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.

Presented here is an assessment of the influences of mechanized thinning with subsequent slash mastication and prescriptive underburning on individual tree and stand level growth in an eastern Sierran mixed conifer stand over the long term. Included is an examination of possible linkages between selected tree and stand level variables quantified at pertinent junctures over the course of study.

Thinning implemented with a cut-to-length harvesting system coupled with on-site slash mastication and redistribution and followed by prescribed under burning were assessed for their impacts on the shrub understory and natural regeneration in an uneven-aged Sierra Nevada mixed conifer stand. Initial suppression of the cover and weight of huckleberry oak, the most prevalent ground cover species, by the combined thinning and mastication operations and those of prostrate ceanothus by the under burn were followed by a pronounced resurgence in abundance for both species in burned stand portions, particularly where thinning had preceded the fire. White fir was most prevalent initially among species represented in the seedling size class of natural regeneration and became predominant thereafter while this species dominated the sapling class throughout the study. White fir seedling establishment was enhanced where the mechanized operations were excluded, and especially so where fire was as well, and such was also the case for incense-cedar initially but its seedling abundance declined precipitously as the study progressed. White fir saplings were most numerous in the unthinned stand subunit but the under burn proved lethal to many of them therein. Jeffrey and sugar pine were little represented among seedlings and absent altogether among saplings.

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