The Amount and Nutrient Content of Litter Fall under Sitka Spruce on Poorly Drained Soils

Litter fall was collected every three months for four years from twenty-one vigorous (Yield Class 18-20 m3 ha"1 y"*1) and sixteen less vigorous (Yield Class 10-12) plots of Sitka spruce on gleyed soils in Northern Ireland. Forty-four per cent of all litter fell in the June-August quarter, and litter fall was heaviest in years when there was green spruce aphis attack. Beneath YC 10-12 crops, both rate and quantity of litter fall was less and nutrient concentrations were lower, than under YC 18-20 crops. As the pool of organic matter and nutrients on the forest floor was greater under trees of YC 10-12, poor growth was associated with a slow organic matter and nutrient turnover