Abstract 4: Contemporary California Indians, Oaks, and Phytophthora ramorum (Sudden Oak Death). Beverly Ortiz, CSUEB/Self/EBRPD

For about 3,000 years, California Indians have used the acorns of several oak species, as well as tanoak, for food. Through lecture, slides, demonstrations, and handouts, this paper will survey the contemporary utilization of acorns for food by California Indians across the state, including an examination of: (1) ancestral burning techniques used to manage oaks; (2) the context in which these techniques are being applied today on certain reservations, rancherias, public lands, and private lands; (3) new and old acorn processing techniques that are still in use today, including cracking stones, winnowing baskets, and hammers, mortars and pestles, electric blenders, and coffee grinders, soaproot brushes, sand leaching beds, porous containers lined with flour sacks, stone boiling, and stovetop boiling in stainless steel pots; (4) the varied foods that result from these processing techniques soups, breads, mushes, and biscuits; (5) familial, community and cultural contexts in which the food is shared and eaten; and (6) the symbolic content of the food in terms of ecological and social relationships that connect people to place, each other, cultural heritage, and sacred time. This paper will also examine the devastating impact that Phytophthora ramorum has had in disrupting, limiting, and sometimes severing these eons-old relationships, by weakening and killing the most important acorn-producing species for food statewide, Quercus agrifolia, Q. kelloggii, and Lithocarpus densiflous, as well as infecting numerous other species found in association with oaks and tanoaks. The paper will conclude with an overview of how California Indians are responding to this threat to cultural continuance.

Abstract 16: Woodland Structure Affects Intensity of Infection by an Exotic Forest Pathogen. Nathan Rank, Sonoma State University; Hall Cushman, Sonoma State University; and Ross Meentemeyer, University of North Carolina at Charlotte

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 laurel (Umbellaria californica), exhibited symptoms of disease throughout the study area, while canker hosts showed no signs of infection in most plots. This suggests that SOD spread among foliar hosts much more rapidly than from foliar hosts to canker hosts. With the high precipitation over the past two rainy seasons, we expect the disease to progress into canker hosts over the next several years. We also found that density of bay stems and degree of infection on bay laurel depended partly on presence of oak species. For example, the proportion of bay stems with symptoms of P. ramorum was 18% greater when coast live oak (Quercus agrifolia) was present than when it was absent. Coast live oak presence was also related to number of symptomatic bay leaves per tree. We suspect that our findings arise from the fact that the pathogen spreads most rapidly in stands where few canker host individuals inhibit dispersal among foliar host trees. Although previous studies have shown that abundance of bay laurel is related to infection levels in oaks, this is the first study that we know of suggesting that the presence of canker hosts affects infection levels on bay laurel, the main foliar host of P. ramorum.

Abstract 18: Consequences of Phytophthora ramorum Infection in Oaks and Tanoaks. Brice McPherson, University of California; David Wood, University of California; Sylvia Mori, United States Forest Service; Richard Standiford, University of California; and Maggi Kelly, University of California

Phytophthora ramorum has a broad host range in coastal California forests, but it disproportionately impacts coast live oaks (Quercus agrifolia), black oaks (Q. kelloggii), Shreve oaks (Q. parvula var shrevei), and tanoaks (Lithocarpous densiflorus). These overstory trees provide the principal high quality plant proteins used by multiple animal species, serve as primary food sources for animals and fungi, and support numerous other species through their architecture. From continuously monitored plots in Marin County, we can describe a broad pattern of tree responses to P. ramorum. The sequence of disease progression in infected coast live oaks and black oaks is consistent: bleeding; ambrosia and bark beetle attacks; development of decay fungi, most notably Hypoxylon thouarsianum; followed by death. Weibull regression model estimates of mean survival associated with these disease stages strongly indicate that the beetle attacks significantly shorten the time to mortality, probably by overwhelming tree defenses. Coast live oaks and black oaks with larger stem diameters have significantly increased probability of P. ramorum infection. Once infected, larger diameter coast live oaks are more likely to be attacked by beetles. Stem breakage of living infected coast live oaks is consistently associated with ambrosia beetle tunneling in the sapwood. Although the rate of new infections has slowed in coast live oaks since 2000, the mean infection level in our study plots and in landscape-scale evaluations is little changed, at 22%. The percentage of infected living tanoaks has increased from 39 to 73% since 2000. We can project that a shift in the age and size structure of these dominant trees is continuing, leading to a number of ecologically significant changes. Loss of oaks and tanoaks and their ecological roles, plus the introduction of weedy invasive plants has begun in these coastal oak woodlands and forests.

Abstract 20: Impacts of Phytophthora ramorum Canker and Other Agents in Sonoma County. Tedmund Swiecki, Phytosphere Research and Elizabeth Bernhardt, Phytosphere Research

To study impacts of sudden oak death (SOD), a lethal bark canker disease caused by Phytophthora ramorum, we established permanent plots in Sonoma County forest types at risk due to SOD. Baseline stand and tree health data were collected in 2001 and the plots were resurveyed in 2004. The 250 plots (0.02 ha each) are located at 11 study locations in stands containing Quercus agrifolia, Q. kelloggii, or Lithocarpus densiflorus as the dominant hardwood species. By 2004, P. ramorum was present at two locations that lacked P. ramorum symptoms in 2001 and caused tree mortality at one of these locations. Between 2001 and 2004, P. ramorum canker incidence increased from 29% in 2001 to 40% in plots containing L. densiflorus and from 2% to 10% in plots containing Q. kelloggii. Plots with Q. agrifolia showed a slight drop P. ramorum canker incidence (from 9 to 7%) due to apparent symptom remission in trees at one location. Between 2001 and 2004, the percentage of trees with P. ramorum canker symptoms increased at three of four locations with symptomatic SOD canker hosts. Mortality due to both P. ramorum and other agents increased at 9 of 11 study locations between 2001 and 2004. P. ramorum accounted for 27% of the mortality increase in Q. kelloggii, 49% in Q. agrifolia, and 30% in L. densiflorus. For most locations, annualized background mortality unrelated to P. ramorum was less than 1% per year between 2001 and 2004. Over this period, mortality rates associated with P. ramorum exceeded background mortality at three locations and was equal to it at a fourth. At one L. densiflorus location, mortality associated with an unidentified bark canker was comparable to levels of mortality associated with P. ramorum at other locations. Only P. nemorosa and P. pseudosyringae were isolated at this location.

Abstract 22: Susceptibility to Sudden Oak Death in California Bay Laurel. Brian Anacker, Sonoma State University; Nathan Rank, Sonoma State University; Daniel Huberli, UC Berkeley; Matteo Garbelotto, UC Berkeley; Sarah Gordon, Sonoma State University; Rich Whitkus, Sonoma State University; and Ross Meentemeyer, University of North Carolina at Charlotte

Sudden Oak Death, caused by the water mold Phytophthora ramorum, is a plant disease responsible for the death of 100s of thousands of oak and tan oak trees. California bay laurel (Umbellularia californica) has been shown to play a key role in P. ramorum inoculum build-up and subsequent spread to oaks. While bay laurel appears to vary in susceptibility to P. ramorum, little is known about the causes or extent of this variability. An understanding of such dynamics helps in identifying the limits of infection, dispersal, and impact of plant pathogens. In this research, we examine how bay laurel susceptibility to P. ramorum is related to bay laurel phenotype, genotype, and environment. Based on data from lab susceptibility trials and field infection data collected from 97 trees from 12 populations in Northern California, we found that lab lesion size and field infection levels varied significantly among both bay laurel trees and populations. The phenotypic trait of leaf area was significantly related to lab lesion size, where bigger leaves produced bigger lesions. Variability in lesion size produced in the lab and infection levels in the field were significantly related to AFLP markers, suggesting a genetic basis to resistance. We also identified markers associated with phenotypic traits putatively involved in conferring susceptibility, including leaf toughness and leaf water content. At the population level, environmental variability significantly explains susceptibility to P. ramorum. This work demonstrates how susceptibility to P. ramorum in bay laurel depends on genetic, phenotypic, and environmental traits, providing useful information for predicting risk of P. ramorum spread from bay laurel to oak and tan oak trees, an important consideration for controlling the spread of Sudden Oak Death.

Abstract 23: Forest Response to an Emerging Disease: Sudden Oak Death in Coastal California. Letty Brown, University of California, Berkeley and Barbara Allen-Diaz, University of California, Berkeley

Over the past century, plant diseases have had major impacts on forested ecosystems worldwide. An important emerging forest disease is Sudden Oak Death, the causal agent of which, Phytophthora ramorum, was first identified in 2000. Currently confined to several counties in coastal California and a small area in Oregon, the disease has the potential to become more widespread. In 2002, we began an investigation into the impacts of the disease on mixed evergreen forest communities dominated by coast live oak (Quercus agrifolia) and bay laurel (Umbellularia californica). We measured understory herbaceous plant and shrub parameters and woody plant seedling densities, over a gradient of disease severity to assess whether newly downed trees serve as refugia for woody seedling recruitment. We found diverse understory assemblages in infected forests, with understory species richness ranging from 19.1 to 32.2 species per hectare. Percent cover of herbaceous plants in these understories ranged from 14.3 to 51.7%, woody seedlings are present at densities of 0.37 to 2.08 seedlings/m2, and course woody debris varies from 1.20 to 46.86 m3/ha. Initial results suggest that newly downed trees do not serve as refugia for woody seedlings, but correlations do exist between forest infection gradients and other understory parameters. Through direct lethality to infected trees, this novel plant-pathogen combination has the potential to indirectly affect the composition and diversity of non-target understory species.

Abstract 25: Effects of Recreation on the Dispersal of Exotic Forest Pathogen, Phytophthora ramorum. Michelle Cooper, Sonoma State University, Department of Biology and Hall Cushman, Sonoma State University, Department of Biology

Although outdoor recreation is often viewed as having minimal impacts on protected wildlands, a growing number of studies have shown that hiking trails can serve as corridors for the spread of exotic plant species. Very little research has focused on recreation as a means of spread for plant pathogens but here, we present research that links two forms of recreation (hiking and mountain biking) with the dispersal of an exotic forest pathogen, Phytophthora ramorum, which causes the disease known as Sudden Oak Death. By sampling soil collected from the shoes and tires of visitors entering and exiting protected wildlands, we found that 7% of visitors entered the site with viable pathogen on their shoes and tires, and 23% carried it out with them. Although hikers and bikers did not differ significantly in their capacity to transport P. ramorum, there was a trend indicating that during dryer conditions, the further a person traveled along a trail, the more likely they were to pick up the pathogen. Lastly, although our data show that humans can disperse P. ramorum, the temporal window for doing so is constrained, as the pathogen could not be cultured from soil on hikers shoes after 24 hr, although this time was extended to at least 72 hr if the soil on shoes remained moist. Collectively, our results suggest that recreation in protected areas can lead to dispersal of the pathogen that causes Sudden Oak Death. However, because P. ramorum is sensitive to desiccation, human dispersal may be limited to situations where the pathogen remains moist. These include further spread of the pathogen during individual visits to already infected areas and movement of the pathogen to previously uninfected areas when visitors move rapidly from one region to another, especially when shoes and tires are stored in moist conditions.

Abstract 27: Human Activity and Spread of the Pathogen That Causes Sudden Oak Death. Hall Cushman, Sonoma State University and Ross Meentemeyer, University of North Carolina at Charlotte

A striking consequence of globalization is the tremendous influx of infectious diseases and invasive, non-natives species worldwide. One invader of great concern is the fungus-like pathogen, Phytophthora ramorum, which causes a devastating forest disease known as Sudden Oak Death (SOD) in many coastal regions of California and Oregon. In addition, P. ramorum has been found in nurseries and managed landscapes throughout Europe (11 countries so far) and recent laboratory studies have indicated that numerous oak species in the eastern United States are extremely susceptible to attack by the pathogen, should it reach these areas in the future. Here, we evaluate the influence of human activity on the distribution of this pathogen at three spatial scales in California. At the local scale, we found that P. ramorum was significantly more common in soil found on hiking trails at Fairfield Osborn Preserve than from adjacent areas off trail. At the landscape scale, forests on public lands in eastern Sonoma County open to recreation had significantly higher proportions of diseased host trees than those on private lands. And at the regional scale, forested areas in northern and central California surrounded by large human populations were significantly more likely to have infected host trees. Collectively, these findings suggest that humans are important dispersal agents of a destructive pathogen and promote its spread. Efforts to address this epidemic may thus require aggressive management of human activity, which could be logistically and politically difficult to achieve.

Abstract 29: GIS-Based Epidemiological Modeling of an Emerging Forest Disease: Spread of Sudden Oak Death Across California Landscapes. Rich Hunter, Sonoma State University and Ross Meentemeyer, University of North Carolina at Charlotte

The number of emerging infectious diseases are thought to be increasing worldwide many of which are non-native, invasive plant diseases in forest ecosystems. A predictive understanding of invasion processes is necessary to manage and prevent further spread, especially in complex spatially heterogeneous landscapes. Mathematical modeling of susceptible-infectious transitions in plant epidemics often incorporate spatial dynamics, but are rarely applied in a GIS to real-world wildland landscapes. In this paper, we present and evaluate a GIS-based epidemiological model of the spreading forest pathogen Phytophthora ramorum, which is causing the devastating forest disease known as Sudden Oak Death. First, we describe a generic mathematical model for a susceptible-infectious epidemic that simulates spatial and temporal patterns of disease spread on a weekly time step for application at large spatial scales. Next, we describe how data from field and lab studies were used to parameterize the driving system variables, including daily rainfall and temperature, host abundance and susceptibility, human density, and dispersal characteristics. The parameterized model was implemented (1990-2005) in a GIS to simulate disease spread across California at a spatial resolution of 250 x 250 meters. We evaluated model performance in the GIS by examining the correspondence between predicted patterns of disease spread and over 1000 geo-located field observations of disease presence. Additionally, we examined the nature of prediction errors by ecoregion, vegetation composition, and climate. The model predicts almost 80% of the spatial variability in current patterns of disease spread and identifies numerous oak woodland systems at high risk of infection. We've found the application of epidemiological models to realistic landscapes in a GIS can allow for a rigorous validation of model performance using geo-located field data of disease presence and can be used as an effective management tool to identify actual landscapes at high risk to disease spread.

Abstract 31: Long-Term Change in Oak Woodlands and Its Influence on a Forest Disease. Ross Meentemeyer, University of North Carolina at Charlotte and Hall Cushman, Sonoma State University

Land-use practices to sustain expanding human populations have resulted in dramatic alterations of forested ecosystems worldwide. One potential consequence of land-use change is the spread of infectious disease. In this research, we investigated patterns of human-related land-cover change between 1942 and 2000 and examined whether or not changes have led to conditions that promote the establishment and spread of the invasive pathogen Phytophthora ramorum, causal agent of the destructive forest disease Sudden Oak Death. We established 102 field sites randomly located within a 275 km2 region of Sonoma County, CA comprised of several land cover types. Within a 150 m radius area around each site, we mapped fine-scale changes in land cover in a GIS using 1942 and 2000 imagery. We found that woodland area increased by 25% from 1942 to 2000, while grassland and chaparral decreased in area by 34% and 49% respectively, and development increased by 1105%; mean size of woodland patches increased by 51% and number of woodland patches decreased by 41%. To examine if these changes influenced the establishment of P. ramorum, we sampled P. ramorum infection level on host species and measured woody species abundance within each 150 radius area in spring 2005. Multiple regression analyses showed that density of the host bay laurel (an important carrier of the disease) was positively related to woodland cover change. Also, there were a greater number of bay trees showing symptoms of P. ramorum in areas that have increased in woodland. We hypothesize that these increases in woodland density and expansion into grasslands and shrublands facilitates spread of P. ramorum by increasing contagion of host and increasing shading and moisture levels. Understanding the influence of land cover change on disease spread is critical for informing land management and preventing intensification and spread of destructive pathogens.

Abstract 33: Gap Dynamics in Oak Woodlands Across a Gradient of Disturbance. Tim De Chant, University of California, Berkeley, Dept. of Environmental Science, Policy and Management and Maggi Kelly, University of California, Berkeley, Dept. of Environmental Science, Policy and Management

Sudden oak death (SOD) is a disease of epidemic proportions, sweeping through many coastal hardwood forests in California. Since 1999, SOD has produced overstory mortality in China Camp State Park (CCSP), creating a number of gaps which effectively alter the structure of the forest. In following year, and the three thereafter (2000-2003), ADAR high-resolution (1 m) multispectral imagery for CCSP was acquired. We classified this existing imagery to identify gaps within the forest mosaic. Once the gaps were identified, they were vectorized and measured for perimeter and area. We also characterized the gaps within their spatial context through closeness to edge and closeness to nearest gap. We then compared these spatial measures of variation to temporal ones, creating a time-sequence of gap formation and the resulting gaps closure or persistence. In addition to multispectral imagery, we sampled basal area measures within CCSP and correlated them with gap size, structure, and configuration, testing the accuracy of remote sensing techniques against field based information in determining forest structure changes. We then scaled our understanding of these structural changes up to a larger landscape scale not covered by the field plots.

Abstract 41: Regeneration of Oaks and Tanoak in Phytophthora ramorum-Affected Forests. Tedmund Swiecki, Phytosphere Research and Elizabeth Bernhardt, Phytosphere Research

Recent mortality in Quercus agrifolia, Q. kelloggii, and Lithocarpus densiflorus exceeds historical levels in forests affected by the pathogen Phytophthora ramorum. We assessed the balance between recent mortality and seedling populations in these species to examine the status of regeneration in stands with varying levels of mortality caused by P. ramorum. Regeneration data was compiled in two sets of plots (all 0.02 ha). In 150 plots distributed across 12 locations primarily in Marin County, seedling counts and mature tree condition were rated annually from 2000 through 2005. In 250 plots distributed across 11 locations in Sonoma County, data were collected in 2001 and 2004. In plots monitored annually, Q. agrifolia seedling populations fluctuated more widely from year to year than tanoak seedling populations. Tanoak seedlings were present in nearly all plots with tanoak trees. Nearly all plots with tanoak mortality had tanoak seedlings which could potentially grow to replace dead trees. Coast live oak plots were less well-stocked with seedlings. Many plots with coast live oak mortality lacked coast live oak seedlings. Mean counts of coast live oak seedlings per plot were significantly lower in 2004 than in 2001 among plots in Sonoma County. Less than half of all plots with California black oak trees had California black oak seedlings. Three-quarters of the plots with California black oak mortality lacked seedlings of this species. In these forests, regeneration of California black oak appears inadequate to maintain stand density even without the additional mortality due to P. ramorum.

Abstract 49: Molecular Markers Show How Pollen and Seed Dispersal Affect Population Genetic Structure in Coast Live Oak (Quercus agrifolia née). Richard Dodd, University of California; Zara Afzal-Rafii, Universite d'Aix-Marseille III; and Wasima Mayer, University of California

Coast live oak (Quercus agrifolia née) occurs in the Coast Range mountains from southern Mendocino County, California to the Sierra San Pedro Martir, Baja California, Mexico. In northern and central California, coast live oak is suffering heavy mortality as a result of infection by Phytophthora ramorum. Earlier work indicated biochemical differentiation of central coast populations from northern and southern California, an important hybrid zone in northern California and possible differential response to inoculation between populations from northern and southern California. Here we report results of a phylogeographic study of this species using chloroplast and nuclear microsatellite markers. The chloroplast genome is inherited uniparentally and is particularly useful for identifying the migration of lineages over evolutionary time scales that include the important events of the Pleistocene glaciations. We sampled 41 populations of coast live oak from throughout the geographic range and analyzed nuclear and chloroplast microsatellies for over 500 individuals. Based upon the chloroplast haplotype distributions, at least 4 biogeographic groups should be recognized within the California range of this species: 1. three common haplotypes in the San Francisco Bay area and northwards, of which only one is found outside of this region in San Luis Obispo Co. and at Ojai in Ventura County. 2. three haplotypes in the Monterey-Big Sur region that were unique to this region, 3. two haplotypes unique to the coastal mountains of San Luis Obispo County and, 4. six haplotypes in extreme southern California, of which 5 were unique to the region. Nuclear microsatellite markers revealed reduced levsl of genetic structure as a result of pollen dispersal. We discuss the roles of seed and pollen dispersal in the evolution of populations of coast live oak and how this information may help in developing strategies for studies of resistance to the sudden oak death disease.

Abstract 59: Determining the Role of Plant Community and Landscape Change in the Sudden Oak Death Disease Complex. Timothy Doherty, University of Berkeley, ESPM; Barbara Allen-Diaz, University of Berkeley, ESPM; and Maggi Kelly, University of Berkeley, ESPM

In the 1920s and 1930s A.E. Wieslander and his crew surveyed much of the California landscape. The data they collected, known as the Wieslander Vegetation Type Mapping collection (VTM), contains vegetation data, detailed vegetation type maps and an extensive photograph collection. Our research will examine VTM plots in the Quercus agrifolia-Umbellularia californica woodlands surrounding San Francisco Bay to determine the role of plant community change and landscape change in the Sudden Oak Death disease complex. The causal agent of this disease, Phytophthora ramorum, has emerged as a significant pathogen within the Quercus agrifolia-Umbellularia californica woodlands. Initially detected in 1994 in Marin County, it has since spread to fourteen counties in California and one county in Oregon. There are still many unanswered questions regarding the ecology of this pathogen including its relationship to historical conditions and its spatial pattern across the landscape. Our research will integrate plot based plant community data with landscape level spatial data to increase our understanding of presence and spread of SOD both spatially and temporally. In the winter of 2005, we selected 15 VTM plots across a gradient of Sudden Oak Death infection and from within the Quercus agrifolia-Umbellularia californica woodlands. We have begun the process of re-sampling each plot location to assess plant community and stand structure to determine if certain plant communities are more prone to Phytophthora ramorum infection. We will also integrate historic aerial imagery into a GIS and compare with modern imagery from the study area to determine the relationship between landscape variables such as woodland fragmentation and land use change and SOD occurrence. At this time we are collecting and analyzing data and expect that we will have conclusive findings to present at the symposium.

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