Yana Valachovic

Landscape epidemiology and control of pathogens with cryptic and long-distance dispersal: Sudden oak death in northern Californian forests

Exotic pathogens and pests threaten ecosystem service, biodiversity, and crop security globally. If an invasive agent can disperse asymptomatically over long distances, multiple spatial and temporal scales interplay, making identification of effective strategies to regulate, monitor, and control disease extremely difficult. The management of outbreaks is also challenged by limited data on the actual area infested and the dynamics of spatial spread, due to financial, technological, or social constraints. We examine principles of landscape epidemiology important in designing policy to prevent or slow invasion by such organisms, and use Phytophthora ramorum, the cause of sudden oak death, to illustrate how shortfalls in their understanding can render management applications inappropriate. This pathogen has invaded forests in coastal California, USA, and an isolated but fast-growing epidemic focus in northern California (Humboldt County) has the potential for extensive spread. The risk of spread is enhanced by the pathogens generalist nature and survival. Additionally, the extent of cryptic infection is unknown due to limited surveying resources and access to private land. Here, we use an epidemiological model for transmission in heterogeneous landscapes and Bayesian Markov-chain-Monte-Carlo inference to estimate dispersal and life-cycle parameters of P. ramorum and forecast the distribution of infection and speed of the epidemic front in Humboldt County. We assess the viability of management options for containing the pathogens northern spread and local impacts. Implementing a stand-alone host-free “barrier” had limited efficacy due to long-distance dispersal, but combining curative with preventive treatments ahead of the front reduced local damage and contained spread. While the large size of this focus makes effective control expensive, early synchronous treatment in newly-identified disease foci should be more cost-effective. We show how the successful management of forest ecosystems depends on estimating the spatial scales of invasion and treatment of pathogens and pests with cryptic long-distance dispersal.

Biodiversity Conservation in the Face of Dramatic Forest Disease: An Integrated Conservation Strategy for Tanoak (Notholithocarpus densiflorus) Threatened by Sudden Oak Death

Abstract 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.

Proceedings of the Redwood Region Forest Science Symposium: What does the future hold?

Policies and strategies that guide use and management of lands in the coastal ecoregion are dependent on objective scientific information. In recent years attention to this region has increased. Correspondingly, there has been much new information collected. Efforts such as the Caspar Creek Watershed Conference and the Scientific Basis for the Prediction of Cumulative Watershed Effects illustrate both the great interest and effort that is devoted to collecting and using scientific information to support resource and land management in this region. Each year the array of decisions that affects lands and natural resources in the redwood region carry more weight; evidence the recent interest in TMDLs, watershed assessment and fish and wildlife recovery efforts. How do we, therefore, promote the development and communication of scientific findings to inform management and policy decisions? No single meeting or institution is capable of providing thorough coverage of current scientific findings and insights. It is the intent of the organizing committee to provide a sampling of current scientific work, to enable access to more detail and other sources of information, and to put these findings into a context where such information can be synthesized and interpreted for applications in land and resource management. This symposium is intended to promote the dissemination of scientific evidence to managers, policymakers, other scientists and interested public, and, in turn, to inform policy decisions. Thus, the presentations will range from the discussion of recently gathered scientific knowledge to the integration of that knowledge into planning and management processes and tools. We support the many other efforts intended to achieve these and similar goals and acknowledge the need to coordinate all such efforts.

Forest Stewardship Series 6: Forest Vegetation Management

Author(s): Nunamaker, Claralynn; Valachovic, Yana | Abstract: Part 6 of the 24-part Forest Stewardship Series. The Forest Stewardship Series is a 24-part free online publication that provides owners of California forestland with a comprehensive source of information pertinent to the management and enjoyment of their lands. This information will help you formulate and implement strategies for achieving your personal goals as a landowner. The series provides an introduction to the lifelong study of forest stewardship that is part of owning forest property.

Forest Stewardship Series 18: Stewardship Objectives and Planning

Author(s): Litman, Laurie; Valachovic, Yana | Abstract: Part 18 of the 24-part Forest Stewardship Series. The Forest Stewardship Series is a 24-part free online publication that provides owners of California forestland with a comprehensive source of information pertinent to the management and enjoyment of their lands. This information will help you formulate and implement strategies for achieving your personal goals as a landowner. The series provides an introduction to the lifelong study of forest stewardship that is part of owning forest property.