Authors:

Emmeline Rose Seest

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About Paper:

For autumn deciduous tree species, leaf senescence marks the end of the growing season and the beginning of winter dormancy. The timing of this event has large implications for carbon assimilation, exposure to cold and freezing temperatures, and the allocation of resources for future growth and metabolism. However, the driving forces behind autumn phenology are less understood compared to the well-documented drivers of springtime phenology. Recent studies suggest sugars may play a significant role by advancing autumn leaf senescence. Our study aims to understand the impact sugars have on the timing of leaf senescence in urban deciduous tree species. To address this question, we selected Quercus rubra (n=5) and Liriodendron tulipifera (n=5) trees planted on Purdue University's campus (West Lafayette, IN, USA). Two branches were girdled, and two branches were non-girdled. Of these pairs, one branch was sampled weekly for stomatal conductance, greenness, chlorophyll content, bulk sugar content, and ABA concentration. The other branch was observed weekly for leaf count and phenology. Sampling will continue until total natural leaf senescence occurs. We hypothesize that 1) leaves on the girdled branches will senesce before the leaves on the ungirdled branches and 2) the girdled branches of the ring-porous red oaks will senesce before the girdled branches of the diffuse-porous tuliptrees. Overall, understanding the drivers of autumn leaf senescence will improve predictions of growing season length and the impacts of increasing drought, extreme weather events, and variable temperatures, thereby improving the ability of land stewards to manage our forests. Keywords: Leaf Senescence; Autumn Phenology; Nonstructural Carbohydrates; Girdle; Temperate Trees

Source:

Purdue University / 2025

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Co-authors:

Emmeline Rose Seest