Banca de DEFESA: LARISSE BIANCA SOARES PEREIRA NUNES

Effects of nutrient addition and invasion by Megathyrsus maximus on ecophysiology of native plants, in an area 

of the caatinga undergoing natural regeneration.

Fertilization, Oxidative stress, Primary metabolism, Anthropogenic disturbance, Native plant, Restoration.

Caatinga, the largest and most populous Seasonally Dry Tropical Forest in the world, is located
predominantly in the Northeast of Brazil. This unique ecosystem is characterized by highly
endemic vegetation, adapted to semi-arid climatic conditions and soils with low nutrient
concentrations. However, it faces several threats, including the unsustainable use of resources
by the population, the intensification of drought due to climate change and the invasion of exotic
species. Such threats compromise local biodiversity and favor desertification processes. This
study aims to evaluate the biochemical behavior of pioneer native plants in response to soil
changes and increasing competition due to invasion by Megathyrsus maximus. We observed
that plants with shorter roots tend to react more efficiently to changes in acidity and the
accumulation of Al3+ in sandy soils in the Caatinga. Although the addition of NPK prior to the
growing season, coupled with the invasion of M. maximus, did not cause significant changes to
the soil over the course of a year, we suggest that these nutrients may have been leached or that
the initial soil conditions may have been altered. restored due to high soil activity and absorption
by the invasive plant. Even without detectable changes in soils, native plants showed signs of
nitrogen reduction, especially in areas invaded by exotic species, indicating an increase in
competition for resources. These results provide important insights into the responses of native
plants to anthropogenic changes, which can be exacerbated by climate change, threatening the
natural regeneration of the Caatinga and the survival of pioneering endemic species. For a more
complete understanding of the effects of environmental fluctuations on these species, we
recommend long-term studies, given the slow nature of responses to fertilization and invasion
by exotic plants.