Banca de QUALIFICAÇÃO: MARIANA MELISSA LIMA VIEIRA DE MELO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : MARIANA MELISSA LIMA VIEIRA DE MELO
DATE: 10/09/2026
TIME: 09:00
LOCAL: Remoto
TITLE:

ECOHYDROLOGICAL DYNAMICS OF A TROPICAL PASTURE UNDER GRAZING CONDITIONS: CARBON ASSIMILATION, EVAPOTRANSPIRATION, AND WATER-USE EFFICIENCY

KEY WORDS:

Biophysical controls, Brachiaria brizantha, Carbon dioxide fluxes, Water Use efficiency

PAGES: 114
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Meteorologia
SPECIALTY: Micrometeorologia
SUMMARY:

Managed grazing ecosystems cover approximately 25% of the global ice-free land surface, exceeding any other land-use class. Their importance for the global CO₂ cycle is therefore undeniable, as they play a central role in food security, global economies, and the livelihoods of more than one billion people. Understanding the mechanisms controlling CO₂ and water vapor exchanges in these agroecosystems is essential for improving their management and representation in ecohydrological models. This study investigated how atmospheric and environmental drivers regulate CO₂ exchange and how the intensity of the diurnal coupling between carbon and water fluxes affects water-use efficiency (WUE) in a tropical C₄ pasture using eddy covariance measurements. Precipitation and soil water content were identified as the main annual regulators of carbon fluxes. The GPP–ET coupling varied seasonally, with moderate coupling prevailing during the rainy season and predominantly weak coupling during the dry season (68.3% of days). This weak coupling resulted from sub-daily asynchrony, with ET peaking early in the morning (~08:00 h) and GPP near midday, leading to a faster decline in ET than GPP and consequently higher WUE during the dry season. At the seasonal scale, ET decline exceeded GPP after a critical threshold of ~20 consecutive rain-free days, increasing WUE under severe water stress. Random Forest analysis indicated vapor pressure deficit as the dominant driver of WUE in the dry season, while surface conductance controlled WUE during the rainy season.

COMMITTEE MEMBERS:
Interno - 2086472 - BERGSON GUEDES BEZERRA
Interno - 1753398 - PABLO ELI SOARES DE OLIVEIRA
Interno - 3217859 - PEDRO RODRIGUES MUTTI
Externo à Instituição - THIAGO RANGEL RODRIGUES - UFMS