Abstract
Mechanical fuel treatments are a primary pre-fire strategy for potentially mitigating the threat of wildland fire, yet there is limited information on how they impact shrubland ecosystems. Our goal was to assess the impact of mechanical mastication fuel treatments on chaparral vegetation and to determine the extent to which they emulate early post-fire succession. Mastication treatments significantly reduced the height and cover of woody vegetation and increased herbaceous cover and diversity. Non-native cover, density, and diversity were also significantly higher in masticated treatments. Comparisons with post-fire data from two studies showed that certain ephemeral post-fire endemics were absent or of limited occurrence from masticated plots in comparison to their abundance on adjacent burned plots. Structurally, masticated sites differed in the dense woody debris cover, whereas burned sites had little such ground cover. Regional comparison of masticated plots to previously published post-fire studies found that burned sites had greater cover, density, and diversity of native species. However, masticated sites and burned sites were broadly similar in distribution of different growth forms. Results from our study show that the use of mastication fuel treatments in chaparral are not in alignment with some resource conservation goals, but in some cases it is recognized that such sacrifice of natural resources may be an acceptable tradeoff to potentially mitigating fire hazard.
Highlights
Pre-fire fuel reduction treatments have often been used to address the threat of wildfire in many ecosystems around the world (Scott et al 2014)
We focused on the effects of mechanical mastication on chaparral ecosystems in southern California
There were 52 species in 21 plant families, over 75 % of the shrub cover and density was from just six species; two obligate resprouters, Cercocarpus betuloides Nutt. and Quercus berberidifolia Liebm.; two obligate seeders, Ceanothus crassifolius Torr. and C. greggii A
Summary
Prescribed fire has traditionally been the most common fuel reduction treatment due to its relatively low cost and because of its potential to emulate natural fire disturbances (Ryan et al 2015), but it has become increasing difficult to conduct due to smoke management regulations, the expanding wildland−urban interface, and lack of community support (Kreye et al 2014a). Mechanical treatments, such as chipping, crushing, and mastication, have become increasingly popular, yet we lack a clear understanding of how these treatments may affect different ecosystems. The shredded, or masticated, debris forms a compacted layer of woody fuel on the soil surface, resulting in a fuel structure that is thought to alter fire behavior by reducing flame lengths, intensity, and rate of spread (Kane et al 2009)
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