segunda, 24/08/2026
A defesa de Doutorado intitulada "The Brejos de Altitude of Northeastern Brazil: Definition, Mapping and Patterns of Land-Cover Changes" ocorrerá no dia 24/08/2026, no Salão Azul / CCS - UFRJ.
Orientadora:
Dra. Mariana M. Vale
Coorientadores:
Dra. Maria Lucia Lorini
Dr. Julian Wimmer
Banca:
Dra. Mariana Moncassim Vale
Dr. Marcus Vinícius Vieira
Dr. Jayme Augusto Prevedello
Dra. Marinez Ferreira de Siqueira
Dr. Carlos Leandro Cordeiro de Oliveira
Suplentes:
Dr. Carlos Eduardo Grelle
Dra. Dulce Montuano
Resumo:
Brejos de altitude are humid forest enclaves perched atop plateaus and mountain ranges embedded within the Caatinga dry forest matrix of Northeastern Brazil. These ecosystems function as biodiversity refugia shaped by Quaternary climatic oscillations, harboring flora and fauna typical of humid forests and exhibiting high levels of endemism. Despite their recognized ecological and biogeographic significance, brejos de altitude remain critically understudied, and their definition fragmented and imprecise. The term brejo, literally referring to waterlogged or marshy ground, is itself misleading, as the vegetation characteristic of these ecosystems consists of tropical humid forests not associated with permanently waterlogged soils. Furthermore, multiple conflicting conceptual frameworks coexist, each linked to distinct sets of environmental variables, and any patch of green vegetation at high elevations in northeastern Brazil tends to be indiscriminately classified as brejo. Some typologies extend the category beyond plateau and mountain summits to include footslope and valley environments, yet none of these classifications have been subjected to rigorous scientific evaluation. Consequently, no reliable inventory of brejos de altitude exists for northeastern Brazil, nor have studies systematically assessed forest cover loss across these ecosystems. Addressing these gaps, this dissertation aimed to synthesize the historical knowledge on brejos de altitude, spatially delineate these ecosystems using self-organizing neural networks, and characterize forest cover dynamics over 39 years. The work is organized into three chapters. The first chapter revisited the definition and geographic distribution of brejos de altitude through a systematic literature review, providing a comprehensive baseline of the state of knowledge on these environments and identifying research gaps and priorities. A total of 103 localities classified as brejos de altitude were identified, along with 14 distinct definitions, unified only by the criteria of elevation and humidity. Additional typologies occurring outside upland environments were also documented, including brejo de vale (valley brejo), brejo de encosta (slope brejo), and brejo de sopé (footslope brejo), none of which were delimited through explicit or reproducible methodology. The second chapter aimed to define brejos de altitude through neural network modeling, identifying the environmental variables that best characterize these ecosystems and mapping their spatial extent across Northeastern Brazil. Results demonstrated that brejos de altitude are most accurately modeled when the calibration area is restricted to the Caatinga phytogeographic domain at elevations ≥ 500 m. These ecosystems occur predominantly on the windward slopes of the major geomorphological units of the Caatinga, with soil temperature and slope aspect emerging as the primary determinant variables. The third chapter identified forest cover transitions within brejos de altitude over the past 39 years, assessed the biophysical and socioeconomic variables associated with forest loss and gain, and evaluated the effectiveness of protected areas in preventing forest loss. All examined brejos exhibited a net forest deficit over time, with losses consistently exceeding regeneration. The probability of forest cover loss was negatively associated with elevation, slope, clay content, and distance to croplands and roads, whereas soil organic carbon exerted a positive effect on both forest loss and gain. Strictly protected areas reduced deforestation within their boundaries, an effect mediated by protected area age. Taken together, the three chapters advance the understanding of brejos de altitude by delivering a comprehensive ecosystem inventory, a spatially reproducible delineation framework, and a multi-decadal analysis of vegetation dynamics across their known range.