Leaf litter redistribution among forest patches within an Allegheny Plateau watershed

Abstract

This study quantified the redistribution of leaf litter in and among distinct patches within Neotoma Valley, a 73 ha watershed in the unglaciated Allegheny Plateau of Ohio. Total vertical litterfall and Quercus litterfall were greater on the Quercus dominated east slope and valley bottom than on the west slope or on the ridgetops. To measure net downslope movement of leaf litter following deposition, sets of littertraps with upslope or downslope sides open were placed at seven sites within this watershed. Net downslope litter movement was as large as vertical litterfall at all sites except the valley bottom. Quercus litter was 1.3–1.5 × as likely to be redistributed as non-Quercus litter, depending on slope. Most redistribution occurred during the January–April leafless season. On the drier, Quercus-dominated ridgetops and east slope, 14–24% of the litter falling within 20 m upslope of a trap subsequently was redistributed down into that trap. In the more mesic patches, only 1–8% of vertical litterfall was redistributed. On an area basis, the west ridgetop and the upper east slope lost the most litter to redistribution (60–80 g m^-2 yr^-1 dry mass); the lower east and west slope positions and the valley bottom received the greatest litter subsidies from redistribution. Donor sites lost 4.5–5.7 kg ha^-1 yr^-1 of N and 0.3–0.5 kg ha^-1 yr^-1 of P through redistributed litter; sink areas received subsidies of 2.2–6.1 kg ha^-1 yr^-1 N and 0.2–0.4 kg ha^-1 yr^-1 of P. Litter redistribution helps maintain and even accentuate the gradient of soil fertility among patches in this watershed by accelerating the normal loss of nutrients during soil development in some patches while retarding it in others.