Treesearch

Oaks depend on hidden diversity belowground. Oregon white oaks (Quercus garryana) form ectomycorrhizas with more than 40 species of fungi at a 25-ha site. Several of the most common oak mycorrhizal fungi form hypogeous fruiting bodies or truffles in the upper layer of mineral soil. We collected 18 species of truffles associated with Oregon white oak. Truffles do not release spores directly into the air, but remain closed belowground. In conifer ecosystems, animals eat truffles and disperse the spores, providing mycorrhizal inoculum for new roots. We did a survey to determine the extent...

Woodland ecosystems often consist of a mosaic of interacting dominant woody species that vary in density and abundance. Local variation in dominant species abundance may influence spread of plant pathogens across this heterogeneous landscape. We investigated this possibility in a 275 km2 study area in eastern Sonoma County, which is being invaded by the pathogen that causes Sudden Oak Death, Phytophthora ramorum. We assessed symptoms of infection by P. ramorum of foliar and canker hosts in 2004 and 2005 in 202 randomly located plots. Our results showed that the widespread foliar host, bay...

Sudden oak death, caused by Phytophthora ramorum, has infected and killed large numbers of oaks (Quercus spp.) and tanoaks (Lithocarpus densiflorus) in California since the mid 1990s. Since March 2000 we have been investigating the interactions between patterns of disease progression and broader landscape-scale patterns of disease incidence and expansion in study plots in Marin County. The incidence of new infections has continued to increase in both coast live oaks (Q. agrifolia) and California black oaks (Q. kelloggii), and very rapidly in tanoaks. The net result of more than 10 years of...

The restoration of dry forest ecosystems in the Squamish Forest District in the past has focused on treating stands with no prior history of selective harvest and containing a large population of remnant historical stand structure. Many 60 to 90 year old stands that date to turn of the century selective harvest operations also exist in the district. These stands contain very high densities of Douglas-fir and ponderosa pine and few historical structures. Silviculture prescriptions were developed to thin these stands to a remnant structure that would be more resilient to future wildfires...

Urban forests have a role to play in reducing levels of carbon dioxide and other greenhouse gases (GHG) in the atmosphere (Abdollahi et al. 2000; Pataki et al. 2006). However, very few tree planting projects have been undertaken because of the uncertainty regarding their performance and permanence. The Urban Forest Project Reporting Protocol was developed to reduce this uncertainty by providing a standard set of guidelines for use throughout the United States. This article is meant to distill the protocol into information that is meaningful to professional arborists and urban foresters.

Miconia calvescens DC. (Melastomataceae) is an invasive tree considered the most serious threat to the natural ecosystems of Hawaii and other Pacific islands. We evaluated nine species natural enemies that feed on inflorescences or leaves of M. calvescens for their potential as biological control agents, comparing their impact on the target plant, host specificity, and vulnerability to biotic interference. Among herbivores attacking reproductive structures of M. calvescens, a fruit-galling wasp from Brazil, Allorhogas sp. (Hymenoptera: Braconidae). and a flower- and fruit-feeding moth from...

California ranchers with substantial private oak woodlands sometimes use public lands as an important component of their production cycle. Yet allowed public grazing has declined and is likely to continue to decline. This, combined with intensifying development pressure and land use change, dramatically affects the resource base for ranch operations, which in turn influences landowner management decisions and practices. Such individual decisions have a significant role in shaping California’s future landscape. As private rangelands are developed and taken out of production, public lands...

The pine-oak rust fungi, which live out their lives as pathogens on pines and oaks, have multiple spore states and complex life cycles. Because they can be severe pathogens of pines, much of what we know about them depends on how damaging they are to management of pine forests for timber, recreation, and ecosystem values. Widely distributed in North America, they are often difficult to identify on their oak hosts, and thus the distributions and frequencies of many species are not well known, especially in urban and rural forest settings. Although they are usually minor pathogens on oaks,...

It is increasingly clear that additional ‘model’ systems are needed to elucidate the genetic and developmental basis of organismal diversity. Whereas model system development previously required enormous investment, recent advances including the decreasing cost of DNA sequencing and the power of reverse genetics to study gene function are greatly facilitating the process. In this review, we consider two aspects of the development of new genetic model systems: first, the types of questions being advanced using these new models; and second, the essential characteristics and molecular tools...

In 2004, the California State Legislature passed Senate Bill 1334 (Bill), titled Oak Woodlands Conservation: Environmental Quality. This Bill states, “A county…shall determine whether a project within its jurisdiction may result in a conversion of oak woodlands that will have a significant effect on the environment”. Once a determination has been made, counties have the option to 1) evaluate the utility of conservation easements as a vehicle for conservation; 2) enforce mitigation planting; 3) make a in-lieu contribution to the Oak Woodlands Conservation Fund (established in 2001 under the...