After a more than a century of fighting to keep fire out of forests, reintroducing it is now an important management goal. Yet changes over the past century have left prescribed burning with a big job to do. Development, wildfire suppression, rising global temperatures, extended droughts, exotic species invasions, and longer fire seasons add complexity to using this practice.
Managers must consider how often, how intensely, and what time of year to burn; for insights they often look to how and when fires burned historically. However, attempting to mimic historical wildfires that burned in hot, dry conditions is risky. Burning in fall or spring when temperature and humidity are low reduces the risk of prescribed fires becoming uncontrollable, but does it have the intended effects? How do forest ecosystems that historically were adapted to fire respond when fire is reintroduced after so much time without it?
Forest Service researchers Becky Kerns and Michelle Day conducted a long-term experiment in the Malheur National Forest, Oregon, to assess how season and time between prescribed burns affect understory plant communities in ponderosa pine forests. They found that some native plants persisted and recovered from fire but didn’t respond vigorously, while invasive species tended to spread. These findings may help forest managers design more effective prescribed-fire treatments and avoid unintended consequences.
In interior Alaska’s 115 million acres of boreal forest, white and black spruce are the dominant tree species. Climate models suggest that the region is becoming warmer and drier, resulting in declining growth of black and white spruce, according to some researchers. These drier conditions also may lead to greater risk of stand-replacing wildfires, resulting in forests dominated by birch and aspen, which are early-successional tree species.
To compare long-term growth trends of the dominant coniferous and deciduous tree species, a team of researchers with the USDA Forest Service Pacific Northwest Research Station and the University of Alaska Anchorage analyzed tree cores collected from the Tanana Valley and measured tree-ring widths of these four tree species over the past 150 years. They also compared growth against monthly temperature and precipitation data to determine if there is a correlation between climate and growth.
The team found that white and black spruce have not experienced as rapid a growth decline as earlier studies suggested; instead, their annual growth remains near the long-term mean. Of the four species examined, aspen showed the greatest recent growth decline, likely reflecting a widespread insect outbreak. Among the climate variables that will affect the future growth of these species, summer rainfall was identified as a significant factor.
The spruce beetle, Dendroctonus rufipennis (Kirby), produces the antiaggregation pheromone 3-methylcyclohex-2-en- 1-one (MCH) (Rudinsky et al. 1974). MCH has reduced the numbers of spruce beetles attracted to infested logs and synthetic semiochemical lures or reduced colonization rates throughout the beetles range (Kline et al. 1974, Rudinsky et al. 1974, Furniss et al. 1976, Dyer and Hall 1977, Lindgren et al. 1989). MCH has not prevented the infestation of live trees (Werner and Holsten 1995), with one exception. MCH in a novel formulation incorporating a microinfusion pump prevented the infestation of live spruce in Alaska in an area with a low spruce beetle population (Holsten et al. 2003). The objective of this study was to test MCH using commercially available diffusion releasers for protecting live trees from spruce beetle infestation in an area with a high spruce beetle population in southern Utah.
Five lichen species were evaluated as element-content pollution bioindicators for a pilot study in Wisconsin and adjacent U.S. states, using data for 20 elements. Goodquality elemental data for aluminum, cobalt, chromium, copper, iron, nitrogen, and sulfur—mostly from nonspecialist U.S. Forest Service Forest Inventory and Analysis staff collections with extensively documented protocols—clearly indicated a site pollution load in the project area. The percentage of nearby land in forest was the strongest predictor for sample collection at study sites of the two most frequent species; such knowledge facilitates improved broad applications. Improved protocols and three lichen species were recommended for implementation as elemental bioindicators in the north-central United States; species were also recommended for three other Eastern U.S. regions. The three reccomended species are Evernia mesomorpha Nyl.; Flavoparmelia caperata (L.) Hale, and the combined Physcia aipolia (Ehrh. ex Humb.) Fürnr var. aipolia and P. stellaris (L.) Nyl.
Monitoring vegetation phenology is important for managers at several scales. Across decades, changes in the timing, pattern, and duration of significant life cycle events for plant groups can foreshadow shifts in species assemblages that can affect ecosystem services. In the shorter term, managers need phenological information to time activities such as grazing, ecological restoration plantings, biocontrol of pests, seed collection, and wildlife monitoring. However, tools to deliver timely seasonal development have been limited either spatially (data from a single tower or weather station, or on a single species, or both) or temporally (annually, quarterly, or monthly summaries). We developed another option called PhenoMap. This is a weekly assessment of land surface “greenness” across the continental United States that employs the Normalized Differential Vegetation Index (NDVI) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. Here we present the PhenoMap Web map and its validation by using 54 in situ PhenoCam camera sites representing six vegetation structure types and 31 different ecoregions. We found that PhenoMap effectively tracks phenology on grasslands, shrublands, deciduous broadleaf and mixed forests. Results for evergreen needleleaf sites were poor owing to the low green-up signal relative to the total amount of foliage detected by NDVI. Issues of extent and field of view were critical when assessing remotely sensed data with in situ oblique camera imagery.
The Arctic and boreal regions are warming more than twice as rapidly as the rest of the world. The timing of plants’ flowering and fruiting is changing, with implications for insects, wildlife, and people who rely on these resources for food and livelihoods in Alaska. Alaska’s boreal forest will undergo significant functional and structural changes within the next few decades that are unprecedented in the past 6,000 years. The Bonanza Creek Long-Term Ecological Research program is critical to Forest Service research because it is the only Forest Service outpost in the boreal forest, which is the biggest forest in the world. Pacific Northwest Research Station scientists are contributing groundbreaking climate research in Alaska, with global implications.
Armillaria species are key components of forest ecosystems throughout most regions of western North America. Their ecological roles range from beneficial saprobes to damaging root pathogens, and their impacts vary with environment and host. Under climate change, the impact of pathogenic species within these regions is predicted to increase (Kliejunas et al 2009), which could result in increased tree mortality, growth loss, and hazard trees that threaten public safety. In 2016, a collaborative project was initiated to survey of Armillaria spp. distributions in western Oregon, western Washington, and Alaska. Methods and preliminary results of the 2016 and 2017 (ongoing) field surveys/collections are described herein. Armillaria isolates derived from collaborative surveys are identified using DNA-based methods (e.g., translation elongation factor-1α gene sequence; tef1). DNA-based identification and 19 location-specific climatic variables are used to develop models to predict areas suitable for the occurrence of Armillaria spp. Preliminary predictions of geographic distributions of suitable habitat for Armillaria under current and predicted future climates are presented, based on Maximum entropy distribution models (MaxEnt). MaxEnt models are especially useful because of their ability to produce statistically robust models using limited occurrence-only data (see Phillips et al. 2006). This information will contribute to habitat-specific management strategies for reducing impacts and increasing the benefits of these ecologically important fungal species.
Armillaria root disease causes extensive damage to tree roots throughout the world, but efficacious management practices are lacking. However, soil interactions among Armillaria species, microbial communities, and trees may determine the impact of pathogenic Armillaria on the growth and survival of trees. Two species, A. solidipes (highly virulent) and A. altimontana (less virulent), frequently co-occur in forests of inland northwestern USA. Soil metagenomics and metatransciptomics may provide key insights into how interactions among soil microbial communities and root pathogens influence disease severity. If we can understand how soil microbial communities influence Armillaria root disease, then we can potentially develop novel management techniques that enhance biocontrol microbes and favor microbial communities that suppress disease caused by virulent Armillaria species.