THE EFFECT OF REPEATED FERTILISATIONS ON VOLUME GROWTH AND NEEDLE NUTRIENT CONCENTRATIONS OF SCOTS PINE (PINUS SYLVESTRIS) ON DRAINED PINE MIRES(ABSTRACT)

摘要

The amount of potassium (K) in surface peat is small on originally open, drained mires or poorly forested wet peatlands. Especially on nitrogen rich mires the shortage of K may cause decrease in tree growth, sudden leader dieback and even death of trees. The deficiency of phosphorus (P) can expose the trees to frost damage. The nutritional status by needle analysis and the volume growth response of Scots pine (Pinus sylvestris) stands to refertilisation were studied on a nitrogen rich drained pine mire in western Finland (61 °59'N, 23° 15'E). The main aim was to find out if K-refertilisation alone could maintain or increase volume growth without causing imbalance between K and P in tree nutrition. The basic fertilisation was carried out in 1961-62 (PK) and the refertilisations in 1976 and 1989 using different combinations of K, P, nitrogen (N) and boron (B). Needle samples were taken and the tree stands were measured in 1996 and 2001. Peat samples were taken in 2002. According to the needle analysis, there was a clear shortage of K in the control treatment. On the refertilised plots the concentration of K in needles was adequate 11 years after the latest K refertilisation. After the second refertilisation the combination of K and P increased the annual volume growth more than mere K refertilisation. The result indicated that about 25 years after the basic fertilisation, there was already some shortage of P. According to the needle analysis, the concentration of P was however above the deficiency level (1.6 mg g~(-1)) in all the treatments still in 2000. The highest total yield was in the refertilisation treatment K_(76)+PK_(89). Refertilisation with N didn't increase the total yield during the study period. The positive correlation between the total N and total P concentrations in peat (0-10 cm) and the annual volume growth during 1995-2000 was statistically significant on the refertilised plots.