts harder, above that the soils are often coarse and thereby havea lower water holding capacity. The inventory shows that a lot of plants in the eastern group have been hitby frost damages. Some forest owners mention that drought have caused big damages, especially in theearly summer of 2007.