Treesearch

The commonly applied comparison-tree method of selection is analyzed as a form of within-family selection. If environmental variarion among comparison- and select-tree groups, c2, is a relatively small proportion (17 percent or less with 5 comparison trees) of the total variation, comparison-tree selection will result in less genetic improvement than individual-tree selection, Even if c2 is large, individual-tree selection may be more effective than comparison-tree selection if comparison and candidate trees are related. Estimates of c2 and of relationships among trees in wild stands...

Experts from relevant disciplines exchanged information on three important problems of pesticide spray technology. The four papers presented are Physical Parameters Relating to Pesticide Applications by N. B. Akesson and W. E. Yates; The Micrometeorology and Physics of Spray Particle Behavior by H. E. Cramer and D. G. Boyle; Impaction of Zectran Particles on Spruce Budnomi Larvae: A Field Experiment by J. W. Barry and Others; and Assessment of Insecticide Spray Processes by C. M. Himel. Summaries of the three workshop sessions are also included.

Use of the chlorinated hydrocarbon insecticide lindane to control bark beetles is controversial. Differences of opinion persist, even among knowledgeable entomologists, on whether use is justified in view of potentially harmful side effects. Effectiveness of lindane treatments, as employed in preventing tree mortality from bark beetles, is also in question. In seven papers, relevant information from many sources is reviewed by investigators who hold divergent views. The papers present data on the biological characteristics of lindane, its persistence in the environment and effects on both...

Pitch pine seedlins were grown at constant temperature and photoperiod. Net CO2-uptake h-1 g-1 leaves decreased stadily during ontogeny until leaf production ceased. Thereafter, there was no change or a slight increase. Though the 0ntogeneic pattern was the same in populations native to different geographic areas, there were differences among populations in the rate of CO2-uptake. Root respiration, calculated from the difference between CO2-uptake and net assimilation rate, accounted for 6 to 69 per cent of diurnal assimilation.

Data products from the Skylab Earth Resources Experiment Package were examined monocularly or stereoscopically using a variety of magnifying interpretation devices. Land use, forest types, physiographic sites, and plant communities, as well as forest stress, were interpreted and mapped at sites in Georgia, South Dakota, and Colorado. Microdensitometric techniques and computer-assisted data analysis and sampling procedures were developed and tested against ground truth. Results indicate that only Skylab S190B color photographs are good for classification of forest and nonforest land (90 to...

Rate of population buildup of dwarf mistletoe, Arceuthobium abietinum Engelm. ex Munz., was slow in most small red firs and white firs 12 to 15 years after inoculation with the parasite. Where population buildup did occur, it remained clustered in the lower portions of tree crowns near inoculation sites. Maximum distance of vertical spread was 16 feet (4.8 m), after 15 years. The mean annual rate of vertical spread of the parasite in 12 to 15 years was 3 inches (7 cm) or less in test trees. No vertical spread occurred in some trees. Rate of vertical spread was much slower in all trees than...

Attitudes and characteristics of campers reached by two Federal campsite reservation programs in experimental use during the summer of 1973 were surveyed. Most campers strongly favored reservations, but preferred that one company sell reservations to all government campgrounds. Questionnaire responses indicated need for a systematic procedure for referring campers to vacant campsites, along with a more effective program of information on the reservation systems. A majority of campers were satisfied to get their first choice of campground, but a few also wanted freedom to choose their...