Long-Term Forest Floor Fuels Accumulations in Sierran Mixed Conifer Subjected to Forest Restoration Treatments

Abstract

Long-term influences of mechanized thinning using a cut-to-length approach combined with on-site slash mastication along with those of prescription under burning on downed and dead fuel accumulations were evaluated in an uneven-aged eastern Sierra Nevada mixed conifer stand. Based on an initial inventory conducted soon after treatment implementation, accumulations in an unburned portion of the stand subunit subjected to thinning were elevated with respect to both 1+10 hr time lag and total fuel loads. In contrast, the near immediate effect of the under burn on these fuels was marked diminishment in their abundance. Nearly a decade later, however, effects of the mechanized and fire treatments had largely dissipated. In the interim between inventories, the thinned but unburned treatment combination exhibited the greatest reduction in 1+10 hr and total fuels while the unthinned and unburned combination also exhibited a large reduction in the former. Furthermore, diminished reductions in 1+10 hr fuels were apparent within the burned portions of the thinned and unthinned stand subunits, and the unthinned but burned combination was the only one to incur an increase in total fuels. These findings offer land managers insight regarding the persistence of fuel bed alterations induced by these increasingly common management practices in Sierran mixed conifer and similar forest cover types.