White sand ecosystems; phytophysiognomies; Quartzarene Neosols

The campinaranas are white sand ecosystems (WSEs) immersed in the Amazon domain and can be classified as forested, wooded, shrubby, and grassland-woody, primarily based on the phytophysiognomy associated with edaphic conditions. However, knowledge of the flora in these ecosystems is limited, especially in the eastermost

Amazon. In this context, we aim to expand the floristic knowledge of the grassland-woody campinaranas in Maranhão. To achieve this, we conducted a floristic survey through free walking in three white sand areas, previously selected from satellite images, located in the northwest portion of Maranhão State. Additionally, analyses were carried out to determine the physical and chemical composition of the soil. The collections took place over four field expeditions, distributed across the beginning of the rainy season, peak of the flooding, beginning of the dry season, and peak of the drought, spanning the years 2023 and 2024. During the survey, 175 angiosperm species were sampled, distributed across 52 families. The most representative families were: Cyperaceae (18 species), Lentibulariaceae (14 species), Rubiaceae (13 species), Melastomataceae (12 species), Poaceae (10 species), Bromeliaceae (7 species), Eriocaulaceae (7 species), Fabaceae (7 species), and Orchidaceae (7 species). The predominance of herbaceous species reflects the ecosystem's adaptation to the harsh conditions of sandy, dystrophic, and acidic soils. Although the flora is predominantly composed of species with a wide geographic distribution (69.4%), the most frequent and widely distributed species in the ecosystem are those exclusive to campinaranas, adapted to oligotrophic environments, and those belonging to the families Cyperaceae, Poaceae, and Lentibulariaceae. The floristic similarity analysis between WSEs revealed that the grassland-woody campinaranas of Maranhão are more similar to each other and heterogeneous in relation to other compared WSEs. It also shows that the geographical proximity between the grassland-woody campinaranas areas influences species sharing. This suggests that spatial proximity plays an important role in the composition of the floristic communities in these areas, and endemism is related to the phytophysiognomy and the occurrence site. Due to the ecological importance of these ecosystems in Maranhão, which are experiencing significant habitat loss due to agricultural expansion, it is crucial to adopt effective conservation strategies. The local flora, specific and adapted to the conditions of these ecosystems, highlights the need to protect the biodiversity and environmental services these environments provide. The creation of new conservation units, along with increased scientific research, is essential to protect and restore these unique ecosystems, ensuring the continuity of ecological processes that supports the life in these areas.