We studied pure and 50/50 mixtures of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) plantations to compare attained total yields between mixed-species stands as opposed to monocultures of equal densities. Whether overall stand density influences this outcome has not been adequately investigated, and to address this we included three density levels (494, 1111, and 1729 trees/ha) in the analysis. At age 12, as components of the mixed stands, Douglas-fir exhibited greater height, diameter, and individual-tree volume than western hemlock at all densities. At 494 and 1111 trees/ha the monocultures had a higher volume per hectare than the mixed stand, but at 1729 trees/ha the mixed stand appeared to be just as productive as the pure stands. The increase in productivity by the mixture at high densities seems to have resulted from the partial stratification observed and most likely also from better use of the site resources. Because of this, less interspecific competition was probably experienced in the mixed stand than intraspecific competition in the pure stands. This study shows the important role density plays in the productivity of mixed stands and thus in comparing mixed and pure stands.

Species information is a key component of any forest inventory. However, when performing forest inventory from aerial scanning Lidar data, species classification can be very difficult. We investigated changes in classification accuracy while identifying five individual tree species (Douglas-fir, western redcedar, bigleaf maple, red alder, and black cottonwood) in the Pacific Northwest United States using two data sets: discrete point Lidar data alone and discrete point data in combination with waveform Lidar data. Waveform information included variables which summarize the frequency domain representation of all waveforms crossing individual trees. Discrete point data alone provided 79.2 percent overall accuracy (kappa = 0.74) for all 5 species and up to 97.8 percent (kappa = 0.96) when comparing individual pairs of these 5 species. Incorporating waveform information improved the overall accuracy to 85.4 percent (kappa = 0.817) for five species, and in several two-species comparisons. Improvements were most notable in comparing the two conifer species and in comparing two of the three hardwood species.

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Marketing timber is shifting from logs, lumber, and veneer measured volumetrically to include carbon storage and energy that are based on dry mass. Conversion between volume and dry mass relies on accurate estimates of wood specific gravity (SG). We measured width and SG of growth rings and their earlywood and latewood components with X-ray densitometry on trees from controlled, thinned, biosolid fertilized, and combined treatments applied to a 55-year-old Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) stand. We developed models to predict interannual SG from climate and treatment effects and compared 20 year changes in dry mass and carbon storage with estimates from biomass equations and from the Wood Handbook average SG. Thinning increased latewood width but did not affect ring SG. Biosolid fertilization increased earlywood and latewood width and decreased ring SG 8% by decreasing earlywood SG, latewood SG, and latewood percentage. SG decreased with increased July soil moisture deficit; alternatively, SG increased with increased July total precipitation. Warmer mean March–May or August–November temperatures also increased SG. Because of the effects on SG, dry mass and carbon storage changes differed from volume changes produced by the treatments. Dry mass estimates using the average Wood Handbook SG or those calculated from biomass equations were inconsistent between treatments, with errors up to 50%.

Forest management demands thorough knowledge of ecological systems. Tree interaction dynamics are one component of these ecological systems. Developing growth models which incorporate ecological "laws" such as the self-thinning rule can lead to better understanding of the laws, to better understanding of what is still unknown, and to what is in need of refinement. To this end a system of simultaneous differential equations incorporating logical, linked hypotheses regarding growth and mortality is proposed and fit to data from red pine (Pinus resinosa Ait.) plantations in the Lake States (Minnesota, Michigan, and Wisconsin). Using this modeling framework it appears that stand initiation history has a large impact on the level of the self-thinning boundary for red pine growing in the Lake States. Stands with initially high density exhibited lower self-thinning boundaries than stands with lower densities. Site quality (as measured by site index) chiefly affected the rate at which stand dynamics progress. Higher quality sites progressed through stand development at faster rates than did sites with lower quality.

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