The locomotion of females of different strains of the parasitic wasp Trichogramma maidis (Hymenoptera, Trichogrammatidae) was measured under standardized conditions and compared to their efficiency in the field for several years. A manual and an automatic method for recording and analysing the locomotion of insects are described and results for differently reared laboratory strains of T. maidis are presented. The correlation between manual and automatic measurements of the travel speed was significant (r = 0.999). The automatic method was developed by means of an Image Processing System. T. maidis females were individually released in an arena, and the walking tracks were recorded by a video camera. To reconstruct the real path, a mathematical model which gives highly accurate path length estimations -termed arcus interpolation -was used. Furthermore the same programme permits the calculation of parameters like turning rate and angles, the activity pattern over the whole observation period or for selected parts of it. The locomotion of different T. maidis strains in the laboratory was compared with their efficiency in the field. An obvious relation between locomotion and parasitization in the field was apparent. The probability for parasitism of Ostrinia nubilalis Hbn.(Lepidoptera, Pyralidae) egg batches decreased linearly with increasing distance from the release point of Trichogramma wasps. The travel speed of the females of different T. maidis strains was found to be positively related to the potential for parasitism in the field. The travel speed can therefore be used as a parameter to estimate the capacity for host location and the efficiency of a T. maidis strain for inundative biological control programmes.

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Planting ponderosa pine in clearcuts below 5,300 feet where vigorous advance reproduction is lacking has resulted in fast growing, well stocked stands and is the preferred reforestation method. At higher elevations, lodgepole pine is a desirable species to plant because of its greater resistance to snow damage. Planting stock should be used that was grown from seed collected in the same geographical and elevational zone as the clearcut. If sufficient numbers of vigorous advance reproduction exist to form the new stand, careful logging and slash disposal methods to save these trees will eliminate the problems associated with natural or artificial regeneration. Natural regeneration after clearcutting is an uncertain reforestation method because so many factors involved are beyond the forester's control. It is, therefore, most useful as a means of supplementing existing advance or planted reproduction.

A study of impacts of forest harvest on volcanic ash soils was conducted on three National Forests in the Blue Mountains of Eastern Oregon and Washington. Surface soil conditions were assessed in 11 forest harvest units; sampling employed a randomly positioned grid of randomly oriented line transects. In addition, air permeameter readings were tested in seven units for correlation with bulk density values obtained from core samples. Most of the detrimental soil conditions detected were attributable to compaction. Displacement, although readily apparent during harvest or slash piling with ground‐based equipment, was nearly undetected by the methods used on these units, which ranged from 14 to 23 yr old. Detrimental compaction averaged 28 or 19% of the harvest unit area when defined as either a 15 or 20% increase in bulk density, respectively. Area percentages included skid trails and landings but not the transportation system. Statistical tests showed that either 5 or 3 of the 11 units exceeded 20% area in detrimental condition, depending on degree of bulk density increase used to define detrimental compaction. Several other units were borderline in exceeding 20% of the area. Given slow recovery from compaction, there is potential for additional area to be adversely impacted by future entries. Air permeameter readings were poorly correlated with bulk density assessments, even though six of seven correlations were statistically significant. Less than 12% of the total variability was accounted for by regression analyses. The air permeameter does not appear to be accurate enough to measure compaction in volcanic ash soils.

The diameter and height growth of advance reproduction of suppressed true fir (Abies spp.) and mountain hemlock (Tsuga mertensiana (Bong.) Carr.) was measured in south-central Oregon after release by overstory removal in clearcuttings, shelterwood units, and uncut stands. Postrelease growth was greatest in clearcuttings, intermediate in shelterwood cuttings, and slowest in uncut stands. Multiple regression analyses were used to predict growth response as a function of tree and stand variables. Overstory basal area, live crown ratio, and past 5-year height growth accounted for the most variation in diameter and height growth after release. Vigorous advance reproduction having live crown ratios greater than 50 percent are the best candidates for crop trees.Keywords: Growth response, release, suppression (tree), advance growth, true fir, mountain hemlock.In 1983 and 1984, a study was conducted in the Cascade Range in south-central Oregon to obtain information about the diameter and height growth response of suppressed advance reproduction of grand fir (Abies grandis (Dougl. ex D. Don) Lindl.), Shasta red fir (Abies magnifica var. shastensis Lemm.), and mountain hemlock (Tsuga mertensiana (Bong.) Carr.) after release by removal of the overstory. The purpose was to compare rates of diameter and height growth before and after release, to determine when increased growth occurs, and to develop models to predict diameter and height growth after release as a function of tree and stand variables, such as live crown ratio and basal area.The study areas were clearcut and shelterwood units and uncut stands in upper slope, mixed conifer/snowbrush-chinkapin and mountain hemlock/grouse huckleberry communities in the Deschutes and Winema National Forests, south-central Oregon. Growth patterns 5 years before and 10 to 20 years after release of the trees were determined by sectioning trees.Both diameter and height growth increased after release from two to four times the prerelease rate for both fir and hemlock. Acceleration of growth generally occurred within 5 years after release with the most rapid growth occurring on clearcut units. Growth curves had a sigmoid form showing constant growth before release, a rapid acceleration during the first 8 to 9 years after release, followed by a flattening of the curves from 10 to 20 years after release.Residual overstory basal area, live crown ratio, and past 5-year height growth were the three variables accounting for most of the variation in diameter and height growth after release. Growth of the advance reproduction after release was directly proportional to live crown ratio or past height growth and inversely proportional to overstory stand density. Both fir and hemlock responded to release regardless of age.The.best potential crop trees are vigorous advance reproduction having live crown ratios greater than 50 percent and those with the greatest height growth before release. Releasing these trees by removing the overstory and by thinning when needed will not only greatly increase grow...