A Comparison of the Short-Term Effects of Two Fuel Treatments on Chaparral Communities in Southwest Oregon

Abstract

Fuel treatments to reduce fire danger are being applied to public lands throughout the western United States, affecting significant acreage at considerable expense. This study compares the short term effects of two fuel treatment methods, shrub mastication and “hand cut, pile, and burn” (HPB), on chaparral communities in southwestern Oregon. Ceanothus cuneatus dominated the study sites where permanent paired plots were established on either side of treatment-control boundaries. Over a two year period, we recorded all vascular plant species within each treatment or control plot, along with an abundance class for each species. The effects of treatment on species composition and abundance of forbs and graminoids, overall as well as by plant trait group, were surprisingly small. Time since treatment, 1 yr or 2 yr, had a stronger effect on species composition than did treatment method. Species abundance and richness were greater in the first year after treatments than in the second year or in controls. In the second year, after both types of treatments, species abundance and richness were reduced, while after mastication treatment, these measures were lower than in control areas. The HPB treatment had a greater effect on plant communities than did mastication, due, at least in part, to the presence of fire rings from burned piles. Compared to their surrounding treated plots, fire rings had greater proportions of both annuals (95% versus 71%) and introduced weeds (35% versus 21%) in the second year after treatment. Ceanothus germination was stimulated in fire rings but also occurred in most plots, including controls. Both types of treated areas had more Ceanothus seedlings than their controls. Short term evidence suggests that the HPB treatment may lead to an increase in weedy and exotic species and the mastication treatment may reduce species diversity. The HPB treatment may also increase native species diversity by allowing fire-cued species to establish. Additional monitoring over time is needed to assess longer term treatment consequences for these northern chaparral communities.