Treesearch

Prior to fire suppression and exclusion, wildfires and other disturbances (e.g., insects, disease, and weather) sustained ecosystem processes in many landscapes of the Western United States. However, wildfires have been increasing in size, frequency, and intensity in recent years (Kellogg and others 2008). Recognizing the value of wildfire, scientists and land managers now promote allowing non- human-caused fires to burn in these landscapes, hoping fire can recreate the historical distribution and mosaic of presettlement, burned forests.

Trees alter their use and allocation of nutrients in response to drought, and changes in soil nutrient cycling and trace gas flux (N2O and CH4) are observed when experimental drought is imposed on forests. In extreme droughts, trees are increasingly susceptible to attack by pests and pathogens, which can lead to major changes in nutrient flux to the soil. Extreme droughts often lead to more common and more intense forest fires, causing dramatic changes in the nutrient storage and loss from forest ecosystems. Changes in the future manifestation of drought will affect carbon uptake and...

Bark beetles (Coleoptera: Curculionidae, Scolytinae) cause widespread tree mortality in coniferous forests worldwide. Constitutive and induced host defenses are important factors in an individual tree’s ability to survive an attack and in bottom-up regulation of bark beetle population dynamics, yet quantifying defense levels is often difficult. For example, in Pinus spp., resin flow is important for resistance to bark beetles but is extremely variable among individuals and within a season. While resin is produced and stored in resin ducts, the specific resin duct metrics that best correlate...

Induced defense is a common plant strategy in response to herbivory. Although abiotic damage, such as physical wounding, pruning, and heating, can induce plant defense, the effect of such damage by large-scale abiotic disturbances on induced defenses has not been explored and could have important consequences for plant survival facing future biotic disturbances. Historically, low-severity wildfire was a widespread, frequent abiotic disturbance in many temperate coniferous forests. Native Dendroctonus and Ips bark beetles are also a common biotic disturbance agent in these forest types and...

Restoring degraded mesic-montane forests represents a major challenge in maintaining functioning ecosystems throughout the tropics. A key example of this lies in Hawai‘i, where restoring native koa (Acacia koa, A. Gray) forests are a top conservation and forestry priority because of the critical habitat and high-value timber products that they provide. Efforts to restore koa forests, however, are directly impeded by extensive, nonnative kikuyu grass (Pennisetum clandestinum Hochst. ex Chiov.) swards occupying deforested montane landscapes. In this study, we implemented a combination of...

We review past trading experiments and present 11 new experiments designed to show how the trading rate responds to alterations of the experimental procedure. In agreement with earlier studies, results show that if the trade decision is converted to one resembling a choice between goods the exchange asymmetry disappears, but otherwise the asymmetry is remarkably robust. Results also indicate that when trading is public herding can occur,which may have caused some of the more extreme examples of the exchange asymmetry,and that some of the lack of trade may result from preference indifference...

Phellinus noxius is an aggressive root rot pathogen affecting tropical and subtropical forests. Causing much damage in tropical Asia, Africa, Taiwan, Japan and the Pacific Islands, its wide host range encompasses more than 200 plant species representing 59 families (Ann et al. 2002). It can devastate agricultural plantations of tea, rubber, cocoa, avocados, and oil palm; tropical fruit trees such as longan, breadfruit, litchi, carambola, and loquat; timber trees including hoop pine (Araucaria), eucalypts, and mahogany (Swietenia); as well as many ornamental trees and woody shrubs. Also...

Armillaria species range from beneficial saprobes to damaging root pathogens, and their ecological roles and impacts vary with environment and host. Armillaria solidipes [pending vote to conserve A. ostoyae . (Redhead et al. 2011 )] is known as an aggressive pathogen of conifers and causes tree mortality and significant growth loss in Wyoming and throughout the world. Armillaria solidipes also seems to exist in a nonpathogenic state under certain conditions that vary depending on environment, host, and community (unpublished data). In this case, A. solidipes can be difficult to differentiat...

Corynespora cassiicola and Cercospora sp. have been identified as the most prevalent and destructive leaf-spot pathogens of garden hydrangea [Hydrangea macrophylla (Thunberg) Seringe] in the southeastern USA, but they are often difficult to accurately detect and distinguish because they often occur together in a disease complex with other pathogenic leaf-spot fungi and produce very similar symptoms. This study was conducted to provide diagnostic PCR primers for detecting and distinguishing Corynespora cassiicola and Cercospora sp. among other leaf-spot pathogens of garden hydrangea. Two...

Metagenomics has illuminated our understanding of how microbial communities influence health and disease. Researchers are beginning to characterize what constitutes healthy microbiota in terms of structure, function, and diversity in a variety of environments. Although investigation lags behind the more well-studied human microbiome, a growing body of research is using next-generation sequencing tools and advances in bioinformatics to explore how microbiota and constitutive microbiomes in soils, and plant tissues can affect crop and forest diseases (Damon et al. 2012, Bonito et al. 2014,...