Treesearch

Trunk diameters of Eucalyptus robusta trees shrink and swell as bark moisture content changes. Diameter variations from this cause as measured on six trees with a dial-gage dendrometer were less than 1 percent of trunk diameter. To compare this variation with the variation in d.b.h. measurements that can result from personal techiques of using a standard diameter tape, seven foresters each independently measured the same 40 robusta trees on the same day. Variations in diameters at breast height from personal measurement techiques exceeded d.b.h. variation due to changing bark moisture content.

A computerized method for gathering market area information from campground permits has been developed. Point-of-origin and length-of-stay of campground users can be estimated and summarized quickly and inexpensively. The method should be equally useful for public as well as private campgrounds-provided basic registration data are available and can be processed according to theprescribed format.

Stabilized pyrethrins were test in a laboratory spray chamber to provide information for planning field trials of this insecticide against the western spruce budworm (Choristoneura occidentalis Freeman). No significant differences were found in toxicity to instars 3 to 6. Stabilizers appear to have had no effect on basic contact toxicity. The commercial formulation of pyrethrins was as toxic as the laboratory formulated standard. Probably only slight residual activity can be expected. No effect on basic contact toxicity could be produced by increasing concentration through a range of about...

Round posts of 10 Hawaii-grown wood species were treated with copper chromate-copper arsenate by the double-diffusion process. These and untreated posts were exposed for 10 years. Except with two coniferous species, the treatment did not lengthen service life enough to be judged worthwhile.

A computer method has been developed for simulating the combustion of wood and other cellulosic fuels. The products of combustion are used as input for a convection model that slimulates real fires. The method allows the chemical process to proceed to equilibrium and then examines the effects of mass addition and repartitioning on the fluid mechanics of the convection column in a fire.

The effects of non-grazing on Ahwahnee coarse sandy loam were studied at the San Joaquin Experimental Range in central California. An exclosure, on which there had been no livestock grazing for 34 years, had a lower surface bulk density and lower acidity than an adjacent range that had been grazed. Bulk density averaged 1.08 gm./cc. on the ungrazed range, and 1.43 gm./cc. on the grazed range. The pH values were 6.15 for the ungrazed area, and 5.65 for the grazed area.

Fourteen insecticides were evaluated for contact toxicity to 3rd and 4th stage pine butterfly larvae (Neophasia menapia F. & F.) in a laboratory spray chamber. All candidate insecticides except trichlorfon were more toxic than the standard DDT. The ranking of toxicity at LD90 and toxicity indexes (times more toxic than DDT) were: SBP-1382 (117), pyrethrins (62), Dowco 214 (22), methomyl (6.2), chlorpyrifos (6.2), Gardona (4.5), Sumithion (3.8), phoxim (2.8), Zectran (2.4), aminocarb (2.2), malathion (1.6), carbaryl (1.6), DDT (1.0), and trichlorfon (

A major browse plant in the central California foothills, wedgeleaf ceanothus (Ceanothus cuneatus) is used by a variety of animals. The canopy effect of the species was studied on the San Joaquin Experimental Range. Total herbage yield was not significantly affected by the canopy. But herbage yields of some individual species were affected by both the position in relation to canopy edge and the direction from a wedgeleaf ceanothus shrub. Range managers concerned about herbage yields will need to consider these effects.

This study presents observations on 15 pairs of White-crowned Sparrows (Zonotrichia leucophys nuttalli) breeding near Point Reyes Bird Observatory, Marin County, California, in the spring of 1969.

Timber RAM (Resource Allocation Method) is a long-range planning method for commercial timber lands under multiple-use management. Timber RAM can produce cutting and reforestation schedules and related harvest and economic reports. Each schedule optimizes an index of performance, subject to periodic constraints on revenues, costs, and, harvest levels. Periodic constraints can also be used to regulate forest stands and to even out the flow of timber during conversion. Schedules are calculated on computers by using linear programing techniques.