Level and pattern of overstory retention shape the abundance and long-term dynamics of natural and created snags

Standing dead trees, or snags, serve myriad functions in natural forests, but are often scarce forests managed for timber production. Variable retention (VR), the of live and trees through harvest, has been adopted globally as a less intensive form regeneration harvest. In this study, we explore how two key elements VR systems — level (amount) spatial pattern live-tree affect carryover post-harvest dynamics artificially created snags. We present nearly decades data from DEMO Study, regional-scale experiment harvests Douglas-fir-dominated Pacific Northwest. Snag losses to harvest were greater at 15 than 40% (67 vs. 47% declines density) dispersed aggregated treatments (64 50% declines). Densities hard tall (≥5 m) snags particularly sensitive low-level retention, declining by 76 81%, respectively. Despite these losses, densities correlated with pre-harvest most snag size decay classes. contrast initial effects, changed minimally over period (years 1 18 19), low rates recruitment offsetting loss. Post-harvest survival was (79 69%), (68 52% transitioned soft). However, had no effect on either process. did not vary scale 13-ha unit, several-fold 1-ha aggregates (14.3–27.8 ha−1) corresponding (4.2–5.3 ha−1). (diameter) distributions showed change treatments, reflecting loss smaller biased toward larger Created uniformly high (97%), irrespective treatment, lower retention. If goal is sustain abundance diversity emphasis should be placed minimizing reducing intensity felling areas locating forest density, diversity, incipient decay.