Treesearch

Large wildfires are an increasing threat to the western U.S. In the 2017 fire season, extensive wildfires occurred across the Pacific Northwest (PNW). To evaluate public health impacts of wildfire smoke, we integrated numerical simulations and observations for regional fire events during August-September of 2017. A one-way coupled Weather Research and Forecasting and Community Multiscale Air Quality modeling system was used to simulate fire smoke transport and dispersion. To reduce modeling bias in fine particulate matter (PM2.5) and to optimize smoke exposure estimates, we integrated...

Wildfires can drastically alter belowground processes such as organic matter (OM) decomposition. We used wood stakes of two different tree species, trembling aspen (Populus tremuloides Michx.) and loblolly pine (Pinus taeda L.), placed at three soil locations (soil surface, forest floor-mineral soil interface, mineral soil), as an index of the long-term (5-year) effects of wildfire on OM decomposition in two forest stands after high-severity wildfire and in an unburned control. Wood stake mass loss was generally higher for aspen, especially in the mineral soil of burned plots, than in...

The objective of this study was to examine the relationship of dormancy break requirements to winter submergence effects on germination and viability in cherrybark, willow, and Nuttall oak acorns. Acorns were submerged in a greentree reservoir and received 0, 21, 42, 63, or 84 days of winter submergence, followed by 8 weeks of incubation in four alternating temperature regimes (15/6°, 20/10°, 25/15°, and 30/20° C). Submergence substituted for cold stratification requirements of cherrybark oak acorns, and dormancy break was achieved with 63 days of submergence. Although submergence exerted...

Foresters have long known that trees under stress from fire injury are vulnerable to bark beetle attacks. Rick Kelsey and Doug Westlind, researchers with the Pacific Northwest Research Station, have developed a new mechanistic model to explain how physiological changes cause heat stress in woody tissues exposed to sublethal fire temperatures and produce a chemical signal that attracts some bark beetles.When heat disrupts normal cell functions and energy production, ethanol is synthesized as a short-term survival strategy. If enough ethanol accumulates and is released to the atmosphere...

Group selection has been proposed as a complementary system to conventional, uneven-aged management in temperate hardwoods (i.e. single-tree selection) to counteract declines in overstory diversity and growing importance of shade-tolerant species caused largely by past management activities. Mixed results from experimental group selection harvests in eastern North America and growing interest in retention forestry have led some scientists and managers to apply ideas from retention forestry into group selection systems. The Yellow Birch Legacy-Tree Project is a group selection experiment...

New technologies may enhance management by enabling quantitative testing of assumptions of vegetation response to climate and management. State-and-transition simulation models can keep track of interactions that are too complicated for us to comprehend using only conceptual models. This tool takes conceptual state-and-transition models to the next level, fostering greater communication and dialogue with stakeholders. Based on the models and climate data used here, increased drought may enhance transitions between vegetative states. It is important to be as explicit and quantitative as...

Forest managers are increasingly focused on promoting or maintaining forest structural complexity, including the heterogeneity of forest structures within stands. However, many of the forest growth models commonly used by forest managers assume that stands are structurally homogeneous. Therefore, using these forest models to project the development of structurally complex stands may provide inaccurate results. We investigated the accuracy and precision of individual tree growth estimates from an individual tree growth model commonly used by forest managers (Central Rockies Variant of the...

Plant invasions can affect fuel characteristics, fire behavior, and fire regimes resulting in invasive plant-fire cycles and alternative, self-perpetuating states that can be difficult, if not impossible, to reverse. Concepts related to general resilience to disturbance and resistance to invasive plants provide the basis for managing landscapes to increase their capacity to reorganize and adjust following fire, while concepts related to spatial resilience provide the basis for managing landscapes to conserve resources and habitats and maintain connectivity. New, spatially explicit approache...

In Wisconsin, as in other states, management goals sometimes include restoration of historical forest conditions, which may prepare forests to be more compatible with future climates, disturbances such as drought and fire, and forest health threats. We quantified historical (1830-1866) composition and structure to develop historical reference conditions for restoration and documented changes based on current (2005-2009) forest surveys in Wisconsin. We provided structural metrics, functional group composition, and forest types for 186 ecological land types, and we also summarized trends in...

Podosphaera pannosa is the causal agent of powdery mildew on eucalypt in Brazil. This powdery mildew disease is important in nurseries causing leaf and shoot distortion, shoot discoloration and reduction in growth, which decreases mini‐cutting production. Improved RNA sequencing (RNA‐Seq) technologies have allowed increased information about the transcriptome of several pathogens and hosts, enabling a better understanding of their interaction at the gene level. For this study, we analysed the transcriptome of P. pannosa during leaf infection of Eucalyptus urophylla leaves using RNA‐Seq and...