Dataset: Embolism resistance supports the contribution of dry-season precipitation to transpiration in eastern Amazon forests

Transpiration plays a pivotal role in maintaining both the water balance and climate in Amazonian forests. During the dry season, transpiration becomes even more critical in supplying atmospheric moisture to produce rainfall downwind. However, identifying the sources of transpiration across different tree species and landscape positions has long posed a challenge for ecohydrologists. This dataset comprises stable isotope data (δ18O and δ2H) and tree hydraulic trait measurements collected during the 2021 dry season (late September to early October) at the Tapajós National Forest, near Santarém, Brazil (3°51′S, 54°58′W). The research utilized two permanent plots established by the Biodiversity Research Program (PPBio Santarém/POPA LTER), one located in a valley and another on the hill, to investigate the sources of tree transpiration and its drivers. This composite dataset holds stable isotopic composition data (δ2H and δ18O) of xylem samples from species on the hill and in the valley, bulk soil collected at different depths in the soil profile at both sites, stream and groundwater data from the valley, and precipitation collected during the sampling period at both sites. Additionally, embolism resistance (P50) measurements were collected from the same tree species. This comprehensive dataset supports a mechanistic understanding of tree water use during the dry season by integrating isotope hydrology with hydraulic trait analysis across topographic gradients. Specifically, this dataset contains three files: “README.txt” "Tapajos.data.isotopes.csv” “Tapajos.P50.MixSIAR.csv” This data repository was used in the following publication (Nehemy et al. 2025). For more detailed information about sampling and methods, please see the following article. We kindly request that any use of this dataset be accompanied by proper acknowledgment of both the dataset itself and the associated primary publication. Nehemy, M. F., Mattos, C., Oliveira, S. R., Hirota, M., Fan, Y., Giacomin, L., Penha, D., Schlickmann, M., Silva, J. G. M., Rocha, M., Rodrigues, G. A., McDonnell, J. J. Embolism resistance supports the contribution of dry-season precipitation to transpiration in the eastern Amazon forests. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.2501585122 For further understanding of this data set and findings, visit the publication, and for any further inquiries, please contact Magali Nehemy. For a more complete list of P50 data, which contains other individuals, at the studied site, please contact Caio Mattos, and consult the following publication: Mattos, C. R., Mazzochini, G. G., Rius, B. F., Penha, D., Giacomin, L. L., Flores, B. M., ... & Hirota, M. (2023). Rainfall and topographic position determine tree embolism resistance in Amazônia and Cerrado sites. Environmental Research Letters, 18(11), 114009. Our work was conducted on the traditional territory of the Mundurukú people. We are grateful to the Mundurukús for letting us into their home and territory, and for their teachings on caring for and respecting the land and Mother Nature. We are also grateful to the Tapajós community; special thanks to Dona Cota, Adriano, Kelvin, Lucas, and Galo during fieldwork campaigns. We thank Kim Janzen for isotopic analysis in laser and mass spectrometry. This research was supported by the American Geophysical – Horton Research Grant 2019 (MFN), Natural Sciences and Engineering Research Council (NSERC) (JJM, MFN), the Rutgers Global Environmental Change grant (YF, CRCM), the Serrapilheira Institute grant, No. 1709-18983 (MH), the National Science Foundation grants, Nos. EAR-825813, AGS—827069 (YF), the joint UK NERC—FAPESP grant, NE/S000011/1, FAPESP-19/07773-1 (RSO), the a CNPQ Productivity Scholarship (RSO), the a CNPQ grant, No. 441443/2016-8 PELD/POPA (LLG) and the PEEX/UFOPA grant 2019 (LLG).