Translating bumblebee dialect…
Examines how cytotype variation and genotypic diversity in quaking aspen shape physiological responses to drought and climate, combining flow cytometry, hyperspectral remote sensing, and field campaigns across Colorado study sites.
Quaking aspen (Populus tremuloides) is the most widely distributed tree in North America and a foundational species of the subalpine forests around the Gunnison Basin. In Colorado, aspen groves shape watersheds, support diverse understories, provide wildlife habitat, and define much of the autumn landscape that draws visitors to places like Gothic and Crested Butte. Yet across the western United States, aspen has been undergoing episodes of rapid, large-scale mortality known as sudden aspen decline — a synchronous die-off linked to recent droughts and rising temperatures. Understanding why some aspen stands persist while others collapse has become an urgent question for land managers and ecologists in the Rocky Mountains.
A central insight from recent research is that not all aspen are genetically alike. Aspen reproduces largely through clonal reproduction: a single seedling can spread underground through roots, sending up genetically identical stems (ramets) that together form a clone (genet). Within and among these clones, individuals differ in cytotype variation — the number of chromosome copies they carry. Most aspen are diploid (two chromosome sets), but a substantial fraction are triploid (three sets). This cytotype variation, together with genotype-by-environment interaction (the tendency of genotypes to perform differently under different conditions), helps determine which trees survive drought stress, when they leaf out in spring, and how they grow.
Because aspen clones can be visually indistinguishable, scientists have increasingly relied on remote sensing observations — particularly airborne imaging spectroscopy that records reflected light across hundreds of wavelengths — to map cytotype, genotype, and canopy traits across landscapes. These hyperspectral data are linked to ground measurements using partial least squares regression, a statistical method that translates spectra into estimates of leaf nitrogen, water content, and other traits. Together, these tools allow researchers to track aspen regeneration, mortality, and physiological stress across thousands of hectares — and to ask how genetics, climate, and topography interact to shape the future of this iconic tree.
Early studies framed aspen as a dynamic, disturbance-driven species of the Colorado mountains. Morgan (Morgan, 1969) described the ecology of aspen in Gunnison County, documenting aspen as small islands within fescue grasslands and subalpine forests and suggesting that aspen was successional to spruce-fir except where seed sources were limited. Decades later, broader landscape analyses by Kulakowski et al. on the Grand Mesa, and Smith & Smith on the Uncompahgre Plateau, found that aspen had largely persisted or even expanded since the late 19th century, complicating the narrative of universal decline.
Physiological stress experienced by plants due to reduced water availability that can harm fitness by inducing leaf loss, reducing flower size, and de...
Differential expression of genotypes across environmental conditions, indicating genetic variation in phenotypic plasticity
Differences in chromosome copy number among individuals, specifically diploid (two copies) versus triploid (three copies) chromosome sets
Rapid, synchronous mortality of aspen across large areas characterized by gradual sudden aspen decline associated with recent drought and temperature ...
A model selection criterion that balances goodness of fit with model complexity by penalizing models with more parameters
The biogeographic transition zone between subalpine forest and alpine tundra, representing the elevational limit of individual trees with an upright g...
Cytotype inference using twelve multinational microsatellites with 97% correct classification for cytotype. Individual plants defined as diploid or tr...
Uses hyperspectral imaging (400-1000 nm) combined with Partial Least Squares Regression to correlate spectral signatures with measured leaf traits lik...
PLSR modeling approach using leaf spectral reflectance measurements to extrapolate functional trait values from subset of direct measurements to large...
Systematic point sampling along transects to quantify vegetation composition and forage quality metrics. Modified from standard methods described in W...
Systematic establishment of gridded plots across watersheds followed by long-term monitoring of tagged individual trees for mortality and recruitment ...
CNN training using image patches for pixel-based tree and shrub species classification at alpine treeline.
Data comprise measurements of spectral reflectance for quaking aspen (Populus tremuloides Michx.) trees at a range of sites in southwestern Colorado n...
The dataset contains region of interest (ROI) polygons for six treeline species found in Rocky Mountain National Park, CO. The tree and shrub species ...
The dataset contains region of interest (ROI) polygons for six treeline species found in Rocky Mountain National Park, CO. The tree and shrub species ...
Species responses to climate change depend on environment, genetics, and interactions among these factors. Intraspecific cytotype (ploidy level) varia...
The purpose of this dataset is to support research aimed at understanding the coupling between hydrologic and biogeochemical processes at watershed sc...
Age-structure work by Binkley et al. (Binkley et al., 2014) added a sobering counterpoint: although aspen was widespread, very few stands on the Uncompahgre Plateau were younger than 50 years, and most current basal area came from cohorts that established after major late-1800s fires. Without renewed landscape-scale regeneration, these aging cohorts pointed to a long-term decline. Greer et al. (Greer et al., 2016) added an evolutionary dimension by showing that northern and southwestern aspen populations occupy distinct climate envelopes, hinting that genetics — not just environment — would matter for predicting aspen's future.
The most consequential recent finding is that cytotype shapes aspen demography and stress response. Blonder et al. (Blonder et al., 2021) monitored 503 plots across Colorado and showed that triploid aspen were more vulnerable to mortality and had reduced recruitment compared to diploids on drought-prone and disturbed sites, with significant interactions between cytotype and environment. Genotype-level variation added further demographic differences beyond cytotype alone, demonstrating that genetic mosaics — not just climate — are needed to explain aspen decline. Banka (Banka, 2021) likewise found that elevation, aspect, and slope strongly influenced growth rates of both diploid and triploid trees.
Remote sensing has made it possible to scale these genetic insights across landscapes. Blonder et al. (Blonder et al., 2020) showed that airborne and leaf-level spectra can classify aspen by cytotype with high accuracy, and that diploids tend to dominate higher, steeper sites while cytotypes interdigitate at sub-kilometer scales. Building on this, Blonder et al. (Blonder et al., 2022) mapped 391 km² of southwestern Colorado at 1-meter resolution and found that triploids had higher leaf nitrogen, higher canopy water content, and shifted carbon isotope signatures compared to diploids — but were also overrepresented in damaged canopies, especially under hotter, drier conditions. Among healthy pixels 54% were triploid, while among damaged pixels 68% were triploid, consistent with greater triploid risk under stress.
Genetics also shapes the timing of aspen's growing season. Blonder et al. (Blonder et al., 2023) found that greenup date, greendown date, and growing season length varied by weeks across the landscape, with heritabilities of 31–61% and lags of up to three years between climate drivers (snowmelt date, soil moisture, air temperature) and phenological response. Triploids tended to green up earlier, senesce later, and have longer growing seasons than diploids. Together, these results paint aspen as a species whose response to climate is filtered through a fine-grained mosaic of cytotype and genotype, with implications visible from leaf chemistry to whole-canopy phenology.
While early work in the 1990s and 2000s focused on stand-level dynamics, fire history, and age structure, research since 2020 has shifted decisively toward integrating genetics, remote sensing, and ecophysiology. The Upper East River watershed near Gothic has become a hub for this work: Chadwick et al. (Chadwick et al., 2020) coordinated the first NEON Airborne Observation Platform survey outside of NEON's core sites, collecting samples from 437 sites and demonstrating that leaf nitrogen, leaf mass per area, and canopy water content could be predicted from imaging spectroscopy with strong accuracy. These airborne products now underpin much of the cytotype mapping in the region.
The newest studies are pushing into trait ecology and intraspecific variation. Rieksta et al. (Rieksta et al., 2025) found that classic trait relationships of the leaf economics spectrum weaken substantially within aspen, and that diploid and triploid genotypes differ in how they respond to microenvironment — triploids tend to be resource-acquisitive, while diploids occupy a broader environmental range. Background herbivory further reshapes these trait relationships. Emerging methodological work on surface mineral and contaminant detection (Grant, 2025) signals continued investment in remote sensing tools that could eventually be linked to belowground drivers of aspen stress.
Several major questions remain. First, why exactly are triploids more vulnerable to drought and canopy damage despite higher leaf nitrogen and water content — is it a hydraulic, carbon-balance, or developmental constraint? Second, how will the heterogeneous, interdigitated mosaic of diploids and triploids reshape aspen distributions over the coming century as Gunnison Basin climate warms and dries? Third, can land managers use cytotype maps to identify stands most at risk, or to prioritize regeneration where younger cohorts are scarce, as Binkley et al. (Binkley et al., 2014) warned? Finally, the multi-year climate lags identified by Blonder et al. (Blonder et al., 2023) suggest that today's phenology and mortality reflect drought conditions from years past — a forecasting challenge that will require sustained, integrated monitoring of genetics, traits, and climate across RMBL's watersheds.
Banka, S. (2021). The effect of cytotype on radial growth rate in quaking aspen (Populus tremuloides) across environmental gradients. →
Binkley, D., Alsanousi, A., Romme, W. (2014). Age structure of aspen forests on the Uncompahgre Plateau, Colorado. Canadian Journal of Forest Research. →
Blonder, B., et al. (2020). Remote sensing of ploidy level in quaking aspen (Populus tremuloides Michx.). Journal of Ecology. →
Blonder, B., et al. (2021). Cytotype and genotype predict mortality and recruitment in Colorado quaking aspen (Populus tremuloides). Ecological Applications. →
Blonder, B., et al. (2022). Remote sensing of cytotype and its consequences for canopy damage in quaking aspen. Global Change Biology. →
Blonder, B., et al. (2023). Climate lags and genetics determine phenology in quaking aspen (Populus tremuloides). New Phytologist. →
Chadwick, K. D., et al. (2020). Integrating airborne remote sensing and field campaigns for ecology and Earth system science. Methods in Ecology and Evolution. →
Grant, K. (2025). Remote sensing strategies for surface mineral and contaminant detection. →
Greer, B., DeLuca, A., Carlin, T., Hu, F., St. Clair, S. (2016). Populations of aspen (Populus tremuloides Michx.) with different evolutionary histories differ in their climate occupancy. Ecology and Evolution. →
Kulakowski, D., Veblen, T., Drinkwater, S. (2004). The persistence of quaking aspen (Populus tremuloides) in the Grand Mesa area, Colorado. Ecological Applications. →
Morgan, M. (1969). Ecology of aspen in Gunnison County, Colorado. American Midland Naturalist. →
Rieksta, J., et al. (2025). Relaxation of the leaf economics spectrum within and across quaking aspen Populus tremuloides genotypes. Oikos. →
Smith, A., Smith, F. (2005). Twenty-year change in aspen dominance in pure aspen and mixed aspen/conifer stands on the Uncompahgre Plateau, Colorado, USA. Forest Ecology and Management. →
Environmental gradient characterized by declining water availability, derived from temperature and precipitation variables
Processing procedure to remove atmospheric effects from hyperspectral radiance data to estimate surface reflectance
Growth of new aspen trees through sexual reproduction (seeds) or asexual reproduction (suckering from root systems)
Influence of forest canopy openness on understory light availability and bee community composition
Process by which plants convert light energy to chemical energy, with formula 6CO2+6H2O → C6H12O6+6O2
Airborne hyperspectral imaging (380-2500 nm) and LiDAR data collection at 1 m resolution, followed by machine learning algorithms to produce aspen cov...
Integration of gridMET temperature data, MODIS snowmelt timing, and PARFLOW-CLM soil moisture simulations to create multi-temporal environmental predi...
A custom atmospheric correction procedure for VSWIR hyperspectral data that uses ACORN-6LX software with 200-meter processing kernels incorporating lo...
Field surveys to quantify percent canopy dieback and tree mortality following severe droughts.
Collection of site spectra to validate airborne hyperspectral data acquired by NEON Aerial Observation Platform.
A custom ray tracing algorithm that generates shade masks for hyperspectral imagery by calculating paths between the sun, ground points, and sensor us...
Laboratory technique to determine ploidy level, validated against Hordeum vulgare standards.
Endmember spectral measurements using contact probe attachment with internal bulb illumination for close-contact surface measurements.
Excavation of soil pits and installation of sensors at 5, 15, and 50 cm depths with proper soil horizon replacement.
Systematic field observation of trophic interactions between organisms, primarily plants and insects, with rotating temporal sampling across multiple ...
Collection of sun-lit leaves from trees and shrubs using slingshots or pole clippers, with samples stored in polyethylene bags with damp paper towels ...
Laboratory analysis of plant samples for nitrogen content using elemental CHNSO analyzer and water content determination through oven-drying weight lo...
This mosaic of visible to shortwave infrared (VSWIR) data was derived from the assignable asset NEON AOP radiance data that was collected by LBNL&rsqu...
Maps of aspen ploidy (diploid or triploid) developed using National Ecological Observatory Network (NEON) Airborne Observation Platform visible to sho...
No description provided.
Old-growth temperate rainforests are, per unit area, the largest and most long-lived stores of carbon in the terrestrial biosphere, but their carbon d...
Structural overshoots, where biomass is overallocated to tree leaf area compared to sapwood area, could result in lethal stress during droughts. Clima...
Lawrence Berkeley National Laboratory (LBNL) contracted the National Ecological Observatory Network Airborne Observation Platform (NEON AOP) to observ...
Structural overshoots, where biomass is overallocated to tree leaf area compared to sapwood area, could result in lethal stress during droughts. Clima...
Carbon (C) and nitrogen (N) weight percent concentrations were obtained from the bulk foliar samples collected across East River, Washington Gulch, Sl...
Foliar and soil spectra colleted during a 2023 metal hotspot survey in Gunnison County, CO.
By reducing current velocity, tidal marsh vegetation can diminish storm surges and storm waves. Conversely, currents often exert high mechanical stres...
This dataset provides site and endmember spectra collected during the 2025 Colorado Headwaters Ecological Spectroscopy Study (CHESS) campaign. The sit...
Predawn and midday plant water potential measurements, collected on terminal twigs using a scholander-type pressure chamber (PMS Instruments, Corvalli...
Predawn and midday plant water potential measurements, collected on terminal twigs using a scholander-type pressure chamber (PMS Instruments, Corvalli...
This dataset provides site and endmember spectra collected during the 2025 Colorado Headwaters Ecological Spectroscopy Study (CHESS) campaign. The sit...