Treesearch

Portions of the ohia (Metrosideros polymorpha) forests on the windward slopes of Mauna Loa and Mauna Kea on the island of Hawaii began dying in 1952. Little mortality has occurred since 1972. About 50,000 ha are affected by the decline. Individual trees exhibit several symptoms, from slow progressive dieback to rapid death. Seven types of decline have been identified on the basis of differential response of the associated rainforest vegetation. Two of the types, Bog Formation Dieback and Wetland Dieback, make up more than 80 percent of the decline area. The decline has affected bird...

A generalized interactive computer model that simulates and predicts insecticide efficacy, over seasonal development of western spruce budworm and Douglas-fir tussock moth, is described. This model can be used for any insecticide for which the user has laboratory-based concentration-response data. The program has four options, is written in BASIC, and can be operated on a microcomputer.

Foresters often lack information on growth of woody shrubs and their effect on conifer seedling survival and growth. Deerbrush (Ceanothus integerrimus H. & A.) was treated by several manual and chemical methods at age 3 and again at age 5 in a Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) plantation on a medium-quality site on the Klamath National Forest, California. Four years after initial release, Douglas-fir stem caliper at 12 inches (30 cm) above mean ground line differed significantly (0.69 ± 0.30 inch or 1.75 ± 0.76 cm) between an entire area (one-seventh acre) sprayed directly...

Australian provenances of Eucalyptus grandis and E. saligna were compared at four locations on the island of Hawaii to seek seed sources better than those in current use which were introduced earlier from unrecorded locations in Australia. A broad range of latitude and elevation was represented among the provenances. At all four locations, most E. grandis provenances outgrew most E. saligna. Considerable consistency was demonstrated among the good and poor provenances at each site. Although most differences between provenances were not statistically significant at the 5 percent level, the...

Measuring suspended sediment concentration in streams provides a way of monitoring the effects of forest management activities on water quality. Collecting data on suspended sediment is an act of sampling. The nature of the delivery process and the circumstances under which data are collected combine to produce highly variable results that are difficult to analyze and interpret. Data-collection stations are set up to compare one set of measurements to another. They should be located with regard to channel morphology. Deciding when to measure suspended sediment is a major problem in...

Two types of problems are related to collecting hydrologic data at stream gaging stations. One includes the technical/logistical questions associated with measuring and transferring data for processing. Effort spent on these problems ranges from improving devices for sensing data to using electronic data loggers.

Atmospheric nitrogen deposition, associated with chronic urban air pollution, has produced stream water nitrate concentrations as high as 7.0 mg of N L-l in chaparral watersheds in the San Gabriel Mountains of Los Angeles County, CA. Stream water [NO3-] and discharge were greatest at high flow and may contribute significantly to existing groundwater NO3- pollution. Annual NO3- discharge ranged from 0.04 to 10.0 kg of N ha-1 over 4 years. Canopy throughfall and precipitation inputs of 23.3 and 8.2 kg of N ha-1 year-1 were high relative to other undisturbed ecosystems nationwide. Dry...

A programmable calculator connected to an interface circuit can control automatic samplers and record streamflow data. The circuit converts a voltage representing water stage to a digital signal. The sampling program logs streamflow data when there is a predefined deviation from a linear trend in the water elevation. The calculator estimates suspended sediment discharge from rating coefficients for the gauging site. When a threshold value of accumulated suspecded sediment discharge is reached, the calculator sends a signal to the interface circuit that activates a pumping sampler. The...

Historically, fire was a natural component in ponderosa pine (Pinus ponderosa)-mixed conifer ecosystems in the Sierra Nevada of California. Wildfires may have reduced the number of shrub seeds in the soil, as well as the density of mature shrubs and young hardwoods, thereby allowing conifers to reinvade a site after disturbance, and grow with reduced competition. With fire suppression activities beginning around the turn of the century, seed populations in the soils of the forest floor, and densities of resprouting shrubs, have increased and created a serious reforestation problem after...

Abstract - The California Department of Forestry and U.S. Forest Service, Pacific Southwest Forest and Range Experiment Station have been conducting a paired watershed study on Jackson Demonstration State Forest for 24 years. The South Fork watershed phase of the study involved monitoring the impacts of road construction (1967) and selective tractor logging (1971-1973) on water and sediment discharge. The present North Fork phase of the study uses an extensive network of flumes with pumping samplers to monitor the impacts of clearcutting a portion of the North Fork utilizing upper slope...