Treesearch

Rationale. Pine needles represent an important fuel source in coniferous forest systems in the western United States. During forest fires, they can be easily ignited and help sustain flame on the ground. Methodology. In this study, a comprehensive chemical analysis was conducted to examine oxygenated organic compounds (OOCs) present in PM2.5 (particles ≤ 2.5 μm in aerodynamic diameter) formed from burning dry and moist ponderosa pine (Pinus ponderosa) needles (PPN) in the presence and absence of fine woody debris (FWD). The effect of fuel moisture content (FMC), a key parameter that...

Assessing the effectiveness and measuring the performance of fuel treatments and other wildfire risk mitigation efforts are challenging endeavors. Perhaps the most complicated is quantifying avoided impacts. In this study, we show how probabilistic counterfactual analysis can help with performance evaluation. We borrow insights from the disaster risk mitigation and climate event attribution literature to illustrate a counterfactual framework and provide examples using ensemble wildfire simulations. Specifically, we reanalyze previously published fire simulation data from fire-prone...

Leptographium wageneri is a native fungal pathogen in western North America that causes black stain root disease (BSRD) of conifers. Three host-specialized varieties of this pathogen were previously described: L. wageneri var. wageneri on pinyon pines (Pinus monophylla and P. edulis); L. wageneri var. ponderosum, primarily on hard pines (e.g., P. ponderosa, P. jeffreyi); and L. wageneri var. pseudotsugae on Douglas-fir (Pseudotsuga menziesii). Morphological, physiological, and ecological differences among the three pathogen varieties have been previously determined; however, DNA-based...

Soils are the largest source of atmospheric nitrous oxide (N2O), a powerful greenhouse gas. Dry soils rarely harbor anoxic conditions to favor denitrification, the predominant N2O-producing process, yet, among the largest N2O emissions have been measured after wetting summer-dry desert soils, raising the question: Can denitrifiers endure extreme drought and produce N2O immediately after rainfall? Using isotopic and molecular approaches in a California desert,we found that denitrifiers produced N2O within 15 minutes of wetting dry soils (site preference = 12.8 ± 3.92 per mil, δ15Nbulk =...

White pine blister rust (WPBR) is caused by the non- native fungus, Cronartium ribicola, a devastating pathogen of North American five-needle pines. Over the past century and a quarter, this pathogen has proven to be one of the most damaging agents of five-needle white pines (Geils et al. 2010; Schoettle et al. 2022) and is the primary factor in the recent ESA listing of whitebark pine (Pinus albicaulis, WBP) as threatened in the USA. Whitebark pine is a high-elevation species of western mountain ecosystems that is highly susceptible to WPBR. Since its detection in the Rocky Mountains of...

Interspecific hybridization plays a key role in the evolution of novel fungal pathogens, and when it occurs between native and invasive species, can lead to potentially serious consequences. In this study, we examined the temporal and spatial distribution of a recently detected hybrid (Cronartium x flexili) of two tree pathogens, invasive to North America Cronartium ribicola and native Cronartium comandrae. In total, 726 and 1452 aecia from 178 Pinus contorta ssp. latifolia and 357 Pinus flexilis trees were collected from 26 sites in four national forests in 2019–2021. Using morphological...

The High-5 comprise a subset of a unique group of related white pine species in the subgenus Strobus that grow across the high mountains of western North America. They include whitebark pine (Pinus albicaulis), limber pine (P. flexilis), southwestern white pine (P. strobiformis), Rocky Mountain bristlecone pine (P. aristata), Great Basin bristlecone pine (P. longaeva), and foxtail pine (P. balfouriana) (Fig. 1). These species grow in small groups on ridges as well as components of extensive forest communities. They have a disproportionally large effect on ecosystem functioning and biodivers...

Researchers have debated the relative importance of environmental versus Indigenous effects on past fire regimes in eastern North America. Tree-ring fire-scar records (FSRs) provide local-resolution physical evidence of past fire, but few studies have spatially correlated fire frequency from FSRs with environmental and anthropogenic variables. No study has compared FSR locations to Native American settlement features in the eastern United States. We assess whether FSRs in the eastern US are located near regions of past Native American settlement. We also assess relationships between...

US federal land management agencies serve the American people and work to ensure that all Americans connect with and value wilderness. As a result, wilderness managers may prioritize diversity, equity, and inclusion (DEI), though may lack wilderness-specific tools and resources to foster commitments to DEI. As agencies and organizations turn to virtual resources to share information - what we refer to as toolboxes - questions remain about their utility and potential to impact DEI outcomes in wilderness. This article describes the process and results of five virtual focus group discussions...

America’s dominant narrative of the origin of a beloved wilderness often centers Aldo Leopold in a heroic fight at the turn of the century against rapid industrialization that occurred at the expense of nature. Wild spaces, so the story goes, needed preservation from and for the people, so that future generations would know what it means to be self-reliant in pristine nature far away from civilization (Nash 2014). These future generations could experience a re-creation of the ancient human connection to nature. In this story, wilderness is at once a safeguard for the environment and wild...