Water table depth modulates productivity and biomass across Amazonian forests
Authors: Sousa Thaiane R. , Schietti Juliana , Ribeiro Igor O. , Emílio Thaise , Fernández Rafael Herrera , ter Steege Hans , Castilho Carolina V. , Esquivel‐Muelbert Adriane , Baker Timothy , Pontes‐Lopes Aline , Silva Camila V. J. , Silveira Juliana M. , Derroire Géraldine , Castro Wendeson , Mendoza Abel Monteagudo , Ruschel Ademir , Prieto Adriana , Lima Adriano José Nogueira , Rudas Agustín , Araujo‐Murakami Alejandro , Gutierrez Alexander Parada , Andrade Ana , Roopsind Anand , Manzatto Angelo Gilberto , Di Fiore Anthony , Torres‐Lezama Armando , Dourdain Aurélie , Marimon Beatriz , Marimon Ben Hur , Burban Benoit , van Ulft Bert , Herault Bruno , Quesada Carlos , Mendoza Casimiro , Stahl Clement , Bonal Damien , Galbraith David , Neill David , de Oliveira Edmar A. , Hase Eduardo , Jimenez‐Rojas Eliana , Vilanova Emilio , Arets Eric , Berenguer Erika , Alvarez‐Davila Esteban , Honorio Coronado Eurídice N. , Almeida Everton , Coelho Fernanda , Valverde Fernando Cornejo , Elias Fernando , Brown Foster , Bongers Frans , Arevalo Freddy Ramirez , Lopez‐Gonzalez Gabriela , van der Heijden Geertje , Aymard C. Gerardo A. , Llampazo Gerardo Flores , Pardo Guido , Ramírez‐Angulo Hirma , do Amaral Iêda Leão , Vieira Ima Célia Guimarães , Huamantupa‐Chuquimaco Isau , Comiskey James A. , Singh James , Espejo Javier Silva , del Aguila‐Pasquel Jhon , Zwerts Joeri Alexander , Talbot Joey , Terborgh John , Ferreira Joice , Barroso Jorcely G. , Barlow Jos , Camargo José Luís , Stropp Juliana , Peacock Julie , Serrano Julio , Melgaço Karina , Ferreira Leandro V. , Blanc Lilian , Poorter Lourens , Gamarra Luis Valenzuela , Aragão Luiz , Arroyo Luzmila , Silveira Marcos , Peñuela‐Mora Maria Cristina , Vargas Mario Percy Núñez , Toledo Marisol , Disney Mat , Réjou‐Méchain Maxime , Baisie Michel , Kalamandeen Michelle , Camacho Nadir Pallqui , Cardozo Nállarett Dávila , Silva Natalino , Pitman Nigel , Higuchi Niro , Banki Olaf , Loayza Patricia Alvarez , Graça Paulo M. L. A. , Morandi Paulo S. , van der Meer Peter J. , van der Hout Peter , Naisso Pétrus , Camargo Plínio Barbosa , Salomão Rafael , Thomas Raquel , Boot Rene , Umetsu Ricardo Keichi , da Costa Silva Richarlly , Burnham Robyn , Zagt Roderick , Martinez Rodolfo Vasquez , Brienen Roel , Ribeiro Sabina Cerruto , Lewis Simon L. , Vieira Simone Aparecida , de Almeida Reis Simone Matias , Fauset Sophie , Laurance Susan , Feldpausch Ted , Erwin Terry , Killeen Timothy , Wortel Verginia , Moscoso Victor Chama , Vos Vincent , Huasco Walter Huaraca , Laurance William , Malhi Yadvinder , Magnusson William E. , Phillips Oliver L. , Costa Flávia R. C. 
Published: May 2022

Aim

Water availability is the major driver of tropical forest structure and dynamics. Most research has focused on the impacts of climatic water availability, whereas remarkably little is known about the influence of water table depth and excess soil water on forest processes. Nevertheless, given that plants take up water from the soil, the impacts of climatic water supply on plants are likely to be modulated by soil water conditions.

Location

Lowland Amazonian forests.

Time period

1971–2019.

Methods

We used 344 long‐term inventory plots distributed across Amazonia to analyse the effects of long‐term climatic and edaphic water supply on forest functioning. We modelled forest structure and dynamics as a function of climatic, soil‐water and edaphic properties.

Results

Water supplied by both precipitation and groundwater affects forest structure and dynamics, but in different ways. Forests with a shallow water table (depth <5 m) had 18% less above‐ground woody productivity and 23% less biomass stock than forests with a deep water table. Forests in drier climates (maximum cumulative water deficit < −160 mm) had 21% less productivity and 24% less biomass than those in wetter climates. Productivity was affected by the interaction between climatic water deficit and water table depth. On average, in drier climates the forests with a shallow water table had lower productivity than those with a deep water table, with this difference decreasing within wet climates, where lower productivity was confined to a very shallow water table.

Main conclusions

We show that the two extremes of water availability (excess and deficit) both reduce productivity in Amazon upland (terra‐firme) forests. Biomass and productivity across Amazonia respond not simply to regional climate, but rather to its interaction with water table conditions, exhibiting high local differentiation. Our study disentangles the relative contribution of those factors, helping to improve understanding of the functioning of tropical ecosystems and how they are likely to respond to climate change.