Phytosphere Research

Selected Long Term and Short Term Projects

California oaks

Factors affecting blue oak recruitment and regeneration

Client: California Department of Forestry and Fire Protection, Strategic and Resources Planning Program
We studied how management practices, stand characteristics, and site factors interact to affect blue oak (Quercus douglasii) sapling establishment. We assessed regeneration and associated variables in a total of 1500 plots distributed among fifteen 150-acre study locations which were dispersed across the range of blue oak in California. We also compiled and mapped historical fire, rainfall, and grazing records over a 30-year interval for use in the analysis of management history. We used logistic regression to analyze the effects of history and environmental variables on sapling recruitment. The final project report is online.

Diseases and insect pests of California oaks

Client: California Department of Forestry and Fire Protection, Forest and Rangeland Resources Assessment Program
In this 2.5 year project, we evaluated the impacts of diseases and insects on the health and regeneration of native oaks in California. Based on our review of the literature and field observations, we produced a PC-based host index database (CODA) listing reported associations between oak species and their diseases and insect pests in California. We also conducted a focused study on the impacts of diseases, arthropods, and other factors on the survival of natural blue oak (Quercus douglasii) seedlings. We established field plots and surveyed native oak stands to determine the types and degree of disease and insect impacts on all oak life stages. Field plot data was organized into a geographically-linked database that was delivered to CDF at the conclusion of the project.

California Oak Disease and Arthropod Database

Clients: California Department of Forestry and Fire Protection, Forest and Rangeland Resources Assessment Program , USDA Forest Service
We provided distribution and support services for the California Oak Disease and Arthropod (CODA) host index database, which we developed under CDF Contract 8CA74545. In addition, we updated and refined the database using information from the literature, unpublished sources, and feedback from CODA users. In 2003, we received a grant from the USDA Forest Service to create a web-based interface for the database and add hyperlinked images of agents and symptoms. We programmed the web interface and uploaded many photos from our collection to the CalPhotos database, which is used as the main image server for CODA. CODA is available online.

Field guide to common pests and diseases of oaks in California

Client: USDA Forest Service
We have developed a field guide to common diseases and insect pests of California oaks which was published by the USDA Forest Service Pacific Southwest Research Station. Using data in CODA and other sources, we developed a list of species to be included and wrote descriptive summaries on the geographic distribution, symptoms, life cycle, and impacts associated with each pest or disease. We also selected photographs for use from our own image collection and obtained images from other sources. We distributed draft versions for review to specialists and incorporated input from these sources in the final version. This publication is distributed free of charge by the USDA Forest Service. Downloading and ordering information is available online.

Techniques for restocking valley oak

Client: California Department of Forestry and Fire Protection, Forest and Rangeland Resources Assessment Program
This was a two-year project to develop minimum input techniques for valley oak (Quercus lobata) restocking on hardwood rangeland. We reviewed the existing literature on natural and assisted regeneration in valley oak and evaluated past valley oak restocking projects. We then established demonstration projects at four sites in northern California to demonstrate and compare methods for restocking valley oaks in rangeland. The results of the demonstration projects, evaluations of previous valley oak restocking projects, and information in the literature were incorporated into a model to predict the cultural inputs necessary to restock valley oaks based on site characteristics.

Oak woodland restoration planting and monitoring

Volunteer public service for the Vacaville Tree Foundation and City of Vacaville
We have organized and conducted seed collection, planting, and monitoring of oak woodland restoration projects on several City of Vacaville open space lands on an annual basis since 1992. Through 1997, hundreds of community volunteers have helped plant over 2,000 sites with seeds of locally-collected oaks (Quercus lobata, Q. wislizeni, and Q. douglasii) and California buckeye (Aesculus californica). We have also conducted pilot-scale plantings of native grasses. In grazed sites, we continue to monitor and maintain over 300 individual planting site exclosures. In nongrazed areas, we use sample monitoring plots to assess growth and survival.

Diagnosis of valley oak decline

Client: CalMat, Fresno
We investigated the causes of mortality in a riparian/floodplain stand of valley oak (Quercus lobata). We conducted site investigations to observe symptoms and identify pathogens present at the site and reviewed historical aerial photos, water table and precipitation records, and management history to determine the contribution of various biotic and abiotic factors to the decline. Our report included recommendations for sustainable stand management.

Oak survey and vegetation assessment

Client: Riverbrook Partners, Stockton
We assessed native oaks and other vegetation for potential impacts from a planned community development project on a 760 acre site near Riverbank. We mapped and rated the condition of 468 individual oaks, and assessed levels of natural regeneration in existing oak stands. We recommended measures to minimize development impacts on individual trees, oak stands, and other existing vegetation resources.

Habitat assessment following firewood harvest

Client: Bruce and Donna Jensen, Windswept Ranch, Tehama County
We evaluated stand quality, density, and general wildlife habitat value in a partially-logged oak woodland and made recommendations for canopy retention within different portions of the site. 

Evaluation of literature on effects of fire and grazing on blue oaks

Client: California Native Plant Society.
We conducted a critical review of published research relating to the effects of fire and grazing on blue oak (Quercus douglasii) ecosystems, primarily focusing on the Sierra Nevada foothills. We analyzed each study's design, methodology, and statistical data analyses to assess the validity and applicability of published findings and assertions.

Phytophthora ramorum canker (sudden oak death): Factors affecting disease risk, disease progress, and failure potential

Client: USDA Forest Service
We initiated this ongoing case-control study in 2000 to examine the role of water stress and various other factors on the development of Phytophthora ramorum cankers (aka "sudden oak death") in coast live oak (Quercus agrifolia) and tanoak (Lithocarpus densiflorus). The study compares subject trees that exhibited symptoms of Phytophthora infection (case trees) with symptomless (control) trees. Data are collected from permanent plots established at 10 locations in Marin County, and one location each in Sonoma and Napa Counties. With additional funding provided by the USDA-FS Pacific Southwest Research Station, additional observations on the plots have been made in annually through 2004. These repeated observations allow us to study disease progress, mortality, and tree failure in these plots. Project reports that present the results from this to date study are available online.

Monitoring effects of Phytophthora-related mortality (Sudden Oak Death) in Sonoma County

Client: Sonoma County Fish and Wildlife Advisory Board/USDA Forest Service/University of California
We established permanent research/monitoring plots in woodland and forest types at risk from Phytophthora-related mortality to monitor disease progression and assess impacts of disease over time. We also assessed the impacts of other agents to develop an overall picture of forest health for the target species. We analyzed the plot data to determine how disease impacts vary across the landscape within a forest type and how different forest associations within the county are impacted. The final report from the original project is available online.
As part of a cooperative project with Dr. David Rizzo (Department of Plant Pathology, UC Davis) with funding from the USDA Forest Service, we resurveyed these plots in 2004 to assess disease spread and disease progress since the original 2001 survey. The final report from this follow-up project is also available online.

Relationships between tree failure potential and Phytophthora ramorum canker (sudden oak death)

Client: USDA Forest Service, Pacific Southwest Research Station
This study was designed to help resolve questions related to the relationship between Phytophthora ramorum canker (sudden oak death) and tree failure. This study uses a case-control design at six study locations to assess tree, disease, and site factors that may influence failure potential in coast live oak (Quercus agrifolia). From the data, we also estimated overall rates of tree failure within the study areas over several time intervals. The results of the study are presented in a report that is available online.

Management of Phytophthora ramorum canker (sudden oak death) in tanoak

Client: Kashia Band of Pomo Indians of Stewart's Point Rancheria/USDA Forest Service
We designed and established a pilot study to determine whether bark-banding treatments with phosphite (a low-risk fungicidal material) can be used to effectively prevent stem cankers caused by Phytophthora ramorum in native tanoak (Lithocarpus densiflorus) stands in Sonoma County, CA. In addition, we coordinated a related study to determine whether phosphite application affects the nutritional or phytochemical composition of acorns on treated tanoaks. Because tanoak acorns are used by the Kashia and other native tribes as a traditional food, the quality of the acorns from phosphite treated trees is a key factor in determining whether use of this material will be acceptable.

Management of Phytophthora ramorum canker (sudden oak death) in tanoak and oak stands

Clients: USDA Forest Service, Pacific Southwest Research Station, USDA Forest Service Forest Health Protection, Midpeninsula Regional Open Space District, San Francisco Public Utilities Commission
We are conducting several related projects designed to test the efficacy of the most promising techniques for managing P. ramorum canker (sudden oak death) in forests containing tanoak, coast live oak, Shreve oak, and California black oak. In these collaborative projects, we have established a network of long-term disease management plots ranging for plots around individual trees to multi-acre plots. Because disease epidemiology differs between different canker hosts, we are testing different control strategies in tanoaks and susceptible oaks, including the use of potassium phosphite (as a topical stem application or injection) and local or area wide bay removal. Results of this project will be used to improve disease management recommendations and will provide additional information on the epidemiology of the disease in treated and untreated stands.

Horticultural and Agricultural Consulting

Tree assessment prior to highway widening

Client: California Department of Transportation
We assessed native and introduced trees potentially impacted by a highway construction project on State Route 29 in the Napa Valley. We recommended specific measures to reduce construction impacts on individual trees.

Street and landscape tree problem diagnosis

Clients: City of Vacaville, Alza Corporation, Marriott Facilities Management, Chalk Hill Winery, and others
We have identified agents and conditions responsible for problems in a variety of street and landscape tree plantings, including Raywood ash, zelkova, chinese pistache, interior live oak, cork oak, Norway maple, and coast redwood. We made recommendations for short and long term remediation, including lists of species to use or avoid in replanting, and modified irrigation regimes.

Diagnosis of walnut decline

Client: Pacific Gas and Electric Company
We investigated the causes of plant decline in a walnut orchard located around a natural gas dehydrator facility. We found that poor plant condition was due to a combination of a viral disease (blackline), soil salinity problems, and inadequate irrigation.

Decline of landscape shrubs

Clients: City of Vacaville and others
In various projects, we have identified soil factors and biotic agents associated with decline of various woody perennial shrubs used in the landscape. We made recommendations for corrective cultural actions.

Diagnosis of ground cover failures in urban landscapes

Clients: City of Fairfield and others
We investigated the cause of repeated failures of perennial ground cover species in median islands and street landscape bed plantings in several different locations. We described several options for improving the plantings.

Integrated pest management guidelines for commercial landscape plantings

Client: Jepson Parkway Associates
We identified pests and beneficials present on landscaping in a shopping plaza, and identified cultural practices that had increased pest and disease problems. We provided guidelines for implementing an integrated pest management program at the site, including a list of pest-resistant plant species to be used to increase habitat for beneficial insects.

Natural Resources

Effects of thinning on a riparian mitigation planting

Client: Santa Clara Valley Water District
We designed and conducted a study to determine how plant water status and condition are affected by thinning in a densely planted riparian mitigation planting along the Guadalupe River in San Jose.  We monitored soil moisture, stomatal resistance, plant growth, and condition in three riparian species (Populus fremontii, Salix laevigata, and Acer negundo) to determine whether plant competition can be reduced to improve plant condition at this site.

Mitigation planting of willows and cottonwoods in an urban floodwater detention basin

Client: City of Vacaville
We conducted investigations on soil conditions and hydrology and developed a mitigation plan to grow willows and cottonwoods in an urban floodwater detention basin using locally-collected cuttings. We also developed a plan to mitigate for the loss of mature valley oaks (Quercus lobata) at the site by conserving and recruiting existing native valley oak seedlings in the project area. A summary of the project is available online.

Weed monitoring program for Jepson Prairie Preserve

Client: Solano Land Trust (formerly Solano County Farmlands and Open Space Foundation)
We designed, tested, and initiated a program for monitoring selected invasive weeds and desirable native species at the Jepson Prairie Preserve, a vernal pool / grassland ecosystem in Solano County, California. We produced reports which present the monitoring results for 2001 and 2002 and discuss the results of our data analyses. We provided training for Solano Land Trust (SLT) staff and volunteers and delivered GIS files, databases, method documentation, and other materials needed to allow SLT to continue monitoring efforts.

Effects of grazing on native and exotic vegetation at Jepson Prairie Preserve

Client: Solano Land Trust
Grazing and prescribed burning have been used to control undesirable vegetation at the Jepson Prairie Preserve, a vernal pool / grassland ecosystem in Solano County, California. As prescribed burning becomes increasingly difficult to implement, interest has turned to optimizing grazing to achieve the maximum benefit. We designed and conducted a study to determine the effectiveness of different grazing regimes at Jepson Prairie. The study addressed the degree to which different grazing regimes can reduce the cover of various target weeds, decrease thatch, and increase the cover of native species.

Effects of different grazing regimes on Viola pedunculata cover

Client: Solano Land Trust
Viola pedunculata or California golden violet is the sole food plant of the larvae of the Callippe silverspot butterfly (Speyeria callippe callippe), a federally-listed endangered species. We designed an experiment to test whether variations in the grazing regime could be used to promote the growth and cover of V. pedunculata to improve habitat quality for Callippe silverspot. We established study plots and collected pretreatment data on variation in V. pedunculata cover for two years before initiating cattle exclosure treatments in 2009.

Impacts of diseases affecting native stands of Ione manzanita (Arctostaphylos myrtifolia)

Client: California Dept. of Fish and Game / San Francisco State University
We evaluated the role of diseases in the of decline of native stands of the endangered species Ione manzanita (Arctostaphylos myrtifolia). We described symptomatology and disease progression, and identified pathogens associated with symptoms of dieback and decline of entire plants. We also investigated whether water stress was associated with differences in disease severity. As part of this study, we identified and described a new disease of both A. myrtifolia and A. viscida (whiteleaf manzanita) that has major implications for developing a conservation strategy for Ione manzanita. The report describing our study and findings is available online.

Distribution of Phytophthora cinnamomi in native stands of Ione manzanita (Arctostaphylos myrtifolia)

Client: Dr. Matteo Garbelotto, University of California, Berkeley/California Dept. of Fish and Game
In our initial project on Ione manzanita (Arctostaphylos myrtifolia), we determined that Phytophthora cinnamomi was the cause of a root and crown rot that results in large patches of plant mortality in stands of this rare species. In this follow-up study, we delineated the geographic extent of P. cinnamomi within the natural range of Ione manzanita and investigated the local distribution of P. cinnamomi in soils around root disease centers. Information developed in this project is critical for developing a strategy to conserve the endangered Ione manzanita.

Distribution of Marin manzanita (Arctostaphylos virgata) at Point Reyes National Seashore
Client: Point Reyes National Seashore
We conducted field surveys to verify and remap the distribution of the rare (CNPS 1B) Marin manzanita (Arctostaphylos virgata) within Point Reyes National Seashore. Using the existing GIS coverage as a starting point, we updated GIS layers to show the current distribution of Marin manzanita. We also collected data on stand density, health, and degree of tree canopy overtopping for mapped polygons of this species and provided field observations and digital images for all mapped polygons.

Baseline documentation of agricultural property and riparian corridor for conservation easement

Client: Solano County Farmlands and Open Space Foundation
We prepared an archival baseline document for a 149 acre agricultural parcel used for row crops and an adjoining riparian corridor. The report documents existing conditions of the natural resources and various improvements at the site through the use of descriptions, vegetation survey data, and both aerial and ground-level photography. The document establishes a baseline for monitoring compliance with separate conservation easements on the agricultural parcel and the riparian corridor.

Assessment of native elderberry for transplanting

Client: Entomological Consulting Services
We identified factors associated with poor condition of native elderberry (Sambucus mexicana) and assessed suitability for transplanting to satisfy mitigation requirements.

Diagnosis of disease problems in elderberry mitigation plantings

Client: Pacific Gas and Electric Company
We identified plant pathogens and other factors responsible for a rapid decline in condition of native elderberry (Sambucus mexicana) in several mitigation planting sites.

Ailanthus control in an urban riparian corridor

Client: City of Vacaville
We produced visual aids and provided training and technical input for a project to eliminate a dense stand of Ailanthus altissima from an urban riparian corridor. A major issue in the project was the protection of native elderberry (Sambucus mexicana), habitat of a federally-listed threatened insect species.

Development of dieback rating scales for Lupinus albifrons var. collinus

Client: Golden Gate National Parks Association
We developed rating scales and datasheets for evaluating dieback in Lupinus albifrons var. collinus, host plant of the endangered Mission Blue butterfly.

Soils and Irrigation

Evaluation of riparian mitigation planting

Client: Santa Clara Valley Water District
We evaluated pest and disease impacts to plants in a mitigation planting along the Guadalupe River in San Jose. We used water use calculations and soil investigations to develop recommendations for sustainable management of existing and planned plantings.

Water efficient landscape documentation

Client: Elmon Development, Inc.
We provided the landscape water use summaries and irrigation schedules for a residential development to satisfy the Yuba County Water Efficient Landscape Ordinance.

Soil water storage calculations

Client: Tire Farms
We calculated the potential effects of a proprietary subsoil water reservoir system on total soil water storage and irrigation water use. We produced a report that applied our findings to several soil types and climates.

Soil sampling and recommendations for proposed sports complexes

Clients: City of Fairfield, City of Vacaville
We evaluated soil physical structure and sampled soil for chemical analysis to identify soil factors that could affect the suitability of proposed sports complex sites for establishment of turf and landscaping.

Soil sampling and recommendations for new landscaping

Clients: City of Vacaville and others
We evaluated soil physical structure and sampled soil for chemical analysis to identify soil factors that could affect proposed landscaping. 

Urban Forestry

Urban Forest Management Plan Toolkit

Client: California Urban Forest Council / Inland Urban Forest Council
In this project, funded by a CalFire urban forestry grant, we developed the content for a website that helps users develop a management plan for their urban forest. We worked with a steering committee to help define the overall scope and structure of the website, conducted polls of prospective users to refine scope, developed the website's extensive content, and worked closely with the project manager and the website developers to help translate the concepts and structure into a unique website. We made several presentations on the Toolkit at professional meetings. The website has subsequently been revised by others. It is available here.

Yolo County Oak Woodland Conservation and Enhancement Plan
Client: County of Yolo
We served as the oak woodlands specialist (Oak Woodlands Adviser) to provide technical direction and assistance to the County of Yolo, Planning, Resources and Public Works Department in its development of a county-wide Oak Woodland Conservation and Enhancement Plan. We provided advice on overall content and organization of the plan; reviewed data on resource conditions; assisted in the development of goals, policies, and programs for the plan; edited sections of the plan drafted by staff; and developed the plan section on establishing priorities for oak woodland conservation and enhancement projects.

Urban forest management plan

Client: City of Rocklin
We developed an urban forest plan for the City of Rocklin, CA. To set the context for the plan and identify needs we evaluated the current status of the urban forest, including changes in canopy cover over the past 50 years; sample surveys of trees in parks, along street, and in parking lots; and a review of the city's current tree management procedures and policies. The plan includes recommendations for urban forest management, including goals, objectives, and specific actions, as well as technical recommendations for state-of-the-art tree care. We worked closely with City staff to collect data on existing practices and conditions and to produce the plan document. Presentations related to the plan included a public workshop to solicit citizen input and a presentation of the final plan to the City Council for adoption.

Electrical utility distribution line clearance study design

Client: Pacific Gas and Electric Company
We designed a multiyear field research project to compare two different pruning methods for maintaining electrical distribution line clearances. The study design included evaluations of tree regrowth rates and overall costs associated with the two pruning methods. The design also included methods for conducting all major evaluations and sample size estimates.

Electrical utility distribution line clearance study

Client: Pacific Gas and Electric Company.
In this multi-year study, we compared two different pruning methods for maintaining electrical distribution line clearances.  Matched pairs of London plane (Platanus x acerifolia) trees in urban street tree plantings were pruned and monitored over four years. We collected and analyzed detailed data on the pruning operations for each pruning method, including time required to prune and the amount of waste produced. We also measured and analyzed the rate of tree regrowth toward the primary power conductors. We developed Monte Carlo computer simulations to model time usage by pruning crews and to run an economic model that calculates the long-term costs for each pruning method.

Guidelines for Developing and Evaluating Tree Ordinances on the web

Client: USDA Forest Service, National Urban and Community Forest Advisory Committee.
This project was supported through the NUCFAC Challenge Cost-Share Grant Program and matching contributions provided by the International Society of Arboriculture, ESRI, Inc., Phytosphere Research, American Forests, and other cooperating organizations.  We established a comprehensive tree ordinance web site based on our CDF publication Guidelines for Developing and Evaluating Tree Ordinances.  Rather than using a “model ordinance” approach, the Guidelines web site describes a process for developing and revising tree ordinances as part of an overall urban forestry management strategy.  We updated and expanded site content and improved the web interface over the two-year grant period, using input from site users and an advisory committee comprised of representatives from major urban forestry-related organizations.  The Guidelines web site can be accessed through the International Society of Arboriculture’s web site and through our local mirror site.

Guidelines for developing and evaluating tree ordinances

Client: California Department of Forestry and Fire Protection, Urban Forest Program.
We collected, reviewed, and analyzed over 160 tree ordinances from cities and counties throughout California. We incorporated information from this analysis and from other sources into a report for local governments, citizens, and organizations interested in tree ordinances. The report presents guidelines for developing tree ordinances that are integrated with municipal urban forest management strategies. Methods for evaluating the performance of tree ordinances are also included. The report was prepared in-house as camera-ready copy, and we had 5000 copies of the report printed and delivered to CDF.  In a follow-up project in 1999, we converted the original report into Adobe Acrobat PDF format for posting at the CDF / UFEI web site.  You can follow this link to the UFEI site to download the report.

Review of tree ordinance

Client: City of Mountain View
We provided a technical evaluation of the city's existing heritage tree ordinance and provided comments and recommendations on the ordinance and a proposed ordinance revision.

1992 California urban forestry survey and report

Client: California Department of Forestry and Fire Protection, Urban Forest Program.
This project is a follow-up to the 1988 California Urban Forestry Survey and report which we completed for CDF. We surveyed all of California's incorporated cities and counties by mail to assess the present status of urban forestry in California communities. We identified recent trends by comparing the new survey data with data from the previous survey. We prepared the final report as camera-ready copy and had 2000 copies of the report printed and delivered to CDF.

1988 California urban forestry survey and report

Client: California Department of Forestry and Fire Protection, Urban Forest Program.
We surveyed all California cities and counties by mail to determine the status of their urban forestry programs. The survey questionnaire was based on a needs assessment conducted through interviews with professionals involved in urban forestry from around the state. We incorporated the results of the survey into a report for city and county tree program managers and other urban forestry professionals. The report was prepared in-house as camera-ready copy, and we arranged for the printing and delivery of 1000 copies to CDF. The data gathered were incorporated into a database, accessible by means of a customized interface.