https://repositorio.ufu.br/handle/123456789/18961 2026-04-23T03:32:51Z https://repositorio.ufu.br/handle/123456789/47946 Title: Reabilitação da biodiversidade e funções ecológicas dos solos em agroecossistemas alto-andinos do Equador sobre Cangahua Abstract: The sustainable management of high-Andean agroecosystems relies heavily on the dynamics of soil organic carbon (SOC), microbial activity, and the maintenance of ecosystem services, particularly in soils with cangahua, a hardened volcanic material highly prone to degradation. This study synthesized the effects of diverse soil management practices—agroecological, traditional, fallow, and degraded ecosystem as control—on organic matter decomposition, carbon content, soil respiration, microbial diversity, and biogeochemical functionality across two Ecuadorian highland sites, Cacha (Chimborazo) and La Merced (Pichincha), which differ in their historical rehabilitation periods (5 versus 15 years, respectively). The methodology integrated tea bag indices (green and rooibos) to evaluate decomposition rates of labile and recalcitrant organic materials, loss-on-ignition for SOC quantification, Solvita® assays for soil respiration, and microbial community assessments through taxonomic and functional diversity metrics. Statistical analyses employed a fully factorial design with 24 experimental units, enabling detection of management, site, and interaction effects. Results consistently demonstrated that agroecological management enhanced green and rooibos tea decomposition, SOC accumulation, and soil respiration relative to traditional, fallow, and degraded systems, with La Merced exhibiting generally higher rates than Cacha, reflecting both climatic and historical management influences. Traditional and fallow practices provided intermediate benefits, insufficient to counteract long-term degradation, whereas degraded ecosystems exhibited severely reduced microbial activity, low SOC content, and diminished biogeochemical functionality, confirming functional collapse under cangahua exposure. Microbial analyses revealed that agroecological soils harbored greater taxonomic richness and functional redundancy, supporting higher nutrient cycling efficiency and resilience to perturbations. Moreover, the study found strong positive correlations between SOC content, microbial biomass, and respiration rates, indicating that sustained organic inputs, permanent ground cover, and crop diversification directly enhance soil functional capacity and carbon stabilization. Integrating these findings, the research demonstrates that systematic agroecological interventions not only rehabilitate degraded soils but also contribute to carbon sequestration and climate change mitigation in fragile mountainous landscapes. Importantly, the comparative analysis across sites and historical contexts highlights the temporal dimension of soil restoration, emphasizing that long-term implementation is critical to realizing full ecosystem benefits. In conclusion, this integrative assessment provides robust scientific evidence supporting agroecological transitions as a key strategy to restore high-Andean cangahua soils, improve soil fertility and structure, enhance microbial diversity and activity, maintain ecosystem services, and strengthen the capacity of rural communities to sustain agricultural production while contributing to global climate mitigation goals. The findings inform policy formulation, extension services, and participatory management approaches, underscoring the value of combining ecological principles with traditional practices to achieve both environmental restoration and socio-economic resilience in highly vulnerable highland territories. 2025-09-29T00:00:00Z https://repositorio.ufu.br/handle/123456789/47805 Title: Atributos funcionais vegetativos e fatores ambientais em savanas sul-americanas: legados históricos da megafauna extinta e pressões atuais de clima, solo e fogo Abstract: South American savannas represent one of the most biodiverse ecosystems on the planet, resulting from the interaction of historical, environmental, and functional factors. Traditionally, their origin and maintenance have been attributed to poor soils, seasonal climate, and recurrent fire regimes, but recent evidence points out to a potential role of extinct megafauna in shaping some South American savannas. In this thesis, I aimed to integrate evolutionary legacies and current environmental pressures to understand the functional ecology of Neotropical savannas. In the first chapter, we investigated the legacy of extinct megafauna in Amazonian savannas and the Cerrado by comparing functional traits associated with defense against herbivory, such as wood density, leaf size, spines, and extrafloral nectaries. We observed that Amazonian savannas contain species with higher wood density and a greater proportion of spines, while no significant differences were detected in leaf size or the presence of extrafloral nectaries, supporting the hypothesis that large herbivores played a relevant role in structuring Amazonian savannas during the Pleistocene, leaving functional legacies that distinguish these areas from the Cerrado, where fire appears to have been the main selective force. In the second chapter, we evaluated how present environmental conditions (soil, climate, flooding, rockiness, and fire) influence functional trait variation in South American savannas, evaluating six vegetative traits (leaf area, wood density, bark thickness, height, spines, and latex) and seven types of savannas. This analysis revealed three main groups of physiognomies: (i) Cerrado, Guiana savannas, and Alter do Chão savannas, characterized by thick bark and low investment in height, in cooler climates and dystrophic soils; (ii) rocky and white-sand savannas, with thin bark and higher investment in height, associated with humid climates and acidic soils; and (iii) hyperseasonal and swampy Amazonian savannas, with intermediate bark, low height growth, and low wood density, occurring in warm, humid climates and acidic, waterlogged soils; the presence of spines and latex did not vary significantly among the physiognomies. Overall, the results show that the functional diversity of South American savannas reflects both historical legacies and current environmental pressures; while the legacy of megafauna may have left traces in the defensive traits of Amazonian savannas, variations in climate, soil, and fire continue to shape distinct ecological strategies across different formations. 2025-09-24T00:00:00Z https://repositorio.ufu.br/handle/123456789/45192 Title: Galhas de insetos: um micro-laboratório de estudos de interações multitróficas e não-tróficas Abstract: Galling insects are one of the most specialized guilds, feeding on neo-formed and complex plant organs, metabolically dependent on their continuous chemical and/or mechanical food stimuli. Thus, any change in the behavior of the gall due to the effect of natural enemies may reflect on the anatomical and chemical configuration of the gall. While some insects use mature plant organs to form their microhabitats, galling insects depend on reactive sites for oviposition. The availability of sites in plants for the induction of galls, however, depends on the phenology of the host plant and, therefore, a synchronization of the phenophases of the galling insect is necessary for compatibility between the emergence of reactive plant sites and oviposition by the galling organisms. Therefore, all organisms that interact directly or indirectly with each galling insect, after the development of their galls, depend on this synchrony of phenophases, and can also adapt their life histories to interact with the galls at certain stages. The galls provide the natural enemies of galling insects with food resources, also functioning as microhabitats for a variety of arthropods that can escape adverse abiotic conditions using the gall structure. Some galling insects also establish non-trophic facilitating interactions in the ecosystems in which they occur through the availability of these microhabitats after emergence. Galls induced at axillary bud sites, for example, can remain for long periods, even years, on host plants. Therefore, the taxa of galling insects and the organ where galls are induced determine their histological characteristics and, as a result, the permanency of these microhabitats in plants after senescence. In this Thesis we investigate galls as microhabitat in different contexts of trophic and non-trophic interactions. Galls induced by Cecidomyiidae on Piptocarpha macropoda (DC.) Baker (Asteraceae) responds to parasitoid wasps Platygaster sp. and, since an individual of Cecidomyiidae supports many parasitoids, we hypothesized that an intense consumption of nutrients by the parasitized galling insect would affect the gall size, the number of cells in each compartment of gall tissues, as well as the histochemical profile. In a multitrophic system established in Macairea radula (Melastomataceae) (involving the galls induced by Palaeomystella oligophaga (Lepdoptera: Momphidae) and its direct and indirect natural enemies) we analyzed how this system is influenced by biotic conditions. And finally, also in galls of M. radula-P. oligophaga, we evaluated why these galls remain attached to the host plant even after the emergence of the galling insect, and also which opportunistic arthropods use the structure of these galls as a micro-habitat. 2022-08-31T00:00:00Z https://repositorio.ufu.br/handle/123456789/45084 Title: Como a suplementação de nitrogênio e fósforo pode alterar a fisiologia de plantas nativas do Cerrado? Abstract: Human activities have globally modified the cycle of essential nutrients for plants, potentially affecting the physiology of native species. In South America, specifically in the Brazilian Cerrado, large areas have been transformed into agricultural lands over time. Due to the oligotrophic conditions of the biome, the use of industrial fertilizers is widely adopted to provide ideal conditions for the growth and development of cultivated plants. In general, among the essential mineral nutrients, nitrogen is the most required in quantity by plants. Consequently, the concentration of this element has increased over the years in natural ecosystems near monocultures that use nitrogen fertilizers. Due to surface runoff, leaching, and volatilization, part of the nitrogen may reach higher concentrations, especially at the edges of remaining natural ecosystems. This can influence not only the dynamics of nitrogen in the soil and plants but also the availability of carbon. Non-radioactive stable isotopes of 15N and 13C have been used in ecological studies to determine the origin and transport of N and C in natural environments. In the first chapter, the presence of 15N in the soil and leaves of a Cerrado plant species was examined at the interior and edges of eight Cerrado fragments was verified, along with 15N in the leaves of Bauhinia holophylla over two years. The relationships between 15N and 13C the edges and interior of the fragments were also analyzed. Intermediate Cerrado fragments showed higher values of 15N in the leaves at the edges. In one of the fragments where 15N was higher at the edge, the physiology of B. holophylla was analyzed, revealing higher values of specific leaf area (SLA) and relative water content (RWC) at the edges. On the other hand, the results of photosynthesis suggest that, inside the fragment, plants have a greater capacity to dissipate excess light energy and maintain a more preserved photosynthetic apparatus, which may indicate stress at the edges. In the second chapter, N, P, and N+P supplementation was applied to 25 permanent plots of 100m² each, and the physiological effects of B. holophylla were analyzed. The specie showed an increase in SLA and RWC in the treatment with N+P supplementation, while the potential quantum yield (Fv/Fm) was higher in the treatment with P supplementation alone. On the other hand, P supplementation showed lower capacity to dissipate excess light energy and less protection against excess light. The third chapter addressed the physiological responses to supplementation with N, P, or N+P in Handroanthus impetiginosus (Mart. ex DC.) grown in a greenhouse. Supplementation with N or P promoted an increase in leaf area and growth, while the combination of N+P increased leaf efficiency for light capture. However, in the combined supplementation of high N+P (2.44 g of N and 2.50 g of P), the plants did not show changes in total size and of chlorophyll fluorescence and exhibited decreased photosynthetic efficiency and stomatal conductance. These results indicate that high availability of N+P may compromise the physiological heath of H. impetiginosus. 2024-12-19T00:00:00Z