Resiliency of ponderosa pine forests to bark beetle infestations following fuel-reduction and forest-restoration treatments
Authors: | Christopher J. Fettig |
Year: | 2015 |
Type: | Book Chapter |
Station: | Washington Office |
Source: | Potter, K.M., and B.L. Conkling, editors. 2015. Forest Health Monitoring: National Status, Trends and Analysis, 2014. General Technical Report SRS-209. Asheville, North Carolina: U.S. Department of Agriculture, Forest Service, Southern Research Station. 190 p. |
Abstract
About 10 million ha of forests are classied as having moderate to high re hazards in the Western United States (Stephens and Ruth 2005), many of which are characterized by ponderosa pine (Pinusponderosa), an integral component of three forest cover types and a major component of >65 percent of all forests in the Western United States (Burns and Honkala 1990). Prior to Euro-American settlement, many ponderosa pine forests were open and parklike, as frequent thinning of small-diameter [<19 cm diameter at breast height (d.b.h.)] and re-intolerant trees by low-intensity surface res and competitive exclusion of tree seedlings by understory grasses maintained such conditions (Covington and Moore 1994). Today, these forests tend to be denser, have more small trees and fewer large trees, and are dominated by more shade-tolerant and re-intolerant tree species such as white r (Abies concolor). Consequently, fuel-reduction and forest-restoration treatments have been widely promoted to reduce the intensity and severity of future wildres and to increase resilience to a multitude of other disturbances. When properly applied, prescribed re, mechanical thinning, and their combination are effective for increasing residual vegetative resilience to wildre (Agee and Skinner 2005, Stephens and others 2012). For example, Ritchieand others (2007) studied the effects of fuel-reduction and forest-restoration treatments at Blacks Mountain Experimental Forest, California on observed re severity between treated and untreated stands impacted by a wildre. Tree survival was highest in areas that were both thinned and prescribed burned. Survival in thinned-only areas was signicantly greater than in untreated areas but less than in areas that had received the combined treatment.