Accelerated Daytime Stem Growth and Respiration of Canopy Trees in the Amazon Basin

Authors

Kolby J. Jardine^1,2* (kjjardine@lbl.gov), Regison Oliveira², Edison Augusto², Bruno O. Gimenez², Gustavo Spanner², Jeffrey M. Warren³, Niro Higuchi², Adriano Lima², Nate McDowell⁴, Robinson Negron-Juarez¹, Jessica Needham¹, Marcos Longo¹, Gilberto Pastorello¹, Charles Koven¹, Jeffrey Chambers^1,2

Institutions

¹Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA; ²National Institute of Amazonian Research, Manaus, Amazonas, Brazil; ³Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN; ⁴Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA

URLs

https://ngee-tropics.lbl.gov

Abstract

Tropical forests cycle a large amount of carbon dioxide (CO₂) between the land and atmosphere with a substantial portion of the return flux due to tree respiratory processes. However, due to the lack of a commercial real-time stem CO₂ efflux (E_s) system, in situ quantification of woody tissue respiratory fluxes remains limited in tropical ecosystems, with little information available on the interacting roles of plant biophysical (wood density and size), physiological (transpiration and growth rates), and environmental (temperature and vapor pressure deficit) factors. In this study, the team hypothesizes that fast-growing tree species with low wood density will have higher respiratory fluxes compared with slower-growing tree species with higher wood density but stem radial growth and its associated respiratory production of CO₂ is highly sensitive to declines in turgor pressure associated with transpiration. Using custom systems for real-time stem E_s observations, researchers quantified diurnal E_s patterns in the BIONTE experimental tropical forest site near Manaus, Brazil. Researchers synthesize diurnal E_s observations over 24 hours from 32 tree species during the 2022 dry and 2022 to 2023 wet seasons. In addition, the team presents a combined analysis of 5- to 7-day continuous observations of E_s, sap velocity and stem water potential during the 2023 dry and 2024 wet seasons as well as vertical gradients in stem E_s for a limited number of species. The observations are presented as a Next-Generation Ecosystem Experiments Tropics data archive and compared with Functionally Assembled Terrestrial Ecosystem Simulator model simulations of maintenance and growth respiration rates.