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Long-term effects of restoration fire and thinning on soil fungi, fine root biomass, and duff levels - Final report to the Joint Fire Science Program

Author(s): Jane E. Smith, Daniel L. Luoma, Robyn L. Darbyshire, James D. McIver, Andrew P. Youngblood
Year Published: 2018

The proposed research will help managers understand how early soil ecosystem responses to fuel reduction treatments with prescribed fire may or may not be indicative of longer term responses. This research is necessary for better establishing, in forest management plans and decision documents, the ecosystem costs and benefits of lessening the risk of stand-replacing wildfire through fire and fire surrogate (FFS) fuel reduction treatments. Early impacts of the restoration treatments at the Hungry Bob FFS research site in the Blue Mountains of northeastern Oregon indicate that both treatments with burning (prescribed burn only, and thinned and prescribed burn) significantly reduced live root biomass, ectomycorrhizal fungal (EMF) species, and duff levels compared to the non-burned treatments (thinned only, non-thinned and non-burned). These results raise questions about whether managers can achieve the desired future condition of stands with large-tree retention and low fuel loads. EMF mortality and complete duff reduction after fire have been implicated with poor tree survival and slow stand recovery in forest ecosystems world-wide. The proposed research will extend our assessment beyond the immediate-effects stages to a period of time more meaningful to managers seeking to understand fuel reduction impacts on soil productivity. Re-measurement of EMF, fine roots, and duff in 2013 will provide information on treatment effects 15 years post-thinning and 13 years post-burning. No significant management has occurred since the stands were subjected to thinning (1998) and burning (2000), and all prior datasets are available.

Citation: Smith JE, Louma DL, Hart BTN. 2018. Long-term effects of restoration fire and thinning on soil fungi, fine root biomass, and litter depth. Joint Fire Science Project 12-1-01-20. Corvallis, OR: USDA Forest Service, PNW Research Station. 37 p.
Topic(s): Fire Effects, Ecological - First Order, Soil Heating, Ecological - Second Order, Soils, Fuels, Fuel Treatments & Effects, Recovery after fire
Ecosystem(s): None
Document Type: Technical Report or White Paper
NRFSN number: 17150
FRAMES RCS number: 24448
Record updated: Jun 21, 2018