About

We take an integrative approach to identifying mechanisms by which climate alters the tree metabolome, and in turn, species interactions and ecosystem function. We couple field and greenhouse studies and employ a range of physiological and chemical techniques to address process-based ecological questions across diverse forest systems.

Research topics

• Ecology
• Biology
• Environmental science
• Computer Science
• Geography
• Demography
• Soil science
• Environmental resource management
• Economics
• Natural resource economics
• Atmospheric sciences
• Geology

Selected publications

• Resin-based defenses in <i>Pinus edulis</i> are only reduced after long-term drought

  Tree Physiology · 2026-01-21 · 1 citations

  articleSenior author

  Constrained carbon allocation toward secondary metabolites involved in chemical defense is a common explanation for widespread drought-related beetle-kill in conifers-we challenge the generality of this explanation. While monitoring drought stress (ψpd), we tracked both carbon reserves (non-structural carbohydrates) and chemical defenses (terpenes, phenolics, resin flow) in mature Pinus edulis Englem. trees experiencing either short-term (3-year) or a 'legacy' long-term (13-year) throughfall exclusion treatments, plus a control. We also quantified the Δ14C-age of resin to measure past allocation to current defense. While 72% of trees in short-term throughfall exclusion plots died (attacked by bark beetles, Ips confusus LeConte), mortality patterns were unrelated to throughfall exclusion intensity and all 'legacy' trees survived. We thus assessed trees in four survivorship categories: control, 'legacy', surviving, and dying trees. We found concentrations of certain defense compounds (leaf phenolics, twig monoterpenes) increased with drought stress, particularly in dying trees. In the main stem, dying trees exhibited similar terpene concentrations (94%) and phenolic concentrations (139%) relative to control trees. Compared with control trees, only 'legacy' trees had reduced stem terpenes (-49%, P < 0.05) after a decade of drought. Δ14C-age of resin could be up to 10.2 ± 0.5 years old, where the oldest resin was exuded from trees with low sugar concentrations and more negative Ψpd. Our results suggest that drought imposes a weak constraint on carbon allocation to resin-based defense. Instead, we primarily found evidence of increased concentrations of terpene and phenolic compounds under drought, even in dying trees, and only observed reductions in resin-based defenses after 10+ years of drought. Δ14C-ages demonstrate limited resin turnover and/or synthesis of resin from old reserves, suggesting that long-term drought is required to reduce resin-based defenses. Persistent allocation coupled with past investments appears to preserve or enhance concentrations of resin-based defenses even under lethal drought stress in P. edulis.

  PublisherDOI

• Drought and methyl jasmonate deplete non-structural carbohydrates to similar levels but induce divergent terpene responses in <i>Pinus edulis</i> seedlings

  Tree Physiology · 2026-03-04

  articleSenior author

  Drought and herbivory are prevalent stressors that often interact to constrain forest regeneration. Drought-induced depletion of nonstructural carbohydrates (NSC) may impair seedling chemical defenses, increasing vulnerability to pests and pathogens. To investigate NSC thresholds influencing defense capacity, we quantified the effects of drought and simulated insect herbivory on NSC (starch, sucrose, glucose and fructose) and mono- and sesquiterpene (MST) defenses in 5-year-old piñon pine (Pinus edulis) seedlings. Seedlings were either well-watered or subjected to drought until stomatal closure before treatment with methyl jasmonate (MeJA) to simulate herbivory. Both drought and MeJA treatments individually reduced NSC content in needles and stems by 50%, with no further decrease observed under combined stressors. Regardless of stressor(s), NSC was depleted to ~0.5% and ~0.7% dry weight in needles and stems, respectively. While drought alone more than doubled MST concentrations in both tissues, total MST concentrations remained unchanged in response to MeJA, suggesting NSC was instead mobilized to support other unidentified metabolic processes. By demonstrating that NSC were depleted to similar lower limits across all stressors and combinations, this study suggests the existence of reserve thresholds below which seedling capacity to respond to subsequent stress may become constrained.

  PublisherDOI

• Spectral biology across scales in changing environments

  2025-02-18 · 3 citations

  preprintOpen accessSenior author

  Understanding ecosystem processes on our rapidly changing planet requires integration across spatial, temporal and biological scales. We propose that spectral biology, using tools that enable near- to far-range sensing by capturing the interaction of energy with matter across domains of the electromagnetic spectrum, will increasingly enable ecological insights across scales from cells to continents. Here, we focus on advances using spectroscopy in the visible to short-wave infrared, chlorophyll fluorescence-detecting systems, and optical laser scanning (light detection and ranging, LiDAR) to introduce the topic and special feature. Remote sensing using these tools, in conjunction with in situ measurements, can powerfully capture ecological and evolutionary processes in changing environments. These tools are amenable to capturing variation in life processes across biological scales that span physiological, evolutionary and macroecological hierarchies. We point out key areas of spectral biology with high potential to advance understanding and monitoring of ecological processes across scales—particularly at large spatial extents—in the face of rapid global change. These include: the detection of plant and ecosystem composition, diversity, structure and function as well as their relationships; detection of the causes and consequences of environmental stress, including disease and drought, for ecosystems; and detection of change through time in ecosystems over large spatial extents to discern variation in and mechanisms underlying their resistance, recovery and resilience in the face of disturbance. We discuss opportunities for spectral biology to discover previously unseen variation and novel processes and to prepare the field of ecology for novel computational tools on the horizon with vast new capabilities for monitoring the ecology of our changing planet.

  PublisherOA PDFDOI

• Spectral biology across scales in changing environments

  Ecology · 2025-07-01 · 6 citations

  reviewOpen accessSenior author

  Understanding ecosystem processes on our rapidly changing planet requires integration across spatial, temporal, and biological scales. We propose that spectral biology, using tools that enable near- to far-range sensing by capturing the interaction of energy with matter across domains of the electromagnetic spectrum, will increasingly enable ecological insights across scales from cells to continents. Here, we focus on advances using spectroscopy in the visible to short-wave infrared, chlorophyll fluorescence-detecting systems, and optical laser scanning (light detection and ranging, LiDAR) to introduce the topic and special feature. Remote sensing using these tools, in conjunction with in situ measurements, can powerfully capture ecological and evolutionary processes in changing environments. These tools are amenable to capturing variation in life processes across biological scales that span physiological, evolutionary, and macroecological hierarchies. We point out key areas of spectral biology with high potential to advance understanding and monitoring of ecological processes across scales-particularly at large spatial extents-in the face of rapid global change. These include: the detection of plant and ecosystem composition, diversity, structure, and function as well as their relationships; detection of the causes and consequences of environmental stress, including disease and drought, for ecosystems; and detection of change through time in ecosystems over large spatial extents to discern variation in and mechanisms underlying their resistance, recovery, and resilience in the face of disturbance. We discuss opportunities for spectral biology to discover previously unseen variation and novel processes and to prepare the field of ecology for novel computational tools on the horizon with vast new capabilities for monitoring the ecology of our changing planet.

  PublisherOA PDFDOI

• From beginning to end: the synecology of tree‐killing bark beetles, fungi, and trees

  Biological reviews/Biological reviews of the Cambridge Philosophical Society · 2025-10-06 · 3 citations

  articleOpen access

  Over a century of research has revealed an amazing complexity of behaviours and physiological adaptations that allow tiny bark beetles to overcome large trees, sometimes resulting in outbreaks that kill millions of trees. Turning a tree into a home and successfully raising offspring involves constant interactions among the beetles, the tree, its microbiome, and the beetles' associated microbes, all influenced by abiotic factors that can determine success or failure. While we have learned much about these systems, substantial knowledge gaps remain. This synthesis aims to clarify and integrate current understanding, identify gaps, challenge long-held assumptions, and address interpretative issues that impede progress toward a holistic understanding of these systems. We advocate for expanding perspectives using synecological approaches to understand these complex systems better. We encourage expanding research into how colonization by the bark beetle-fungi complex influences subsequent tree decay and forest carbon dynamics. An explicit goal is to provide a comprehensive resource for new researchers while encouraging them to question established hypotheses and to explore new avenues of enquiry.

  PublisherOA PDFDOI

• Author response for "Budworms, beetles and wildfire: Disturbance interactions influence the likelihood of insect‐caused disturbances at a subcontinental scale"

  2024-07-29

  peer-reviewSenior author
  PublisherDOI

• Applications of Defense Elicitors to Roots of Containerized Eastern White Pine (<i>Pinus strobus</i>) Stimulate Increased Defensive Enzyme Activities of Fine Roots

  Arboriculture & Urban Forestry · 2024-09-27

  articleOpen access

  Abstract The expansion of the use of induced resistance (IR) has been, and remains, an attractive prospect for the management of woody plants, but little research has occurred assessing the ability of elicitors to induce the root defenses of woody plants. Eastern white pine ( Pinus strobus ) was used as a model plant to assess IR elicitation. Containerized plants were treated with phosphite (Phi), chitosan, curdlan (a β-1,3-glucan polymer), or silicon (Si) on 2022 June 7. The soluble phenolic levels, tissue levels of major resin acids (abietic and neoabietic), as well as the activities of peroxidase (POX), chitinase (CHI), and β-1,3-glucanase (βGLU) of fine roots were compared across elicitor treatments and nontreated controls on June 10, June 14, and June 27. There were no changes post-treatment to soluble phenolics or resin acids at any sampling point, but chitosan treatment resulted in an increase in POX and CHI activities, while curdlan increased CHI activity on June 10. On June 14, curdlan-treated plants had significantly higher POX and CHI activities, while Phi-treated plants had significantly higher POX activity. By June 27, curdlan- and Phi-treated trees had significantly higher CHI activities. Our data suggest that chitosan, curdlan, and phosphite stimulate biochemical responses and potentially prime root systems to respond to subsequent stresses, but there appears to be variation between these elicitors regarding rapid versus longer lasting IR effects.

  PublisherOA PDFDOI

• Budworms, beetles and wildfire: Disturbance interactions influence the likelihood of insect‐caused disturbances at a subcontinental scale

  Journal of Ecology · 2024-09-19 · 13 citations

  articleSenior author

  Abstract Irruptive forest insects are a leading biotic disturbance across temperate and boreal forests. Outbreaks of forest insects are becoming more frequent and extensive due to anthropogenic drivers (e.g. climate and land‐use), perhaps increasing the likelihood that forests will experience multiple insect‐caused disturbances. Across the fire‐prone Douglas‐fir forests of western North America, recent outbreaks of the western spruce budworm and Douglas‐fir beetle have impacted large expanses of forests, with a higher degree of overlap than expected in some ecoregions. Outbreaks of both insects are positively related to host availability and exhibit density‐dependent population dynamics that are affected by climate and weather. Here, we leverage data from aerial detection surveys, estimates of host availability, climate and weather, and categorized fire severity to describe the spatial overlap between western spruce budworm and Douglas‐fir beetle and assess: (1) how climate and host availability influence the biogeography of outbreaks; (2) how weather incites outbreaks; and finally, (3) how prior disturbances (fire and biotic) affect the subsequent outbreak likelihood of western spruce budworm and Douglas‐fir beetle. Models demonstrate that western spruce budworm and Douglas‐fir beetle share similar predisposing drivers of outbreaks. Outbreaks of both insects were more likely to occur following warm weather, but only beetle outbreaks were more likely following drought. When controlling for differences in outbreak distribution and inciting factors, results indicate that both prior fire and interspecific disturbance altered the likelihood of subsequent insect‐caused disturbance. Specifically, Douglas‐fir beetle outbreaks were more likely to occur for several years following low severity fire, but less likely otherwise. Prior defoliation, especially longer duration defoliation, increased the likelihood of beetle outbreak within stands and across the landscape. On the contrary, western spruce budworm outbreaks were less likely to occur following fire, while prior beetle activity dampened budworm outbreak likelihood for several years, and then eventually increased outbreak likelihood. Synthesis : Biotic–biotic disturbance interactions have the potential to amplify the incidence of insect‐caused disturbance across subcontinental scales. Our findings highlight the need for future work on mechanistic linkages between biotic disturbance agents as well as the ramifications for forest trajectories and function.

  PublisherDOI

• Author response for "Budworms, beetles and wildfire: Disturbance interactions influence the likelihood of insect‐caused disturbances at a subcontinental scale"

  2024-02-06

  peer-reviewSenior author
  PublisherDOI

• Author response for "Budworms, beetles and wildfire: Disturbance interactions influence the likelihood of insect‐caused disturbances at a subcontinental scale"

  2024-05-21

  peer-reviewSenior author
  PublisherDOI

Recent grants

• Collaborative Research: How to live on a (carbon and water) budget: Tree investment in chemical defenses across a gradient of physiological drought stress

  NSF · $172k · 2021–2023

• Collaborative Research: How to live on a (carbon and water) budget: Tree investment in chemical defenses across a gradient of physiological drought stress

  NSF · $499k · 2018–2021

• NSF Postdoctoral Fellowship in Biology FY 2013

  NSF · $138k · 2013–2015

Frequent coauthors

• Paul C. Stoy

  University of Wisconsin–Madison

  53 shared

• Tobias Gerken

  34 shared

• José D. Fuentes

  33 shared

• Marcelo Chamecki

  University of California, Los Angeles

  33 shared

• Gilberto Fisch

  Universidade de Taubaté

  32 shared

• Rosa Maria Nascimento dos Santos

  30 shared

• Livia S. Freire

  30 shared

• Gabriel G. Katul

  Duke University

  28 shared

Labs

• Forest Chemical Ecology LabPI