Treesearch

Integrating cover crops into a nut orchard can have some unique benefits and problems not found when used cover crops during the fallow period between cash crops. Studies show ground covers can reduce hardwood tree growth anywhere from a few percent to more than 70 percent in the case of tall fescue. This means if it takes 3 years to put on one inch of diameter growth in a weed-free planting, it will take more than 9 years if growing in a tall fescue sod. Impacts on nut production appear to be even greater.

A strong focus on tree germplasm that can resist threats such as non-native insects and pathogens, or a changing climate, is fundamental for successful conservation efforts. This project is predicated on the fact that genetic resistance is the cornerstone for protecting plants against pathogens and insects in environments conducive to the attacking organisms, a principle we have extensively applied to the study of coast live oak (CLO – Quercus agrifolia) interactions with Phytophthora ramorum in California wildlands. The largest obstacle to the implementation of host resistance as a tree...

Over the past 15 years, the USDA Forest Service, Pacific Southwest Region, State and Private Forestry (S&PF) has provided grants which have supported over 200 projects to address sudden oak death (SOD) in California. To date, over $10 million has been provided by US taxpayers, plus an additional $8 million of non-federal matching funds. These funds have provided the infrastructure for California’s SOD response: supporting laboratory diagnostics, monitoring, management, and education and outreach. Grantees have included CAL FIRE, five California universities, UC Cooperative Extension in...

In 2006, three isolated sudden oak death- (SOD) infested locations within Humboldt County were selected for silvicultural treatments that targeted the removal and/or reduction of tanoak (Notholithocarpus densiflorus Hook. & Arn.) and California bay laurel (Umbellularia californica Hook. & Arn), the main hosts supporting sporulation of Phytophthora ramorum (Valachovic and others 2010). In these treatment areas, subsequent rates of infection on re-sprouting tanoak and bay laurel varied widely, but were very low where bay laurel was either absent or in low densities at the time of treatment....

Forest CO2 emissions, which have recently become a more regular concern in forest management, can radically increase following pest and disease outbreaks. We inventoried trees in a stand adjacent to an infested area in northern Humboldt County, California, and used a stand-level dynamic disease model to forecast Phythophthora ramorum-caused tanoak mortality with and without a proposed treatment to mitigate disease spread and impacts. Using forest growth simulations employing model-predicted mortality rates, a proposed treatment that removes California bay laurel and reduces tanoak stem...

On Mt. Tamalpais, after nearly 20 years of accumulated disease impacts, some tanoak- (Notholithocarpus densiflorus) dominated forests where Phytophthora ramorum first emerged have converted to brushy fields of tanoak resprouts. Phytophthora ramorum has invaded throughout the greater San Francisco Bay Area, and damaged the culturally, ecologically, and economically important forests of Mount Tamalpais, including many stands managed by the Marin Municipal Water District (MMWD) for water yield and recreation. Sustained inoculum loads have resulted in extensive tanoak mortality, in some places...

Since 2001, approximately 5,350 acres of tanoak forests in Curry County, Oregon have been treated to eradicate Phytophthora ramorum and slow the spread of sudden oak death. Over 1,300 of these acres are on lands administered by the USDI Bureau of Land Management (BLM CB), Coos Bay District and the USDA Forest Service, Rogue River-Siskiyou National Forest (USFS RRS). Treatments include using herbicides to reduce tanoak sprouting, cutting, piling and burning known infected tanoaks, and cutting, piling, and burning exposed tanoaks and other selected hosts in a buffer area around known...

Prior to 2000 the etiology, effects on host trees, and possible consequences for northern California’s forests of the syndrome known as sudden oak death were unknown. We designed a plot-based study to address these issues and to set a baseline for future evaluations. In March-April 2000 we established a total of 20 plots in two forested areas in Marin County: China Camp State Park [CCSP] (10) and Marin Municipal Water District [MMWD] (10). The host species monitored were coast live oak [CLO] (Quercus agrifolia) and California black oak [CBO] (Q. kelloggii) in both sites and tanoak [TO]...

Novel interactions between compounded disturbances can leave lasting ecological legacies on communities and alter regeneration trajectories. Sudden oak death (SOD), caused by Phytophthora ramorum, is a biotic disturbance, an emerging disease causing widespread oak and tanoak mortality in California’s coastal forests. In these redwood-tanoak forests, wildfire is a keystone process, shaping stand structure and composition. Dominant tree species can resprout rapidly after being “top-killed” by fire, in addition to regenerating via seed. Yet, in SOD-impacted areas, fuels generated by disease-re...

An understanding of long-term patterns of forest structural and compositional development is critical for anticipating management outcomes and developing appropriate silvicultural strategies for restoring complex forest conditions. In most cases, this information comes from stand-level assessments; however, the impacts and outcomes of management and other disturbances on forest development occur over multiple spatial scales across a landscape. We compared historical (1941) and contemporary (2012–2014) forest structure and composition on 301 plots distributed across managed and unmanaged,...