Treesearch

Permits were first needed for visits to wilderness areas in California during summer 1971. A computerized system for analyzing these permits and summarizing information from them has been developed. It produces four types of summary tables: point-of-origin of visitors; daily variation in total number of persons present; variations in group size; and variations in length of stay. The Wilderness Information system was tested by analyzing 23,936 permits issued for six California wilderness areas in summer 1971.

Xylem resin of Pinaceae is closely linked with their resistance and suseptibility to tree-killing bark beetles. This review of the literature on attacking adults suggests that all three resistance mechanisms proposed by Painter -- preference, antibiosis, and tolerance -- are active in this relationship: preference by attraction, repellency, and synergism; antibiosis by both chemical and physical properties; tolerance by healing and secondary resinosis.

Balsam fir seedlings were grown under uniform conditions from seed collected along an elevational gradient in the White Mountains of New Hampshire. Photosynthetic temperature optimum of the seedlings decreased with increasing elevation of the seed source. The change in temperature optimum with elevation was similar to the adiabatic lapse rate, suggesting a precise adaptation to temperature through natural selection.

Twenty insecticides were tested by topical application on mixed groups of 4th- and 5th -stage larvae of Symmerista canicosta Franclemont. Four exceeded DDT in toxicity at LD50 but only resmethrin was significantly mor toxic. Most of the compounds showed unusually high toxicities. Twelve, listed in decreasing order of toxicity, caused 50% mortality with <5μg/g body weight: resmethrin, methonmyl, phoxim, pyrethrins, DDT, Zectran (4-dimethylamino-3.5-xylyl methylcarbamate), chlorpyrifos, Landrin (3,4,5- (93%) and 2,3,5-trimethylphenyl methylcarbamate (7%)), Gardona (2-chloro-1-(2,4,5-trichloro...

To quantify production rates for small trees, this study examined the components of log-making and tractor yarding at the Challenge Experimental Forest, Yuba County, California. Rates were calculated over a range of 12 to 40 inches d.b.h. The rate for incense-cedar was lowest; for ponderosa pine it was intermediate; and for Douglas-fir, white fir, and sugar pine combined, it was highest. Log size strongly influenced production. For log-making, production for 38-inch d.b.h. trees was two and a half times that for 14-inch d.b.h. trees; for yarding, production for a turn of logs averaging 22...

Leaflike samples, approximately 8 cm in diameter, are held at the end of a mechanical arm which reproducibly controls sample movement during the ignition and burn ing process. Glowing combustion is induced by bringing the sample into contact with a small loop in an electrically heated nichrome wire. The ultimate burned-out area is measured 1n an ultraviolet detection system utilizing a vacuum photodiode. The system, calibrated using black construction paper with a series of standard holes in the range 0.002 to 20 cm2, has a sensitivity close to 5 mv/cm2.

By providing continuous weight measurement, thermogravimetry, even for isothermal experiments, offers a major advantage over the classical methods of determining weight-change curves in complex pyrolysis reactions. Thus, even minor weight changes, readily detectable on a continuous record, furnish clues concerning the reaction sequences and indicate conditions under which confirmatory experiments may be undertaken. Unfortunately, such perturbations are frequently ignored, being considered part of the "experimental error" which they often represent in the traditional experiments. This paper...

Young-growth ponderosa pine seed trees were evaluated in terms of seed production. Seed trees ranging from 3 to 9 per acre produced 5,000 to 35,000 seeds per acre in years of moderate and heavy cone crops. Seed-tree selection before harvesting by the seed-tree method of cutting must be keyed to evidence of past cone production to assure best seed production in the future.

The conversion of brush areas to grassland increased soil slip erosion on mountainous watersheds in southern California during the intense winter storms of 1969. The incidence of soil slippage, site factors affecting slope stability, and amount of debris generated by slippage were investigated for sample brush and grass areas in the San Dimas Experimental Forest. Soil slippage occurred on 5.5% of the brush areas and 16.7% of the grass areas, the values for both areas being about twice those measured in 1966 for a less intense storm period. The effectiveness of linear discriminant analysis...