Do soil fauna increase rates of litter breakdown and nitrogen release in forests of British Columbia, Canada?

The objective of this study was to improve our understanding of the role of soil invertebrates in the breakdown of litter, cycling of nitrogen, and gr owth of seedlings in forests of British Columbia by comparing two experimen tal approaches. First, in the laboratory, breakdown of birch leaves was sli ghtly higher in the presence of millipedes in the microcosms of forest floo r collected from two coastal forests. Presence of smaller animals (mesofaun a) and contaminant Diptera larvae did not hasten litter breakdown in microc osms made from forest floor from either a sub-boreal or a coastal forest. I n general, inorganic nitrogen release was higher in the presence of fauna, but results were highly variable. Growth of seedlings was slightly greater in the coastal microcosms that included millipedes. In the second approach, a field experiment was conducted using intact forest floor cores enclosed with one of three mesh sizes (54 mum, 1 mm, and 5 mm) and defaunated with l iquid nitrogen. Comminution of birch leaves, and to some extent, greater in organic nitrogen release occurred in sacs that allowed access to larger ani mals compared with sacs with fine mesh that excluded them. Although differe nces among treatments were small, the results from both approaches agree an d indicate that soil invertebrates increase rate of breakdown of forest lit ter and cycling of nutrients in coastal forests.