Emerging infectious diseases represent a substantial threat to wildlife biodiversity in the 21st century. Not only is their prevalence increasing, their geographic range also is expanding and the number of host species they affect is rising.
Publishing of scientific findings is central to the scientific process, and it is traditional to consider findings ‘‘provisional’’ until accepted by a peer-reviewed journal. Until publication, communication of provisional findings beyond participants in the study is typically limited. This practice helps assure scientific integrity. However, a dilemma arises when a provisional finding has urgent societal consequences that may be exacerbated by delay. This dilemma may be particularly pronounced when a discovery concerns wildlife health, which could have implications for conservation, public health (i.e., zoonoses), or domestic animal health (e.g., avian influenza). A scientist may see a need for prepublication communication but consider such communication to be problematic. We suggest that common concerns about directed prepublication communication are generally misplaced. Our perspective comes from natural resources science and management, but we suspect that this situation could arise in any branch of science and that discussing these issues will help scientists who may not routinely work with public officials navigate an unfamiliar situation.
Logging debris has the potential to benefit forest regeneration by increasing resource availability, modifying microclimate, and altering plant community structure. To understand potential mechanisms driving these benefits, we initiated research at a forested site on the Olympic Peninsula, WA that contained the invasive, nonnative competitor, Scotch broom (Cytisus scoparius). Immediately after harvesting the stand of mature coast Douglas-fir (Pseudotsuga menziesii var. menziesii) in late 2011, two levels of logging debris retention were created on replicated plots: 18.9 and 9.0 Mg ha−1, with debris depths averaging 32 and 17 cm, respectively. Within each plot, three herbicide treatments (aminopyralid (A), triclopyr ester (T), and A+T) and a non-sprayed control were applied to split plots in August 2012. Douglas-fir seedlings were planted in early 2013, and microclimate and seedling performance were monitored through 2016. During the growing seasons of 2012–2014, soil water content was greater and soil temperature was lower under heavy debris than under light debris. Survival of planted Douglas-fir seedlings declined an average of 45 and 11 percentage points after intense summer droughts in 2015 and 2016, respectively, but it averaged 7–10 percentage points greater in heavy debris than in light debris during this period. Douglas-fir stem diameter growth was consistently greater in heavy debris than in light debris, with the exception of treatment A+T where diameter did not differ between debris treatments. A reciprocal regression model (R2 = 0.55) predicted that total stem volume of Douglas-fir increased from 19 to 84 dm3 ha−1 as Scotch broom cover decreased from 20% to 0% as a result of the logging debris and herbicide treatments. There were limited treatment effects on mineral soil chemical and physical properties, but forest floor mass and nutrient content were increased in the heavy debris treatment. Five years after forest harvesting (2016), logging debris mass in heavy debris differed little from that in light debris at study initiation, indicating a substantial reduction in fuels and the potential for severe wildfire. Results suggest that, on gravelly soils and possibly other droughty forest ecosystems in the Pacific Northwest, heavy debris will benefit planted Douglas-fir by improving growing conditions and by limiting abundance of nonnative competitors, such as Scotch broom.
Purpose of Review The continued, rapid development of novel molecular genetic tools is contributing to a better understanding of forest-associated fungi and their interactive roles within diverse forest ecosystems. This paper focuses on recent developments of DNA-based diagnostics/detection, phylogenetics, population genetics, genomics, and metagenomics tools that have been applied to forest-associated fungi to better understand their roles in forest ecosystems and provide key insights for managing forest health. Recent Findings With the advent of new molecular technologies, we can better understand the biology of forest fungi by examining their genetic code. By utilizing genomics, fungal pathogens’ biological functions can be deduced from its genomic content. Further, high-resolution marker systems allow the determination of a pathogen’s population genetics and genomics, which provides important insights into its global movement and genetic shifts in local pathogen populations. Such genetic information has diverse applications for forest management to improve forest health. Lastly, new technologies in metagenomics will enhance the abilities to detect, describe, and utilize the complex interactions among fungal pathogens/symbionts, host trees, and associated microbial communities to develop novel management strategies for forest ecosystems. Summary Continued development and applications of molecular genetic and genomic tools provide insights into the diverse roles of forest-associated fungi in forest ecosystems, but long-term, wide-scale research is needed to determine how ecological functions are influenced by complex ecological interactions among microbial communities, other forest ecosystem components, and the environment. Such approaches may foster a paradigm shift away from single microbial pathogens, decomposers, or symbionts interacting with a single host or substrate, and provide more holistic approaches toward understanding interactions among microbial communities that drive forest health processes.
Tree-killing bark beetles are major disturbance agents affecting coniferous forest ecosystems. The role of environmental conditions on driving beetle outbreaks is becoming increasingly important as global climatic change alters environmental factors, such as drought stress, that, in turn, govern tree resistance. Furthermore, dynamics between beetles and trees are highly nonlinear, due to complex aggregation behaviors exhibited by beetles attacking trees. Models have a role to play in helping unravel the effects of variable tree resistance and beetle aggregation on bark beetle outbreaks. In this article we develop a new mathematical model for bark beetle outbreaks using an analogy with epidemiological models. Because the model operates on several distinct time scales, singular perturbation methods are used to simplify the model. The result is a dynamical system that tracks populations of uninfested and infested trees. A limiting case of the model is a discontinuous function of state variables, leading to solutions in the Filippov sense. The model assumes an extensive seed-bank so that tree recruitment is possible even if trees go extinct. Two scenarios are considered for immigration of new beetles. The first is a single tree stand with beetles immigrating from outside while the second considers two forest stands with beetle dispersal between them. For the seed-bank driven recruitment rate, when beetle immigration is low, the forest stand recovers to a beetle-free state. At high beetle immigration rates beetle populations approach an endemic equilibrium state. At intermediate immigration rates, the model predicts bistability as the forest can be in either of the two equilibrium states: a healthy forest, or a forest with an endemic beetle population. The model bistability leads to hysteresis. Interactions between two stands show how a less resistant stand of trees may provide an initial toe-hold for the invasion, which later leads to a regional beetle outbreak in the resistant stand.
Puccinia psidii (Basidiomycota, Uredinales) is a biotrophic rust fungus that was first reported in Brazil from guava (Psidium guajava) in 1884 (Winter 1884) and later from nonnative eucalypt (Eucalyptus capitelata and Corymbia citriodora, syn. Eucalyptus citriodora; Joffily 1944). Considered to be of Neotropical origin, the rust has also been reported to infect diverse myrtaceous hosts elsewhere in South America, Central America, the Caribbean, Mexico, the United States (California, Florida, and Hawaii), Japan, Australia, China, and most recently South Africa and New Caledonia (Carnegie et al. 2010; Giblin 2013; Kawanishi et al. 2009; MacLachlan 1938; Marlatt and Kimbrough 1979; Mellano 2006; Pérez et al. 2011; Roux et al. 2013; Uchida et al. 2006; Zambino and Nolan 2011; Zhuang and Wei 2011). Given the rate at which the pathogen is spreading and its wide host range, the objectives of this study are to determine how much genetic diversity exists within populations across the species’ putative native range as well as areas of recent introduction, evaluate possible pathways of spread, and predict the geographic area that is climatically suitable for the species to determine areas at risk of invasion.
Armillaria mexicana (Agaricales, Physalacriaceae) is described as a new species based on morphology, DNA sequence data, and phylogenetic analyses. It clearly differs from previously reported Armillaria species in North, Central, and South America. It is characterized by the absence of fibulae in the basidioma, abundant cheilocystidia, and ellipsoidal, hyaline basidiospores that are apparently smooth under light microscope, but slightly to moderately rugulose under scanning electron microscope. It is differentiated from other Armillaria species by macromorphological characters, including annulus structure, pileus and stipe coloration, and other structures. DNA sequence data (nuc rDNA internal transcribed spacers [ITS1-5.8S-ITS2 = ITS], 28S D-domain, 3' end of 28S intergenic spacer 1, and translation elongation factor 1-α [TEF1]) show that A. mexicana sequences are quite distinct from sequences of analogous Armillaria species in GenBank. In addition, sequences of ITS of the A. mexicana ex-type culture reveal an ITS1 of 1299 bp and an ITS2 of 582 bp, the longest ITS regions reported thus far in fungi. Phylogenetic analysis based on TEF1 sequences place A. mexicana in a well-separated, monophyletic clade basal to the polyphyletic A. mellea complex.
We examined plant community organization over the first five growing seasons after clearcut harvesting with retention of two levels of logging debris (light and heavy) and application of four vegetation control treatments (non-sprayed control, aminopyralid (A), triclopyr (T), and A+T). Our study site was 44 km northwest of Olympia, WA., USA, and before forest harvesting it was dominated by Pseudotsuga menziesii. We used a randomized split plot experimental design replicated in 6 blocks (each debris-treatment main plot had four herbicide-treatment split plots). We estimated percent canopy cover by species before forest harvesting and in postharvest seasons 1–3 and 5 on 100m2 plots centered in each split plot. We analyzed species composition and diversity and report the response of 10 species groups and several major species to the treatments over five seasons. We used ANOVA to examine annual treatment effects on abundance of major species and species groups as well as ordination and graphical methods to examine succession. Abundance of ruderal species, especially exotics and graminoids, was lower but abundance of native woody shrubs and vines was higher in heavy debris than in light debris. The vines developed higher cover in heavy debris where they used debris as a scaffold to gain a competitive advantage over other species. Heavy debris controlled Cytisus scoparius better than the herbicide treatments. Triclopyr reduced woody dicot, vine and native herb covers, while aminopyralid reduced these groups and Cytisus scoparius, but aminopyralid had less effect on total canopy cover. The combination herbicide treatment reduced woody dicots, vines and Cytisus scoparius, and had the biggest impact on total canopy cover. By year 5 there was little difference in total canopy cover among the herbicide treatments; however, for some species, both debris and herbicide treatment effects were still apparent. The ordination indicated that, by the fifth season, the floristic characteristics distinguishing the debris treatments were still distinct, but not for the herbicide treatments. We conclude that heavy debris is a viable treatment alternative to prevent aggressive exotic species from competing with planted conifers and the native plant community on edaphically dry western Washington sites.