Banca de DEFESA: DELIANE VIEIRA PENHA DE OLIVEIRA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : DELIANE VIEIRA PENHA DE OLIVEIRA
DATA : 13/09/2019
HORA: 14:30
LOCAL: Sala 107 - Amazônia
TÍTULO:

O USO DA ÁGUA POR ÁRVORES DE UMA FLORESTA TROPICAL EM RESPOSTA À SAZONALIDADE

PALAVRAS-CHAVES:

Hydraulic strategies, iso/anisohydric, vulnerability to embolism, leaf water potential at turgor loss point, nonstructural carbohydrate.

PÁGINAS: 99
GRANDE ÁREA: Outra
ÁREA: Ciências Ambientais
RESUMO:

The Amazon rainforest affects the regional and global climate. Climate models foresee an increase in the frequency and intensity of drought in the region, so knowledge about how vegetation responds to changes in seasonal environmental conditions is helpful to understanding the vulnerability of the forest to water stress. Despite of important advances in understanding the effect of drought on tropical rainforests in the Amazon, the relationship between water use strategies and functional attributes of xylem and leaf as well as the effects of these strategies on leaf nonstructural carbohydrate dynamics is not well understood. The main objective of this work was to identify the strategies of water use by trees of the Tapajos National Forest. Questions were raised and discussed in two chapters. Chapter 1 refers to the identification of water use strategies based on iso/ anisohydric classification and the relation with xylem and leaf hydraulic functional attributes. While in chapter 2 we tried to describe the dynamics of non-structural leaf carbohydrates (CNE) of trees occupying different extracts in the vertical structure of the tropical forest in the daily and seasonal scales. The results reveal that canopy, middle canopy and understory trees represent a continuum of water use strategies, with strong stomatal control (isohydric strategy) prevailing in canopy trees and lower stomatal control (anisohydric strategy) in the understory. Middle canopy trees showed intermediate behavior. Regulation of gas exchange by stomata and maintenance of leaf water potential are associated with xylem vulnerability to embolism and tolerance to loss of leaf turgor. The water potentials that impose maximum and minimum stomatal conductance (gs) limits on the community indicate that these limits are determined by soil water content and vapor pressure deficit. Regarding the CNEs, it was identified that the daily and seasonal patterns of soluble sugars and leaf starch differ according to the axis of water and light availability in each microenvironment where plants of different habits occur. Overall, canopy and understory trees showed similar daily and seasonal response patterns, while mid-canopy trees differed from the other groups. Results suggest that C-related leaf metabolism was not limited by canopy and understory drought, but the opposite may have occurred for the canopy medium. The mechanisms for understanding these processes have yet to be explored. The results of this work support the hypothesis of niche segregation by the use of water and light in seasonal rainforests of the Amazon and demonstrate a diversity of hydraulic strategies rather than an iso/anisohydric dichotomy. In addition, they have important implications for understanding how different stomatal conductance patterns influence functional diversity in a seasonal rainforest, as well as for creating more realistic representations in vegetation dynamics models, allowing greater accuracy in climate change predictions and understanding of the relationship between vegetation and atmosphere.

MEMBROS DA BANCA:
Externo ao Programa - 1385154 - ADVANIO INACIO SIQUEIRA SILVA
Externa à Instituição - GRAZIELLE SALES TEODORO - UFPA
Interno - 1520271 - JOAO RICARDO VASCONCELLOS GAMA
Presidente - 1794276 - JOSE MAURO SOUSA DE MOURA
Externa à Instituição - LUCIANA FERREIRA ALVES
Interno - 1549120 - RODRIGO DA SILVA