Early forest dynamics in stand-replacing fire patches in the northern Sierra Nevada, California, USA
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RESEARCH ARTICLE
Early forest dynamics in stand-replacing fire patches in the northern Sierra Nevada, California, USA Brandon M. Collins • Gary B. Roller
Received: 17 September 2012 / Accepted: 29 July 2013 / Published online: 15 August 2013 Ó Springer Science+Business Media Dordrecht (outside the USA) 2013
Abstract There is considerable concern over the occurrence of stand-replacing fire in forest types historically associated with low- to moderate-severity fire. The concern is largely over whether contemporary levels of stand-replacing fire are outside the historical range of variability, and what natural forest recovery is in these forest types following standreplacing fire. In this study we quantified shrub characteristics and tree regeneration patterns in stand-replacing patches for five fires in the northern Sierra Nevada. These fires occurred between 1999 and 2008, and our field measurements were conducted in 2010. We analyzed tree regeneration patterns at two scales: patch level, in which field observations and spatial data were aggregated for a given standreplacing patch, and plot level. Although tree regeneration densities varied considerably across sampled fires, over 50 % of the patches and approximately 80 % all plots had no tree regeneration. The percentage of patches, and to a greater extent plots, without pine regeneration was even higher, 72 and 87 %, respectively. Hardwood regeneration was present on a higher proportion of plots than either the pine or nonpine conifer groups. Shrub cover was generally high, with approximately 60 % of both patches and
B. M. Collins (&) G. B. Roller USDA Forest Service, Pacific Southwest Research Station, 1731 Research Park Drive, Davis, CA 95618, USA e-mail: [email protected]
individual plots exceeding 60 % cover. Patch characteristics (size, perimeter-to-area ratio, distance-toedge) appeared to have little effect on observed tree regeneration patterns. Conifer regeneration was higher in areas with post-fire management activities (salvage harvesting, planting). Our results indicate that the natural return of pine/mixed-conifer forests is uncertain in many areas affected by stand-replacing fire. Keywords Fire ecology High severity Tree regeneration Mixed-conifer
Introduction There is considerable concern over the occurrence of stand-replacing fire in forest types historically associated with low- to moderate-severity fire. Characterizations of fire patterns in these forest types prior to Euro-American settlement vary in inferring the role of stand-replacing fire historically. Some studies demonstrate that stand-replacing fire was a relatively minor component of the fire regime, accounting for a small proportion of the total area burned (Brown et al. 2008; Scholl and Taylor 2010), and other studies demonstrating stand-replacing fire did occur at larger spatial extents, but occurred infrequently (Brown et al. 1999; Beaty and Taylor 2008). Irrespective of these inconsistencies, it almost ubiquitously acknowledged that contemporary patterns of stand-replac
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