Weight and Calcium Losses from Decomposing Tree Leaves on Land and in Water

The losses of weight and calcium from decomposing leaves of red maple (Acer rubrum), tuliptree (Liriodendron tulipifera) and white oak (Quercus alba) proceeded at much greater rates in perennial stream than they did on land. Complete decomposition of Acer leaves in water required less than 24 weeks, while that of Liriodendron and Quercus both required less than 44 weeks. First-year losses on land also varied among species: from Acer, 55% of weight and 54% of calcium; from Liriodendron, 44% of weight and 38% of calcium; and from Quercus, 33% of weight and 35% of calcium. Constant leaching and scouring of leaves by bottom sediments probably accounted for the greater loss rates in water. Variation in weight and calcium losses among samples in the stream far exceeded the variation among samples on land. Weight losses from leaves that had partially decomposed on land sharply increased when they were placed in the stream 9 months after abscission, showing that allochthonous material may influence stream chemistry by inputs throughout the entire year. The losses of weight and calcium from the leaves did not significantly differ at the 0.05 probability level in either environment; this suggests that the estimate of weight loss from decomposing deciduous leaves may also serve as an adequate index of the rate of calcium release. 8 references, 2 figures.