The role of soils in phenology and herbivory in a tropical grassland–Savanna–forest gradient

Abstract

The evolutionary responses of plants vary according to the soil availability resources, which is one of the main factors responsible for species communities’ composition. In old, climatically buffered, infertile landscapes (OCBILs), such as campo rupestre, functional traits specialized in resources acquisition and conservation are expected. However, these adaptations are associated with less investment in growth and reproduction. Interspersed with campos rupestres, two main vegetations occur under relatively more fertile soils: cerrado stricto sensu (cerrado) and forest fragments. This vegetation diversity under the same climatic regime creates an environmental gradient towards campo rupestre < cerrado < forest, which is a true natural laboratory to investigate the edaphic resources influence on plant ecology. At this gradient, we surveyed vegetative and reproductive phenological strategies of 70 plant species from the three vegetation types over a year. Cerrado and forest communities had similar phenological strategies, while the campo rupestre species presented strategies that maximize resources acquisition and conservation, such as the exploitation of the rain pulses for a continuous leaf flushing. We also investigated herbivory levels variation of plant communities in the three vegetation types. We collected 22.250 leaves from 74 species and analyzed leaf functional characteristics related to growth investment (leaf area – FA) and defenses (specific leaf area – SLA) of plants, as well as the percentage of leaf area removed (%LAR). We found increasing AF and SLA values and positively related to %AFR along the gradient. We also observed that trees (fast growing life form) had mean values of SLA, FA and %LAR higher than shrubs (slow growth). Our results bring new empirical data that point to the scarcity of edaphic resources as an environmental filter capable of selecting phenological and morphophysiological functional traits that promote, respectively, resources acquisition in seasonally dry environments, and resources conservation by decreasing herbivory levels