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Agradecimentos: This work was supported by many research agencies. M.B., P.R.L.B., F.B. and L.P. were supported by CAPES PhD scholarship. M.A.V. and H.A. were supported by a NASA Interdisciplinary Science grant (NNX14AD31G). V.I. and S.R.S. acknowledge DOE Grant DE-SC0011078 ("GoAmazon"). M.B., R.S.O., L.A. and L.E.O.C.A. thank GO-AMAZON FAPESP (2013/50533-5) and L.E.O.C.A. thanks CNPq Productivity Fellowship (305054/2016-3). V.I., R.S.O. and M.B. also thank FAPESP-UoM (2014/50332-2) and FAPESP-Microsoft (2011/52072-0). We are also grateful to the LBA-INPA assistance in Santarém with special respect to Louro Lima, Adão Silva Santos, Cleuton Pereira, Sarah Mião, Elizangela Rebelo, Marduk (in memoriam), Neill Prohaska and Gregory Ewing. We also thank Dr. Michael Keller for reviewing and commenting in the manuscript. The authors confirm they do not have any conflict of interest Abstract: The relationship between rooting depth and above-ground hydraulic traits can potentially define drought resistance strategies that are important in determining species distribution and coexistence in seasonal tropical forests, and understanding this is important for predicting the effects of future climate change in these ecosystems. We assessed the rooting depth of 12 dominant tree species (representing c. 42% of the forest basal area) in a seasonal Amazon forest using the stable isotope ratios (d18O and d2H) of water collected from tree xylem and soils from a range of depths. We took advantage of a major ENSO-related drought in 2015/2016 that caused substantial evaporative isotope enrichment in the soil and revealed water use strategies of each species under extreme conditions. We measured the minimum dry season leaf water potential both in a normal year (2014; psi non-ENSO) and in an extreme drought year (2015; psi ENSO). Furthermore, we measured xylem hydraulic traits that indicate water potential thresholds trees tolerate without risking hydraulic failure (P50 and P88). We demonstrate that coexisting trees are largely segregated along a single hydrological niche axis defined by root depth differences, access to light and tolerance of low water potential. These differences in rooting depth were strongly related to tree size; diameter at breast height (DBH) explained 72% of the variation in the d18Oxylem. Additionally, d18Oxylem explained 49% of the variation in P50 and 70% of P88, with shallow-rooted species more tolerant of low water potentials, while d18O of xylem water explained 47% and 77% of the variation of minimum psi non-ENSO and psi ENSO. We propose a new formulation to estimate an effective functional rooting depth, i.e. the likely soil depth from which roots can sustain water uptake for physiological functions, using DBH as predictor of root depth at this site. Based on these estimates, we conclude that rooting depth varies systematically across the most abundant families, genera and species at the Tapajós forest, and that understorey species in particular are limited to shallow rooting depths. Our results support the theory of hydrological niche segregation and its underlying trade-off related to drought resistance, which also affect the dominance structure of trees in this seasonal eastern Amazon forest. Synthesis. Our results support the theory of hydrological niche segregation and demonstrate its underlying trade-off related to drought resistance (access to deep water vs. tolerance of very low water potentials). We found that the single hydrological axis defining water use traits was strongly related to tree size, and infer that periodic extreme droughts influence community composition and the dominance structure of trees in this seasonal eastern Amazon forest FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES Fechado

Agradecimentos: We thank Grazielle Sales, David Lapola, Giuliano Locosseli and Tomas Domingues for reviewing earlier versions of this manuscript. We thank the UNICAMP post-graduate programs in Ecology and Plant Biology. This research was funded by FAPESP/Microsoft research (grant 11/52072-0) awarded to R.S.O.; the Higher Education Co-ordination Agency (CAPES) scholarship award to P.R.L.B and FVB. RSO received a CNPq productivity scholarship. We thank Newton International Fellowship (grant NF170370) who funded P.R.L.B. in the final writing of this manuscript Abstract: Fog is a frequent phenomenon in tropical montane cloud forests (TMCFs). These ecosystems are important to the water supply of adjacent lowland regions which is largely determined by the effect of fog on TCMF evapotranspiration rates and hydrological balance. Understanding fog regimes at fine-grained temporal resolution is key to predict plant functioning and effects of climatic changes in TMCFs, especially on key hydrological services that these forests provide. Here, we combine a suite of micrometeorological and hydrological sensors with a visibilimeter, a reliable sensor of fog occurrence, to gather fine-grained information on fog frequency, duration and timing and its contribution to water inputs, light availability and microclimatic variability in a Brazilian TMCF. Despite occurring on 64% of days, fog was highly variable at daily and seasonal scales, occurring mostly at night and during the rainy season. Approximately 1200 liters of fog were intercepted per tree per year (259 mm or 10.7% of total net precipitation). Fog also increased net precipitation provided by concomitant fog-rain events. Monthly net precipitation to precipitation ratio, a measure of how much water arrives at the soil and how much evaporates or is intercepted by the canopy, was 0.96 - much higher than the 0.72 typical of lowland rainforest, due to the additional fog water input on TMCF. Cloudiness, and not fog, dominated light availability and inter-day microclimatic variability (air temperature and vapor pressure deficit). High fog regime variability indicates that understanding TMCFs functioning requires integration of plant function with fine-grained data of fog and cloud occurrence. We discuss possible consequences of our results to TMCFs plant functioning FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES Fechado

Orientador: Rafael Silva Oliveira Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia Resumo: A água é um dos principais fatores afetando quase todos os processos bióticos e abióticos que ocorrem na superfície do planeta. Sobre a superfície do planeta, plantas modulam fortemente a dinâmica da água. Plantas conectam o solo com a atmosfera através de suas raízes até as folhas, através do seu sistema de transporte hídrico, formando o contínuo solo-planta-atmosfera. Entretanto, temos muitas lacunas no nosso entendimento do transporte de água de plantas, desde os mecanismos atmosféricos determinando o transporte de água, disponibilidade de água no solo até a fisiologia do sistema de transporte hídrico de plantas e seus custos e demandas conflitantes. Para preencher essas lacunas, nesta tese eu uso novas abordagens para entender a demanda atmosférica de água, o transporte de água da atmosfera para o solo e os custos nutricionais do sistema de transporte de água de plantas em uma Floresta Tropical Nebular e uma Floresta Tropical Chovosa. No primeiro capítulo, eu uso um método inovador para estudar com alta resolução temporal os efeitos da neblina na água do solo e da atmosfera. No segundo capítulo, eu estudo um processo frequentemente ignorado, o transporte de água da atmosfera para o solo. No terceito capítulo, eu estudo e proponho novas perspectivas para entender os custos e as eficiências do sistema de transporte hídrico de plantas. No quarto capítulo, eu estudo os custos nutricionais da madeira e suas relações com o sistema de transporte hídrico de plantas. Por fim, eu discuto os principais resultados e suas implicações para a ecohidrologia e ecofisiologia de plantas Abstract: Water is one of the key drivers of almost all biotic and abiotic process that occurs in the surface of the planet. Over the terrestrial surface of the planet, plants modulate most of water dynamics. Plants connect water in the soil with the atmosphere throught their roots and up to the leaves passing through its water transport system, forming the soil-plant-atmosphere continuum. However we have many gaps in the understanding of plant water transport, from the understanding of the atmospheric drivers of water transport, soil water availability up to the plant water transport system physiology and its costs and tradeoffs. To adress those gaps, in this Thesis I use novel approaches to understand atmospheric water demand, water transport from the atmosphere to the soil and the nutritional costs of the water transport system of plants in a Tropical Cloud Forest and in a Tropical Rainforest. In the first chapter of this work, I use an innovative method to study with high temporal resolution fog effects on atmospheric and soil water inputs. In the second chapter, I study an often overlooked process, water flow from the atmosphere to the soil. In the third chapter, I study and propose new perspectives to understand the costs and efficiencies of a plant is water transport system. In the forth chapter, I study the nutritional cost of wood and its relations with plant is water transport system. Finally, I discuss the key results and its implications to plant ecohydrology and ecophysiology Doutorado Ecologia Doutor em Ecologia CAPES CNPQ

Orientador: Rafael Silva Oliveira Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia Resumo: Matas nebulares montanas tropicais (MNMT) são ecossistemas frequentemente inundados por neblinas, o que influencia quase todos os aspectos de seu funcionamento. MNMTs são extremamente importantes devido aos serviços ecossistêmicos que provêm, principalmente hidrológicos, e devido a sua alta biodiversidade. Com mudanças climáticas e de uso de terra já acontencendo há urgência em compreender o funcionamento de MNMTs para o desenvolvimento de estratégias de conservação e restauração. O objetivo deste trabalho é analisar e quantificar os efeitos da neblina no microclima e funcionamento foliar de MNMTs. Medimos a ocorrência de neblina, variáveis microclimáticas, parâmetros fotossintéticos e usamos uma nova metodologia para medir a capacidade de absorção foliar de água de cinco espécies abundantes de uma MNMT na região de Campos do Jordão, Brasil. Utilizamos esses dados para estimar os efeitos da neblina na disponibilidade hídrica, na demanda de água da atmosfera, na fotossíntese potencial, na absorção foliar de água e no balanço térmico foliar de MNMTs. A neblina teve um forte efeito no aumento da disponibilidade hídrica do solo e na redução da demanda atmosférica de água. A neblina apresentou um efeito negligível na redução da fotossíntese potencial das espécies estudadas. Nós apresentamos, pela primeira vez, estimativas do efeito da neblina no balanço térmico foliar mostrando que ela possui um importante papel em amenizar as temperaturas foliares médias durante o dia, reduzindo-as em 0.5oC por cada hora de ocorrência de neblina. Nós encontramos que a absorção foliar de água constituí uma fonte importante de água para as espécies estudadas, com a neblina noturna possuindo o potencial de reidratar as folhas de duas das espécies estudadas das suas condições mais secas até hidratação total em mais de 50% das noites. Diferenças na capacidade de absorção foliar de água das espécies estudadas sugere que a absorção foliar é um nicho importante de recursos com o potencial de selecionar características foliares relacionadas à eficiência de absorção foliar de água em espécies de MNMTs Abstract: Tropical montane cloud forests (TMCFs) are ecosystem with frequent fog immersion influencing almost all aspects of its functioning.TMCFs are extremely important both due to the ecosystem services it provides, particularly hydrologically, and because of its high biodiversity. With climate and land use changes already happening there is urgency on understanding TMCFs functioning to devise conservation and restoration strategies. The objective of this work is to analyze and quantify fog effects on the microclimate and leaf functioning of TMCFs. We measured fog occurrence, microclimatic variables, photosynthetic parameters and used a new methodology to measure foliar water uptake capacity of five abundant TMCFs tree species in the region of Campos do Jordão, Brazil, We used these data to estimate fog effects on water availability, atmospheric water demand, potential photosynthesis, leaf water uptake and leaf thermal balance of TMCF. Fog had a pronounced effect on increasing soil water availability and reducing atmospheric water demand. Fog had a negligible effect on reducing potential photosynthesis of the studied species. We provide for the first time estimates of fog effects on leaf thermal balance showing it has an important effect on buffering mean daytime leaf temperatures by reducing it 0.5oC for each hour of fog occurence. We found that foliar uptake of fog water constitutes an important water source for the studied species, with nocturnal fog having the potential to rehydrate leaves of two of the studied species from its driest conditions to fully rehydration more than 50% of the nights. Differences in foliar water uptake capacity in the studied species suggests leaf water uptake is an important resource niche with potential of selecting leaf water uptake related traits in TMCFs species Mestrado Ecologia Mestre em Ecologia