U.S. Joint Fire Science Program


Date of this Version


Document Type



Matchett, J., M. Brooks, A. Halford, D. Johnson, and H. Smith, 2010, Evaluating the effects of pinyon thinning treatments at a wildland urban interface: El Portal, CA., 28 pp.


US government work.


This study evaluated the short-term effects of thinning methods for pinyon pine woodlands at two sites in the southwestern Great Basin. Both cut/pile/burn and mastication treatments were equally effective at reducing the target fuels which were mature, live pinyon trees. Application costs though differed substantially, with the cut/pile/burn technique being less expensive. Thinning treatments increased the abundance of herbaceous vegetation, although in some cases the strength of the increase was constrained by the level of pre-treatment tree dominance. Increases in perennial grass cover and density in response to thinning were usually greatest at lower levels of pre-treatment pinyon dominance, whereas native annual forb density and cover responded fairly equally along the tree-dominance gradient. Shrub abundance declined in response to pre-treatment tree dominance and the response to thinning treatments appeared more subtle than for herbaceous vegetation. Shrub cover within the control decreased slightly during the 3 post-treatment years, while it increased slightly within both thinning treatments. The response of slower-growing plants such as shrubs will need to be evaluated during future years to determine differences between thinning treatments. Species richness within the two thinning treatments steadily increased relative to the control over the course of the 3 years following treatment. Species richness was also consistent across the pinyon-dominance gradient, which suggests that the ability for vegetation to recover at this location may not be significantly limited by a lack of seed availability or lack of species diversity within highly tree-encroached shrublands. Cover of herbaceous live fuels (perennial and annual forbs and grasses) and live woody fuels (live shrubs and trees) were also similar between the two thinning treatments and higher than the control. The greatest difference in fuel structure between the two fuel treatments appeared to be dead woody fuel loads— mastication clearly resulted in greater fine fuel loads (1–100 hour fuels) as well as the shredded woody particles. The stimulation of live herbaceous cover—especially at lower pre-treatment pinyon dominance—may have important implications for fire spread by enhancing the continuity of surface fuels, especially during dry years.