Treesearch

Blue (Quercus douglasii Hook. & Am.) and valley (Quercus lobata Née) oak seedlings were planted on a foothill rangeland site in 1987 and 1988. Both species were watered their first year but received no irrigation thereafter. They were evaluated during each subsequent spring and summer for survival, weekly height growth and total year-end height. Seedling survival was extremely high for both species and height growth was rapid and vigorous. Blue oak seedlings four growing seasons after planting averaged over 2.3 m and valley oaks after three seasons averaged 2.0 m in height. Yearly height...

The purpose of this study was to simulate the caching of acorns by jays and rodents to see if less costly procedures could be developed for the establishment of coast live oak (Quercus agrifolia). Four treatments [(1) random - single acorn cache, (2) regular - single acorn cache, (3) regular - 5 acorn cache, (4) regular - 10 acorn cache] were planted in January 1990. No efforts were made to protect the acorns nor the emerging seedlings from herbivory. Emergence of epicotyls ranged from 23.4 percent (single acorn, random) to 64.6 percent (five acorn, regular). By October 1990 the percentage...

Microhabitat preferences and species-environment patterns were quantified for bryophytes in blue oak woodlands and forests of central coastal California. Presence data for mosses collected from 149 400 m2 plots were analyzed using canonical correspondence analysis (CCA), a multivariate direct gradient analysis technique. Separate ordinations were performed for terricolous, saxicolous and epixylic mosses using 14 environmental variables. Fifty-six species of bryophytes were collected from the study area. Only the terricolous moss CCA was shown to be significantly related to environmental...

Low profitability of hardwood rangeland management, and oak tree harvesting for firewood markets and forage enhancement has led to concern about the long-term sustainability of the oak resource on rangelands. New markets for recreational hunting may give value to oaks for the habitat they provide for game species, and broaden the economic base for managers. A ranch level optimal control model has been developed to assess optimal oak tree canopy and livestock stocking under different biological and economic conditions. The impact of recreational hunting on management was also assessed. In...

Although winter-deciduous species are presumed to be "out-of-phase" with the mediterranean climate regime, distributional evidence suggests some taxa may be more tolerant of summer drought than evergreen sclerophylls. Deciduous species possess several features that confer advantage in extreme summer dry regions: drought-deciduousness, an efficient response to severe seasonal drought; high photosynthetic rates especially during the optimum late spring period; and a phenology similar to evergreens (but with more rapid growth) during the critical first year. I present a preliminary model of...

A geographic information system was used to assess wildlife species richness (number of species) in valley-foothill hardwood habitats throughout California to set priorities for conservation attention. Species richness values were assessed and compared using three methods: one that included all species without considering canopy cover conditions and species preferences; a second that restricted the analysis to sensitive species; and a third that used sensitive species and considered canopy cover conditions and species canopy preferences. The identified locations of species rich areas were...

Our knowledge of the long-term history of oaks is primarily based on biogeographical analysis of anomalous distribution patterns and paleobotanical macrofossil evidence. Neither of these provide a continuous record of change. In this paper, we present fossil pollen evidence which records significant changes in oak abundance over the last 10,000 years. Between 10,000-5,000 years ago, oaks in the Sierra Nevada increased at the upper altitudinal limit of their range. Since the mid-19th century, oaks at low elevations in the Coast Ranges have increased. We believe that the early increase...

Digital Thematic Mapper (TM) satellite data from September 1986 and December 1985 were analyzed to determine seasonal reflectance properties of blue oak rangeland in the La Panza mountains of San Luis Obispo County. Linear regression analysis was conducted to examine relationships between TM reflectance and oak canopy cover, basal area, and site topographic variables. September reflectance in TM3 was strongly negatively correlated with oak canopy cover (r2=0.62), less strongly related to oak basal area or density (r2=0.2-0.4). December reflectance was not as strongly correlated as September...

We developed methods to assess the impacts of diseases and arthropods on sapling and mature rangeland oaks, and applied these methods at 18 sample plot locations in northern California. The impact of arthropod damage was generally rated as minor. Leafy mistletoe (Phoradendron villosum) was found on 5 percent of the rated trees. There was a slight correlation between mistletoe infestation levels and dieback ratings. Characteristic canker rot symptoms were seen in 9 percent of the trees surveyed, and 16 percent of the trees had at least 20 percent of the bole volume decayed by fungi. In...

Habitat characteristics and diversity of terrestrial vertebrates were studied September 1989 to August 1990 in valley-foothill riparian habitat on two study areas: Dye Creek, Tehama County, and Avenales Ranch, San Luis Obispo County, California. The assumption considered was that differences between study areas in physical and vegetation characteristics would be reflected in wildlife diversity. Spring-season results showed that species richness of both higher plants and terrestrial- vertebrate wildlife averaged about twice as great at Dye Creek as at Avenales Ranch. No differences in...