Dry Season Transpiration and Soil Water Dynamics in the Central Amazon

Gustavo C. Spanner, Bruno O. Gimenez, Cynthia L. Wright, Valdiek Silva Menezes, Brent D. Newman, Adam D. Collins, Kolby J. Jardine, Robinson I. Negrón-Juárez, Adriano José Nogueira Lima, Jardel Ramos Rodrigues, Jeffrey Q. Chambers, Niro Higuchi, Jeffrey M. Warren

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

With current observations and future projections of more intense and frequent droughts in the tropics, understanding the impact that extensive dry periods may have on tree and ecosystem-level transpiration and concurrent carbon uptake has become increasingly important. Here, we investigate paired soil and tree water extraction dynamics in an old-growth upland forest in central Amazonia during the 2018 dry season. Tree water use was assessed via radial patterns of sap flow in eight dominant canopy trees, each a different species with a range in diameter, height, and wood density. Paired multi-sensor soil moisture probes used to quantify volumetric water content dynamics and soil water extraction within the upper 100 cm were installed adjacent to six of those trees. To link depth-specific water extraction patterns to root distribution, fine root biomass was assessed through the soil profile to 235 cm. To scale tree water use to the plot level (stand transpiration), basal area was measured for all trees within a 5 m radius around each soil moisture probe. The sensitivity of tree transpiration to reduced precipitation varied by tree, with some increasing and some decreasing in water use during the dry period. Tree-level water use scaled with sapwood area, from 11 to 190 L per day. Stand level water use, based on multiple plots encompassing sap flow and adjacent trees, varied from ∼1.7 to 3.3 mm per day, increasing linearly with plot basal area. Soil water extraction was dependent on root biomass, which was dense at the surface (i.e., 45% in the upper 5 cm) and declined dramatically with depth. As the dry season progressed and the upper soil dried, soil water extraction shifted to deeper levels and model projections suggest that much of the water used during the month-long dry-down could be extracted from the upper 2–3 m. Results indicate variation in rates of soil water extraction across the research area and, temporally, through the soil profile. These results provide key information on whole-tree contributions to transpiration by canopy trees as water availability changes. In addition, information on simultaneous stand level dynamics of soil water extraction that can inform mechanistic models that project tropical forest response to drought.

Original languageEnglish
Article number825097
JournalFrontiers in Plant Science
Volume13
DOIs
StatePublished - Mar 24 2022

Funding

This material was based upon work supported as part of the Next Generation Ecosystem Experiments-Tropics (NGEE-Tropics) funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research through contract no. DE-AC02-05CH11231 to LBNL, as part of DOE’s Terrestrial Ecosystem Science Program. Additional funding for this research was provided by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Fundação de Amparo à Pesquisa do Estado do Amazonas (FAPEAM). This material was based upon work supported as part of the Next Generation Ecosystem Experiments-Tropics (NGEE-Tropics) funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research through contract no. DE-AC02-05CH11231 to LBNL, as part of DOE?s Terrestrial Ecosystem Science Program. Additional funding for this research was provided by the Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) and Funda??o de Amparo ? Pesquisa do Estado do Amazonas (FAPEAM).

Keywords

  • allometry
  • basal area
  • ecohydrology
  • root distribution
  • root water uptake
  • sap flow
  • tropical forests

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