Treesearch

In a search for competition, limiting factors, and other patterns in a community of small passerine birds in Hawaii, we recorded the foraging behaviors, resource abundances, and climatic variables believed to influence resource levels. Some definite patterns were found, showing that the rare, endangered birds were specialists; however, some specialists were quite abundant. We also identified some potential competitive interactions by an introduced species; however, no overriding theme of organization was apparent. Rather, each species appeared to have its own suite of adaptations, largely...

Many young, understory Jeffrey pines (Pinus jeffreyi Grev. & Balf.) were found to be infected by western dwarf mistletoe (Arceuthobium campylopodum Engelm.) on Laguna Mountain, Cleveland National Forest, in southern California. Under heavily infected overstory, about three-fourths of the young pines (about 15 years old on the average) were infected by dwarf mistletoe. Infections per tree averaged about two and a half, two-thirds of these on the bole. Attempts to regenerate Jeffrey pine under an infected overstory in southern California will probably lead to a severely infected and damaged...

Two mathematical models are given to determine the best locations for initial attack resources in terms of travel time: a linear programmingmodel and a statistical model. An example for the Clearwater National Forest in Idaho illustrates some of the differences between the two models.

Using a Vegetation Drought Index (VDI) for estimating the susceptibility of California red and white firs to the fir engraver beetle (Scolytus venttralis) was evaluated in northern California forests where these true firs (Abies species) occur in mixed conifer and true fir stands. Midway through the summer drought, true fir moisture stress–a known predisposing factor–was highest on sites with highest VDI values (most xeric). In mixed conifer stands, the susceptibility of white firs–as indicated by the mean percentage of their basal area killed annually–was highest on sites with highest VDI...

Each of five insecticides was applied at two or three application rates by helicopter to 20-ha plots. Effectiveness of each application rateagainst eastern spruce budworm (Choristoneura occidentalis) was judged by comparing larval population reduction at 15 or 20 days aftertreatment against populations in untreated check plots. Performance of each insecticide was then compared with the levels of control normally obtained with two registered insecticides, carbaryl and acephate (90 + pct) usually used for western spruce budworm control. Maximum populationreduction from sulprofos (58 pct),...

The distribution of snags by tree species in the eastern Sierra Nevada of California generally reflects the associated timber type. Where present, however, lodgepole pine (Pinus contorta Dougl.) forms a large proportion of the snags present. Few snags of any species were present in the Jeffrey pine (P. jeffreyi Grev. & Balf. in A. Murr.) timber type in a study at Sagehen Creek Basin, in Nevada County. Simple regression analysis showed weak but significant relationships betweensnag density and canopy height, canopy cover, and slope. Multiple regression analysis were also weak, but revealed...

Overstory removal cutting, the most common means of converting old-growth stands to young growth stands in California, can produce excessive residues that pose management problems. Utilization is an attractive option for managing residues. However, the cost of residue retrieval and utilization is often prohibitive. Residue retrieval by a private contractor was studied to determine production rates and effectiveness after overstory removal on three blocks in true fir stands in northeastern California. Residues were inventoried before and after residue retrieval to determine the amount...

Smoked aluminum track stations are a useful technique for studying patterns of abundance and distribution of northern flying squirrel (Glaucomys sabrinus). They are easily transported to remote field sites, allow permanent preservation of tracks, and yield frequency-of-occurrence information. A study in Douglas-fir (Pseseudotsuga menziesii) forests of northwestern California illustrates the use ofthe track stations, methods of data analysis, and habitat associations of the northern flying squirrel.

Overstory removal can offer economic and esthetic advantages over clearcutting and regeneration, but projecting success is difficult. Twenty-nine units on nine operational overstory removal cuts in northern California were studied to determine what factors are related to satisfactory or unsatisfactory stocking after harvest. Stocking determinations were based on number of trees meeting minimum crop tree standards. Although all of the postharvest stands contained adequate numbers of trees, only about half passed minimal stocking standards based on number of trees meeting crop tree criteria....

Abstract - SALT (Selection At List Time) is a variable probability sampling scheme that provides unbiased estimates of suspended sediment yield and its variance. SALT performs better than standard schemes which are estimate variance. Sampling probabilities are based on a sediment rating function which promotes greater sampling intensity during periods of high sediment yield. When preparing to monitor using SALT, the quality of the existing suspended sediment rating data is an important consideration. SALT variance, based on an intensive data set from a river in northwestern California,...