Ten-year decomposition in a loblolly pine forest

Abstract

A litter sandwich approach was used to examine the loss of mass, acidity, and nutrients through 10 years of decomposition in a stand of loblolly pine (Pinus taeda L.). Each year, a new layer of 3-mm mesh fiberglass was placed on the annual accumulation of litterfall. Ten years of decomposition led to a loss of about 80% of the litter organic matter (giving a decomposition constant of 0.1655), which predicted a steady-state mass of the forest floor within 10% of the observed value. The pH (in 0.1 M KCl) showed little variation over time, ranging just from 3.2 to 3.5. The decline in titratable acidity appeared related primarily to the loss of organic matter rather than to any change in the acid characteristics of the material. Nitrogen loss was slow; the 10-year-old cohort of material contained 70% as much nitrogen as the original material. The loss of other nutrients was rapid, exceeding 80% loss by 6 years for phosphorus, potassium, calcium, and magnesium. The litter-sandwich method for examining decomposition is an easy, long-term approach that appeared to provide reasonable representation of the dynamics of unconfined forest floor materials. Future work should test this method for examining the decomposition effects of litter quality, nutrient supply, and environmental conditions.