Treesearch

Tree-killing bark beetles are major disturbance agents affecting coniferous forest ecosystems. The role of environmental conditions on driving beetle outbreaks is becoming increasingly important as global climatic change alters environmental factors, such as drought stress, that, in turn, govern tree resistance. Furthermore, dynamics between beetles and trees are highly nonlinear, due to complex aggregation behaviors exhibited by beetles attacking trees. Models have a role to play in helping unravel the effects of variable tree resistance and beetle aggregation on bark beetle outbreaks. In...

Recent changes in precipitation patterns and in the occurrence of extreme temperature and precipitation events have been documented in many forested regions of the United States (Ryan and Vose 2012). Changes in drought intensity and frequency have the potential to alter populations and impacts of tree-damaging forest insects and pathogens (Ayers and Lombardero 2000, Dale and others 2001, Weed and others 2013). Scientists, forest managers, and environmental policymakers need to better understand the role of drought in outbreaks of forest insects and diseases in order to anticipate the...

A one-dimensional vertical numerical model for coupled water flow and heat transport in soil and snow was modified to include all three phases of water: vapor, liquid, and ice. The top boundary condition in the model is driven by incoming precipitation and the surface energy balance. The model was applied to three different terrestrial systems: A warm desert bare lysimeter soil in Boulder City, NV; a cool mixed-grass rangeland soil near Laramie, WY; and a snow-dominated mountainous forest soil about 50 km west of Laramie, WY. Comparison of measured and calculated soil water contents with...

Black-backed woodpeckers (Picoides arcticus, [BBWO]) and American three-toed woodpeckers (P. dorsalis, [ATTW]) are uncommon inhabitants of conifer forests and are sympatric in some areas, including the Black Hills. Both species exhibit genetic characteristics associated with isolated populations, are species of special management concern, and for which data are lacking concerning populations and habitats. We developed resource selection models of forest vegetation within 500 m radius plots (78.5 ha) for BBWOs and ATTWs to provide forest managers with stand-level information to estimate how...

Whitebark pine plays a prominent role in high elevation ecosystems of the northern Rocky Mountains. It is an important food source for many birds and mammals as well as an essential component of watershed stabilization. Whitebark pine is vanishing from the landscape due to three main factors: white pine blister rust, mountain pine beetle outbreaks, and successional replacement by more shade-tolerant species. Between 1990 and 1994, 116 research plots were established to determine the health and status of whitebark pine populations in the Bob Marshall Wilderness Complex in Montana, USA. In...

We tested lethal trap trees and repellent semiochemicals as area treatments to protect host trees from spruce beetle (Dendroctonus rufipennis Kirby) attacks. Lethal trap tree treatments ("spray treatment") combined a spruce beetle bait with carbaryl treatment of the baited spruce. Repellent treatments ("spray-repellent”) combined a baited lethal trap tree within a 16-m grid of MCH (3-methylcyclohex-2-en-1-one) and two novel spruce beetle repellents. After beetle flight, we surveyed all trees within 50 m of plot center, stratified by 10-m radius subplots, and compared attack rates to those...

We review the West Indian species of Arachnocoris, a genus of spider-web dwelling kleptoparasitic nabids. We recognize five species: A. berytoides Uhler from Grenada, A. darlingtoni n. sp. from Hispaniola, A. karukerae Lopez-Moncet from Guadeloupe, A. portoricensis n. sp. from Puerto Rico, and A. trinitatis Bergroth from Trinidad. West Indian Arachnocoris antennal and profemoral color banding patterns are useful diagnostic characters and may have evolved to mimic their spider hosts, which are often island endemic spiders in the family Pholcidae. We provide a simplified and illustrated key...

Heavy disturbance-induced mortality can negatively impact forest biota, functions, and services by drastically altering the forest structures that create stable environmental conditions. Disturbance impacts on forest structure can be assessed using structural sustainability - the degree of balance between living and dead portions of a tree population’s size-class distribution - which is the basis of baseline mortality analysis. This analysis uses a conditionally calibrated reference level (i.e., baseline mortality) against which to detect significant mortality deviations without need for...

Recently, wildfires and prescribed burning have become more frequent in conifer forests of western North America. Most studies examining the impacts of insects on trees with post-fire injury have focused on contributions to tree mortality. Few studies have examined fire-caused injuries to estimate the probability of attack by insects. Scant data quantifying insect associations with one another, or with live and dead fire-injured trees, are available. We examined live and dead trees with varying levels of fire injury in wildfires in Colorado, Montana, Arizona and the Black Hills aiming to...

Applying biochar to forest sites can be problematic and costly because of the need to keep the forest floor as undisturbed as possible during and after harvest operations. The Missoula Technology and Development Center of the U.S. Forest Service, working with Rocky Mountain Research Station scientists, developed and tested a high-capacity biochar spreader that can be mounted on a log forwarder and used on skid trails and log landings to distribute either pelleted or bulk biochar. This spreader can be modified to carry a variety of payloads and adjusted to apply biochar at many different...