Some relations between forest litter and growth of Sitka Spruce on poorly drained soils.
A study was made in 1971-72 of leaf litter from 119 inventory plots, each of 0.025 ha, in Picea sitchensis plantations (8-42 years old) on gleyed soils in Northern Ireland. The plots were classified as good or bad according to the yield class of the trees. On 69 of the 119 sites, a peaty horizon overlaid the gleyed mineral soil. Results of chemical analyses of the litter showed that as the trees became older, the litter became more acid and some N was accumulated in it. These effects were slight, however, and there was little evidence that P. sitchensis was causing serious site degradation. The total depth of litter did not increase significantly with the age of the stand, and there was no evidence of a massive build-up of organic matter on the forest floor. Gleys with a peaty horizon had a higher proportion of bad plots than did gleys without a peaty horizon. When the effect of soil type was eliminated, litters under trees on bad plots contained significantly less N than trees on good plots. There was no significant difference in the content of any other nutrient. It is suggested that the trees growing on bad sites are N-deficient. [Cf. FA 35, 162]