Treesearch

The optimum interval at which to plant loblolly pine (Pinus taeda L.) is being studied on the island of Maui, Hawaii. Four spacings are being tried: 6, 8, 10, and 12 feet. Measurements of trial plots in 1968-7 years after plots were set up-show that (a) survival rate exceeded 95 percent; (b) height growth averaged about 30 feet in all spacings; (c) average d.b.h. increases ranged from 5.3 inches at the 6-foot spacing to 7.8 inches in the 12-foot spacing; and (d) basal area ranged from 95 sq. ft. per acre in the 12-foot spacing to 193 sq. ft. per acre in the 6-foot spacing.

Firetree (Myrica faya) has infested more than 40,000 acres of range and forest lands in Hawaii. If the land is to be planted to more desirable range and timber species, this plant pest must be controlled. In trials on the Hamakua Forest Reserve, island of Hawaii, firetrees were effectively controlled by squirting Tordon 22K into notches cut by machetes. The treatment gave complete canopy kill, and 99 percent control of sprouting. The cost of silvicide to treat each stem was about 5 cents.

The feasibility of reducing fuel hazard in chaparral during safe weather conditions was studied in an experimental prescribed burn in southern California. Burning was done under fuel and weather conditions when untreated brush would not bum readily. Preparatory treatment included smashing of brush on strips with a bulldozer, and reduction of moisture content of leaves and fine twigs with a desiccant. Seventy percent of green fuels were consumed by the fire. Costs per acre for the treatments were about $13.50.

Frost crack, a radial split of wood and bark, reduces the merchantability of commercial timber. Data on this defect in white fin stands of the Sierra Nevada, California, showed that frost cracks were two to three times more prevalent on trees of the east slope than those of the west slope. Percent of trees with frost cracks increased as tree diameter growth increased on the east slope, but decreased on good sites of the west slope. About 85 percent of the frost cracks were in the first 16-foot log of the lower trunk. Slow-growing trees less than 30 inches d.b.h. were the most susceptible...

Six insecticides were tested in the laboratory as aerosols against larch casebeare1 larvae. Their toxicity was determined by both direct contact and residual contact on filter paper. All six were highly toxic at less than 1.05 µg/ cm2 (the equivalent of 1.5 oz./acre). In decreasing order of toxicity at LD90 (direct contact) the insecticides tested were: Zectran, malathion, Sumithion (0.24 - .26 oz./acre), pyrethrins, Matacil (0.45 - .5O oz./acre), and Gardona (1.4 oz./acre). For field trial of the three most toxic materials, a dosage of 2 oz./acre is suggested.

Among the lignin stains tested in trying to identify growth rings in koa (Acacia koa Gray), phloroglucinol was the most effective. The light colored sapwood of mature trees stained readily, with growth rings apparent. But staining failed to emphasize rings in the dark colored heartwood. Growth rings were not apparent on samples from young fast growing, sapling size trees. In none of the samples could growth rings be used to estimate tree age or periodic growth.

Selected shrub species are being studied in southern California for their possible fuel volume or slow burning characteristics. In propagation tests, five species-fourwing, Gardner's, Nuttall's, and allscale saltbushes; and creeping sage - rooted successfully from green tip and ripewood stem cuttings taken in spring and fall and placed under intermittent mist. Practically no rooting resulted from cuttings of two other species studied: hairy yerbasanta and woolly nama. Green tip cuttings treated with hormone rooted faster and more often than similar cuttings without hormone, or ripewood...

The effects of herbicides or other cultural treatments of low shrubs can be sampled by a new technique using crown volume as the key variable. Low shrubs were grouped in 12 crown volume classes with index values based on height times surface area of crown. The number of plants, by species, in each class is counted on quadrats. Many quadrats are needed for highly precise measurements. Shrub dry-weight was highly correlated with crown volume for each of the four species studied, but ratios of weight to volume were variable.

Temperature and humidity were compared and precipitation measured during an 8-year period (1958-1966) for two types of harvest cuttings on the Redwood Experimental Forest, north coastal California. Only small differences in temperature and humidity were found between clearcuttings and selection cuttings in old-growth stands on west-facing and east-facing aspects, and between westerly and easterly clearcuttings. The bioclimate data reported can help researchers in evaluating regeneration and growth studies and in extending the experimental results to other areas, and in ecological studies...

A study is underway at the Pacific Southwest Forest and Range Experiment Station to develop computer techniques for planning suppression efforts in large wildfires. A mathematical model for allocation of firefighting resources in a going fire has been developed. Explicit definitions are given for strategic and tactical planning functions. How the model might be used is illustrated by a fictitious but realistic problem. Limitations in the approach and ways in which the model might be improved are described.