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The quantity and characteristics of coarse woody debris (CWD) were examined in four distinct pine ecosystems of north-western (NW) Spain, NW Russia and the NW USA. The average CWD volume and biomass ranged from 3.76 m³ ha-1, 1.55 Mg ha-1 in pine plantations in NW Spain to 24.86 m³ ha-1, 6.69 Mg ha-1 in Scots pine forest in NW Russia to 55.35 m³ ha-1, 20.38 Mg ha-1 and 77.04 m³ ha-1, 28.84 Mg ha-1 in ponderosa and lodgepole pine forests in the NW USA. Despite differences in species, ecological conditions and management histories, in all four ecosystems the mean snag volume was less than that of logs, most of the CWD mass was in an intermediate degree of decay, and mature stands had the greatest amount of CWD mass, followed by middle-age and then young stands. The CWD ratio (ratio of dead to live wood volume) ranged from 2.8% to 126.6%, depending on pine ecosystem and stand age, and was influenced by the type of natural and human disturbance. The difference in CWD amount and distribution among the regions studied reflected differences in disturbance history and management practices. Only in NW USA was the sample size large enough to examine the effect of disturbance type on CWD amount and distribution. There, fire and insect damage were found to considerably influence the amount of CWD in both lodgepole and ponderosa pine forests. Comparison of how different factors affect the amount and distribution of CWD in different ecosystems could be useful in developing ecologically sustainable forest management guidelines. [ABSTRACT FROM AUTHOR]

Discusses the study of mixed conifer and hardwood stands in southwestern Oregon. Purpose of the study to explore the hypothesis that competition effects on individual-tree growth and survival will differ according to the species comprising the competition measure; Description of hypothesis that competition measures should extrapolate best if crown-based surrogates are given preference over diameter-based surrogates; Modeling of diameter growth and probability of survival for individual Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees growing in pure stands; Application of alternative models to other plots in which Douglas-fir was mixed with other conifers and (or) hardwood species; Performance of crown-based variables compared to basal area based variables; Differences in crown morphology of surrogates among species found to relate more closely to the mechanics of competition for light and, hence, facilitate extrapolation to species combinations for which no observations are available.