Metlen, K.L.; C.E. Fiedler; A. Youngblood.  2004.  Understory response to fuel reduction treatments in the Blue Mountains of northeastern Oregon.  Northwest Science 78:175-185.

This study evaluated the response of undergrowth vegetation to fuel reduction treatments in ponderosa pine/Douglas-fir forests at the Hungry Bob Fire/Fire Surrogate site in northeastern Oregon.  Short-term responses to thin-only, burn-only, and thin/burn treatments were assessed one growing season after burning and three growing seasons after thinning.

The thin-only treatment involved thinning-from-below with a singlegrip harvester.  All trees greater than 30 cm diameter at breast height were retained and slash was left on site.

The prescribed burning treatment was conducted in the fall.  Burns were low intensity and fairly uniform.

The thin/burn treatment entailed thinning-from-below followed by prescribed fall burning.  Burning tended to be more intense due to additional harvest-generated fuels

• The thin-only treatment reduced species richness, but did not affect Shannon-Weaver’s index of species diversity.  Forb cover was reduced in the thin-only treatment, while the cover of other lifeforms was unchanged.
• The burn-only treatment significantly reduced shrub cover and overall cover.  Frequency of fire-adapted undergrowth species increased.
• The thin/burn treatment reduced forb, shrub, and total cover, similar to the thin-only and burn-only treatments.  Species that responded to fire did so most strongly in the thin/burn.
• Due to the modest intensity of treatments, short response time, disturbance history, or the evolutionary background of these forest communities, fuel reduction treatments did not strongly influence undergrowth vegetation.  Individual species responded consistent with their life history characteristics.