Banca de DEFESA: Lucas Silva Costa

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : Lucas Silva Costa
DATE: 16/02/2024
TIME: 14:00
LOCAL: Auditório IB - formato híbrido
TITLE:

"Woody plant encroachment in wet grasslands in the Federal District".

KEY WORDS:

tree-herbaceous interactions, woody plant encroachment, remote sensing, environmental changes

PAGES: 200
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUMMARY:

Savannas are biomes composed of a continuous herbaceous stratum and scattered woody plants. Among the factors that allow this co-dominance is the seasonal availability of water. The Brazilian Cerrado is the second-largest tropical savannah in the world and is a biodiversity hotspot. Environmental changes, especially hydrological ones, can interfere with the interaction of the vegetation strata. The integrity of the Cerrado's vegetation cover is also fundamental to continental eco-hydrological functioning. The phenomenon of woody densification, i.e., an increase in the density of woody plants, has been observed frequently in savannas. However, the possible causes, as well as their likely environmental consequences, are still poorly understood. One of the increasingly important tools for ecological monitoring is remote sensing, especially in detecting and understanding the processes involved in woody densification. Therefore, the central question of this study was to understand how the relationship between hydrology and the interaction of woody and herbaceous strata is affected by environmental changes in tropical savannas. To answer this question, the following objectives were proposed: i) to investigate the water dynamics of tropical savannas under conditions of imbalance between the herbaceous and woody strata; ii) to assess the accuracy of remote classification of woody densification in a tropical savanna; iii) to investigate which environmental factors and disturbances (lowering of the water table, fire history, and climate change) may be related to this phenomenon as well as the possible environmental impacts. A systematic review was conducted to achieve the first objective. About the other objectives, data collection in the field involved surveying aerial images with Unmanned Aerial Vehicles (UAVs) and satellites, soil collection, floristic surveys, and monitoring water stocks. The UAV images obtained during the rainy season showed the best accuracy in classifying woody density, especially using the Random Forest machine learning algorithm. Regional factors such as the lowering of the water table influenced the seasonality of soil moisture, especially in wet grasslands. The absence of waterlogging allowed woody species to colonize and establish themselves. The imbalance between the strata, whether woody densification or grass invasion, harmed herbaceous-grass diversity. In addition to the decrease in water stocks, the water balance showed a negative trend, probably influenced by the increase in temperature and decrease in air humidity over the last two decades. Finally, feedback studies on processes related to environmental change, such as the one presented here, are urgently needed, as these phenomena tend to reach their tipping points more quickly.

COMMITTEE MEMBERS:
Externa à Instituição - ANE AUXILIADORA COSTA ALENCAR - IPAM
Interna - 5192951 - CASSIA BEATRIZ RODRIGUES MUNHOZ
Presidente - 1122706 - MERCEDES MARIA DA CUNHA BUSTAMANTE
Externo à Instituição - NILSON CLEMENTINO FERREIRA - UFG
Interno - 1334398 - RICARDO BOMFIM MACHADO