Treesearch

Ten insecticides were tested against larvae of Calocalpe undulala (L.). The decreasing order of toxicity at LD50 was: bioethanomethrin, phenothrin, pyrethrins, phoxim, tetrachlorvinfos, mexacarbate, carbaryl, phosmet, DDT, and malathion. At LD90,the decreasing order of toxicity was the same, except that phoxim and tetrachlorvinfos switched positions. Malathion was not toxic at the highest dose level tested (500 µ/g body weight). When the response of C. undulata was compared with that of 4 other forest geometrid species, the data showed that pyrethroids were always the most toxic candidates...

In studies of genetic differences among trees, forest biologists have found that variations fall into two categories. In the first, characterized by metric traits, the phenotypic response results from the combined activity of many genes having minor effects. In the other, characterized by mutants and some resin and disease resistance factors, the phenotypic response results from the activity of a few genes having major effects. The genetic analysis of enzymes falls into both categories. Enzyme polymorphs are likely to have only slight effect on tree phenotypes. But they allow the specific...

Growth habit, occurrence, and use. The genus Pinus, one of the largest and most important of the coniferous genera, comprises about 95 species and numerous varieties and hybrids. Pines are widely distributed, mostly in the Northern Hemisphere from sea level (Pinus contorta var. contorta) to timberline (P. albicaulis), They range from Alaska to Nicaragua, from Scandinavia to North Africa. and from Siberia to Sumatra. Some species, such as P. sylvestris, are widely distributed-from Scotland to Siberia-while other species have restricted natural ranges. Pinus canariensis, for example, is...

The optimum spacing interval at which to plant loblolly pine (Pinus taeda L.) is being studied on Maui, Hawaii. Four spacings are being tried: 6,8, 10, and 12 feet. Measurements 11 years after the plots were set up show that (a) survival rates exceeded 94 percent, (b) average d.b.h. ranged from 6.4 inches at the 6-foot spacing to 9.8 inches in the 12-foot spacing; (c) basal area ranged from 168 sq. ft. per acre in the 12-foot spacing to 278 sq. ft. per acre in the 6-foot spacing; (d) spacing did not markedly affect height growth; and (e) percent of stem in live crown ranged from 44...

A defoliator of oak and witch-hazel, the oak leaf roller (Archips semiferanus [Walker]) is found in large numbers in northeastern United States and in southwest Ontario, Canada. DDT was formerly used to control this insect. As a preliminary step in finding alternatives to DDT for field testing against the oak leaf roller, four insecticides were evaluated in the laboratory. All four—bioethanomethrin, mexacarbate, phoxim, pyrethrins—caused 90 percent kill with less than 1 pg per insect.

Regression sampling is widely used in natural resources management and research to estimate quantities of resources per unit area. This note brings together results found in the statistical literature in the application of this sampling technique. Conditional and unconditional estimators are listed and for each estimator, exact variances and unbiased estimators for the variances are offered.

The sawtimber potential of 12-year-old Eucalyptus saligna Sm. trees grown in Maui, Hawaii, was studied by using simple field techniques. Lumber manufactured from the trees was predominantly of low grade, but had lower average density than wood from older trees, and therefore was more desirable. Logs end-split badly, and sawed with the usually encountered amount of difficulty due to growth stress that averaged 1,350 psi per log. The wood shrank moderately in drying, but lumber degrade was not serious. Bending strength, except for modulus of elasticity, was high for the specific gravity. The...

Television public service directors in California were asked to rate fire prevention film spots they had received from the California Division of Forestry. Most directors recalled receiving the spot announcements and rated them high in technical quality and interest. Delivery of the films by a fire prevention officer impressed directors favorably. Fire prevention announcements generally ranked low in likelihood of selection for showing, however. Showing might be increased by giving the announcements a local flavor; tying them in with public health, conservation, and the environment; and...

In southern California, many fires start and burn under conditions that permit their control with little burned acreage and fire damage. In contrast, under other conditions of weather and topography, on a small group of fires, control effort is relatively ineffective; they become large and destructive. A major reason for these "conflagration fires" is the extreme difficulty of stopping the head of a hot, fast-running fire in dry fuels and strong winds. No radically new concept of suppression can be anticipated. The best prospect for alleviation of the problem is modification of the...

A new procedure for constructing one-sided truncated sequential t-tests and its application to natural resource sampling are described. Monte Carlo procedures were used to develop a series of one-sided truncated sequential t-tests and the associated approximations to the operating characteristic and average sample number functions. Different truncation points and decision boundary patterns were examined. The fixed sample size t-test and Barnard's open one-sided sequential t-test were compared with the new procedure. The upper one-sided test described can easily be modified to a lower...