Treesearch

Plots in a manzanita brushfield at Mount Shasta, California, were prepared for burning by aerially spraying with 2,4-D and 2,4,5-T on November 3, 1966, and with paraquat on June 3, 1967. On plots burned June 23-24, only the leaves and twigs were dead and dry; most of the green stems were not consumed. On plots burned under similar conditions 1 year later, the stems had dried and were completely consumed. Spraying of herbicides appears to be a practical means of lowering the moisture content of brush fuels for burning.

Building firelines in logging slash or dense brush can be costly and hazardous. A new liquid explosive was tested in these and other forest fuel types, It proved effective in brush, understory vegetation, and light-medium slash, but was not effective in deep, heavy slash. Fireline construction by this technique shows promise, but will require more testing and engineering before it is ready for operational use.

Probability fire weather forecasts were compared with categorical and climatological forecasts in a trial in southern California during the 1965-1967 fire seasons. Equations were developed to express the reliability of forecasts and degree of skill shown by the forecaster. Evaluation of 336 daily reports suggests that probability forecasts were more reliable. For probability forecasting to be used operationally, fire weather forecasters will need help in the necessary computations and some decision criteria for planning.

Can hybridization between species and races produce superior forest trees?" In the 1920's and 1930's, some lumbermen and scientists alike were asking this question. They were impressed by the work of Luther Burbank, whose improvements in vegetables and .flowers were being achieved by hybridization. And some of his hybrids far surpassed varieties previously available. Could not some of this techniques be tried to develop better forest trees? James G. Eddy and others interested in tree improvement provided a means of finding the answer. They founded at Placerville, California, the Eddy...

Ginkgo biloba resembles other woody plants with long and short shoots in having variable leaves, and this variability in shape and other characteristics is closely related to the specialization of the shoots. The unlobed or bilobed early leaves of short shoots are preformed in the winter bud, and their nearly synchronous expansion in the spring is not accompanied by stem elongation. The leaves clustered at the base of long shoots are like short-shoot leaves in origin, time of appearance, and form, but they are succeeded by a second set of leaves whose internodes elongate. These multilobed...

Boston ivy, a common ornamental vine in the grape family, successively produces two kinds of leaves during the growing season. The two "early leaves" at the base of each shoot are preformed in the winter bud, and their expansion in the spring is accompanied by little stem elongation. At maturity they have large three-lobed blades and long petioles. Most short shoots produce no more leaves, but "late leaves" develop on all long shoots at intervals of less than 2 days. All but the first few undergo their entire development during the growing season. They are much smaller than early leaves,...

Damage by snow breakage to pole-sized ponderosa pine (Pinus pondvosa Laws.) increased as stand density increased. In a plantation on the west slope of California's Sierra Nevada, the tallest trees were most often broken. Thinning in the sapling stage is recommended as a preventative measure in dense plantations subject to heavy snowfall.

Australian toon (Toona australis) was planted at four spacing intervals-6, 8, 10, and 12 feet-in a trial on the island of Hawaii. Measurement of 8-year-old trees showed that spacing interval did not affect diameter or height growth or survival; but basal area per acre decreased as spacing increased. A goal of 400 acceptable and desirable pole-sized trees per acre can be reached by using good planting technique and an initial spacing of slightly less than 9 by 9 feet, and by weeding the first year.

Seventeen types of fenceposts from 15 tree species installed in 1945 on the San Joaquin Experimental Range, Calif., were evaluated for durability in 1968. Post butts of one-half of each type had been soaked overnight in 5 percent pentachlorophenol in diesel oil; the other half of each type was untreated. After 22 years, every untreated post except split incense-cedar heartwood and manzanita had rotted, but most of the treated posts were still sound and serviceable.

In a small-scale test, a silvicide consisting of cacodylic acid was injected during the growing season at dosages recommended by the manufacturer. The treatment did not thin adequately two of three mixed-conifer stands. Ponderosa pine and lower crown classes seemed more susceptible to the silvicide than Douglas-fir and upper crown classes. No flashback was recognized. But bark beetles killed leave trees in one stand.