Forest reconstructions and limited historical data are often used to infer desired conditions for fuels-treated forests. Most of these studies, however, provide incomplete information for how fire regimes and resulting forest structure varied across the landscape. Uniform fuels treatments do not provide high canopy cover habitat preferred by some threatened and endangered species, and consequently can be stalled by legal challenges. Varying fuel reduction treatment characteristics with topography could provide greater habitat diversity for wildlife, and promote ecological processes while still reducing the risk of crown fires. Data from forests with an active-fire regime could provide a foundation for new restoration guidelines in fire-suppressed forests. This study quantified how structure and composition vary with topography in unmanaged forests with the best available approximation (> 2 low intensity fires within the last 50 years) of an active-fire regime under recent climate conditions. Objectives of the study were to determine the species composition, diameter distribution, spatial pattern, regeneration dynamics, and fuel loads of active-fire forests and what topographic conditions influence these stand characteristics.
Results/Conclusions
Preliminary stand structure results found more trees in the midrange size classes, 40-79.9 cm diameter at breast height (dbh), than would be predicted by a multi-age reverse J-shaped size distribution. Although 64% of the trees had a dbh of 5-39.9 cm, only 28.2% of stems were in the smallest size class of 5-19.9 cm dbh, and there were clustered, but few, seedlings and saplings. Species composition was 42.5% shade-tolerant fir and cedar, 42.7% shade-intolerant pine, and 14.7% oak species. Average live stem density was 235 stems/ha, and average basal area was 40.4 m2/ha. There were 88 Mg/ha of downed woody material and an average fuel depth of 12 cm and duff depth of 2.4 cm. As distance from water and upslope position increased, stem density and fuels generally decreased. There was also a slight trend of decreased stem density on southwesterly aspects. In all plots, stems were significantly clustered. Identifying how active-fire forest conditions vary with topographic features can help develop restoration guidelines by letting managers use topography as a template for producing different stand structures and wildlife habitats across managed landscapes.
