Palm Density and Woody Encroachment in Southern Brazil

Butia palm groves (butiazais) in southernmost Brazil are ecosystems characterized by the predominance of Butia palms standing out over native grasslands. They hold significant ecological and sociocultural relevance, providing essential ecosystem services and contributing to the cultural identity of local communities. Human activities have played a determining role in the configuration and conservation of these ecosystems, especially when they occur in mosaics with forests. The Brazilian municipalities of Tapes and Barra do Ribeiro (Rio Grande do Sul) host the largest remnant of Butia odorata in the country, representing one of the most expressive examples of this ecosystem. This study investigated the role of palm density in the encroachment of woody vegetation in open grassland areas, particularly near forest edges. Fixed georeferenced plots were used along a forest–grassland gradient to quantify the density of Butia odorata, trees, and shrubs. Linear regression models were applied to assess the influence of palm density and proximity to forest edges. The expansion of woody vegetation from 2003 to 2023 was analyzed using satellite imagery and GIS. Results indicated a significant positive association between palm and shrub density (p = 0,006), especially within 100 m of the forest edge. Most of the woody encroachment occurred in areas with high palm density, suggesting that palms act as nurse plants. A Priority Management Zone (PMZ) is proposed based on palm density and forest proximity. Sustainable grazing and adaptive management practices are recommended to maintain open grassland structure and ensure palm regeneration.