THE IMPACT OF CLIMATE, DRAINAGE AND FERTILIZATION ON THE SURVIVAL ANDGROWTH OF PINUS-SYLVESTRIS L IN AFFORESTATION OF OPEN, LOW-PRODUCTIONPEATLANDS

The objective of this study was to analyse the conditions for forest p roduction on open, low-production peatlands in Sweden with respect to climate, and water and nutrient regimes. The study focused on survival and growth of Scots pine (Pinus sylvestris L.) seedlings, planted 18 yrs ago in five experimental areas evenly distributed between south an d north Sweden. Different ditch spacing and NPK fertilizer treatments were combined systematically in all experiments. Survival was positive ly correlated with temperature sum, fertilization and drainage intensi ty. Tree growth was not influenced by variations in temperature sum af ter merely draining, but in combination with fertilization, growth was strongly correlated with climate. In the southern experiments, fertil ization increased stand growth eight to nine times, whereas stands on the northern sites did not respond to fertilization. The most importan t fertilizer element was P. The application of N had no effect on grow th. More intensive drainage increased stand growth by 60%. In the sout hern areas, height development in the most intensive drainage and fert ilizer treatments indicates a mean annual increment of 6-7 m3 ha-1, an d no sign of decline in growth was seen. Turf-planting had positive ef fects on both survival and growth, especially in less intensively drai ned plots. A large proportion of damaged trees was observed in the exp eriment. The frequency of damaged trees was positively correlated with treatment intensity but negatively correlated with temperature sum. T he results show clearly that merely draining is not sufficient for suc cessful afforestation of low-production peatland sites. Fertilization by P and K is a necessary prerequisite, but the effect of fertilizatio n varies with climatic conditions, probably owing to the amount of pla nt-available N.