Amount, position, and age of coarse wood influence litter decomposition in postfire Pinus contorta stands

Spatial variation in vegetation and coarse wood is a major source of forest heterogeneity, yet little is known about how this affects ecosystem processes. In 15-year-old postfire lodgepole pine (Pinus contorta var. latifolia Englem.) stands in Yellowstone National Park, Wyoming, we investigated how the decomposition rate varies with the position of coarse wood and other dominant structures within and among stands. Tongue depressors (TD) (made of birch (Betula sp.)) and litterbags containing herbaceous litter (HL) and needle litter (NL) were deployed for 2 years within 3 burned stands and among 17 burned stands (each 0.25 ha). Within stands, the decomposition rate varied among six microsite treatments (above and below legacy wood, below logs on the ground and elevated logs, below saplings, and on open soil). Two-year mean mass loss from all litter types was least under elevated logs (HL 34.0%, NL 8.6%, TD 3.5%) and greatest under legacy wood (HL 55%, NL 33%, TD 12%). The moisture level was consistently lowest under elevated logs and highest beneath logs on the ground. Among forest stands, 2-year mass losses from HL and TD were negatively related to the amount of elevated wood. The influence of coarse wood on litter decomposition at two spatial scales suggests that coarse-wood accumulation creates long-term spatial heterogeneity in carbon and nu-