Kevin Willson

Trees in Fire‐Maintained Forests Have Similar Growth Responses to Drought, but Greater Stomatal Conductance Than Trees in Fire‐Excluded Forests

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@kgwillson.bsky.social @mhurteau.bsky.social

17.06.2025 23:25 — 👍 9    🔁 3    💬 0    📌 0

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.

09.06.2025 14:41 — 👍 1    🔁 1    💬 0    📌 0

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.

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

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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.

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

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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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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

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