Estruturas relacionadas ao potencial de rebrotamento de duas espécies de Myrtaceae do Cerrado: análises morfoanatômicas e químicas / Gabriela Santos da Silva.-Piracicaba, 2017. 53 p. Dissertação (Mestrado)-USP / Escola Superior de Agricultura "Luiz de Queiroz". 1. Banco de gemas 2. Coléteres 3. Gemas acessórias 4. Sistemas subterrâneos 5. Rebrotamento I. Título

This study was carried out in a Cerrado (the largest savanna in the Neotropics) area where pine plantations, introduced in the 1970s, were removed by clear cutting of the trees and burning of the remaining material. After the removal and burning, some native shrub species resprouted. Since resprouting is dependent on buds that can be in the belowground bud-bearing (BBB) organs containing reserves, we selected three resprouting Myrtaceae species for analysis of morphology and anatomy of their BBB organs, to determine which compounds could be accumulated and to investigate the bud protection features. Standard histological techniques were used to analyse the BBB organs. The belowground bud bank at a depth of 10cm was determined. Nonstructural carbohydrates, total phenolics, and flavonoids were quantified on the roots. The large size of BBB organs suggest that these species were present before plantation establishment and survived plantation management treatments. All species produced a large number of axillary buds. All BBB organs exhibited significant lignification and stored starch and phenolic compounds in the parenchyma cells. The protective features and the storage of reserves associated with the bud-bank allowed the survival and subsequent resprouting of these species, contributing to the regeneration of this disturbed area.

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Question: The Cerrado represents the largest savanna of the Neotropics. Nowadays, this ecosystem is threatened by the afforestation by monocultures, such as Pinus spp., leading to serious damage to native herbaceous species. Afforestation of savanna ecosystems can affect their ability to regenerate naturally, which relies on different strategies, such as resprouting from below-ground bud-bearing organs. Therefore, we investigated the impact of ca. 50 years of Pinus elliottii plantations, compared to undisturbed areas of Cerrado savanna, estimating the bud bank size by counting buds on bud-bearing organs. We hypothesized that long-term P. elliottii plantations negatively affected the bud-bearing organs, leading to decreases in the bud bank. Location: Cerrado savanna areas and Pinus elliottii plantations, southeastern Brazil. Methods: Open savanna areas (hereafter Cerrado) and "P. elliottii plantations" were considered the vegetation types. Within each vegetation type, we designated three areas. In each area, we established 10 plots (1 m 2). For each plot, the bud bank was sampled from 5 cm above to 10 cm below ground level in subplots (0.25 m 2). We developed generalized linear mixed models (GLMM) for each response variable to test differences between both vegetation types. Results: The presence of the P. elliottii plantations for almost 50 years has led to massive reductions in the bud bank size and the number of bud-bearing organs, when compared to the Cerrado areas (p < 0.0001). Conclusions: The reduction in the below-ground bud-bearing organs density led to decreases in the bud bank and thus, loss of resilience in these areas. Regeneration in planting areas may not occur naturally after the removal of the plantations. Restoration of the herbaceous layer after P. elliottii removal will rely on the introduction of a new source of propagules through active interventions.

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