Local hydrological conditions influence tree diversity and composition across the Amazon basin

Marca-Zevallos, M.J. and Moulatlet, G.M. and Sousa, T.R. and Schietti, J. and Coelho, L.D.S. and Ramos, J.F. and Lima Filho, D.D.A. and Amaral, I.L. and de Almeida Matos, F.D. and Rincón, L.M. and Cardenas Revilla, J.D. and Pansonato, M.P. and Gribel, R. and Barbosa, E.M. and Miranda, I.P.D.A. and Bonates, L.C.D.M. and Guevara, J.E. and Salomão, R.P. and Ferreira, L.V. and Dantas do Amaral, D. and Pitman, N.C.A. and Vriesendorp, C. and Baker, T.R. and Brienen, R. and Carim, M.D.J.V. and Guimarães, J.R.D.S. and Núñez Vargas, P. and Huamantupa-Chuquimaco, I. and Laurance, W.F. and Laurance, S.G.W. and Andrade, A. and Camargo, J.L. and Monteagudo Mendoza, A. and Vasquez, R. and Valenzuela Gamarra, L. and Mogollón, H.F. and Marimon-Junior, B.H. and Marimon, B.S. and Killeen, T.J. and Farias, E.D.S. and Neill, D. and de Medeiros, M.B. and Simon, M.F. and Terborgh, J. and Carlos Montero, J. and Licona, J.C. and Mostacedo, B. and García-Villacorta, R. and Araujo-Murakami, A. and Arroyo, L. and Villarroel, D. and Dávila, N. and Coelho de Souza, F. and Carvalho, F.A. and Comiskey, J.A. and Alonso, A. and Dallmeier, F. and Oliveira, A.A. and Castilho, C.V. and Lloyd, J. and Feldpausch, T.R. and Ríos Paredes, M. and Castaño Arboleda, N. and Cárdenas López, D. and Aymard Corredor, G.A. and Di Fiore, A. and Rudas, A. and Prieto, A. and Barbosa, F.R. and Noronha, J.C. and Rodrigues, D.D.J. and Carpanedo, R.D.S.á. and Honorio Coronado, E.N. and Peres, C.A. and Milliken, W. and Fuentes, A. and Tello, J.S. and Cerón, C. and Klitgaard, B. and Tirado, M. and Sierra, R. and Young, K.R. and Rivas-Torres, G.F. and Stevenson, P.R. and Cano, A. and Wang, O. and Baider, C. and Barlow, J. and Ferreira, J. and Berenguer, E. and Stropp, J. and Balslev, H. and Ahuite Reategui, M.A. and Mesones, I. and Valderrama Sandoval, E.H. and Gonzales, T. and Pansini, S. and Reis, N.F.C. and Sampaio, A.F. and Vos, V.A. and Palacios Cuenca, W. and Manzatto, A.G. and Farfan-Rios, W. and Silman, M.R. and Garcia-Cabrera, K. and von Hildebrand, P. and Guedes, M.C. and Costa, J.B.P. and Phillips, J.F. and Vela, C.I.A. and de Toledo, J.J. and Pauletto, D. and Valverde, F.C. and Umaña, M.N. and Phillips, O.L. and Magnusson, W.E. and ter Steege, H. and Costa, F.R.C. (2022) Local hydrological conditions influence tree diversity and composition across the Amazon basin. Ecography, 2022 (11): e06125. ISSN 0906-7590

Abstract

Tree diversity and composition in Amazonia are known to be strongly determined by the water supplied by precipitation. Nevertheless, within the same climatic regime, water availability is modulated by local topography and soil characteristics (hereafter referred to as local hydrological conditions), varying from saturated and poorly drained to well-drained and potentially dry areas. While these conditions may be expected to influence species distribution, the impacts of local hydrological conditions on tree diversity and composition remain poorly understood at the whole Amazon basin scale. Using a dataset of 443 1-ha non-flooded forest plots distributed across the basin, we investigate how local hydrological conditions influence 1) tree alpha diversity, 2) the community-weighted wood density mean (CWM-wd) – a proxy for hydraulic resistance and 3) tree species composition. We find that the effect of local hydrological conditions on tree diversity depends on climate, being more evident in wetter forests, where diversity increases towards locations with well-drained soils. CWM-wd increased towards better drained soils in Southern and Western Amazonia. Tree species composition changed along local soil hydrological gradients in Central-Eastern, Western and Southern Amazonia, and those changes were correlated with changes in the mean wood density of plots. Our results suggest that local hydrological gradients filter species, influencing the diversity and composition of Amazonian forests. Overall, this study shows that the effect of local hydrological conditions is pervasive, extending over wide Amazonian regions, and reinforces the importance of accounting for local topography and hydrology to better understand the likely response and resilience of forests to increased frequency of extreme climate events and rising temperatures.