Treesearch

Provenance in forestry refers to the population of trees growing at n particular place of origin. Provenance research defines the genetic and environmental components of phenotypic variation associated with geographic source. Information on provenance is important in assuring sources of seed to give well-adapted, productive trees and in directing breeding of interracial and interspecific hybrids toward adaptation to particular localities. Concepts of the species, of variation within species, of continuity in this variation, and of relation of variation to factors of the environment have...

Many silviculturists and geneticists, concerned with the problem of increasing the rate of production of forest plantations, advocate or practice the selection of the larger seedlings in the nursery bed. Such selection implies a hypothesis that size of seedlings is positively correlated with size of the same plants at some more advanced age. Two tests were established at the Institute of Forest Genetics to determine whether seedlings selected as tallest within one-parent progenies maintain a growth superiority.

The genetic improvement of red pine (Pinus resinosa Ait.) presents tree breeders with one of their most difficult problems. Not only is this valuable species remarkably uniform, but until 1955 it resisted all attempts to cross it with other pines. In that year red pine and Austrian pine (P. nigra var. austriaca [Hoess] Aschers. & Graebn.) were successfully crossed at the Institute of Forest Genetics, Placerville, California. The few hybrid trees from this cross have been .mentioned and illustrated by Duffield and Snyder (1958) and Righter (1962).

In 5 years after a 1954-56 outbreak of Hemerocampa pseudotsugata in Calaveras and Tuolumne Counties, California, 20 percent of the merchantable white fir, or 11,071 board feet per acre, died in heavily defoliated stands. Another 1,113 board feet per acre was lost owing to radial growth reductions in partly defoliated trees; 12 percent of these trees were top-killed. Defoliation alone, and the combined effects of defoliation and attacks of cambium-mining beetles were the main causes of mortality.

An analytical technique that may be used in evaluating log-grading systems is described. It also provides means of comparing two or more grading systems, or a proposed change with the system from which it was developed. The total volume and computed value of lumber from each sample log are the basic data used.

Survival counts were made of 84 exotic tree species planted during 1956-1960 in a cleared rain-forest area near Hilo, Hawaii. Growth measurements were recorded for 5- and 6-year-old plantings. Most species had good survival, but some failed entirely. Soil depth was found to have a strong influence on rate of growth, but not on survival. Several valuable timber species showed remark-able growth. The report lists possibilities for future uses and contains recommendations for development of the arboretum.

Abstract - The quantity of summer soil moisture loss from logged forest openings was related to the length of time since the creation of the opening in a study made in the subalpine forest zone of the Sierra Nevada west-side near the Central Sierra Snow Laboratory, California, within the elevational range of 6,000 to 7,000 feet. Soil moisture depletion was measured in logged forest openings which were created in 1959, 1955, 1950, and 1948, and in the forest surrounding these openings. At the period of maximum soil moisture depletion, openings 1 year old were found to have 6.9 inches more...

Abstract - Only in a bulldozed brush field and with heavy applications of hexadecanol under snow did significant reductions in evapotranspiration occur with application of hexadecanol to natural stands. Marked reductions in evaporation from snow occurred when hexadecanol emulsion was applied to the snow surface. More than two-thirds of the precipitation in the United States is used by forest, browse, and non-economic vegetation areas (Wolman 1963). If transpiration or evaporation in these areas could be suppressed, important savings of water for other uses might be effected. One way of...

Mass fires are likely to follow a nuclear attack. Since it is important to the civil defense program to be able to predict rate, duration, and extent of spread of such fires, the Office of Civil Defense, U.S. Department of Defense, issued a joint contract to the Forest Service and to United Research Services, Inc., to study this field. We surveyed the literature, interviewed some 30 urban and wildland fire-control personnel, studied nearly 2,000 fires, collected 1,687 rates of spread, and determined the conditions when fires would not spread significantly and the conditions when fires...