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Heat and drought affect plant chemical defenses and thereby plant susceptibility to pests and pathogens. Monoterpenes are of particular importance for conifers as they play critical roles in defense against bark beetles. To date, work seeking to understand the impacts of heat and drought on monoterpenes has primarily focused on young potted seedlings, leaving it unclear how older age classes that are more vulnerable to bark beetles might respond to stress. Furthermore, we lack a clear picture of what carbon resources might be prioritized to support monoterpene synthesis under drought stress. To address this, we measured needle and woody tissue monoterpene concentrations and physiological variables simultaneously from mature piñon pines (Pinus edulis) from a unique temperature and drought manipulation field experiment. While heat had no effect on total monoterpene concentrations, trees under combined heat and drought stress exhibited ~ 85% and 35% increases in needle and woody tissue, respectively, over multiple years. Plant physiological variables like maximum photosynthesis each explained less than 10% of the variation in total monoterpenes for both tissue types while starch and glucose + fructose measured 1-month prior explained ~ 45% and 60% of the variation in woody tissue total monoterpene concentrations. Although total monoterpenes increased under combined stress, some key monoterpenes with known roles in bark beetle ecology decreased. These shifts may make trees more favorable for bark beetle attack rather than well defended, which one might conclude if only considering total monoterpene concentrations. Our results point to cumulative and synergistic effects of heat and drought that may reprioritize carbon allocation of specific non-structural carbohydrates toward defense.

91 I. 91 II. 92 III. 92 IV. 92 V. 94 VI. 96 96 References 96 SUMMARY: Recently, widespread piñon pine die‐off occurred in the southwestern United States. Here we synthesize observational studies of this event and compare findings to expected relationships with biotic and abiotic factors. Agreement exists on the occurrence of drought, presence of bark beetles and increased mortality of larger trees. However, studies disagree about the influences of stem density, elevation and other factors, perhaps related to study design, location and impact of extreme drought. Detailed information about bark beetles is seldom reported and their role is poorly understood. Our analysis reveals substantial limits to our knowledge regarding the processes that produce mortality patterns across space and time, indicating a poor ability to forecast mortality in response to expected increases in future droughts.

Extreme drought conditions accompanied by rising temperatures have characterized the American Southwest during the past decade, causing widespread tree mortality in piñon-juniper woodlands. Piñon pine (Pinus edulis Engelm.) mortality is linked primarily to outbreaks of the pinyon ips (Ips confusus (Leconte)) precipitated by drought conditions. Although we searched extensively, no biotic agent was identified as responsible for death in Juniperus L. spp. in this study; hence this mortality was due to direct drought stress. Here we examine the relationship between tree abundance and patterns of mortality in three size classes (seedling/sapling, pre-reproductive, reproductive) during the recent extended drought in three regions: southwest Colorado, northern New Mexico, and northern Arizona. Piñon mortality varied from 32% to 65%, and juniper mortality from 3% to 10% across the three sites. In all sites, the greatest piñon mortality was in the larger, presumably older, trees. Using logistic regression models, we examined the influence of tree density and basal area on bark beetle infestations (piñon) and direct drought impacts (juniper). In contrast to research carried out early in the drought cycle by other researchers in Arizona, we did not find evidence for greater mortality of piñon and juniper trees in increasingly high density or basal area conditions. We conclude that the severity of this regional drought has masked densitydependent patterns visible in less severe drought conditions. With climate projections for the American Southwest suggesting increases in aridity and rising temperatures, it is critical that we expand our understanding of stress responses expected in widespread piñon-juniper woodlands.

Bark beetles are among the most influential biotic agents in conifer forests, and forest management often focuses on bark beetle chemical communication for tree protection. Although acoustic communication occurs in many bark beetle species, we have yet to utilize acoustic communication for bark beetle control. Here, we describe the stridulatory organs and ‘stress’ chirps of the pinyon engraver, Ips confusus, a significant pest and mortality agent of pinyon pine in western North America. Only females possessed stridulatory organs and their stress chirps varied significantly in duration, pulses per chirp, and dominant frequency. We tested an array of acoustic-vibrational treatments into logs but were unable to disrupt male entry into logs or alter female–male interactions, female tunneling, and female oviposition. We found acoustic–vibrational treatments had little effect on I. confusus behavior and suggest further studies if acoustic methods are to be utilized for bark beetle control.

Widespread piñon (Pinus edulis) mortality occurred across the southwestern USA during 2002–2003 in response to drought and bark beetle infestations. Given the recent mortality and changes in regional climate over the past several decades, there is a keen interest in postmortality regeneration dynamics in piñon–juniper woodlands. Here, we examined piñon and Utah juniper (Juniperus osteosperma) recruitment at 30 sites across southwestern Colorado, USA that spanned a gradient of adult piñon mortality levels (10–100%) to understand current regeneration dynamics. Piñon and juniper recruitment was greater at sites with more tree and shrub cover. Piñon recruitment was more strongly facilitated than juniper recruitment by trees and shrubs. New (post-mortality) piñon recruitment was negatively affected by recent mortality. However, mortality had no effect on piñon advanced regeneration (juveniles established pre-mortality) and did not shift juvenile piñon dominance. Our results highlight the importance of shrubs and juniper trees for the facilitation of piñon establishment and survival. Regardless of adult piñon mortality levels, areas with low tree and shrub cover may become increasingly juniper dominated as a result of the few suitable microsites for piñon establishment and survival. In areas with high piñon mortality and high tree and shrub cover, our results suggest that piñon is regenerating via advanced regeneration.

The Oscura Mountains Colorado chipmunk (Neotamias quadrivittatus oscuraensis) is a rare subspecies of the Colorado chipmunk that is listed as threatened by the state of New Mexico, primarily because it is an endemic subspecies with a small, isolated habitat and the potential for continuing habitat loss. Knowledge about its ecology is limited, which has hindered the development of scientifically defensible management plans. Our goal was to better understand the ecological factors related to the distribution and habitat selection of this chipmunk. We deployed baited camera traps in the Oscura Mountains, New Mexico, USA, using an occupancy modeling framework to determine which ecological factors are associated with occupancy and detection probability. We collected microhabitat and landscape-level data for use as covariates in the occupancy models. We detected the Oscura Mountains chipmunk at 26 of the 137 survey sites. Occupancy probability was not influenced by the microhabitat characteristics measured and the final model contained only landscape-level covariates on occupancy. Probability of occupancy was positively associated with proximity to an escarpment, two-needle pinyon (Pinus edulis) woodland vegetation community type, and elevation. Detection probability was positively associated with the presence of mature two-needle pinyons at the site. Habitat loss is a major concern for this taxon, especially because climate change is expected to exacerbate threats to pinyon woodlands. Drought, wildfire, bark beetle (Ips confusus) outbreaks, and other diseases pose a large risk to conifer woodlands throughout the southwestern United States. Conserving the pinyon woodlands on the Oscura Mountains, particularly in areas near escarpments, will help maintain habitat that is important for the Oscura Mountains chipmunk.

Widespread mortality in the pinyon-juniper forest type is associated with several years of drought in the southwestern United States. A complex of drought, insects, and disease is responsible for pinyon mortality rates approaching 100% in some areas, while other areas have experienced little or no mortality. Implementation of the Forest Inventory and Analysis (FIA) annual inventory in several states coincided with the onset of elevated mortality rates. Adjunct inventories provided supplemental data on damaging agents. Preliminary analysis reveals the status and trends of mortality in pinyon-juniper woodlands.

Research Highlights: Forest pest outbreaks that cross jurisdictional boundaries pose particular challenges, since both ecological and social factors influence the effectiveness of management responses. This study found that difficulties emerge from the misalignment of management objectives and policies that deter collaboration. The sharing of resources and collaborative responses to outbreaks may improve management outcomes. Background and Objectives: This study examines if and how boundaries influence the effectiveness of forest pest management within the protected area-centered ecosystems of Rocky Mountain National Park and Grand Canyon National Park, USA. Materials and Methods: Using semi-structured interviews and a survey distributed to forest managers, we explored how partitioning affects pest management effectiveness and identified barriers to and strategies for managing outbreaks that cross boundaries. Results: Cross-boundary outbreaks are uniquely challenging due to federally mandated policies, agency mission misalignment, a lack of formal collaboration, and a lack of public support for timber management programs. Strategies that may improve outcomes include reevaluating problematic policies; ensuring messaging is consistent across agencies; and developing a preventative cross-boundary forest insect outbreak management team. Conclusions: Measures to increase collaboration in multi-jurisdictional landscapes will help managers prepare for future forest pest outbreaks, which are expected to increase in frequency with climate change.

During a severe drought, a large-scale outbreak of pinyon ips between 2002 and 2004 in the southwestern United States, resulted in over 3 million ac of damage to pinyon pine forests in the southwestern United States. Previous studies suggest that damage was most severe in stands that encroached in lower elevation ecosystems. To gain a regional perspective on the outbreak, we did a geographical analysis of ips damage in association with land cover and elevation. Our analysis indicates that the overall distribution of the ips damage mirrors the distribution of pinyon-juniper woodlands in the region, with more intense damage occurring at higher elevations in Utah and Arizona, where pinyon pines are more common and have likely become denser with time. Our results suggest during droughts even historical stands of pinyon pine are at risk of pinyon ips damage, not just stands at the ecological extreme.