Is leaf water repellency related to vapor pressure deficit and crown exposure in tropical forests?

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Environmental conditions can have major influences in shaping biophysical properties of leaf surfaces. In moist environments, high leaf water repellency (LWR) is expected because the presence of a water film on leaf surfaces can block stomatal pores, reduce the diffusion of CO(2), promote pathogen incidence, colonization of epiphylls and leaching of leaf nutrients. However, LWR can also increase in dry environments as a consequence of higher epicuticular wax deposition induced by high temperatures, high radiation loads and vapor pressure deficits (VPD), which could also lead to a high leaf mass per area (LMA). The aim of this study was to determine how LWR varies among tropical trees with contrasting crown exposures and subjected to distinct vapor pressure deficits at different altitudes in the Atlantic Rain Forest. We hypothesized that (i) LWR will be higher in overstory species because they are more frequently exposed to higher radiation and higher vapor pressure deficit; (ii) In the Montane Forest, LWR will be higher for overstory species in comparison to those in Lowland Forest because radiation and VPD increase with altitude; (iii) Overstory species will also show higher LMA in response to exposure to drier conditions. We measured LWR by observing angles of droplets on adaxial and abaxial leaf surfaces in five species co-occurring at lowland and a montane forest. LWR was positively related to crown exposure and VPD at both sites but not to LMA. LWR was significantly higher in the Montane forest (mean angle 66.25 degrees) than in the Lowland forest (mean angle 61.33 degrees). We suggest that atmospheric conditions associated with contrasting crown exposures may exert important controls over leaf surface properties involved in the repellence or direct absorption of water. (C) 2010 Elsevier Masson SAS. All rights reserved.366645649Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)COTEC/IF [41.065/2005]IBAMA/CGEN [093/2005]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [03/12595-7]COTEC/IF [41.065/2005]IBAMA/CGEN [093/2005

Diversity in nighttime transpiration behavior of woody species of the Atlantic Rain Forest, Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Nighttime transpiration (NT) has been documented in many plant species but we do not yet have a thorough understanding of the abiotic and biotic controls of this phenomenon. In this study we examined interspecific variation in NT behaviors in plants with distinct crown exposures (CE) and occurring at lowland (100 m) and montane forests (1000 m) in the Brazilian Atlantic rainforest to answer the following questions: are there different NT behaviors in plants subjected to distinct conditions associated with degree of CE and/or altitude? Are there higher rates of NT relative to daily maximum values at the montane forest due to higher vapor pressure deficit (VPD)? Taking into account that low VPD should generally produce low relative NT fluxes, should we expect that understory species in both altitudes will have quite uniform low relative rates of NT in comparison to overstory species owing to the buffered nature of within-canopy microclimate? NT did show differences between altitude and species. Of most significance was a prominent non-linear relationship between the NT and VPD, observed at the montane site. This non-linearity is in contrast to most previously published NT kinetics and suggests stomatal and/or leaf energy balance controls on NT. Our findings raise a new perspective concerning thermodynamic contributions to non-linear NT kinetics and some possible reasons for this interesting behavior are discussed. (C) 2012 Elsevier BM. All rights reserved.1581320Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)COTEC/IF [41.065/2005]IBAMA/CGEN [093/2005]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [03/12595-7]COTEC/IF [41.065/2005]IBAMA/CGEN [093/2005

Multidimensional ecological analyses demonstrate how interactions between functional traits shape fitness and life history strategies

Traditionally, trait‐based studies have explored single‐trait‐fitness relationships. However, this approximation in the study of fitness components is often too simplistic, given that fitness is determined by the interplay of multiple traits, which could even lead to multiple functional strategies with comparable fitness (i.e. alternative designs). Here we suggest that an analytical framework using boosted regression trees (BRT) can prove more informative to test hypotheses on trait combinations compared to standard linear models. We use two published datasets for comparisons: a botanical garden dataset with 557 plant species (Herben, 2012, Journal of Ecology, 100, 1522) and an observational dataset with 83 plant species (Adler, 2014, Proceedings of the National Academy of Sciences, 111, 740). Using the observational dataset, we found that BRTs predict the role of traits on the relative importance of survival, growth and reproduction for population growth rate better than linear models do. Moreover, we split species cultivated in different habitats within the botanical garden and observed that seed and vegetative reproduction depended on trait combinations in most habitats. Our analyses suggest that, while not all traits impact fitness components to the same degree, it is crucial to consider traits that represent different ecological dimensions. Synthesis. The analysis of trait combinations, and corresponding alternative designs via BRTs, represent a promising approach for understanding and managing functional changes in vegetation composition through measurement of suites of relatively easily measurable traits