Fire and frost can slow down tree colonization in cerrado wet grasslands

Abstract Forests, savannas, and grasslands occur as mosaics in many tropical regions, yet the drivers of different vegetation types under similar climates remain unclear. In this study, we evaluated fire and frost as potential constraints on tree establishment in a cerrado wet grassland at the transition from gallery forests to savannas. We planted nursery-raised seedlings of three species: one restricted to gallery forests, one to dry savannas, and one generalist. Five months later, a frost affected the site, and three years later, a prescribed fire was applied. Seedlings were assessed before and after each disturbance to quantify survival, height, and growth. Frost reduced the survival of the gallery forest species by 13% and caused greater above-ground damage in the gallery forest (36%) and generalist (35%) species than in the savanna species (20%), also delaying growth in all species, with recovery of pre-frost height estimated at up to four years. Fire reduced survival by 22% in the gallery forest and 45% in the savanna species and caused widespread topkill across species. Nevertheless, seedlings were estimated to recover pre-fire height within 13 months. The flood-intolerant savanna species showed the lowest recovery after both disturbances, suggesting resilience depends on tolerance to hypoxic and anoxic conditions. Disturbance severity and frequency can play a crucial role in maintaining open vegetation where environmental and climate change may drive a shift toward woodlands.