Tree populations exhibited considerable individual plant mortality and replacement over a 36-year period in a 500-year-old Pseudotsugamenziesii (Mirb.) Franco var. menziesii (Douglas-fir)–Tsugaheterophylla (Raf.). Sarg. (western hemlock) forest in the Cascade Range of southern Washington, U.S.A. Nearly 22% (113/ha) of the original stems died at an annual rate of 0.75%. This was balanced by recruitment (117/ha) of Tsuga, Abiesamabilis Dougl. ex Forbes (Pacific silver fir), and Taxusbrevifolia Nutt. (Pacific yew) saplings. Diameter distributions and relative species composition were nearly identical at the beginning and end of the 36 years. Compositional changes were slow despite the high turnover; extinction of Pseudotsuga is predicted in 755 years at its current mortality rate. Mortality was generally caused by wind (45.5%) or suppression and unknown causes (39.4%). Additional long-term studies of old-growth forests are needed to understand the direction and rate of successional change.

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A 10-year research and development program was conducted by the BioEnergy Development Corporation, USDA Forest Service, and U.S. Department of Energy on the island of Hawaii, where nearly 230,000 acres are suitable for growing biomass in short-rotation Eucalyptus plantations. Successful techniques are described for seedling production, plantation establishment (site preparation, weed control, planting), maintenance (weed control, fertilization), biomass yield estimation, and harvest. Basic biological relationships are described to aid decisions on site selection, initial spacing, fertilizer schedules, and rotation length. Environmental issues likely to be faced by growers of Eucalyptus plantations are discussed, including soil erosion, nutrient depletion, and monocultures. Continuing programs for tree improvement, monitoring, and silviculture research are recom mended. Production costs for biomass yields are estimated for three promising management regimes, representing pure Eucalyptus plantings at dense and wide spacings and a mixed species plantation where Albizia is used as a nurse crop to provide nitrogen needed for optimum Eucalyptus growth. This information will help prospective investors decide whether to invest in Eucalyptus plantations, and will help growers develop or choose among alternative management regimes.

Stand structure and crown architecture of loblolly pine (Pinustaeda L.) spacing trials in Hawaii and South Carolina were examined for attributes that would explain markedly different stockabilities (stand density per mean stand DBH), respectively, 1740 and 850 trees/ha at a quadratic mean stand DBH of 25 cm. In plots spaced at 2.4 × 2.4 m, these stockabilities produced 604 m3/ha at age 25 in Hawaii, and 297 m3/ha in South Carolina. Data collected in these stands indicate that stockability differences were associated with differences in tree size-class structure, crown length, and leaf area. Both stands were characterized by a two-tiered height structure, but the crown bases of trees in the subdominant class in Hawaii extended 1–2 m below the bases of the crowns of the dominant height class. In the South Carolina stands the crown bases of both height classes were at the same level. Green crown lengths in Hawaii were 4–7 m longer than in South Carolina, and the associated crown leaf area of 63.9 m2 was five times greater. The differences in stockability was attributed to the Hawaiian site and climate, which provide a long growing season, high solar radiation, high sun angle, favorable temperatures, and a favorable soil moisture regime and foliage nutrient status, and to a lack of significant insect and disease pests. The influence of genotype on stockability was not testable with these data.