Dinâmica da água no sistema solo-vegetação-atmosfera em floresta de Vochysia divergens Pohl monodominante no Pantanal

• Autor(a) principal: Sallo, Fernando da Silva
• Data de Publicação: 2017
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFMT
• Texto Completo: http://ri.ufmt.br/handle/1/2211
• topic: Estoque de água na vegetação; Déficit de água na vegetação; SVAT; Modelagem; Transpiração; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA; Stem water storage; Stem water deficit; SVAT; Modelling; Transpiration

Models transfer of soil-vegetation-atmosphere system (SVATs) have been enhanced with the inclusion of information about the processes and mechanisms of water transport and gas exchange with the atmosphere. This update occurs as the studies advance towards understanding of these processes. One of the processes that can improve the transfer models is the vegetation or plant water storage. This process is dynamic, it varies according to the conditions of atmosphere water demand and soil water availability, and influences the transpiration rate and CO2 assimilation. From this, this study aimed to investigate the water storage dynamics in V. divergens, a monodominant species in the Pantanal of Mato Grosso, through two approaches: (i) mining high-resolution dendrometric data using temporal analysis technique over 2-year study, from which evaluated the plant water deficit (∆W), and stem water storage dynamics (stem daily cycle) using a phase methodology (i.e, contraction, recovery and increment) and correlating the water storage with environmental variables (V PD, ea, Ta and θs); (ii) modeling the dynamics of water storage, with qualitative validation, and subsequently estimatives by the model of water vapor and CO2 gas exchanges, taking into account the variation of soil water availability and the atmospheric CO2 concentration (ca). In the first approach, the variation of the water deficit (∆W) and the water storage in V. divergens showed well-defined seasonality, in which the lower levels occurred during the dry season (September), while in the wet season (flooded period , March) occurred the highest levels. The water deficit correlated (R2 = 0,71) non-linearly with the environmental variables but followed the variation of soil water content (θs), while the average daily variation of the stem cycle correlated sinusoidally with exponential damped associated to water vapor pressure (ea mean) with SE ± 0.093 (Standard Error). In the second approach, the dynamics of change in the water storage was consistently modeled by SVAT, obtaining a R2= 0.725 with SE± 0.213. The averaged estimated transpiration rate was 3.45 mm d−1 and the vegetation water storage corresponded between 15-33% of the daily transpiration. The CO2 assimilation rate was on average 15 µmol m−2 s −1 when ca = 380 ppm, in this condition, the water use efficiency (WUE) and stomatal conductance decreased with the reduction of soil water availability and with increased V PD. For a scenario of ca = 580 ppm, the CO2 assimilation increased by about 40% and WUE about 70%, while transpiration reduced approximately 10%, suggesting some positive feedback due to temperature. In this scenario, stomatal conductance and CO2 assimilation tend to increase with the reduction of water availability and increase with V PD, meaning lower sensitivity to dry periods.