Studies of the Composition of Deciduous Forest Tree Leaves Before and After Partial Decomposition
The studies were undertaken in connexion with an investigation into the fundamental processes of podzol development and the part played by acid components leached by natural rainfall from decomposing leaves. Measurements of leaf fall from Maple (Acer saccharum), Beech (Fagus grandifolia), Birch (Betala populifolia) and Poplar (Populus grandidentata and P. tremuloides) gave the following results in annual weight (lb. dry matter) per acre: Maple 3, 010, Beech 1, 943, Birch 1, 503, Poplar 1, 489. For freshly fallen leaves, Maple had the highest ash and extractive content and the lowest lignin content. Beech had the lowest extractive content and the highest lignin and holocellulose content. Maple and Birch leaves, when exposed to weathering in trays, decomposed twice as fast as Beech, but the difference was not so marked in leaves lying on the soil. Extent of decomposition was related to leaf composition and moisture content. Ash extractives and alpha-cellulose were readily removed during decomposition. Lignin and hemicelluloses were relatively resistant. The species showed much variation. Natural rainwater leachates from Maple leaves were strongly acid, from Birch least acid, with Beech and Poplar intermediate [cf. For. Abstr. 13 (No. 61)]. In all cases the leachates became progressively more alkaline as the duration and extent of decomposition increased. From authors' summary.