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Kevin Willson @kgwillson.bsky.social · 02/09/2026

Managers can use our findings to predict the historical range of variability in Front Range dry conifer stands, inform management plans and prescriptions based on that historical range, and select a specific condition within that range to achieve desired treatment outcomes (7/7).

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Kevin Willson @kgwillson.bsky.social · 02/09/2026

Very coarse sand may have influenced historical structure by increasing water percolation deeper into the soil. If so, sites with more very coarse sand had more water for deep-rooted trees but less water for shallow-rooted grasses and forbs, which can reduce fire frequency (6/n).

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Kevin Willson @kgwillson.bsky.social · 02/09/2026

CARTs from top-performing models also included elevation and latitude, with greater elevation predicting more basal area and lower latitudes predicting less basal area comprised of #PonderosaPine. Note the variability of structure among plots that were sorted into each end node (5/n).

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Kevin Willson @kgwillson.bsky.social · 02/09/2026

CARTs placed very coarse sand at the top node for our 4 top models, including basal area, basal area comprised of #PonderosaPine, open space, & clumped space. Less very coarse sand predicted open #PonderosaPine savannas, while more very coarse sand predicted closed #DryMixedConifer forests (4/n).

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Kevin Willson @kgwillson.bsky.social · 02/09/2026

Historical forests typically contained low tree density and basal area with lots of open space. #PonderosaPine often dominated stands, but reconstructions showed structure varying from areas with no trees to #DryMixedConifer ecosystems predominately composed of non-pines (3/n).

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Kevin Willson @kgwillson.bsky.social · 02/09/2026

We used 10,000+ tree cores from 172 stem-mapped plots to reconstruct structure in 1860 along environmental gradients. With #RandomForest, we identified the 5 most important predictors for spatial and nonspatial structure to inform representative Classification and Regression Trees (CARTs, 2/n).

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Reposted by Kevin Willson

Matthew Hurteau @mhurteau.bsky.social · 26/04/2026

The Hummingbird Fire on the Gila NF has grown with the high winds. Suppression efforts are focused on structures in Willow Creek. The other map is from a paper by @kgwillson.bsky.social showing all of the fire activity in the Gila and Aldo Leopold wilderness.

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Reposted by Kevin Willson

Global Change Biology @globalchangebio.bsky.social · 18/06/2025

Trees in Fire‐Maintained Forests Have Similar Growth Responses to Drought, but Greater Stomatal Conductance Than Trees in Fire‐Excluded Forests 🔗 buff.ly/qyhBjCh @kgwillson.bsky.social @mhurteau.bsky.social

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Kevin Willson @kgwillson.bsky.social · 09/06/2025

Our findings indicate that reintroducing frequent fire reduces tree water stress without inhibiting growth response to prolonged aridity. This suggests that frequent-fire regimes may help forests better withstand increasingly hot and dry conditions expected under climate change.

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Kevin Willson @kgwillson.bsky.social · 09/06/2025

Growth responses varied with climate and topography while water use efficiency varied with climate, topography, and competition. Trees were more water-efficient in stands with more small trees, which helped explain greater water stress in denser, fire-excluded forests. 4/n

FIGURE 6 | Tree densities (±one standard error) by diameter class in fire-maintained (orange, n = 22 plots) and fire-excluded (purple, n = 20 plots)
forests. The inset shows boxplots of quadratic mean diameter (QMD) in fire-maintained and fire-excluded plots. ** represents p < 0.01.

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Kevin Willson @kgwillson.bsky.social · 09/06/2025

Fire-maintained trees grew faster to begin the first drought, but growth rarely differed among trees for the remaining 21 years. Interestingly, similar growth rates occurred as fire-excluded trees became increasingly more efficient with water, signaling greater water stress. 3/n

FIGURE 5 | Chronologies of tree-ring width index (RWI) and annual evaporative water use efficiency (eWUE) values with 95% confidences intervals (CI) among trees analyzed for isotopic discrimination from fire-maintained (orange, ntrees = 46) and fire-excluded forests (purple, ntrees = 46). The solid black line represents average growth (RWI = 1). Years are delineated by drought period. * represents p < 0.05, ** represents p < 0.01, *** represents p < 0.001.

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Kevin Willson @kgwillson.bsky.social · 09/06/2025

We quantified stomatal and growth responses to 4-year and 7-year droughts using tree cores, which let us compare wood carbon isotopes and ring-widths among trees over several decades. We also modeled these responses against climate, topography, competition, and fire history data. 2/n

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Kevin Willson @kgwillson.bsky.social · 09/06/2025

That's a wrap, my last chapter has been published in @globalchangebio.bsky.social! Another (huge) thank you to @mhurteau.bsky.social for helping assess #PonderosaPine stomatal and growth responses to #drought in fire-maintained and fire-excluded forests 1/n onlinelibrary.wiley.com/share/author...

onlinelibrary.wiley.com

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