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Federal Way, CA, United States

Hanson C.T.,Earth Island Institute | Odion D.C.,University of California at Santa Barbara | Odion D.C.,Southern Oregon University
Natural Areas Journal

There is significant debate about restoration targets for ponderosa pine (Pinus ponderosa) and mixed-conifer forests in the Sierra Nevada, California, USA. On one side are recommendations to create both extensive open and park-like pine forests, and to reduce high-severity fire occurrence by mechanical thinning of forests. These recommendations drive current management. On the other side are recommendations to manage landscapes for both dense, old forest, and complex early-seral forest that is created by both high-severity and moderate-severity fires characteristic of historical fire regimes. Our research suggests that the latter approach may best maintain forest associated with two imperiled species that are top management concerns of federal agencies in the Sierra Nevada: the California Spotted Owl (Strix occidentalis occidentalis) and the Pacific Fisher (Pekania pennanti). We used spatially extensive US Forest Service forest survey data from 1910 and 1911, and synthesized research from other parts of this region for comparison, to assess reference conditions in low/mid-elevation Sierra Nevada forests. We found that historical ponderosa pine and mixed-conifer forests had a mixed-severity fire regime, with an average of 26% high-severity fire effects, and varied more widely in species composition and density than suggested by previous research. Our findings are contrary to other reports using a very small subset (∼6%) of the available data from these same 1910 and 1911 surveys. Therefore, we suggest that historical reference conditions of forests in the Sierra Nevada range of these species are not like that reported previously in other studies, and that mixed-severity fire, and forests defined by strong contrasts and dynamic natural processes, were characteristic of historical ponderosa pine and mixed-conifer forests of the western Sierra Nevada. Our analysis indicates that managing for both dense, old forests, and protecting complex early-seral forest created by high-severity fire, will likely advance conservation and recovery of the Spotted Owl and Pacific Fisher, while current management direction may exacerbate threats. Source

Odion D.C.,University of California at Santa Barbara | Odion D.C.,Southern Oregon University | Hanson C.T.,Earth Island Institute | DellaSala D.A.,Geos Institute | And 2 more authors.
Open Ecology Journal

The Northern Spotted Owl (Strix occidentalis caurina) is an emblematic, threatened raptor associated with dense, late-successional forests in the Pacific Northwest, USA. Concerns over high-severity fire and reduced timber harvesting have led to programs to commercially thin forests, and this may occur within habitat designated as "critical" for spotted owls. However, thinning is only allowed under the U.S. Government spotted owl guidelines if the long-term benefits clearly outweigh adverse impacts. This possibility remains uncertain. Adverse impacts from commercial thinning may be caused by removal of key habitat elements and creation of forests that are more open than those likely to be occupied by spotted owls. Benefits of thinning may accrue through reduction in high-severity fire, yet whether the firereduction benefits accrue faster than the adverse impacts of reduced late-successional habitat from thinning remains an untested hypothesis. We found that rotations of severe fire (the time required for high-severity fire to burn an area equal to the area of interest once) in spotted owl habitat since 1996, the earliest date we could use, were 362 and 913 years for the two regions of interest: the Klamath and dry Cascades. Using empirical data, we calculated the future amount of spotted owl habitat that may be maintained with these rates of high-severity fire and ongoing forest regrowth rates with and without commercial thinning. Over 40 years, habitat loss would be far greater than with no thinning because, under a "best case" scenario, thinning reduced 3.4 and 6.0 times more dense, late-successional forest than it prevented from burning in high-severity fire in the Klamath and dry Cascades, respectively. Even if rates of fire increase substantially, the requirement that the long-term benefits of commercial thinning clearly outweigh adverse impacts is not attainable with commercial thinning in spotted owl habitat. It is also becoming increasingly recognized that exclusion of high-severity fire may not benefit spotted owls in areas where owls evolved with reoccurring fires in the landscape. © Odion et al.; Licensee Bentham Open. Source

Odion D.C.,University of California at Santa Barbara | Odion D.C.,Southern Oregon University | Hanson C.T.,Earth Island Institute | Baker W.L.,University of Wyoming | And 2 more authors.

In a recent PLOS ONE paper, we conducted an evidence-based analysis of current versus historical fire regimes and concluded that traditionally defined reference conditions of lowseverity fire regimes for ponderosa pine (Pinus ponderosa) and mixed-conifer forests were incomplete, missing considerable variability in forest structure and fire regimes. Stevens et al. (this issue) agree that high-severity fire was a component of these forests, but disagree that one of the several sources of evidence, stand age from a large number of forest inventory and analysis (FIA) plots across the western USA, support our findings that severe fire played more than a minor role ecologically in these forests. Here we highlight areas of agreement and disagreement about past fire, and analyze the methods Stevens et al. used to assess the FIA stand-age data. We found a major problem with a calculation they used to conclude that the FIA data were not useful for evaluating fire regimes. Their calculation, as well as a narrowing of the definition of high-severity fire from the one we used, leads to a large underestimate of conditions consistent with historical high-severity fire. The FIA stand age data do have limitations but they are consistent with other landscape-inference data sources in supporting a broader paradigm about historical variability of fire in ponderosa and mixed-conifer forests than had been traditionally recognized, as described in our previous PLOS paper. © 2016 Odion et al. Source

Dellasala D.A.,Geos Institute | Bond M.L.,Wild Nature Institute | Hanson C.T.,Earth Island Institute | Hutto R.L.,University of Montana | And 2 more authors.
Natural Areas Journal

Complex early serai forests (CESFs) occupy potentially forested sites after a stand-replacement disturbance and before re-establishment of a closed-forest canopy. Such young forests contain numbers and kinds of biological legacies missing from those produced by commercial forestry operations. In the Sierra Nevada of California, CESFs are most often produced by mixed-severity fires, which include landscape patches burned at high severity. These forests support diverse plant and wildlife communities rarely found elsewhere in the Sierra Nevada. Severe fires are, therefore, essential to the region's ecological integrity. Ecologically detrimental management of CESFs, or unburned forests that may become CESF's following fire, is degrading the region's globally outstanding qualities. Unlike old-growth forests. CESFs have received little attention in conservation and reserve management. Thus, we describe important ecological attributes of CESFs and distinguish them from early serai conditions created by logging. We recommend eight best management practices in CESFs for achieving ecological integrity on federal lands in the mixed-conifer region of the Sierra Nevada. Source

Numerous avian species are positively associated with "snag forest" habitat created by patches of high-severity fire, mainly because of the abundance of standing fire-killed trees (snags) and fire-following shrubs. There is now considerably less severe fire than there was historically in the forests of California's Sierra Nevada, owing to fire suppression. Moreover, under current policies for management of public and private forest, much of the snag forest created by fire is subjected to post-fire logging of snags. Mechanical mastication and herbicide spraying of shrubs, followed by planting of conifers, are also common, and large-scale programs of mechanical thinning seek to prevent creation of this habitat. Thus there is reason for concern for birds associated with snag forest. I synthesized existing research to identify the species positively associated with this habitat and assessed their population trends according to the Breeding Bird Survey. In the Sierra Nevada 24 species are associated with snag forest, and half of these are declining or are too rare for the Breeding Bird Survey to detect any trend. For snag-forest species, there are significantly more declines than increases (all snag-forest species with statistically significant population trends are declining), whereas species of unburned forest manifest no such pattern. These results indicate a need for more managed wildland fire, and for current management policies, both pre- and post-fire, to be revisited, particularly in national forests where most of the post-fire habitat exists. Source

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