Treesearch

Natural regeneration of harvested old-growth stands of redwood (Sequoia sempervirens) is one way to start a new forest that is needed quickly for continuous timber production. Natural seedlings and sprouts developing after stands were cut were studied on the Redwood Experimental Forest, northern California. Three types of regeneration cuttings were investigated: small clear-cutting, shelterwood, and selection. All three types provided satisfactory results–chiefly in redwood, but also in Douglas-fir and other conifers. Red-wood sprouts added many potential crop trees. Of the two main...

Ohia forest decline–its severity and rate of spread–was studied by aerial photographic techniques on a 197,000-acre (80,000-ha) portion of the island of Hawaii. In 1954, only 300 acres (121 ha) showed signs of severe decline; by 1972, the acreage of severely affected forest had increased to 85,200 acres (34,480 ha). Rate of decline and current severity were related to mean annual precipitation and to elevation. The epidemic is continuing. Some forests on other Hawaiian islands also display decline symptoms.

Autoradiographs of mature cotton bolls which earlier had radioglucose introduced via a thin incision into their peduncles show a marked asymmetry in distribution of the label. Radio-assay shows the specific activity of the cotton fibres on the treated side to be as much as 30-fold that on the opposite side.

Extremes in rainfall on the Hawaiian Islands make it difficult to judge forest fire danger conditions. The use of an automatic data collection and computer processing system helps to monitor the problem.

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.