Formas de vida e a dinâmica temporal da riqueza e abundância de herbáceas da caatinga

Abstract

The Raunkiaer system classifies plants based on the degree of protection of their vegetative buds during the unfavorable period, serving as an important tool for understanding plant survival strategies in seasonal environments. In habitats marked by strong water seasonality, herbaceous plants form a highly diverse and abundant component. However, the temporal dynamics of life forms, richness, and abundance in this stratum remain underexplored. To address this gap, we conducted monthly monitoring of species richness and abundance of flowering plants in nine 1m2 quadrants within an herbaceous community throughout the 2024 rainy season in an open area of the Caatinga in Ceará, Brazil. We registered 44 species from 17 families, with Fabaceae and Malvaceae being the most representative. The herbaceous community responded rapidly to rainfall. Therophytes were the dominant life form. However, herbaceous life forms occupied the rainy season distinctly: hemicryptophytes in flower were more abundant at the beginning of the rains, which can be explained by the presence of underground storage organs, while therophytes dominated after the peak of precipitation (>97% of individuals). Furthermore, phenological analysis revealed distinct reproductive timing patterns among life forms. Geophytes concentrated their flowering at the very beginning, hemicryptophytes maintained extended flowering, and therophytes exhibited their highest peaks in the middle of the rainy season. The results corroborate Raunkiaer's assertion of the predominance of therophytes in extreme and unpredictable environments, but we also demonstrate that life forms in the Caatinga can occupy distinct temporal windows within the favorable season.