Seedling Recruitment and Sapling Retention Following Thinning, Chipping, and Prescribed Fire in Mixed Sierra Nevada Conifer

Abstract

Thinning implemented with a cut-to-length harvesting system coupled with on-site slash mastication and redistribution and followed by prescribed underburning were evaluated for their impacts on seedling and sapling demography in an uneven-aged, eastern Sierran mixed conifer stand. Species composition consisted of California white fir (Abies concolor var. lowiana [Gord.] Lemm.), Jeffrey pine (Pinus jeffreyi Grev. & Balf.), sugar pine (Pinus lambertiana Dougl.), incense-cedar (Libocedrus decurrens Torr.), and red fir (Abies magnifica A. Murr.), but the former was preponderant in both the overstory and regeneration. The mechanized treatments facilitated the establishment of white and red fir and incense-cedar seedlings more so than those of Jeffrey and sugar pine, but sapling losses incurred from their implementation were severe and largely of white fir. Prescription fire promoted the establishment of Jeffrey pine seedlings, and to a lesser degree those of white fir, over incense-cedar and red fir, while it diminished sapling abundance in the absence of the mechanized treatments and essentially eliminated this size class when preceded by them, with sapling losses again largely white fir. Continuous establishment of natural regeneration and its survival are essential in perpetuating an uneven-aged forest structure, and these results provide land managers insight into the impacts of treatments designed for sensitive sites on seedlings and saplings in eastern Sierra Nevada mixed conifer and similar forest types.