Project Title: Impacts of watershed restoration and road decommissioning on tailed frogs, Ascaphus truei, in Redwood National and State Parks, California.

Investigators: Christopher R. Currens & Mary Ann Madej USGS-Western Ecological Research Center Redwood Field Station 1655 Heindon Road Arcata, CA 95521 707-825-5189 FAX: 707-822-8411 ccurrens@usgs.gov

Adult tailed frog (Ascaphus truei) Credit: Jens V. Vindum © California Academy of Sciences

Larval stage of tailed frog (Ascaphus truei) © 1999 Joyce Gross

BACKGROUND

Anthropogenic landscape disturbances, such as road construction and timber harvests, can have a negative effect on both terrestrial and aquatic habitats (see Trombulak & Frissel, 2000 for review). Although many land management activities (e.g. timber harvest, road building) might directly alter only a small percentage of the actual aquatic environment (i.e. stream crossings), increased sedimentation of a large portion of the entire sub-basin is a common outcome from such activities (Waters 1995). Watershed restoration and road decommissioning are designed to decrease sediment loads to fish-bearing streams over the long term, however, within the first few years of heavy equipment work, sediment loads commonly increase (Klein 2003). The short-term effect of watershed restoration on aquatic biota remains largely elusive. Previous work has shown that tailed frogs, Ascaphus truei, may be sensitive to sedimentation (Corn & Bury, 1989) and can be indicators of suitable stream conditions for several obligate cold-water vertebrate species (Welsh & Ollivier 1998). We designed a study to investigate the effects of watershed restoration on the biomass and condition of larval tailed frogs, in 3rd and 4th order tributaries to Redwood Creek, Redwood National and State Parks, California. We sampled stream reaches in sub-basins classified as pristine (no restoration), recovering (restoration occurred >15 yrs ago) and recently disturbed (restoration occurred 1-7 yrs ago).

PURPOSE

The purpose of the current research is to determine whether recent (1997 – present) disturbance from RNP road decommissioning and watershed restoration work has had a negative impact on tailed frog biomass and condition and whether density of active roads in each sub-basin has a negative effect on tailed frog biomass and condition. If the study demonstrates that the parks’ current road and watershed restoration practices have a negative affect on tailed frogs, the park may alter its current restoration practices in an effort to reduce the impacts to tailed frogs and other aquatic vertebrates.

RESULTS

Study sites located in eleven sub-basins; Little Lost Man, Upper Prairie (undisturbed), Bond, Emerald, Miller (recovering) and Bridge, Forty-four, Larry Damm, Lost Man, McArthur and Tom McDonald (recently disturbed) were sampled for tailed frogs. We found a significantly higher biomass of tailed frogs in pristine study reaches (3.66 ? 0.77 gms / m2) versus recently disturbed reaches (1.43 ? 0.29gms / m2) (figure 1). We also found that tailed frog condition (measured as individual mass) was significantly greater in undisturbed than recovering or recently disturbed study reaches. Tailed frog mass was 43% greater in pristine compared to recently disturbed sites. Eight factors, including year of most recent watershed restoration and total km of roads removed, explained 63% of the variation in tailed frog biomass. The results of this study indicate that the parks’ current watershed restoration and road decommissioning practices have a negative impact on tailed frog biomass and condition.

Figure 1

LITERATURE CITED

Corn, P.S. & R.B. Bury. 1989. Logging in western Oregon: responses of headwater habitats and stream amphibians. Forest Ecology Mgmt.29: 39-57.

Klein, R. 2003. Duration of turbidity and suspended sediment transport in salmonid bearing streams, North coastal California. 37 pp.

Trombulak, S.C. & C.A.Frissel. 2000. Review of ecological effects of roads on terrestrial communities. Conservation Biology 18: 18-30.

Waters, T.F. 1995. Sediment in streams: sources, biological effects and controls. Monograph 7. American Fisheries Soc. Bethesda, MD.

Welsh, H.H. & L.M. Ollivier. 1998. Steam amphibians as indicators of ecosystem stress: a case study from California’s redwoods. Ecological Applications 8:1118-1132.

Keywords: Tailed frogs, Ascaphus truei, sediment, watershed restoration, road decommissioning, Redwood National and State Parks