EGU2020-11215
https://doi.org/10.5194/egusphere-egu2020-11215
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Reduction in lumen area increases the amount of δ18O exchange with source water during cellulose synthesis

Jia Hu1, Paul Szejner1, Timothy Clute2, Erik Anderson1, and Michael Evans3
Jia Hu et al.
  • 1University of Arizona, School of Natural Resources and Environment, USA (jiahu@email.arizona.edu)
  • 2Department of Ecology, Montana State University, Bozeman, USA
  • 3Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, USA

Fine-scale sampling of secondary growth, isotopic composition and wood anatomical features has enabled the study of intra-seasonal tree growth dynamics in response to environmental and ecophysiological processes, and this fine-scale sampling approach has led to a re-examination of our fundamental understanding of how environmental factors are recorded in δ18O of cellulose (δ18Ocell). High resolution xylem anatomical analyses, such as wood density, lumen area (LA), cell wall thickness (CWT), and blue intensity have also been used to understand tree response to climate. However, linking wood anatomical traits with their isotopic signature has not yet been explored, but can provide new insights on the interpretation of the δ18Ocell through time. In this study, we test the response of wood anatomical features in Pinus ponderosa and Pseudotsuga menziesii, including cell-wall thickness (CWT) and lumen area (LA), along with the oxygen isotopic composition of α-cellulose (δ18Ocell) to shifts in relative humidity (RH) in two treatments: one from high to low RH and the second one from Low to high RH. We observed a significant decrease in LA and a small increase in CWT within the experimental growing season in both RH treatments. The measured δ18Ocell along the tree ring was also responsive to RH variations in both treatments. However, estimated δ18Ocell did not agree with measured δ18Ocell when the proportion of exchangeable oxygen during cellulose synthesis (Pex) was kept constant. We found that modeled δ18Ocell agreed with measured δ18Ocell only when Pex increased through the ring formation; we also found that Pex linearly decreased with an increase in standardized LA. Based on this varying Pex within an annual ring, we propose a targeted sampling strategy for different hydroclimate signals: earlier season cellulose (larger LA) is a better recorder of relative humidity while late season cellulose (smaller LA) is a better recorder of source water.

How to cite: Hu, J., Szejner, P., Clute, T., Anderson, E., and Evans, M.: Reduction in lumen area increases the amount of δ18O exchange with source water during cellulose synthesis, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11215, https://doi.org/10.5194/egusphere-egu2020-11215, 2020

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