Leaf Litter Redistribution in a West Virginia Hardwood Forest

Abstract

The deposition, decomposition and movement of leaf litter were studied on steep southwest-facing slopes in Coopers Rock State Forest, West Virginia. The significance of downslope leaf movement was assessed by an enclosure experiment. The mass of leaves deposited was uniform at all positions along a southwest-facing slope and averaged 335 g per m2 per yr. Leaf litter decomposition rates after 1 yr were 31% of the original material weight at mid-slope stand, 43% at the ridge crest, and 41% at the valley bottom. After redistribution, there was more litter, measured both by mass and by cover, in stands of moderate steepness (whether on ridge crests, terraces or valley bottoms) than in steep mid-slope stands. Fallen logs and microtopographic depressions affected leaf redistribution. The mass of leaf litter upslope from fallen logs was as much as 11 times greater than the average stand value for litter mass. Episodic downslope leaf movement through wind action was demonstrated using marked leaves. Results from replicate 100 m2 enclosures showed that 40% of deposited leaves (31.7 kg per enclosure) were downslope. On steep forested slopes of southwest aspect, patterns of leaf deposition and leaf decomposition alone did not account for the observed distribution of leaf litter cover and mass; downslope leaf movement was an important process. This downslope movement of material may help to determine the concentrations of soil organic matter and of soil nutrients.