Effects of prescribed burning and frost on plant diversity and structure in Cerrado ground layer

Abstract

Fire and frost are important drivers of structure and composition of grasslands and savannas around the world. However, little is known about how plant communities respond to these natural disturbances. This knowledge gap has direct implications for both conservation and restoration of Cerrado vegetation. In this context, this project aims to elucidate the response of plant communities to complete suppression of fire, prescribed burning or frost, targeting plant species occurring in the ground layer. This study will be conducted at the Ecological Station of Santa Barbara, SP, Brazil, where a biomass gradient from open grassland to forest vegetation exists in the preserved Cerrado. The sampling units comprise 480 plots of 1 m² distributed in different sectors of the ecological station, that were sampled in 2015 before fire and in 2016 before frosts. Of the 480 plots, 120 were submitted to controlled burning and 360 will be maintained without fire. Control plots have been monitored every six months over three years. In the burned plots, changes in the plant community were assessed before and after fire, and recovery was monitored every two months over a year. The effects of frosts will be assessed in all control plots, by comparing the community composition before the severe frosts occurred in the winter 2016, just after frosts and two months later. Changes in community structure due to fire suppression, prescribed fire or frosts will be also assessed. All plant species sampled will be categorized according to their response to the disturbance (benefited, indifferent or impaired), in search for functional attributes that explain the persistence of the species in the community. Each species sampled will be characterized by a number of functional traits, in search for functional patterns behind resistance/resilience to fire or frost. Our expectation is that fire suppression results in plant diversity loss, especially for Cerrado endemic species and that controlled burning can maintain or even increase richness of these communities. We expect frosts acting as an abiotic filter favoring frost resistant species, as it has been observed for tree species. Additionally, we expect resistance/resilience to fire or frost related to a set of plant functional traits. We consider that this study has the potential to inform policy and practice of Cerrado management and conservation, as well as to enhance predictive models for the future of savannas in a scenario of climate changes. (AU)