Treesearch

Fire suppression has significantly increased canopy cover, litter depth, and stem density in many western forests, altering microsite conditions that affect tree seedling establishment. We conducted studies in a mixed-conifer forest in the Sierra Nevada, California, to determine relationships between established understory trees and microsite quality, and to examine the effect of fire intensity and shrub cover on seedling establishment. Most of the conifer species were found on microsites with relatively high soil moisture and relatively low direct solar radiation. All species had greater...

During the past 30 years, spruce forests of Alaska’s Kenai Peninsula have undergone dramatic changes resulting from widespread spruce bark beetle(Dendroctonus rufipennis (Kirby)) infestation. In 1987 and again in 2000, the Pacific Northwest Research Station's Forest Inventory and Analysis Program conducted initial and remeasurement inventories to assess broad-scale impacts of this infestation. Changes in regeneration of Sitka spruce(Picea sitchensis (Bong.) Carr.) and white spruce (Picea glauca (Moench) Voss) are examined by using data collected on 130 plots. Regeneration of Sitka and...

Taxonomic relationships among red tree voles (Phenacomys longicaudus longicaudus, P. I. silvicola), the Sonoma tree vole (P. pomo), the white-footed vole (P. albipes), and the heather vole (P. intermedius) were examined using 664 base pairs of the mitochondrial cytochrome b gene. Results indicate specific differences among red tree voles, Sonoma tree voles, white-footed voles, and heather voles, but no clear difference between the 2 Oregon subspecies of red tree voles (P. I. longicaudus and P. I. silvicola). Our data further indicated a close relationship between tree voles and albipes,...

Oregon white oak is reportedly a deeply rooted species, but its rooting habit on coarse-textured soils is undocumented. In the Puget Trough of western Washington, Oregon white oak grows in coarse-textured glacial outwash soils on lowland sites. Our objective was to quantify the gross root system morphology of Oregon white oak in these soils, thereby improving our understanding of its belowground resource acquisition on these sites. Study trees were located on a Spanaway gravelly sandy loam soil near Olympia, Washington. Root systems of 27 oak trees (age 3-95 yr) were excavated and measured....

We simulated forest dynamics of the regional ponderosa pine-white fir conifer forest of the San Bernadino and Sierra Nevada mountains of California to determine the effects of high ozone concentrations over the next century and to compare the responses to our similar study for loblolly pine forests of the southeast. As in the earlier study, we linked two models, TREGRO and ZELIG, to consider both physiological effects within individual trees and competitive interactions within forest communities. We represented regional effects by simulating at three sites in California, Lassen National...

The 1980 eruptions of Mount St. Helens created a complex mosaic of disturbance types over a 600 km2 area. From 1980 through 2000 we monitored beetle species relative abundance and faunal composition of assemblages at undisturbed reference sites and in areas subjected to tephra-fall, blowdown, and pyroclastic flow volcanic disturbance. We collected 27,074 beetles representing 39 families and 279 species. Five families made up 64 percent of all species collected. Patterns of beetle recolonization and succession were consistent with predicted patterns from relay succession theory, with...

American diploid cottons (Gossypium L., subgenus Houzingenia Fryxell) form a monophyletic group of 13 species distributed mainly in western Mexico, extending into Arizona, Baja California, and with one disjunct species each in the Galapagos Islands and Peru. Prior phylogenetic analyses based on an alcohol dehydrogenase gene (AdhA) and nuclear ribosomal DNA indicated the need for additional data from other molecular markers to resolve phylogenetic relationships within this subgenus. Toward this end, we sequenced three nuclear genes, the anonymous locus A1341, an alcohol dehydrogenase gene...

The ITS region including the 5.8S rRNA gene as well as the 5' end of the 28S rRNA gene of hypogeous Pezizaceae and Tuberaceae were studied to clarify the generic placement of two southern African desert truffles, Terfezia pfeilii and Choiromyces echinulatus. The results show that neither species belongs in the genus to which it has been assigned on the basis of morphological characters. As expected, two Choiromyces spp. grouped close to the representative of the Tuberaceae (Tuber melanosporum). However, C. echinulatus diverged from the other Choiromyces species and emerged near members of...

Ecosystem structure and function are strongly affected by disturbance events, many of which in North America are associated with seasonal temperature extremes, wildfires, and tropical storms. This study was conducted to evaluate patterns in a 19-year record of global satellite observations of vegetation phenology from the advanced very high resolution radiometer (AVHRR) as a means to characterize major ecosystem disturbance events and regimes. The fraction absorbed of photosynthetically active radiation (FPAR) by vegetation canopies worldwide has been computed at a monthly time interval...

This report provides a multiownership assessment of oak woodlands and other hardwood forests in California, excluding only reserved lands outside of national forests. Because sampling intensity on woodlands was doubled from the previous 1981-84 inventory, and because national forests were inventoried, this is the most complete assessment to date for California hardwoods. Tables provide estimates for hardwood forest type area, hardwood volume, biomass, numbers of trees, change in forest area, growth, harvest, and mortality. The dates of the inventories used in the assessment, 1991-94 for...