Treesearch

For more than a decade, the Rizzo lab and collaborators have monitored northern and central coastal California watersheds each spring and early summer for the presence of Phytophthora using submerged Rhododendron leaves as bait. This served as an early detection tool for the sudden oak death (SOD) pathogen, P. ramorum, but other species of Phytophthora were encountered and notable isolates occasionally saved; in recent years a more concerted effort was made to isolate species of Phytophthora other than ramorum. Twenty-three species were identified using a combination of morphological...

The Santa Clara Valley Water District (District) is a wholesale water supplier for 1.8 million people in Santa Clara County, California. Capital, water utility, and stream maintenance projects result in extensive, long-term mitigation requirements in riparian, wetland, and upland habitats throughout the county. In 2014, several restoration sites on the valley floor and in the upper watershed were found to be contaminated by Phytophthora spp. Subsequently, an extensive baseline study of restoration sites planted in the last 3 years revealed 31 different species of Phytophthora in 16 sites,...

In partnership with the California Native Nursery Network, the three agencies of the Golden Gate National Parks (National Park Service, Golden Gate National Parks Conservancy, and Presidio Trust) hosted the Symposium, “Responding to an Expanding Threat: Exotic Phytophthora Species in Native Plant Nurseries, Restoration Plantings, and Wildlands” in December of 2014. The symposium was intended to educate and inform the regional restoration and native plant nursery communities on recent findings and concerns of Phytophthora species that are being discovered in native plant nurseries and...

The prevalence of Phytophthora species in surface waters has earned increasing attention in the past decades, in great part as a result of “stream monitoring” programs for detection and monitoring of Phytophthora ramorum and other invasive species. The potential for Phytophthora to survive and reproduce in streams has significant implications for evaluating and managing the risk of spread of pathogenic species. Therefore, it is important to understand the ecology of both introduced and endemic species in aquatic environments. Leaf litter is a potential substrate for the persistence and...

Soilborne Phytophthora spp. can be important for initiating disease through movement of inoculum with surface water to roots or splashing onto foliage. Nursery beds infested with Phytophthora spp. can contaminate container plants set on them, causing disease year after year and posing a risk of additional spread. Persistent sources of soilborne inoculum are especially problematic for quarantine pathogens such as P. ramorum. Unfortunately, infested nursery beds are challenging to disinfest because of restrictions on the use of soil fumigants and the difficulty of accessing equipment for...

Water is a critical resource in dry forest and rangeland environments of western North America, largely determining the distribution of plant and animal species across a broad range of elevations and ecosystems. Water is also essential for human endeavors, directly affecting where and how human communities and local economies have developed. The Blue Mountains of northeast Oregon and southeast Washington are an important source of water for forest ecosystems and human uses. Surrounding communities rely on water from national forest lands in the Blue Mountains for drinking water, industrial...

In 2012, Phytophthora tentaculata was detected for the first time in North America on the roots and crowns of declining sticky monkey flower plants (Diplacus aurantiacus) in a Monterey County, CA native plant nursery. At the time, P. tentaculata was listed among the top five exotic Phytophthora species of concern to the US due to its potential economic and environmental impacts. In 2014, P. tentaculata was detected on toyon (Heteromeles arbutifolia) and again on sticky monkey flower plants that had been outplanted at a restoration site in CA. These plants originated from a different CA...

In the Blue Mountains, climate change is likely to have significant, long-term implications for freshwater resources, including riparian areas, wetlands (box 7.1), and groundwater-dependent ecosystems (GDEs, box 7.2). Climate change is expected to cause a transition from snow to rain, resulting in diminished snowpack and shifts in streamflow to earlier in the season (Leibowitz et al. 2014, Luce et al. 2012; see chapter 3). Additional effects include changes in extreme high- and low-flow events; alteration of groundwater recharge rates; changes in the fate and transport of nutrients;...

Fire is returning to many conifer-dominated forests where species composition and structure have been altered by fire exclusion. Ecological effects of these fires are influenced strongly by the degree of forest change during the fire-free period. Response of fire-adapted species assemblages to extended fire-free intervals is highly variable, even in communities with similar historical fire regimes. This variability in plant community response to fire exclusion is not well understood; however, ecological mechanisms such as individual species’ adaptations to disturbance or competition and...

Determining how changes in abiotic conditions influence community interactions is a fundamental challenge in ecology. Meeting this challenge is increasingly imperative in the Anthropocene where climate change and exotic species introductions alter abiotic context and biotic composition to reshuffle natural systems.