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Prescribed fire and tanoak (Notholithocarpus densiflorus) associated cultural plant resources of the Karuk and Yurok Peoples of California

  • Author(s): Halpern, Arielle
  • Advisor(s): Sousa, Wayne P
  • Carlson, Thomas J
  • et al.
Abstract

The targeted application of prescribed fire has long been used by Native Californian peoples to manage plant resources of cultural value. Their ability to employ this management tool has been increasingly restricted by local, state and federal agencies in response to recent drought conditions and the highly flammable state of most western U.S. forests, where, for decades, fires of any magnitude have been suppressed as a matter of policy. This diminished access to cultural prescribed fire has impacted tribal access to many of the plant resources and cultural activities upon which Karuk and Yurok cultures are based. The research presented in this dissertation: 1) uses historical and modern references to describe fire management practices of tribes throughout California, specifically targeting acorns as food resource, 2) investigates the effect of non-traditional spring burns on rates of tanoak (Notholithocarpus densiflorus, Fagaceae) acorn infestation by frugivorous Filbertworms (Cydia latiferreana, Tortricidae) and Filbert weevil larvae (Curculio occidentalis, Curculionidae), 3) evaluates the effectiveness of indigenous acorn collection criteria in correctly assessing the consumption quality of acorns, and 4) examines the responses of culturally significant plant species found in tanoak gathering areas to prescribed fire applied non-traditionally in spring. Assessed metrics were species diversity, species richness, and vegetative cover.

Traditionally, fires used to maintain productive heritage tanoak stands were set in late summer and fall. However, prescribed burns at this time of year have become very difficult to implement, so this study focused on the responses of the assemblages to a more easily executed, spring burn. During the two year study of acorn infestation rates in response to fire, I found that spring prescribed fire reduced acorn infestation in both the year of the fire and one year post-fire. Indigenous acorn collection criteria were very effective in distinguishing edible acorns from both inedible and insect-infested acorns. However, the traditional method of acorn evaluation did misclassify a sizeable proportion of the acorns as inedible, when they were actually of good food quality. Intended or not, this conservative misidentification provides added insurance that insect-infected acorns are not added to those stored within a household for future use. Over the three years that the responses of culturally valuable understory taxa to fire were monitored, all three metrics (species diversity, species richness, and vegetative cover) were sharply reduced by fire. Species diversity and richness showed substantial recovery by the second post-fire year, but neither had fully recovered. Understory plant cover showed very little, in any, recovery two years after the experimental fires. In particular, the percent cover of tanoak seedlings and lignotuber sprouts were greatly reduced, which may increase visibility of abscised acorns to tribal gatherers. As a single cultural fire targets multiple resource goals, these results indicate that some, but not all, resource goals traditionally achieved with fall fire were met with spring prescribed fire.

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