John C. Zasada

Tree growth and stand development in short-rotation Populus plantings: 7-year results for two clones at three spacings

Two Populus hybrids (11-11 and D-01) were planted in monoclonal block plantings at three spacings (0.5, 1.0, and 2.0 m) near Olympia, Washington, and evaluated over a 7-year period for individual tree growth rates and above-ground stand productivity. Differences were substantial between clones and among spacings in both individual tree characteristics (height and diameter growth) and stand productivity (leaf area, basal area, or biomass production). Relative differences in growth between the clones tended to increase with spacing. Woody biomass production of clone 11-11 averaged 18.2 Mg ha−1 yr−1 at the 1.0 m spacing, whereas clone D-01 averaged only 10.1 Mg ha−1 yr−1 at that spacing. The clones differed in phenology of height and diameter growth, maximum rate of periodic height growth, tendency to produce sylleptic branches, partitioning of woody biomass, and sensitivity of growth rates to competition. All of these characteristics have important influences on the productivity of short-rotation plantations.

The impact of forest structure on near-ground temperatures during two years of contrasting temperature extremes

The thermal environment of clear-cut, partially cut, and uncut forest sites in northern Wisconsin are examined for a warm year and a cool year. Temperatures at 0.5 m above and 0.05m below ground, as well as base 5 degree C heat sums are computed for each site between May and September and differences between cut and uncut sites compared for the 2 years. differences in average and minimum air temperature and soil temperature are less than instrumental error, E = 0.3 degree C. Maximum air temperature differences between the clear-cut and uncut sites drop from 5.7 degree C in the cool year to 4.7 degree C in the warm year, while the difference for the partial cut drops from 3.2 to 2.7 degree C. The results suggest that studies of tree growth or forest development and climate change should consider the effects of forest structure on changes in daily extreme temperatures.

Alternative Fuel Reduction Treatments in the Gunflint Corridor of the Superior National Forest: Second year results and sampling recommendations

Fuel loadings need to be considered in two ways: 1) the total fuel loadings of various size classes and 2) their distribution across a site. Fuel treatments in this study affected both. We conclude that 1) mechanical treatments of machine piling and salvage logging reduced fine and heavy fuel loadings and 2) prescribed fire was successful in reducing fine fuel loadings (fuels less than 3 inches in diameter) but less successful than salvage logging and mechanical piling in reducing heavy fuel loadings (fuels greater than 3 inches diameter).

Microclimatic variation between managed and unmanaged northern hardwood forests in Upper Michigan, USA.

Temperature, light, wind, and precipitation were measured in the understory of managed and unmanaged northern hardwood forests in the Upper Peninsula of Michigan from 1995 through 2001. These measurements provide a baseline of information to compare the microclimate under managed and unmanaged conditions. Extreme climatic events may influence growth and development of forests.

Annual, local, and individual variation in the inflorescence and fruit production of eastern leatherwood (Dirca palustris L. Thymelaeaceae)'

through time when vegetative growth must also be supported from a limited pool of photosynthate. We compared reproductive performance characteristics among natural stands in Upper Michigan, USA across seven years. In addition, we inquired whether small or deeply shaded shrubs tended to be less consistent fruit producers. Fruit set fluctuated considerably over the period, but several conspicuously good and poor years did not correspond to temperature patterns. Flower production was largely stable at the stand level over the seven year period, with increases in years 2000 and 2001. Fruit production was a function of shrub size and did not differ between years or between stands. At an individual level, small and deeply shaded individuals tended to have one or two conspicuously good fruiting years against a background of low fruit production; sunlit and larger individuals were more consistent fruit producers. Fruit production was not related to the previous years fruit crop. Shrub size and, secondarily, light availability were the important determinants of fruit production, implying that stand age and history govern the population recruitment of leatherwood.

Commercial thinning in small-diameter aspen stands in Northern Minnesota: study establishment report.

In the spring of 1999, a long-term study was established to examine the physical and biological aspects of thinning young aspen stands in Minnesota. Three aspen stands ranging in age from 25 to 35 years were selected on lands owned by the State of Minnesota and UPM Kymmene. Two thinning treatments (low and high density) and an unthinned control were installed at each of the three locations. Permanent plots were installed to measure tree, shrub, and herb growth, and to monitor harvesting damage, insect and disease damage, soil strength, and fuel loadings. After 4 years, tree mortality was greater in the unthinned controls. Thinning treatment had no significant effect on the incidence of white trunk rot (Phellinus tremulae), Hypoxylon canker, or Saperda calcarata. No differences in post-harvest fuel loadings were detected among locations and treatments. Thinning increased the amount of light reaching the forest floor that resulted in greater herb and shrub biomass in the year immediately following thinning.

In Pursuit of a Better Seed Trap

Seed and litter traps are tools used by foresters and ecologists. We describe two different types of a durable trap constructed from plastic plumbing pipe, which are easily assembled/disassembled for efficient transportation and storage.

Increasing the productivity of short-rotation Populus plantations. Final report

This final report represents the culmination of eight years of biological research devoted to increasing the productivity of short rotation plantations of Populus trichocarpa and Populus hybrids in the Pacific Northwest. Studies provide an understanding of tree growth, stand development and biomass yield at various spacings, and how patterns differ by Populus clone in monoclonal and polyclonal plantings. Also included is some information about factors related to wind damage in Populus plantings, use of leaf size as a predictor of growth potential, and approaches for estimating tree and stand biomass and biomass growth. Seven research papers are included which provide detailed methods, results, and interpretations on these topics.