Mechanical Restoration of California Mixed‐Conifer Forests: Does it Matter Which Trees Are Cut?

Restoration Ecology (Impact Factor: 1.84). 10/2009; 17(6):784 - 795. DOI: 10.1111/j.1526-100X.2008.00414.x


The montane ecosystems of northern California have been subjected to repeated manipulation and active fire suppression for over a century, resulting in changes in community structure that contribute to increased wildfire hazard. Ecosystem restoration via reduction of stand density for wildfire hazard mitigation has received substantial attention in recent years; however, many ecological questions remain unanswered. This study compares belowground effects of two alternative forest thinning treatments designed to restore the large, old tree component of late-seral structure, one of which focuses on restoring Pinus ponderosa dominance (Pine-preference) and the other of which promotes development of large trees regardless of species (Size-preference). We evaluated forest floor and soil chemical and microbial parameters in six experimental thinning treatment units of 40 ha each in the Klamath National Forest of northern California 5–6 years after thinning. Inorganic N availability, soil organic C content, phenol oxidase activity, and forest floor C:N ratio were greater in the Size-preference treatment, whereas forest floor N and soil pH were greater in the Pine-preference treatment. Our results indicate that these two thinning strategies produce differences in the soil environment that has the potential to affect growth rates of trees that remain, as well as the growth and survivorship of newly established seedlings. Thus, which species/individuals are removed during structural restoration of these mixed-conifer forests matters both to the belowground components of the ecosystem today and the vegetation and productivity of the ecosystem in future decades.

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Available from: Jessica R. Miesel, Jun 12, 2014
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    • "This experimental design substitutes space for time (using data from control sites instead of pre-fire data), which is similar to other fire and restoration studies (LeDuc and Rothstein, 2007; Miesel et al., 2008), comparing treatments and reference controls within each year. Within each unit, ten modified Whittaker plots (50 m  20 m) were installed at randomly selected gridpoints for vegetation sampling (shown in Fig. 1 of Knapp et al., 2007). "
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    ABSTRACT: Restoring the natural fire regime to forested systems that have experienced fire exclusion throughout the past century can be a challenge due to the heavy fuel loading conditions. Fire is being re-introduced to mixed conifer forests in the Sierra Nevada through both early season and late season prescribed burns, even though most fires historically occurred in the late season. We assessed the impact of early and late season prescribed fires on soil biogeochemical and microbiological parameters that are important for ecosystem recovery. We found that the late season burns had more dramatic short-term effects on soil abiotic conditions (temperature, moisture and pH), mineral soil carbon levels, total inorganic nitrogen, and microbial activity than the early season burns, relative to unburned sites, suggesting a higher severity burn. However, the total soil nitrogen pools and fluxes and soil respiration rates were not differentially impacted by burn season. These burn season effects suggest that soil variables may be regulated more strongly by fire severity than by the season in which the prescribed fire is conducted.
    Forest Ecology and Management 01/2008; 256:367-374. DOI:10.1016/j.foreco.2008.04.030 · 2.66 Impact Factor
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    Forest Ecology and Management 11/2012; 284:163–173. DOI:10.1016/j.foreco.2012.07.054 · 2.66 Impact Factor
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