Evaluation of annual ring width and ring density development following fertilisation and thinning of Scots pine

Effects of nitrogen fertilisation and thinning, 40% basal area removal, on annual ring width and ring density were studied in a 2 x 2 factorial field experiment in northern Sweden, in an even aged 56-year-old Scots pine stand twelve years after treatment. Each treatment was replicated six times. From four stem heights, wood specimens were measured using direct scanning X-ray microdensitometry. For the whole period, mean ring width increased by 14% following fertilisation and by 40% after thinning. Neither fertilisation (<1%) nor thinning (-4%) significantly (p>0.05) changed ring density during the twelve-year period. Based on four-year mean values at 1.3 m, ring width increased in all cases, except for fertilisation in the last four-year period. The only significant effect on wood density was a 5% decrease following thinning during the second four-year period. Linear regression showed negative correlation between ring density and ring width and no additional effects of treatments per se.