2024 Abstracts

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


Kolby J. Jardine1,2* (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 Chambers1,2


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



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 (Es) 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 Es observations, researchers quantified diurnal Es patterns in the BIONTE experimental tropical forest site near Manaus, Brazil. Researchers synthesize diurnal Es 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 Es, sap velocity and stem water potential during the 2023 dry and 2024 wet seasons as well as vertical gradients in stem Es 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.