PS 72-141
Effects of altered fire regimes on tanoak understory assemblage diversity and cultural resources of the Karuk and Yurok Peoples of California
Prescribed fire is used as a primary agroforestry tool by many Native Californian peoples for the maintenance of diverse terrestrial and aquatic resource systems. Tanoak dominated stands within the Tanoak-Douglas Fir-Madrone alliance are of particular importance to mid- and lower-Klamath River Tribes as gathering sites for Tanoak acorns and habitat associated shrub and herbaceous plants of cultural value. Tanoak resource areas were typically burned in the fall to foster diverse, culturally valuable plant assemblages, and reduce acorn infestation by insect frugivores. This project is conducted under the auspices of the Karuk-U.C. Berkeley Collaborative with the support and approval of the Karuk and Yurok Tribes of California: We ask whether altered fire regimes effect the assemblage composition and the diversity of culturally valuable species in Tanoak-dominated resource procurement areas in the Klamath River watershed. Five sites in cultural resource gathering areas were identified on private property and reservation lands within the ancestral territories of the Karuk and Yurok Tribes. Treatment areas (spring/fall prescribed fire) and adjacent control (unburned) areas were developed at each site. Between the five research sites, 143 replicate 2mX1m exclusion cages were constructed under the drip lines of large (>30cm dbh) Tanoak trees to prevent herbivory. Vegetation surveys documenting presence/absence, percent cover, and stem counts were conducted within each exclusion cage yearly during the summer months from 2011 to 2014. Prescribed broadcast burns were applied to treatment areas in the spring and fall of 2013. Ignitions occurred at temperatures between 65-73°F and relative humidity between 35-45%. Duff pins were used to assess litter consumption and scorch height measured to calculate fire line intensity. Species diversity data was analyzed using diversity profiles and PERMANOVA (R-vegan function Adonis).
Results/Conclusions
31 species were identified within exclusion cages of which 15 are of cultural value. Two month post-fire results indicate a significant difference in overall species diversity (p<0.001) between treatment and control with a reduction in plant species diversity and percent cover in burned cages. Leaf litter cover within exclusion cages was reduced from 90-100% in unburned cages to 10-20% in burned cages. Between 3 and 5cm of duff was consumed during all treatment fires exposing bare mineral soil. One year post-fire analyses are expected to show an overall increase in species diversity for treatment areas with fall fire promoting a greater richness of culturally valuable species and overall species evenness.