Treesearch

Wildland fire smoke can severely degrade downwind air quality and impact responding firefighters and the public. Accurate and timely monitoring of particulate matter (PM) and gaseous pollutants around wildland fires are needed to support management activities like protecting responders and the public from the health and safety hazards of wildland fire smoke. This study systematically evaluates the performance of commercially available, non-regulatory PM and gas instruments/ sensors under controlled wildland fire smoke conditions. We assessed accuracy, precision, and linearity by comparing...

Leaf mass area (LMA) is a dominant trait quantifying tradeoffs between structure and physiology. LMA variations are driven by a combination of leaf density and morphology. LMA is widely used in ecosystem process models and in fire research to model live fuel moisture content (LFMC), a dominate predictor of wildland fire behavior. Despite its importance, LMA is often assumed as invariant both seasonally and between species. Here, we measured density, LMA, and foliar chemistry across 10 Intermountain USA conifer species and used these data to develop mechanistic models of foliar density and...

Managers of seasonally dry western North American conifer forests are tasked with increasing forest resilience to both wildfire and drought. Wildfire hazard reduction techniques, like prescribed fire, that reduce forest density may also lessen forest vulnerability to drought and enhance growth by reducing competition for water. However, fire may also come with costs, if fire-caused injuries impair growth and the maintenance of tree water balance. We examined whether fire-caused injuries and their physiological impacts limit the degree to which fire-induced reductions of competition improve...

Whitebark pine (Pinus albicaulis, WBP) is an important high-elevation conifer in the Western USA that was listed as ‘‘threatened’’ under the Endangered Species Act in 2023. Consequently, land managers are tasked with ensuring the longterm viability of WBP populations through conservation and restoration efforts. The effects of mountain pine beetle (Dendroctonus ponderosae, MPB) outbreaks on WBP dynamics are poorly understood, especially for smaller-diameter trees that typically escape attack due to their size, allowing for persistence in the understory through outbreak events. Here, we...

Fire has played a driving role in the speciation and evolution of the genus Pinus (pines) and continues to exert dominant influences on Pinus-dominated forests around the world. This chapter is divided into two major sections: fire ecology and fire ecophysiology. In the fire ecology section, we review fire-adapted traits of Pinus that allow persistence and recovery after fire, including how traits cluster to form fire syndromes. Fire regimes are described as an emergent property of fire syndromes and climate. In the fire ecophysiology section, we review the effects of fire on Pinus carbon...

The spatial patterns of fire effects and tree mortality have profound consequences for forest resilience. Costeffective, medium-resolution, and spatiotemporally extensive fire severity measurements are essential for informing post-fire restoration and improving our understanding of wildfires—from forest stands to continents and from days to decades. Remote sensing advancements have improved burn severity mapping, but methods vary in interpretability, scalability, generalizability, and alignment with field measurements. One meaningful metric of fire effects on forests is proportion basal...

To make strategic decisions about safety and resource allocation, managers must understand when prescribed burn windows of opportunity occur, how they vary throughout the year, and how to anticipate them. For two burn types—pile and broadcast—we characterize the temporal and spatial distributions of past “go-burn” days identified from a database of 15,468 burn permits from 2011 to 2024 in the Northern California Geographic Area Coordination Center’s region. We assess the mean temporal evolution of daily anomalies of local- and synoptic-scale environmental variables that occurred in the 2...

Burned area and wildfire damages in the western United States (WUS) have increased dramatically in recent decades. Wildfire frequency, however, has shown trends that vary by data set, region, and fire size. Using a comprehensive fire occurrence data set screened for reporting artifacts from 1992 to 2020, we show a significant downward trend in annual fire frequency in WUS, with a significant contribution from decreasing human ignitions. Human‐caused fires significantly declined in California and Arizona, but increased in Wyoming. The relationship between human‐caused fires and population...

The extent of alpine land cover influences the chemistry of streams draining mountain catchments and may determine how they respond to ecosystem change. During the first two decades of the 2000s, the Southern Rockies, USA, experienced both severe bark beetle infestation and significant decreases in atmospheric nitrogen (N) and sulfur (S) deposition. To evaluate the consequences of these events, we compared the chemistry of samples collected during 2004–2006 and 2017–2019 in streams draining 18 headwater catchments comprised of mixtures of forest and alpine land cover. Stream total dissolved...

Have you ever looked at a towering ponderosa pine forest and wondered how old the trees are? Were all the trees of a similar age, known as an “even-aged structure,” such as often results from a reforestation effort where all the seedlings were planted at the same time. Or were there a mixture of young and old trees? That sort of “multi-aged structure” in ponderosa pine forests is desirable as it can meet many of the goals of multi-use land management. A forest stand with different-aged trees can support timber production, livestock grazing, recreation opportunities, wildlife habitat, and...