Simulations of carbon storage suggest that conversion of old-growth forests to young fast-growing forests will not decrease atmospheric carbon dioxide (CO(2)) in general, as has been suggested recently. During simulated timber harvest, on-site carbon storage is reduced considerably and does not approach old-growth storage capacity for at least 200 years. Even when sequestration of carbon in wooden buildings is included in the models, timber harvest results in a net flux of CO(2) to the atmosphere. To offset this effect, the production of lumber and other long-term wood products, as well as the life-span of buildings, would have to increase markedly. Mass balance calculations indicate that the conversion of 5 x 10(9) to 1.8 x 10(9) megagrams of carbon to the atmosphere.

A new model, FORPROD, for estimating the carbon stored in forest products, considers both the manufacture of the raw logs into products and the fate of the products during use and disposal. Data for historical patterns of harvest, manufacturing efficiencies, and product use and disposal were used for estimating the accumulation of carbon in Oregon and Washington forest products from 1900 to 1992. Pools examined were long-and short-term structures, paper supplies, mulch, open dumps, and landfills. The analysis indicated that of the 1,692 Tg of carbon harvested during the selected period, only 396 Tg, or 23%, is currently stored. Long-term structures and landfills contain the largest fraction of that store, holding 74% and 20%, respectively. Landfills currently have the highest rates of accumulation, but total landfill stores are relatively low because they have been used only in the last 40 years. Most carbon release has occurred during manufacturing, 45% to 60% lost to the atmosphere, depending upon the year. Sensitivity analyses of the effects of recycling, landfill decomposition, and replacement rates of long-term structures indicate that changing these parameters by a factor of two changes the estimated fraction of total carbon stored less than 2%.

During progressive stages of drought and subsequent recovery through rewatering, foliage of 2‐year‐old seedlings of Douglas‐fir was sampled for water potential, stomatal resistance, and abscisic acid content (ABA). Simultaneous measurements of soil matric potential were also made. There was a rapid rise in stomatal resistance in the range of 1500–2000 ng ABA g−1 dry weight of foliage corresponding with a plant water potential of –10 to –12 bars. Soil matric potential seemed more closely associated with ABA increase than did plant water potential. After rewatering, seedlings returned to normal ABA levels within 6 days.

We have developed a model, HARVEST, that predicts the mass of woody detritus left after timber harvest in Pacific Northwest forests from 1910 to the present. Inputs to the model include the species, diameter at breast height, and age distribution of trees: the minimum tree size to be harvested; the minimum top diameter; and stump height and slope steepness. Model output includes the absolute amount and the proportion of bole biomass removed as well as that left as stumps, tops, breakage, and decay. The model also predicts the biomass of nonmerchantable parts such as branches, coarse roots, and fine roots left after harvest. Model predictions were significantly correlated to residue levels reported in the literature over this period. Both model output and historical data indicate that the total amount of aboveground woody residue left after logging has decreased at least 25% over the last century. This means that release of carbon to the atmosphere from woody residue has decreased by a similar amount.

Douglas—fir seedlings from a number of seed origins were subjected to drought conditions in the greenhouse and laboratory. Interior mountain seedlings showed significantly greater drought resistance than seedlings from origins west of the Cascade Mountains. Differences were also found within each of these groupings. In the Corvallis, Oregon, area seedlings produced from seed on a south slope had more drought resistance than those from a short distance away of a north slope. Differences in drought resistance may involve either drought hardiness or drought avoidance, or both.