About

Leander Anderegg is an Assistant Professor in the Ecology, Evolution, and Marine Biology department at UC Santa Barbara. He grew up in rural Colorado and developed an early interest in spending time in the woods. He earned a BA in Human Biology from Stanford University in 2011, where he conducted honors research on the water use of trembling aspen trees. He then studied plant ecology with Janneke Hille Ris Lambers at the University of Washington, receiving a PhD in Biology in 2017. His dissertation focused on within-species physiological variation and species geographic range constraints. Before joining UCSB, Anderegg spent two years as an NSF Biological Collections postdoctoral fellow and two years as a NOAA Climate and Global Change fellow, working with Todd Dawson at UC Berkeley and Joe Berry at the Carnegie Institution for Science. His research aims to scale up the physiological responses of plants to biotic and abiotic stress to explain population, community, and biogeographic processes. He seeks to understand how plants respond physiologically to climatic, biotic, and anthropogenic stresses to forecast future ecosystem structure and function. His work combines plant physiology and ecology to explain processes such as forest mortality, tree biogeography, and global photosynthesis, focusing on how plants cope with stress and the biophysical and evolutionary constraints that define plant stress response strategies.

Research topics

• Biology
• Ecology
• Computer Science
• Geology
• Environmental science
• Psychology
• Geography
• Physical geography
• Climatology

Selected publications

• Complex trajectories of tree growth in the southwestern United States after severe drought

  Ecosphere · 2026-03-01

  articleOpen access

  Abstract Climate change driven extreme droughts have major impacts on forest ecosystems, including large‐scale mortality and reduced primary production, which feedback to affect the global carbon cycle. The long‐term impacts of extreme drought events on forest mortality, ecosystem responses, and recovery/post‐drought trajectories are poorly understood. In this study, we combine annual tree ring widths of five major species occurring in the southwestern United States and data obtained from long‐term forest inventory and monitoring plots to study the effect of an extreme drought event in 2002 on subsequent tree growth. We quantified the extent to which trees that survived the drought had increased growth due to potential increases in resources from reduced stand density or reduced growth due to lingering impacts of drought stress. We found diverse patterns of post‐drought growth trajectories across species, with drastic increases in growth in some species such as trembling aspen ( Populus tremuloides ) and clear growth suppression in other species such as ponderosa pine ( Pinus ponderosa ), reflecting notable drought legacy effects. Total basal area was the best predictor of post‐drought growth responses, though the regression effect (positive or negative) varied by species; for example, ponderosa pine showed less growth than predicted in higher density stands while spruce had greater growth than expected in the higher density stands. Climatic water deficit and stand age also emerged as important drivers of post‐drought growth trajectories for multiple species. The results of this study can help to elucidate how different forest types in the southwestern United States will respond to future drought events and the ramifications for carbon cycling in this region.

  PublisherDOI

• Do stomatal traits modulate leaf microbiome assembly?

  New Phytologist · 2026-01-15

  article

  Elucidating the factors controlling plant microbiome assembly is a major research goal in plant biology given a growing awareness of microbial community contributions to host plant health and fitness. While stomata have long been recognized to influence pathogen colonization, less is known about whether or how stomatal traits regulate diverse communities of nonpathogenic microbes that make up the majority of the leaf microbiome. In this Viewpoint, we propose that stomata are a primary filter by which plants influence the assembly of leaf-associated microbial communities. We discuss three nonmutually exclusive hypotheses for how stomatal traits influence leaf microbes, including preliminary support for each based on published studies of foliar fungi and bacteria. The stomatal density hypothesis argues that a greater density of pores increases the rate of microbial entry into the leaf, while the stomatal function hypothesis posits that the duration and speed of stomatal opening and closing regulate microbial access into the leaf. The stomatal covariation hypothesis recognizes that many other leaf traits covary with stomatal traits and thus could contribute to observed relationships between stomatal traits and leaf microbiome structure. Finally, we propose research priorities to improve our understanding of stomatal control over leaf microbiome assembly.

  PublisherDOI

• Unlocking ecological insights from sub‐seasonal visible‐to‐shortwave infrared imaging spectroscopy: The <scp>SHIFT</scp> campaign

  Ecosphere · 2025-03-01 · 11 citations

  articleOpen access

  Abstract We stand at the threshold of a transformative era in Earth observation, marked by space‐borne visible‐to‐shortwave infrared (VSWIR) imaging spectrometers that promise consistent global observations of ecosystem function, phenology, and inter‐ and intra‐annual change. However, the full value of repeat spectroscopy, the information embedded within different temporal scales, and the reliability of existing algorithms across diverse ecosystem types and vegetation phenophases have remained elusive due to the absence of suitable sub‐seasonal spectroscopy data. In response, the Surface Biology and Geology (SBG) High‐Frequency Time Series (SHIFT) campaign was initiated during late February 2022 in Santa Barbara County, California. SHIFT, designed to support NASA's SBG mission, addressed mission scoping, scientific advancement, applications development, and community building. This ambitious endeavor included weekly Airborne Visible InfraRed Imaging Spectrometer‐Next Generation (AVIRIS‐NG) imagery acquisitions for 13 weeks (spanning February 24 to May 29, 2022), accompanied by coordinated terrestrial vegetation and coastal aquatic data collection. We describe the rich datasets collected and illustrate how the complex sub‐seasonal patterns of change can be linked to biological science and applications, surpassing insights from multispectral observations. Leveraging open‐source processing methods and cloud‐based analysis tools, the SHIFT campaign showcases the readiness of the scientific community to harness ecological insights from remotely sensed hyperspectral time series. We provide an overview of SHIFT's goals, data collections, preliminary results, and the collaborative efforts of early career scientists committed to unlocking the transformative potential of high‐frequency time series data from space‐borne VSWIR imaging spectrometers.

  PublisherDOI

• The Unstable Relationship Between Drought Status and Leaf Water Content Complicates the Remote Sensing of Tree Drought Stress

  Global Change Biology · 2025-04-01 · 6 citations

  articleOpen accessSenior author

  Remote sensing holds promise for ecosystem-level monitoring of plant drought stress but is limited by uncertain linkages between physiological stress and remotely sensed metrics of water content. Here, we investigate the stability of relationships between water potential (Ψ) and water content (measured in situ and via repeat airborne VSWIR imaging) over diel, seasonal, and spatial variation in two xeric oak tree species. We also compare these field-based relationships with ones established in laboratory settings that might be used as calibration. Due to confounding physiological processes related to growth, both in situ and remotely sensed metrics lacked consistent relationships with stress when measured across space or through time. Relationships between water content and physiological drought stress measured over the growing season were stronger and more closely related to established laboratory-based drydown methods than those measured across space (i.e., between wet trees and dry trees). These results provide insight into the utility of "space for time" approaches in remote sensing and demonstrate both important limitations and the potential power of high temporal resolution remote sensing for detecting drought stress.

  PublisherOA PDFDOI

• Contrasting pathways to tree longevity in gymnosperms and angiosperms

  Nature Communications · 2025-12-19 · 3 citations

  articleOpen access

  Tree longevity is thought to increase in growth-limiting, adverse environments, but a quantitative assessment of drivers of global variation in tree longevity is lacking. We assemble a global database of maximum longevity for 739 tree species and analyse associations between longevity and climate, soil, and species' functional traits. Our results show two primary pathways towards long lifespans. The first is slow growth in resource-limited environments, consistent with the "adversity begets longevity" paradigm. The second pathway is through relief from abiotic constraints in productive environments. Despite notable exceptions, long-lived gymnosperms tend to follow the first path through slow growth in cold environments, whereas long-lived angiosperms tend to follow the second ("productivity") path reaching maximum longevity generally in humid environments. For angiosperms, we identify two mechanisms for increased longevity under humid conditions. First, higher water availability increases species' maximum tree height which is associated with greater longevities. Secondly, greater water availability increases stand density and inter-tree competition, limiting growth which may increase tree lifespan. The documented differences between gymnosperm and angiosperm longevity are likely rooted in intrinsic differences in hydraulic architecture that provide fitness advantages for gymnosperms under high abiotic stress, and for angiosperms under increased productivity or competition.

  PublisherOA PDFDOI

• Stomatal traits covary with leaf mycobiome diversity and composition

  New Phytologist · 2025-11-24 · 1 citations

  article

  The scope of plant control over its microbiome is a central question in evolutionary biology and agriculture. Leaf traits are known to shape pathogen colonization and disease development, but their impact on the broader community of largely non-pathogenic fungi that colonize plant leaves remains an open question. We used reciprocal common gardens of the model tree, Populus trichocarpa (black cottonwood), to examine relationships between leaf traits and the leaf mycobiome in two strongly contrasting environments. We measured six leaf traits (stomatal length, stomatal density, carbon-to-nitrogen ratio, leaf thickness, leaf dry matter content, and specific leaf area) and used fungal marker gene sequencing to characterize leaf fungal communities for 57 tree genotypes replicated in one mesic and one xeric common garden (809 trees). Several leaf traits covaried with the leaf mycobiome, yet one relationship was paramount: plant genotypes with longer, sparser leaf stomata hosted a greater richness and diversity of more similar fungal species compared to plant genotypes with shorter, denser leaf stomata. These relationships, while modulated by the environment plants were sourced from and grown in, suggest that stomatal traits may be a general mechanism through which plants and the leaf mycobiome influence one another.

  PublisherDOI

• Mapping Tree Hydraulics and Assemblages at Continental Scale

  2025-03-15

  preprintOpen access

  Plant hydraulic traits are critical in regulating plant&amp;#8211;water interactions and essential for understanding vegetation responses to environmental stress. Building on our earlier methodology for mapping global plant functional traits, we now incorporate a newly-available dataset of hydraulic traits for 55,779 tree species. This integrated framework leverages remotely sensed imagery, crowdsourced biodiversity data, and trait databases to estimate and map key hydraulic parameters, including maximum stomatal conductance (gsMAX), xylem pressure at 50% and 88% conductance loss (P50, P88), and photosynthetic water use efficiency (WUE).The tree trait data underlying our study accounts for the large phylogenetic signals inherent in these hydraulic traits by leveraging phylogenetically-informed machine learning models and novel trait imputation methods. These enhanced predictions of hydraulic traits are subsequently integrated into our trait-mapping workflow, which has previously demonstrated high accuracy (r &gt; 0.5; rME &lt; 6%; rRMSE &lt; 11%) for leaf-level traits at a 1 km spatial resolution. While the hydraulic trait maps have not yet been validated due to a lack of independent validation data, the observed patterns are consistent with a meta-analysis based on recent literature.We also capture the full distribution of hydraulic traits (standard deviation, skewness, and kurtosis) at the grid-cell level to reflect the non-Gaussian variability of community-level traits.&amp;#160; This added detail helps elucidate the ecological strategies of species assemblages and refines our understanding of ecosystem vulnerability to climate extremes. Overall, this work offers a new avenue for improving global ecosystem models and Earth system simulations by providing spatially explicit community-level hydraulic trait estimates at large scales. Our results highlight the importance of merging global remote sensing data with state-of-the-art trait imputation and phylogenetic information to advance research on plant functioning and ecosystem dynamics.

  PublisherDOI

• Towards predicting flammability of Sierra Nevada mixed conifer forests: drought stress and fuel moisture are strongly linked in angiosperms but decoupled in gymnosperms

  Research Square · 2025-06-27

  preprintOpen access
  PublisherOA PDFDOI

• Correction: A global dataset of tree hydraulic and structural traits imputed from phylogenetic relationships

  Scientific Data · 2025-06-05

  erratumOpen accessSenior author

  The published analysis of Specific Leaf Area (SLA) was errantly based a Newick tree file that included only a subset of all available tree species with SLA data within the TRY database.Correcting the dataset to include all presently available SLA records in TRY provides a very slight improvement to the imputation accuracy of SLA values.This correction updates Figs. 1, 2, 3, 5, 7, 8, 9 as well as Tables 1 and2.This correction also resolves a typo concerning the number of species included in the Water Use Efficiency analysis.

  PublisherOA PDFDOI

• Betting on rains that do not come: Monsoon failure and leaf area overshoot relate to increased tree mortality from drought

  Functional Ecology · 2025-04-30 · 4 citations

  articleOpen access

  Abstract Structural overshoots, where biomass is overallocated to tree leaf area compared to sapwood area, could result in lethal stress during droughts. Climate change may alter climatic cues that drive leaf area production, such as temperature and precipitation, as well as seasonal dynamics that underlie summer rainfall due to the North American Monsoon (NAM). Combined, this could lead to temporal mismatches between leaf area‐driven water demand and availability, and increased drought‐induced mortality events. We used leaf area to sapwood area ratios to investigate the prevalence of overshoots and whether overshoots increase drought‐induced mortality. We measured populations of aspen spanning the northern transition zone of the NAM during and following severe droughts. We observed increased overshoots and drought‐induced mortality in southern latitude populations that rely more on summer monsoon rainfall. Changes in convective activity from low snowpack the preceding winter may be a climatic driver of heightened summer monsoon rainfall in the region and therefore may also trigger increased production of leaf area during wetter summers. Our results suggest that an overshoot of leaf area to sapwood area (A L :A S ) ratios is associated with drought‐induced tree mortality and highlight that climate‐change driven alterations to the NAM could have major consequences for tree species' acclimation to environmental change. Read the free Plain Language Summary for this article on the Journal blog.

  PublisherOA PDFDOI

Recent grants

• NSF Postdoctoral Fellowship in Biology FY 2017: Reconstructing CO2 fertilization with herbaria

  NSF · $138k · 2017–2021

• RAPID: Mapping drought stress and hydraulic refugia with repeat hyperspectral data

  NSF · $188k · 2022–2024

Frequent coauthors

• William R. L. Anderegg

  University of Utah

  41 shared

• Anna T. Trugman

  University of California, Santa Barbara

  25 shared

• Todd E. Dawson

  University of California, Berkeley

  20 shared

• Joseph A. Berry

  Carnegie Institution for Science

  19 shared

• Daniel M. Griffith

  Oregon State University

  18 shared

• Grayson Badgley

  15 shared

• Janneke HilleRisLambers

  ETH Zurich

  13 shared

• Robert P. Skelton

  South African Environmental Observation Network

  11 shared

Labs

• Anderegg Landscape Physiology LabPI

  Principal investigator, project scientists, researchers, students and staff.

Education

• B.A., Human Biology

  Stanford University

  2011

• Ph.D.

  University of Washington

  2017