Caracterização florística de campinarana gramíneo-lenhosa da Amazônia maranhense.

Abstract

Campinaranas are white-sand ecosystems (WSEs) embedded within the Amazon domain and can be classified as forested, wooded, shrubby, or grassy-woody, based primarily on their phytophysiognomy in relation to hydro-edaphic conditions. However, knowledge about the flora of these ecosystems is still limited, especially in the easternmost portion of the Amazon. In this context, we aimed to expand the floristic knowledge of the grassy-woody campinaranas of the Maranhão Amazon. To achieve this, we conducted a floristic survey through free-walking sampling in three white-sand areas, previously selected using satellite imagery, located in the northwestern region of Maranhão. In addition, analyses were conducted to determine the physical and chemical composition of the soil. Field collections were carried out during four expeditions, distributed across different seasonal phases: the beginning of the rainy season, peak flooding, the onset of the dry season, and peak drought, between the years 2023 and 2024. During the survey, 175 species of angiosperms were recorded, distributed across 52 families. The most representative families were: Cyperaceae (18 species), Lentibulariaceae (14), Rubiaceae (13), Melastomataceae (12), Poaceae (10), Bromeliaceae (7), Eriocaulaceae (7), Fabaceae (7), and Orchidaceae (7). The predominance of herbaceous species reflects the adaptation of the ecosystem to the harsh conditions of the sandy, dystrophic, and acidic soil. Although the flora is mostly composed of species with a wide geographic distribution (70.3%), the most frequent and widely distributed within the ecosystem are those exclusive to campinaranas, adapted to oligotrophic environments, and primarily from the families Cyperaceae, Poaceae, and Lentibulariaceae. The floristic similarity analysis among WSEs revealed that the grassy-woody campinaranas of Maranhão are more similar to each other and more heterogeneous when compared to other WSEs. This indicates that the geographic proximity between the areas of grassy-woody campinaranas influences the sharing of species. It suggests that spatial proximity plays an important role in the composition of plant communities in these areas and that endemism is related to both the phytophysiognomy and the specific location of occurrence. Given the ecological importance of these ecosystems in Maranhão, which are undergoing significant habitat loss due to agricultural and livestock expansion, the adoption of effective conservation strategies is essential. The local flora, specific and adapted to the conditions of these ecosystems, underscores the need to protect the biodiversity and ecosystem services they provide. The creation of new conservation units, along with increased scientific research, is fundamental to protect and restore these unique ecosystems, ensuring the continuity of the ecological processes that sustain life in these areas.