Treesearch

Western pine beetle (Dendroctonus brevicomisLeConte) is a major cause of ponderosa pine (Pinus ponderosaDougl. ex. Laws.) mortality in western North America. Twenty-first century epidemics are among the largest in history and have affected hundreds of thousands of hectares. We synthesize literature on the chemical ecology of western pine beetle and on efforts to exploit our understanding of the western pine beetle-ponderosa pine system to reduce host tree losses. This literature dates back to the early 20th century and focuses on populations in California and Oregon, U.S., where western...

The 2012–2016 hotter drought in the Sierra Nevada, California, USA led to the mortality of millions of trees. This disruption to the disturbance regime is an example of how climate extremes can exacerbate current and future wildfire risks. In this study, we used data from an extensive network of forest plots across 13 different sites in the Sierra Nevada to characterize ground (i.e., duff) and surface fuels and their potential drivers shortly after the drought (2016–2018), but before snag (standing dead tree) fall associated with this massive tree mortality event occurred. Overall, we...

The long-term effects of harvesting on stand carbon (C) pools were assessed in a dry, interior pine-dominated forest at the Blacks Mountain Experimental Forest in northeastern California. Six 8-hectacre plots, established in 1938–1943, were treated as either an uncut control or a heavy-cut harvest (three-quarters of the stand volume removed). Response variables included C pools in overstory tree and shrub, coarse woody debris (CWD), forest floor, mineral soil (to 30 cm depth), cubicle brown root fragments of wood, fine roots, and ectomycorrhizal root tips. CWD was further classified as...

Outbreaks of several bark beetle species can develop rapidly in response to drought and may result in large transfers of carbon (C) stored in live trees to C stored in dead trees (10s of Tg C yr-1in the western U.S. alone), which over time will be released back to the atmosphere. The western pine beetle (WPB) outbreak incited by the 2012–2015 mega-drought in the Sierra Nevada, California, U.S., could portend more frequent and/or severe bark beetle outbreaks as the temperature warms and drought frequency and intensity increase in the future. However, changes in the frequency and/or severity...

Climate change is expected to lead to higher temperatures in the Mediterranean region of northern California in the Sierra Nevada. Dendroclimatic studies typically focus on large, old trees, but there relatively limited understanding on how climatic sensitivity can vary with trees of different size classes. We collected tree increment cores and compared radial growth responses of small (20.32 to ≤40.64 cm), medium (40.64 to ≤60.96 cm), and large (>60.96 cm) diameter mixed conifer species in the Sierra Nevada to different climate variables (temperature, precipitation, and climate moisture...

1. Bergmann's rule—which posits that larger animals live in colder areas—is thought to influence variation in body size within species across space and time, but evidence for this claim is mixed. 2. We used Bayesian hierarchical models to test four competing hypotheses for spatiotemporal variation in body size within 20 bat species across North America: (1) the heat conservation hypothesis, which posits that increased body size facilitates body heat conservation (and which is the traditional explanation for the mechanism underlying Bergmann's rule); (2) the heat mortality hypothesis, which...

Salvage logging using ground-based heavy equipment can impact soils and vegetation and lead to various effects that can increase or decrease post-fire runoff and erosion (removal of soil or sediment from its initial position). This document briefly outlines the current understanding of these effects and provides an overview of best management practices (BMPs) designed to mitigate the negative effects related to sediment delivery to streams and other aquatic resources. This document is based on the authors' knowledge and best available scientific information and is intended to supplement...

Tree allergenicity has been documented as a relevant ecosystem disservice, a tradeoff to the many co-benefits of urban trees. However, information on the allergenic tree dynamics in Neotropical urban environments is scarce. We used species-level Allergenic Potential Value (APV) and pollen-emission capacity as well as data on treestructure and diversity to explore the spatial dynamics of tree allergenicity in Bogota Colombia's public urban forest. We then statistically and spatially analyzed this data along with socioeconomic and vulnerability information to better understand tree allergenic...

Livestock grazing supports a considerable amount of economic activity across the United States. Federal grazing permits support numerous ranching operations by providing relatively low-cost grazing on federal lands. While grazing supports employment, labor income, and economic activity within a given state, the extent to which federal grazing permits play a role remains uncertain. In this paper we develop a method for estimating state-level economic contributions of livestock grazing for cattle grazing, as well as sheep and goat grazing, that is applicable to both the US Forest Service and...

We assessed attraction of pine engraver, Ips pini(Say) (Coleoptera: Curculionidae; Scolytinae), to pheromone-baited funnel traps treated with repellent semiochemicals in ponderosa pine, Pinus ponderosa var. scopulorumEngelm., forests in northern Arizona. Treatments included: 1) baited control (B, ipsdienol + lanierone), 2) 70 g of SPLAT Verb (a flowable, biodegradable formulation containing 10% verbenone, ISCA Technologies Inc., Riverside, CA, USA) + B, 3) 70 g of SPLAT Verb + (E)-2-hexen-1-ol+(Z)-2-hexen-1-ol + acetophenone + B, 4) 7.84-g verbenone pouch (Product #3413, Synergy Semiochemic...