Papers by Yana Valachovic
Land managers, fire suppression professionals, and research scientists have speculated about the ... more Land managers, fire suppression professionals, and research scientists have speculated about the relationship between increased Phytophthora ramorum-caused hardwood mortality and wildfire incidence, severity, and behavior in coastal California. Little quantitative data has emerged to measure the nature of any such relationship. The Basin Complex and Chalk fires in the summer and fall of 2008 along the Big Sur Coast provided the first opportunity for observers to confirm or disconfirm speculations about fire and P. ramorum. In an effort to focus research, outreach, and technical assistance, we conducted an information-gathering survey targeted at select personnel who worked on the Basin Complex and Chalk fires, and followed the survey with a series of meetings with land management professionals and scientists to obtain recommendations for how these firefighters' experiences should inform future research and outreach efforts. Recommendations included more effective provision of needed maps and safety information; future research into the best methods for sanitizing water or ensuring that infested stream water is not used to fight fire; investigation into characteristics of live fuels in areas of increased hardwood mortality to aid fire behavior analysts with predictions; and increased coordination with firefighting agencies for information distribution and standardization of demobilization procedures.
Canadian Journal of Forest Research, Oct 1, 2004
The effects of initial leaf litter chemistry on first-year decomposition rates were studied for 1... more The effects of initial leaf litter chemistry on first-year decomposition rates were studied for 16 common Pacific Northwest conifers, hardwoods, and shrubs at the H.J. Andrews Experimental Forest in western Oregon. Leaf litters were analyzed for C, N, P, K, Ca, Mg, proximate organic fractions (nonpolar, polar, acid-hydrolyzable extractives, acid-hydrolyzable lignin, and acid-unhydrolyzable residue, previously termed "Klason lignin"), and biochemical components (total phenolics, reactive polyphenols, water-soluble carbohydrates, water-soluble proanthocyanidins, and waterand acid-unhydrolyzable proanthocyanidins). By including measurements of reactive and residual phenolic fractions and acid-hydrolyzable lignin, these analytical methods improve upon traditional proximate leaf litter analyses. Significant differences in litter chemistries and decomposition rates were found between species. For all species combined, the 1-year decay rate (k) values had highly significant correlations (P < 0.001) with 30 out of the 36 initial chemistry variables tested in this study. The three highest correlations were with acid-unhydrolyzable proanthocyanidins, lignocellulose index, and acid-unhydrolyzable residue (r = 0.83,-0.81,-0.80, respectively, with P < 0.0001 and n = 339). We found that no single litter chemistry variable was a universal predictor of the 1-year k value for each of the individual 16 species studied, though phenolic components were more frequent significant (P < 0.001) predictors of decomposition rate. Résumé : L'effet des caractéristiques chimiques initiales de la litière de feuilles sur le taux de décomposition au cours de la première année a été étudié pour 16 conifères, feuillus et arbustes communs du Pacific Northwest à la forêt expérimentale H.J. Andrews dans l'ouest de l'Oregon. Les litières de feuilles ont été analysées pour C, N, P, K, Ca, Mg, des fractions organiques (produits d'extraction non polaires, polaires et hydrolysables dans l'acide, lignine hydrolysable dans l'acide, résidus non hydrolysables dans l'acide antérieurement qualifiés de « lignine Klason »), et des composantes biochimiques (composés phénoliques totaux, polyphénols réactifs, hydrates de carbone solubles dans l'eau, proanthocyanidines solubles dans l'eau, proanthocyanidines non hydrolysables dans l'eau et proanthocyanidines non hydrolysables dans l'acide). En incluant des mesures des fractions phénoliques, réactives et résiduelles, et de la lignine hydrolysable dans l'acide, ces méthodes analytiques constituent une amélioration par rapport aux analyses immédiates traditionnelles de la litière de feuilles. Il y avait des différences significatives entre les caractéristiques chimiques et les taux de décomposition de la litière des différentes espèces. Pour toutes les espèces combinées, le taux de décomposition pendant la première année (k) était significativement corrélé (P < 0,001) avec la valeur initiale de 30 des 36 variables chimiques testées dans cette étude. Les trois variables les plus fortement corrélées étaient les proanthocyanidines non hydrolysables dans l'acide, l'indice de lignocellulose et les résidus non hydrolysables dans l'acide (r = 0,83,-0,81 et-0,80 respectivement avec P < 0,0001 et n = 339). Aucune des variables chimiques de la litière n'était un prédicteur universel de la valeur de k pendant la première année pour chacune des 16 espèces étudiées bien que les composés phénoliques aient été les prédicteurs du taux de décomposition les plus souvent significatifs (P < 0,001).
One hundred-thirteen sites were established in perennial watercourses and sampled for 1 to 3 year... more One hundred-thirteen sites were established in perennial watercourses and sampled for 1 to 3 years between 2004 and 2006 to monitor for presence of Phytophthora ramorum throughout coastal central and northern California watersheds as well as portions of the Sierra Nevada mountain range (Murphy and others 2006). The majority of the monitored watersheds have limited or no P. ramorum at this time, but are near the epidemic range of P. ramorum and/or are considered high-risk for invasion by P. ramorum. Three currently infested watersheds in Sonoma and Mendocino counties were included as a baseline for successful recovery of P. ramorum. Rhododendron leaves were placed in fiberglass mesh bags, secured to streambanks, and floated on the water surface for 1 to 3 week intervals to bait for Phytophthora species (von Broembsen 2002; E. Hansen, personal communication 2003; P. Maloney and J. Davidson, personal communication 2003). The interval time was adjusted year round with the minimum time during periods of warm stream and air temperatures and longer intervals in cold conditions. Recovered symptomatic leaves were described and isolated onto Phytophthora-selective medium augmented with 25 mg/L hymexazol to inhibit growth of Pythium species (PARP-H). Experiments have shown minimal inhibition of P. ramorum and other Phytophthora species growth with this concentration of hymexazol (Fichtner and others 2006; Murphy, unpublished data; E. Hansen, personal communication 2004; S. Jeffers, personal communication 2005). Plates were incubated at 18°C for three weeks and checked microscopically twice weekly for growth of Phytophthora species; any Phytophthora-like organisms were transferred and further examined for identification.
Canadian Journal of Botany, 2002
Knowledge of the community structure of ectomycorrhizal fungi among successional forest age-class... more Knowledge of the community structure of ectomycorrhizal fungi among successional forest age-classes is critical for conserving fungal species diversity. Hypogeous and epigeous sporocarps were collected from three replicate stands in each of three forest age-classes (young, rotation-age, and old-growth) of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) dominated stands with mesic plant association groups. Over four fall and three spring seasons, 48 hypogeous and 215 epigeous species or species groups were collected from sample areas of 6300 and 43 700 m2, respectively. Cumulative richness of hypogeous and epigeous species was similar among age-classes but differed between seasons. Thirty-six percent of the species were unique to an age-class: 50 species to old-growth, 19 to rotation-age, and 25 to young stands. Seventeen species (eight hypogeous and nine epigeous) accounted for 79% of the total sporocarp biomass; two hypogeous species, Gautieria monticola Harkn., and Hysterangium...
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activi... more The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.
Phytophthora ramorum, an introduced invasive plant pathogen that causes sudden oak death, has kil... more Phytophthora ramorum, an introduced invasive plant pathogen that causes sudden oak death, has killed over a million tanoak, coast live oak, Shreve oak, and California black oak trees along the California coastal region from Monterey through Humboldt Counties. Most trees infected with P. ramorum will eventually die, including prized landscape trees. Be aware that P. ramorum can infect California bay laurel trees in advance of oak and tanoak infection and that the symptoms of bay laurel infection are not obvious. This publication provides advice to landowners, land managers, arborists, foresters, and the general public about protecting trees from sudden oak death in areas where trees are not currently infected by P. ramorum, but where it is suspected that the pathogen will infect trees in the future because infested areas are nearby. Such areas might include, for example, those at the outer edges of the known infested areas in California. Other publications, such as the UC IPM publication Sudden Oak Death (Swain and Alexander, 2010), outline measures you can take to care for trees in areas where the pathogen is already known to be present on oaks and tanoaks. To determine whether this information is appropriate to your situation, review the next section for the best ways to find out whether your trees are already infected or whether infected trees exist in your area.
Ecosphere, 2018
Many fire-maintained savannas and woodlands are suffering the effects of fire exclusion and the c... more Many fire-maintained savannas and woodlands are suffering the effects of fire exclusion and the concomitant invasion of fire-sensitive trees. In the Pacific West, woodlands dominated by either Oregon white oak (Quercus garryana) or California black oak (Quercus kelloggii) have transitioned from oak-dominated to conifer-dominated (primarily by the native Douglas-fir; Pseudotsuga menziesii) forest conditions with corresponding losses of plant and animal biodiversity. In spite of the prevalence of this transition, few studies have documented these temporal shifts and the consequences for oak woodland ecosystems. To better understand this process, we assessed tree species composition and age structure across 10 sites in northwestern California, USA. Species composition varied, but Douglas-fir, Oregon white oak, and California black oak had the greatest proportional dominance within and across sites. Across all ten sites, we cored 1747 trees from 10 different species. The majority (>80%) of oak stems dated between 1850 and 1910 (69% plots dated within a 40-yr period from 1860 to 1900). Less than 1% of the oak stems originated after 1960. Across the gradient of encroachment (i.e., oak to conifer dominance) at each site, the most common encroaching species was Douglas-fir, which primarily established after 1970 (73% across all sites). Douglasfir structural attributes were not associated with any of the abiotic factors evaluated, although non-significant trends show greater densities of Douglas-fir in oak stands at the northern end of the study region. Oak seedlings were common in all 10 study sites; however, we documented very few oak saplings regardless of the biophysical conditions. This study highlights that (1) the process and severity of encroachment is consistent across the region, resulting in substantial oak habitat loss and a shift toward conifer dominance and vegetative homogeneity in formerly diverse woodlands of northwestern California; and (2) Oregon white oak and California black oak woodlands require concerted management effort to ensure their survival and future persistence.
The effects of initial leaf litter chemistry of 16 common coniferous and deciduous hardwoods and ... more The effects of initial leaf litter chemistry of 16 common coniferous and deciduous hardwoods and shrubs on their annual decomposition patterns were studied on the H.J. Andrews Experimental Forest (Oregon). Leaf litters were characterized by their chemical qualities, which included measurement of elemental fractions (C, N, P, K, Ca, Mg), proximate fractions (non-polar, polar, acid-soluble extractives, acid-soluble lignin and acid-insoluble "Klason lignin"), and colorimetric characters (total phenolics, reactive polyphenolics, watersoluble carbohydrates, water-soluble condensed tannins, and water and acidinsoluble condensed tannins). These analytical methods improve upon traditional proximate analysis (Ryan et al. 1990) used to characterize leaf litters, through measurement of reactive and residual phenolic fractions and acid-soluble lignin. This paper discusses the procedures that are involved in improving proximate analysis and the link between leaf chemistry and one year decomposition rates. Significant differences were found in leaf litter qualities and in decomposition rates (expressed as decay) among species. The annual decay (k) for the leaf litter ranged from 0.27 to 1.02. The decay values for all species combined had highly significant (p 0.0001) correlations with 29 out of the 36 initial chemistry variables tested. The three highest correlations were with acidinsoluble condensed tannins (r= 0.83 p 0.0001 n 339), the lignocellulose index (r=-0.81 p0.0001, n=339) and acid-insoluble residue or 'Klason lignin" (r=-0.80 0.0001, n=339). A multiple regression model with all 16 species suggested that annual decomposition was best related to acid-insoluble condensed tannins, Klason lignin, water-insoluble condensed tannins, Ca and total phenolic:N (R2=0.84, p 0.0001, n= 339). Correlation and multiple linear regression models with each species' decay rate revealed that no one single initial chemical predictor could best explain the decomposition rates for each of the 16 species and that there were a wide range of chemical predictors related to the patterns of decomposition for each species.
Madroño, 2013
Non-native diseases of dominant tree species have diminished North American forest biodiversity, ... more Non-native diseases of dominant tree species have diminished North American forest biodiversity, structure, and ecosystem function over the last 150 years. Since the mid-1990s, coastal California forests have suffered extensive decline of the endemic overstory tree tanoak, Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S. H. Oh (Fagaceae), following the emergence of the exotic pathogen Phythophthora ramorum and the resulting disease sudden oak death. There are two central challenges to protecting tanoak: 1) the pathogen P. ramorum has multiple pathways of spread and is thus very difficult to eradicate, and 2) the low economic valuation of tanoak obscures the cultural and ecological importance of this species. However, both modeling and field studies have shown that pathogen-centric management and host-centric preventative treatments are effective methods to reduce rates of spread, local pathogen prevalence, and to increase protection of individual trees. These management strategies are not mutually exclusive, but we lack precise understanding of the timing and extent to apply each strategy in order to minimize disease and the subsequent accumulation of fuels, loss of obligate flora and fauna, or destruction of culturally important stands. Recent work identifying heritable disease resistance traits, ameliorative treatments that reduce pathogen populations, and silvicultural treatments that shift stand composition hold promise for increasing the resiliency of tanoak populations. We suggest distinct strategies for pathogen invaded and uninvaded areas, place these in the context of local management goals, and suggest a management strategy and associated research priorities to retain the biodiversity and cultural values associated with tanoak.
California Agriculture, 2011
Forty-two percent of California's forests and rangelands are privately owned (34 million acres). ... more Forty-two percent of California's forests and rangelands are privately owned (34 million acres). These lands provide important ecosystem services such as carbon sequestration, pollination and wildlife habitat, but little is known about the people who own and manage them. We surveyed forest and rangeland owners in California and found that these long-time landowners value their properties for their natural amenities and as a financial investment. Owners of large properties (500 or more acres) were significantly more likely to use their land for income production than owners of smaller properties, and they were also more likely to carry out or be interested in environmental improvements. Many forest and rangeland owners reported they had been previously approached to sell their land for development. Only about one-third had participated in conservation programs; few had conservation easements. This survey can help guide outreach and education efforts, and the development of information, policies, programs and financial incentives for landowners. A survey of forest and rangeland property owners in California found that the vast majority value their land for its natural beauty, and they voluntarily undertook environmental improvements and management practices. Above, an exurban development in coastal California.
Although there is no known cure or preventative on a landscape scale for sudden oak death (SOD), ... more Although there is no known cure or preventative on a landscape scale for sudden oak death (SOD), the plant disease caused by Phytophthora ramorum, a variety of management options has been tested with the goal of developing an integrated program of treatment for the pathogen. This paper presents a first attempt to gather together individual management trials into an overall decision-making tool for landowners contemplating treatments for the disease. It conceptualizes these treatments as a matrix that matches available strategies—some of which are still substantially untested—to management goals for properties or landscapes of varying sizes. The major goals we envision for landowners who are making decisions about P. ramorum treatments include 1) minimizing property impacts from the pathogen when it is already established on a property; 2) strategically protecting particular geographic locations, areas of high-quality oak and tanoak resources, or “islands” of old-growth oak and tanoa...
It is assumed that large numbers of dead and down tanoak in forests infested by Phytophthora ramo... more It is assumed that large numbers of dead and down tanoak in forests infested by Phytophthora ramorum contribute to increased fire hazard risk and fuel loading. We studied the impact of P. ramorum infestation on surface fuel loading, potential fire hazard, and potential fire behavior in Douglas-fir- (Pseudotsuga menziesii) dominated forest stands with a significant tanoak (Lithocarpus densiflorus) component in Sonoma, Mendocino, Humboldt, and Del Norte Counties in northern coastal California. We also tested the feasibility of using stands in which tanoaks were treated with herbicides as a proxy for stands that have been heavily impacted by P. ramorum over a long time period, especially in areas where stands have not been impacted by the pathogen over the desired timeframe. In each county, plots were established to assess surface fuel loadings in both P. ramorum-infested and uninfested forest stands. Plots were stratified by (1) whether tanoaks were killed by P. ramorum or by herbicid...
Reducing the Vulnerability of Buildings to Wildfire: Vegetation and Landscaping Guidance
Author(s): Valachovic, Yana; Quarles, Stephen L.; Swain, Steven V. | Abstract: A key element of r... more Author(s): Valachovic, Yana; Quarles, Stephen L.; Swain, Steven V. | Abstract: A key element of reducing homes’ vulnerability to wildfire is to implement a three-zone strategy whereby the most restrictive measures for preventing ignition apply to areas closest to the home.
In 2006, three forested sites infested with Phytophthora ramorum in Humboldt County, California w... more In 2006, three forested sites infested with Phytophthora ramorum in Humboldt County, California were subjected to different combinations of treatments designed to reduce inoculum and control spread. One treatment, consisting of removal of all California bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.) and tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh) trees, was applied at all three sites, and other treatments were applied as case studies at single sites. The sites were monitored for 6 years. Results to date suggest that the treatments that involved the cutting of California bay laurel and tanoak substantially reduced P. ramorum inoculum levels. However, in treatment areas where scattered California bay laurel trees were inadvertently missed because of a restricted time window for operations, a relatively minor component of residual California bay laurel trees may have become infected following treatment and/or harbored prior cryptic infection...
In the United States, water and soil baiting have been part of the U.S. Department of Agriculture... more In the United States, water and soil baiting have been part of the U.S. Department of Agriculture, Animal and Plant Health Inspection Service (USDA APHIS) Confirmed Nursery Protocol (CNP) to prevent the spread of Phytophthora ramorum from infected nursery stock since 2005. Additionally, the U.S. Department of Agriculture, Forest Service (USDA FS) has, since 2006, supported the national early detection stream baiting survey of forests and urban areas to monitor the potential spread of this pathogen from nurseries and other high-risk settings. These surveys have been conducted in cooperation with universities and state forestry agencies. As a result of these activities, P. ramorum has been detected in waterways at 10 sites in six states between 2006 and June 2009 (fig. 1). Below is a brief overview of these positive sites. Florida - In 2006 and 2007, P. ramorum was recovered from standing and flowing water inside, but not outside, a retail garden center where P. ramorum-positive plant...
Imported forest pests have changed North American forests and caused staggering monetary losses i... more Imported forest pests have changed North American forests and caused staggering monetary losses in the centuries since the country was founded. Since most problem-causing non-native pests are innocuous in their home ranges, where they have coevolved with their host trees, experts cannot predict which pathogens or insects will have lethal effect on other continents. Many non-native pests are unknown to science until they cause problems in their new homes. One common response to the threat of non-native insects and diseases in our forests is to appeal to science to develop technical means for management or eradication, yet common sense tells us that it would be more cost-effective and ecologically efficient to prevent pest introductions in the first place. The discipline of political ecology explores the ways in which many environmental issues that are usually presented as scientific or technical problems are actually policy issues that have been redirected into scientific discussion ...
Reducing CO 2 emissions by managing for sudden oak death...is it possible
Uploads
Papers by Yana Valachovic