Influence of Topographic Heterogeneity on Deciduous Litter Decomposition

Abstract

Woodlot floor topography, consisting of rises (high sites), hollows (low sites) and more extensive level areas (level sites) about 1 m in diameter with a 0.5 m vertical maximum, affected structural and functional components of the litter system. Topographic effects were measured on litter accumulation, substrate temperature and moisture, bacterial populations, litter decomposition, and organic matter incorporation in soil. Average litter accumulation (April to October) was 416.2 g m-2, 1209.9 g m-2 and 2438.3 g m-2 on high, level and low sites, respectively. Greater litter weight and depth in low sites reduced moisture loss from underlying litter and soil by up to 63%. At low sites, temperature variability of the litter-soil interface was reduced 13% of the mean by surface litter and by the heat capacity of a greater moisture content. Average bacterial populations were approximately 3.5 times larger in low sites. Litter decomposition in mesh bags averaged an exponential weight loss of -0.015 over 16 months. Interaction of low topographic site and litter composition enhanced decay. Finally, the soil of low sites was characterized by greater incorporation of organic fragments and humus formation.