Treesearch

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...

Reported here are the results of studies on the unusually abrupt genetic transition that occurs in several traits in continuous bishop pine stands of northern Sonoma County, California. The genetic nature of this anomalous cline was investigated using allozyme, common garden, crossability, and controlled-soil analyses. Data from these analyses allowed a preliminary interpretation on the evolutionary relationships of the pines of this region. Initially, seeds were collected from 78 green foliaged trees in 8 stands south of the transition at Sea Ranch, from 27 blue, green or intermediate...

A three-dimensional diagnostic wind model for use in complex terrain has been combined with a three-dimensional trajectory and puff air quality model. The wind model utilizes a terrain following coordinate system and conserves both mass and momentum. The wind model provides the winds required by the predictive trajectory and puff dispersion model. Both the wind model and the dispersion models were compared with more complicated models and with wind and tracer gas data from the 1980 ASCOT experiment. Comparison of the wind model with Yamada's three-dimensional primitive equation solution...

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...

Estimating rate of fire spread is a key element in planning for effective fire control. Land managers use the Rothermel spread model, but the model assumptions are violated when fuel, weather, and topography are nonuniform. This paper compares three averaging techniques--arithmetic mean of spread rates, spread based on mean fuel conditions, and harmonic mean of spread rates--used to estimate the effective rate-of-spread in heterogeneous environments. For particular ranges of the independent variables of the spread model, there is a well-defined ordering of the averages-a consequence of the...

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...

Lodgepole and jack pines (Pinus contorta Dougl. ex. Loud, and Pinus banksiana Lamb.), components of the North American boreal forest, have pioneering roles after major disturbances such as fire or glaciation. These species are closely related and hybridize in western Canada, but their fossil records and contemporary variation patterns suggest they had completely different late Quaternary histories. Several taxonomically recognized geographic races of lodgepole pine apparently survived the last glaciation without drastic modification, the northern races either persisting in far-northern...

In recent years the term stem unit (SU) has increasingly supplanted internode in the literature of conifer shoot growth, especially since the adoption of SU in a collection of papers titled "Tree Physiology and Yield Improvement" (Cannell and Last 1976). In standard botanical terminology, a node is the point on a stem where one or more lateral appendages (foliage or scale leaves) are attached, and an internode is the portion of stem between two successive nodes. The original meaning of SU was more inclusive than internode, and the current practice of using SU and internode interchangeably...

A nonrandom sample of 90 arsonists in California and New York was interviewed for the California Department of Forestry from 1977 to 1979. About two-thirds of them were in prison for arson, and the others were in mental hospitals. The 90 interviewees were mostly unmarried males ranging in age from 17 to 51 years. Survey results show that those who set their first arson fire at a young age tended to set many fires, and had more arson convictions and repeated visits to mental hospitals than those who set their first fire at an older age.