Treesearch

The effects of grazing and oak tree removal on soil quality and fertility were examined in a blue oak (Quercus douglasii) woodland in the northern Sierra Nevada foothills. Low to moderate grazing intensity has little affect on soil quality; however, oak tree removal resulted in a decrease in most soil quality parameters investigated (carbon, nitrogen, phosphorus, pH) within 5 to 15 years following tree removal. Following tree removal, total C and N pools in the 0-15 cm depth increment decreased by 10 to 20 percent after 5 years and 20 to 40 percent after 21 years. These changes were...

A long-term thinning study was established in 10 stands of coast live oak (Quercus agrifolia Née) in the Central Coast of California. Information about diameter, basal area, and volume growth and yield has been obtained from unthinned control plots and from plots thinned to 50 and 100 square feet of basal area per acre measured in 1984, 1989 and 1996. Both basal area and total volume growth percentages were significantly greater in the thinned plots compared to the control plots.

At three sites in a blue oak woodland in northeast California, we studied seasonal patterns of blue oak (Quercus douglasii Hook and Arn.) fine root (< 2 mm diameter) production and ectomycorrhizal (ECM) colonization using root ingrowth cores. In a short-term study, ingrowth cores were installed and harvested in 3-month intervals for one year. Oak fine root production was lower in fall and winter, higher in spring, and intermediate in summer. ECM roots were found only in spring and fall. In a long-term study, ingrowth cores were installed in January 1998 and harvested after 6, 9, and 12...

The lack of valley oak (Quercus lobata Neé) regeneration throughout much of its historical range appears to be related to both habitat destruction and soil moisture availability. The water relations, growth and survival of greenhouse potted seedlings, field-planted and natural seedlings were monitored through the growing season, 1989. The age structure of the valley oak population of a riparian forest at the Cosumnes River Preserve was determined. The history of fluvial events of the Cosumnes River was ascertained to determine whether such fluvial events are associated with past seedling...

Hardwood forests are principal features of the landscape of both California and Britain and indigenous oak species are important components. In both locales these "oak woodlands" have historically provided a wide variety of commercial and non-commercial products and benefits and are deeply valued and appreciated by those who live in and around them. However, human-induced impacts have reduced the original forest cover in each area and there is concern that oak woodlands are still at risk, especially from impacts associated with increasing residential land-use conversion. While there are...

We examine inconsistencies in the application of environmental laws and policies to California's oak woodlands and associated resources. Specifically, large-scale vegetation removals receive different levels of environmental oversight depending on location, tree species, and the final land use designation. Hence, situations arise where the scale of impacts to the ecosystem can be similar but are regulated differently depending on forest type. These inconsistencies can lead to environmental impacts, confusion, and inherent inequities among private landowners. The historical, institutional,...

Decisions on how much land should be devoted to oak woodland preservation is ultimately determined by society's valuation of its benefits and relative scarcity. Scarcity value can be measured by people's willingness-to-pay (WTP) to prevent oak woodland conversion to higher value land uses. In this study, we used the contingent valuation (CV) method to estimate WTP for oak woodland preservation in San Luis Obispo County (over 700,000 acres). Estimates ranged between $75 and $83 per voter, providing only about $12 million for land or easement purchases.

Oak woodland habitat is being degraded or replaced by vineyards in many areas of central-coastal California. Oak woodlands are home to many insectivorous, cavity-nesting birds that would be beneficial in and around vineyards. During March to June 2001, we used bluebird nest boxes to study nest box use and productivity of cavity-nesting birds in vineyards versus adjacent oak woodlands. In February 2001, we placed 18 nest boxes 50 m apart in vineyards and in adjacent oak woodland at four woodland/vineyard paired sites in Santa Barbara and San Luis Obispo counties. During April to June, we...

Ecosystem restoration requires a set of reference vegetation conditions which are difficult to find for Garry oak (Quercus garryana) ecosystems in Canada because contemporary sites have been drastically altered. A survey of historical information provides only limited clues about the original understory vegetation. Although there is considerable variation in the soils, climate, and successional status of current ecosystems, an exploration of the ecology of contemporary, native grass species existing in association with Garry oaks can point to which species may have been adapted to the...

Purple martins are cavity-nesting swallows that once nested fairly widely in California’s oak woodlands but are now rare in that habitat. The old oaks of the Tehachapi Range (southern Sierra Nevada) may now host the last martins that nest in oak woodlands, with approximately 100-200 pairs or about 15 percent of the California population. In summer of 2000, we found 57 nests in 46 valley and blue oaks and measured over 20 variables at nest sites and random paired sites. Martins selected large-diameter trees [x = 104.3 cm diameter at breast height (dbh)] that were more prominent than random...