Multilevel modelling of height growth in young Norway spruce plantations in southern Finland

Saksa, T., Heiskanen, J., Miina, J., Tuomola, J. & Kolstrom, T. 2005. Multilevel modelling of height growth in young Norway spruce plantations in southern Finland. Silva Fennica 39(1): 143–153.Height development of Norway spruce (Picea abies (L.) Karst.) transplants was studied on 22 sites prepared by disc trenching or mounding. At the age of 4–9 years the planta-tions were surveyed using a multistage sampling design. For every planted spruce on a plot, the past annual height increments were measured as far into the past as possible. Multilevel mixed linear modelling was used to analyse the variation in growth at different levels (year, stand, cluster, plot, tree) and the effects of climatic and site characteristics on height growth. The within-plantation variation in height growth was higher on mounded sites than on disc-trenched sites. The mean temperature and the precipitation sum of the summer months affected height growth positively. Soil characteristics measured from undisturbed soil did not explain the height growth of seedlings on mounded sites, whereas on disc-trenched sites, the depth of the organic layer and the soil temperature had a positive effect and the depth of the eluvial horizon a negative effect. The modelling approach used proved to be a useful method for examining the sources of variation in development of young plantations.Keywords Picea abies, Norway spruce, container seedlings, mounding, disc trenching, height growth, intra-level correlation, variance-component modelAuthors’ addresses Saksa and Heiskanen, The Finnish Forest Institute, Suonenjoki Research Station, FI-77600 Suonenjoki, Finland; Miina, The Finnish Forest Institute, Joensuu Research Centre, P. O. Box 68, FI-80101 Joensuu, Finland; Tuomola and Kolstrom, The University of Joensuu, Mekrijarvi Research Station, FI-82900 Ilomantsi, FinlandReceived 10 December 2003 Revised 19 November 2004 Accepted 28 December 2004