Treesearch

Phytophthora ramorum, causal agent of sudden oak death (SOD) and ramorum leaf blight, remains a persistent problem of regulatory concern within the horticultural industry. Damages to nurseries have been realized as a result of enforced quarantine and sanitation efforts designed to prevent the spread and establishment of this invasive pathogen. Additionally, the introduction of P. ramorum to heritage gardens provides a treatment challenge when the goal to prevent local spread conflicts with the preservation of plant collections. There is a need for the development for alternative treatments...

Soilborne inoculum (infested leaf debris which has become incorporated into the soil) may be an important contributor to the persistence of the sudden oak death pathogen Phytophthora ramorum in recurrently positive nurseries. To initiate new epidemics, soilborne inoculum must not only be able to survive over time, but also be capable of producing sporangia during times favorable to infection of plant material at the soil surface. To accompany field studies of the epidemiological risk of soilborne inoculum in nurseries, laboratory assays were performed investigating how incubation of...

Phytophthora ramorum causes stem and bole cankers (sudden oak death) and foliar and twig dieback (ramorum blight) of susceptible plants. To date, more than 100 tree, shrub and herbaceous hosts of P. ramorum have been identified. In March 2015, plant samples were submitted to the CDFA Plant Pest Diagnostics Lab from the Marin Municipal Water District for disease analysis. The samples were collected near Bolinas Ridge in Marin County, CA in a maritime chaparral-live oak woodland forest with a history of P. ramorum and P. cinnamomi. The collectors noticed a large amount of unusual die-back in...

Warming-induced range shifts along elevational and latitudinal gradients have been observed in several species from various taxa. The mobility and behavioral plasticity of large endothermic mammals, however, complicate the detection of climatic effects on their spatial distributions. Here, we analyzed 230,565 hunting locations of the four most abundant ungulate species in the European Alps: ibex, chamois, red deer, and roe deer. Year-to-year and inter-decadal range shifts toward higher elevations in Switzerland coincided with warmer, snow-free, and thus more favorable autumn conditions in...

The activity of extracellular phenol oxidases is believed to play a critical role in decomposition processes in peatlands. The water logged, acidic conditions, and recalcitrant litter from the peatland vegetation, lead to exceptionally high phenolics in the peat. In order to quantify the activity of oxidative enzymes involved in the modification and break down of phenolic compounds two types of assays are primarily utilized: L-DOPA and ABTS. This note focuses on the strengths and weaknesses of both approaches. Both assays involve a redox reaction and the resulting oxidized chromophore is...

Across the western United States, the three primary drivers of tree mortality and carbon balance are bark beetles, timber harvest, and wildfire. While these agents of forest change frequently overlap, uncertainty remains regarding their interactions and influence on specific subsequent fire effects such as change in canopy cover. Acquisition of pre- and post-fire Light Detection and Ranging (LiDAR) data on the 2012 Pole Creek Fire in central Oregon provided an opportunity to isolate and quantify fire effects coincident with specific agents of change. This study characterizes the influence...

Measuring post-fire effects at landscape scales is critical to an ecological understanding of wildfire effects. Predominantly this is accomplished with either multi-spectral remote sensing data or through ground-based field sampling plots.While these methods are important, field data is usually limited to opportunistic post-fire observations, and spectral data often lacks validation with specific variables of change. Additional uncertainty remains regarding how best to account for environmental variables influencing fire effects (e.g., weather) for which observational data cannot easily be...

The ability to rapidly estimate wind speed beneath a forest canopy or near the ground surface in any vegetation is critical to practical wildland fire behavior models. The common metric of this wind speed is the "mid-flame" wind speed, UMF. However, the existing approach for estimating UMF has some significant shortcomings. These include the assumptions that both the within-canopy wind speed and the canopy structure are uniform with depth (z) throughout the canopy and that the canopy roughness length (z0) and displacement height (d) are the same regardless of canopy structure and foliage...

Armillaria possesses several intriguing characteristics that have inspired wide interest in understanding phylogenetic relationships within and among species of this genus. Nuclear ribosomal DNA sequence–based analyses of Armillaria provide only limited information for phylogenetic studies among widely divergent taxa. More recent studies have shown that translation elongation factor 1-α (tef1) sequences are highly informative for phylogenetic analysis of Armillaria species within diverse global regions. This study used Neighbor-net and coalescence-based Bayesian analyses to examine...