How can seasonal flooding create and maintain a grassland?

Seasonal flooding creates and maintains grasslands by acting as a natural disturbance that prevents the establishment of woody vegetation, such as trees, which would otherwise dominate in environments where moisture is otherwise sufficient for their growth.1

In many regions, particularly in the highly seasonal subtropics, periodic flooding or waterlogging creates conditions that are inhospitable to trees. Because trees require specific soil and drainage conditions to thrive, the regular cycle of inundation—where an area may be a shallow wetland for part of the year and a dry grassland for the remainder—favors the dominance of grasses.1

A prominent example of this process is the Pantanal in Brazil. In this region, the landscape is shaped by a predictable hydroperiod, where trees are restricted to small, elevated patches that do not flood during the wet season, while the surrounding low-lying areas remain as expansive grasslands. By limiting the growth of woody plants, seasonal flooding effectively maintains these open, grass-dominated ecosystems.12