Large-diameter trees, snags, and deadwood in southern Utah, USA

Abstract Background The epidemic Dendroctonus rufipennis (spruce beetle) outbreak in the subalpine forests of Colorado Plateau 1990s killed most larger Picea engelmannii (Engelmann spruce) trees. One quarter century later, snags are beginning to fall, transitioning deadwood (down woody debris) where they may influence fire behavior, regeneration, and habitat structure. Methods We tracked all fallen trees ≥ 1 cm diameter at breast height (1.37-m high) mapped pieces 10-cm m length within 13.64 ha a high-elevation mixed-species forest Picea–Abies zone annually for 5 years from 2015 through 2019. examined relative contribution snag pools other species contributions large-diameter (≥ 33.2 this site). compared spatially explicit mapping traditional measures surface fuels introduce new method approximating vertical distribution deadwood. Results In forest, there was relatively high density basal area live 20 after beetle (36 −1 1.94 2 diameter) contrasting with near total mortality mature nearby. Wood tree boles on ground had biomass 42 Mg , 7 35 species. Total aboveground 119 while 36 . Mean fuel loading measured planar transects 63 but varied more than three orders magnitude (0.1 257 ). Planar recorded 32 wood 7.62-cm by mapping. Multiple were often stacked, forming structure likely contribute active behavior. Conclusion Bark has made an important local constituent 20-m scales, dominate due slow decomposition rates multi-centennial intervals between fires. Explicit measurements improve ecological insights into heterogeneity potential