Effect of Site Preparation and Reforestation Method on Survival and Height Growth of Scots Pine
The influence of site preparation and reforestation method on the performance of Scots pine (Pinus sylvestris L.) was followed during 16 growing seasons in northern Finland using a split-plot design in randomized blocks. The site-preparation methods were prescribed burning (BURN), patch scarification (PATCH), disk trenching (DISK) and ploughing (PLOU). The reforestation methods were sowing (SOW) and planting with containerized seedlings (CON) and bare - rooted transplants (BARE). The reforestation was repeated in three successive years. A total of 72 000 reforestation spots was sown or planted on the 288 plots using the reforestation density of 2500 spots ha-1. Four of the eight clear-cut forest sites were dryish pine - dominated sites and four were moist, formerly Norway spruce-dominated sites. After 16 growing seasons, average survival was 49% on the pine sites and 33% on the spruce sites. Site preparation significantly affected survival on the spruce sites (PLOU 44%>DISK 23%) but not on the pine sites. The reforestation method had a significant effect only on the pine sites (CON 58%>SOW 36%). The effect of site preparation on mean height was significant on the pine (BURN 271 cm>DISK 222 cm) and spruce sites (PLOU 269, BURN 256 cm>DISK 212 cm). The differences between the reforestation methods were highly significant on the pine (BARE 295 cm>CON 261 cm>SOW 186 cm) and spruce sites (BARE 309 cm>CON 255 cm>SOW 171 cm). The results of this study indicate that different site-preparation methods can be used successfully in Scots pine reforestation on dryish, formerly pine-dominated sites in northern Finland. Intensive site-preparation methods, such as ploughing or mounding, are needed if Scots pine is to be established on moist, formerly spruce-dominated sites. However, the low survival and wide variation in survival indicated that there is a high risk of failure on such sites.