ORIGINAL PAPER Changes in plant functional traits and water use in Atlantic rainforest: evidence of conservative water use in spatio-temporal scales Bruno H. P. Rosado • Carlos A. Joly • Stephen S. O. Burgess • Rafael S. Oliveira • Marcos P. M. Aidar Received: 30 January 2014 / Revised: 13 December 2014 / Accepted: 26 January 2015 Ó Springer-Verlag Berlin Heidelberg 2015 Abstract Key message Relationship between sap flow and functional traits changes with altitude and changes in water availability can impose a conservative water use in woody species of tropical rainforest. Abstract Using a trait-based approach, we have identified that tropical trees are vulnerable to decreases in water availability, especially in montane areas, where higher ra- diation and vapor pressure deficits lead to higher water loss from trees. Changes to functional traits are useful de- scriptors of the response of species to variation in resource availability and environmental conditions. However, how these trait-environment relationships change with altitude remains unclear. We investigated changes in xylem sap flow along an altitudinal variation and evaluated the con- tribution of morphological traits to total plant water use. We hypothesize that (1) at the Montane forest, plant spe- cies will show a more conservative water use and (2) seasonally, there will be a much greater increase in con- servative water use during the dry season at the Lowland site, since the climate conditions in the Montane site im- pose constraints to water use throughout the year. Re- markably, although water is assumed to be a non-limiting resource for Atlantic rainforest in general, we observed ecophysiological adjustments for more conservative water use in Montane forest. Our findings demonstrate that changes to water supply and demand as determined by rainfall, VPD and soil water storage can impose restrictions to water loss which differ across spatio-temporal scales. We suggest that the next steps for research in Montane forest should focus on traits related to hydraulic failure and carbon starvation to address the question whether the higher conservative water use observed at the Montane Forest translates into a higher or lower susceptibility to intensification of drought which might arise due to climate change. Keywords Functional ecology  Drought  Wood density  Specific leaf area  Sap flow  Altitudinal variation Introduction One of the most concerning possibilities for climate change scenarios is the intensification of drought which may result in tree mortality due to hydraulic failure, carbon starvation and biotic agents (McDowell et al. 2008, 2011). In this context, trait-based approaches have identified changes in tropical rainforests due to different susceptibilities of spe- cies to decreases in water availability (Fauset et al. 2012; Phillips et al. 2010; Tobin et al. 1999). Thus, the search for functional traits as proxies of community responses to environmental changes has been considered one of the Communicated by A. Braeuning. B. H. P. Rosado (&) Departamento de Ecologia, IBRAG, Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ, Brazil e-mail: brunorosado@gmail.com C. A. Joly  R. S. Oliveira Departamento de Biologia Vegetal, IB, Universidade Estadual de Campinas, Campinas, SP, Brazil S. S. O. Burgess School of Plant Biology, University of Western Australia, Perth, WA, Australia M. P. M. Aidar Centro de Pesquisa em Ecologia e Fisiologia, Nu ´cleo de Pesquisa em Fisiologia e Bioquı ´mica, Instituto de Bota ˆnica de Sa ˜o Paulo, Sa ˜o Paulo, SP, Brazil 123 Trees DOI 10.1007/s00468-015-1165-8