Effect of arginine-phosphate addition on early survival and growth of Scots pine, Norway spruce and silver birch

Applying arginine-phosphate (AP) to tree seedlings at planting is a novel silvicultural practice in Northern Europe to improve the success of forest regeneration. We present three case-studies of the potential advantages of adding AP at planting on the establishment and damage susceptibility of seedlings in pure and mixed plantings of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst.) and silver birch (Betula pendula Roth) over two years in the field. Location of study sites were in southern (S), northeastern (NE) and northwestern (NW) Sweden. The main agents of damage were pine weevil (Hylobius abietis L.) on conifers at the south site, browsing of birch at all sites and browsing/other top damage to conifers at the north sites. The effect of adding AP varied between the sites. It was positive for survival of pine at site S, despite considerable damage by pine weevil. However, at the S site more of the surviving spruce and birch were browsed when treated with AP. At the NE site AP-treatment had positive effects on conifer growth. At the NW site adding AP positively affected survival and growth of all three species, and AP-treated seedlings of all species were less browsed than untreated seedlings. AP treatment presents a potential tool to improve the success of forest regeneration, especially when establishing pine stands in south Sweden.