Decomposition of Norway spruce and Scots pine needles: Effects of liming

The effect of liming on the decomposition of Norway spruce needle litter was studied in 40-60-year-old Norway spruce stands. Finely-ground limestone had been spread about 30 years ago at a dose of 2 t ha(-1) and reliming was carried out about 20 yr later at a dose of 4 t ha(-1). Needle litter was collected from both control and limed plots, and it was placed in litter bags in the middle of the humus layer of the plot from which they originated, and similarly to the other plot in May. Litter bags were sampled after 4, 12 and 16 months. The site of origin of the needle litter, whether from control plot or from limed plot, affected mainly the early stages of decomposition. Initially the effect of liming was seen as decreased concentration of water soluble material and then, during decomposition, as decreased mass loss and decreased degradation of lignin, and increased C/N ratio. The incubation site, whether the control or the Limed plot, did not affect decomposition significantly. Decomposition of Scots pine needles in a young Scots pine plantation was also studied. The treatments were: 2 t ha(-1) of finely-ground limestone and 2.5 t ha(-1) of bark ash spread 8 months before this study. The treatments did not affect decomposition much, but some stimulation of the treatments on decomposition was observed. Compared to spruce needles, the C/N ratio of pine needles was lower, they contained less lignin and more water soluble material, and decomposed faster in the first summer.