Temporal and spatial dynamics of coarse woody debris in harvested and unharvested lodgepole pine forests

Coarse woody debris (CWD) biomass was measured and mapped in burned, clearcut, and intact lodgepole pine forests in two areas of the Rocky Mountains of Wyoming: the Medicine Bow National Forest (MBNF) and Yellowstone National Park (YNP). In addition, the amount of CWD consumed or converted to charcoal by fire was estimated in a recently burned stand in YNP. A spatially explicit simulation model (DEADWOOD) was then created to simulate the effects of various clearcutting and fire regimes on CWD over a 1000-yr period. Approximately 8% of downed CWD were consumed during a single fire and an additional 8% was converted to charcoal. After 1000 yr of simulation, 100-yr fire-return intervals produced CWD that occupied more of the forest floor than did 200- or 300-yr intervals. The time required for 100% occupancy of the forest floor by CWD was 1125, 1350, and 1300 yr for 100-, 200-, and 300-yr fire-return intervals, respectively. Simulations suggest that current harvest and post-harvest slash treatment regimes will require at least four centuries longer for 100% of the forest floor to be occupied by CWD (1800–3600 yr) than under fire regimes. This may have important effects on soil characteristics. Only when post-harvest CWD slash was doubled over the current amounts did clearcutting leave sufficient CWD to maintain forest floor CWD within the historic range of variability for naturally developing post-fire stands.