Treesearch

Genetic variation among loblolly pine (Pinus taeda L.) samples from a natural stand and among clones in seed orchards was analyzed using simply inherited isozyme markers. Alleles for eleven enzyme loci were found useful for genotyping trees in a natural stand in North Carolina. The pines were highly variable with as many as seven alleles per isozyme gene. On the average, close to 30 percent of the loci per tree were heterozygous. Similar levels of variability and heterozygosity were found /among the clones in two seed orchards. Such variability makes it possible to uniquely identify most,...

The pines have been more successful than most of their coniferous relatives in occupying marginal habitats at the upper and lower edges of the forest zone in western North America. Among the groups restricted to such habitats is subsection Baljourianae of Pinus, comprising the fox tail and bristlecone pines. These pines characteristically grow on cold dry sites at high elevations, and in most places have few tree associates. Perhaps because of their inaccessibility and limited economic importance, not much was known about them until E. Schulman's discovery in the mid-1950's that some...

On a short trip into the northern Olympic Mountains of Washington in the summer of 1896, Professor Charles Sprague Sargent found a fir tree that he thought might be a natural hybrid between Abies amabilis (Dougl.) Forbes and A. lasiocarpa (Hook.) Nutt. The founder and Director of the Arnold Arboretum, Sargent was generally recognized as America's preeminent dendrologist. His brief description of the putative hybrid (Sargent, 1898) is still the only report of natural hybridization between A. amabilis and any of the firs with which it grows (Klaehn & Winieski, 1962). On the same trip Sargent...

Plant moisture stress (PMS) regimes over the summer were determined in planted Douglas-fir seedlings in clearcut and partial-cut blocks on the south slope clearcut, PMS reaches levels that after June could seriously reduce seedling growth. The PMS of the clearcut plots exceed 15 atmospheres at midmorning in June, but partial-cut plots do not exceed this level until September. The greater PMS of the south clearcut plot has not retarded height growth of the Douglas-fir. This is the only plot, however, on which regeneration stocking is not adequate.

Regeneration was studied on a mixed conifer stand on granitic soils on the Klamath National Forest. Six years after logging and hand planting with Douglas-fir, stocking and growth on cutblocks where slash had been broadcast burned was compared with that on similar unburned cutblocks. Conifers were seven times more plentiful on the unburned areas, the average height of the tallest conifer on each plot was nearly twice as great, and the yearly height growth was 27 percent greater. Results suggest that modification of burning policies on this soil type may improve regeneration.

An electronic calculator with trigonometric functions can be used to compute times of sunrise, sunset, or twilight, or time of desired illumination at any location in mountainous terrain. The method is more convenient and versatile, and less cumbersome than using tables. Latitude, longitude, elevation, day of the year (1 to 366), and slope to the horizon at the azimuth of the sun at sunrise and sunset are necessary for the computations. The effects of elevation of the observation point and blocking of the sun's radiation by terrain surrounding the observation point are included in the...

...The Arboretum must be viable...the Arboretum must be dynamic, offering programs, new programs, and repeat programs, to share the knowledge that we have accumulated..." Francis Ching, Director, Los Angeles State and County Arboretum.¹ ¹Excerpt from: Proceedings of a Symposium: The Urban Arboretum in a Time of Crisis. 1972. University to notes which they have taken on previous of Washington Arboretum Foundation.

Mass wasting is the dominant erosional process in most steep-sloped catchments. major mechanism in this process is the landslide (2, 6, 8, 19, 24, 25, 29). In this paper, unless explicitly stated to the contrary, the reference to debris avalanches and other forms of shallow failures

Abstract - Granitic batholiths around the Pacific Ocean basin provide examples of landslide types that characterize progressive stages of weathering. The stages include (1) fresh rock, (2) corestones, (3) decomposed granitoid, and (4) saprolite. Fresh granitoid is subject to rockfalls, rockslides, and block glides. They are all controlled by factors related to jointing. Smooth surfaces of sheeted fresh granite encourage debris avalanches or debris slides in the overlying material. The corestone phase is characterized by unweathered granitic blocks or boulders within decomposed rock....

Data from two watersheds in northern California were used to develop an interpretation of the erosion hazard rating (EHR) of the Coast Forest District as amount of sedimentation. For the Caspar Creek Experimental Watershed (North Fork and South Fork), each EHR unit was estimated as equivalent to 0.0543 cubic yards per acre per year, on undisturbed forest. Experience within the District provided estimates of average excess sediment produced by logging: 17.5 cu. yd/acre for tractor yarding, and 6.3 cu. yd/acre for cable yarding. These estimates based on limited data should be supplemented by...