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

Abstract

Litter fall was collected every three months for four years from twenty-one vigorous (Yield Class 18–20 m ³ 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.