Coarse Woody Debris in Mature Pinus ponderosa Stands in Colorado

Abstract

ROBERTSON, PHILW A. AND YvoNNE HALL BOWSER. (Department of Plant Biology, Southern Illinois University, Carbondale, IL 62901-6509). Coarse woody debris in mature Pinus ponderosa stands in Colorado. J. Torrey Bot. Soc. 126:255-267. 1999.-During summer of 1994, 328 0.1 ha circular plots were sampled to determine the volume of coarse woody debris (CWD) and standing dead density and basal area in 53 mature or older Pinus ponderosa stands in the Front Range and Southwestern mountains of Colorado. Standing dead volume was estimated using height derived from living trees in the plots. Generally, CWD amounts were lower in these forests than have been reported for Pinus ponderosa forests in Arizona and New Mexico and other forest types in North America. Mean volume for all plots was 15.9 m3/ha ? 20.85 SD. Mass, estimated from published wood density values, was 3.4 Mg/ha ? 5.07. CWD in the Southwestern mountains of Colorado averaged about 7.5 m3/ha > in the Front Range. Sixty-three percent of the CWD was in decay class 4 followed by class 5 with 16%. CWD showed considerable variation across stands and habitat types with generally higher amounts in more mesic conditions. No significant relationships existed between CWD and the various environmental factors measured. CWD volume and variability both increased with stand age. Standing dead density was highly variable with an mean density of 11.9 stems/ha. Most standing dead trees were small with a mean diameter of 34.6 cm and mean basal area of 1.25 m2/ha. Eighty-eight percent of the class 1 CWD was standing dead, but class 1 comprised only 8% of the total CWD. High values of standing dead may be related to disturbance and stand age. In Pinus ponderosa stands, it appears CWD is affected by disturbance, such as fire, timber harvesting and insect infestation > by physical factors of the environment.