Treesearch

This exploratory study indicated that considerable variation in the moisture content of litter can occur within short horizontal distances. The variations ere found to be caused primarily by differences in the amount of solar radiation received by the litter and in the degree of cooling by radiation at night. Because actual fuel moisture lags behind equilibrium moisture, the history of the previous exposure of an area to solar radiation is more important in determining the litter moisture at any given time than the conditions at that time. The variations were affected by timber stand...

To investigate local adaptation to soil fertility, seeds were collected from trees in natural stands selected on one fertile and one nearby ultramafic soil in four geographic areas in the northern Sierra Nevada. Germinants from all seed parents in an area were planted in soils dug from the A horizon of both parent stands. Seedling growth on the fertile and ultramafic soils suggested no specific adaptation ofparent stands to native soil. For every stand, the growth of seedlings from individual trees varied widely on both soils. Differences among families were highly significant, and...

Observations of fire-related behavior of wildland visitors were made in three types of areas-wilderness, established campground, and built-up commercial and residential areas-within the San Bernardino National Forest, California. Interviews were conducted with all persons so observed. Types of fire-related behavior differed markedly from one area to another, as did the proportions of observed proper and hnproper use of fire. Persons who misused fire could not be distinguished from those who did not, when interview data were analyzed in relation to selected social and demographic characteris...

Vegetation that is low-growing and either low in volume, slow burning, or both, is needed for reduction of fire hazard on fuelbreaks and other brush cleared areas in California. Of over 50 shrub species and many grass species that were test planted, about 20 shrubs and an equal number of grasses were chosen for plot and field trials. Creeping sage, a few saltbushes, and a few grasses-mostly perennials-are adapted within the wide range of chaparral site conditions, and were successfully established by direct seedings as well as by other cultural methods on these sites. Shrub test results...

Mass divergence influences on plume dispersion modify classic Gaussian calculations by as much as a factor of two in complex terrain. The Gaussian plume was derived in flux form to include this process. Authors' response to comments and criticism received following this publication: Author's response

Ponderosa pine seed trees, numbering 4, 8, and 12 per acre, were left standing for 9 years after harvest cutting on the Challenge Experimental Forest, Calif. Seedling heights were measured at ages 5, 9, and 14, and for all ages were poorest if within 20 feet of a seed tree. Seedlings 20 feet or less from a seed tree at the ages given lost the equivalent in years of height growth: 5(4.1); 9(6.8); 13(10.6). Seed-tree density greatly affected seedling height-the greater the density, the poorer the height growth. The inhibitory effect of the seed trees extended outward at least 40 feet, and...

The abundance, distribution, growth, and mortality of koa (Acacia koa Gray) seedlings after fires were monitored periodically on two burned areas on Oahu for 2.5 years. On one area, seedling density peaked at 95,300/ha 6 months after the fire; 21 months later it had declined to 18,500/ha. On the other area, peak seedling density occurred at 2 -months, with 20,400/ha; 26 months later, density had dropped to 7900/ha. Seedlings were not distributed uniformly over the burned areas but were concentrated near koa seed trees. Height growth for seedlings on one area averaged 2.6 cm/mo; on the...

The contact toxlaty of 100 insecticides to last stage larvae of Choristoneura occidentalis Freeman was tested by topical application in a 10-yr series of screening experiments. Pyrethroids were generally the most toxic group of chemicals tested. Compounds more toxic than the standard, mexacarbate, at LD90 were: bioethanomethrin, (+) cis-resmethrin, (+) trans-resmethrin, (+) cis-phenothrill. ENT 29l17 (5-benzyl-3-furylmethyl (IR,3S,E) 2,2-dimethyl-3- (2-oxo-3-tetrahydrothiophenylidenmethyl) cyclopropanecarboxylate), resmethrin, and NRDC 143 (3-phenoxybenzyl (±) -3- (2,2-dichlorovinyl-2,2-dim...

The abundance and distribution of Acacia koa regeneration after logging were studied on a 500-acre (202-ha) tract of koa forest heavily infested with Passiflora mollissima vines on the island of Hawaii. Koa seedling density was about three times greater in disturbed areas than in undisturbed ones. Most of the koa seedlings in the sample tha t grew in response to ground disturbance during logging were established. None of those found in undisturbed areas were established. Seedlings in disturbed areas tended to be clustered near koa seed trees, with twice as many growing within 50 feet (15.2...