Effect of prescribed burning on the spatial structure and dynamics of Cerrado invasive grasses populations: subsidies for long-term adaptive management

• Grant number: 23/06557-9
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Effective date (Start): July 01, 2023
• Effective date (End): June 30, 2025
• Field of knowledge: Biological Sciences - Ecology - Applied Ecology
• Principal Investigator: Giselda Durigan
• Grantee: Bruna Helena de Campos
• Host Institution: Instituto de Pesquisas Ambientais (IPA). Secretaria de Meio Ambiente, Infraestrutura e Logística (São Paulo - Estado). São Paulo , SP, Brazil
• Associated research grant: 20/01378-0 - Grasslands in the State of São Paulo: diagnosis, management and conservation, AP.BTA.TEM
• Associated scholarship(s): 24/05823-0 - The effects of cattle grazing in savanna ground layer invaded by exotic grasses, BE.EP.PD

Abstract

Invasive exotic species are a threat to the conservation of natural ecosystems across the globe, a situation also faced by open areas in the Cerrado of São Paulo. One of the main groups of invasive plants that threaten these ecosystems is the African grasses. These species present a high risk of invading conservation units, causing negative impacts on native vegetation and demanding human and financial resources for their control. Recent studies have demonstrated the beneficial effects of prescribed burning for the management of African grasses in invaded communities in the Cerrado, but have also demonstrated that fire alone can do more harm than good, requiring the combination of other practices to be successful. The control of invasive plants has recently been incorporated into the portfolio of restoration techniques, but empirical studies on the subject are rare. Fire is seen as a useful control tool, but the response of vegetation in invaded fields to the occurrence of fires is complex, making it difficult to generalize about the use of fire for this purpose. Although it is already known that exotic grasses intensify fire and its impacts, it has not yet been demonstrated whether fire, in fact, accelerates invasion by exotic grasses and at what rates this would occur, although this statement is often found in the literature. It is known that invasions by African grasses in the Cerrado are associated with the existence of roads and trails, which facilitate the arrival and establishment of propagules. After the establishment of founding individuals, the expansion process of the invasion takes place through the recruitment of new individuals and subsequent coalescence of isolated patches. However, there are no studies that investigate how prescribed fires influence the spatial dynamics of invasive populations, even though this is crucial information to simulate management scenarios and guide long-term adaptive management plans. Furthermore, different species of grasses may respond differently to fire, due to functional differences related to their reproductive processes (by seeds or by vegetative propagation). To elucidate these issues, this project will address the response to fire in terms of expanding populations of two species of African grasses that behave as invasive in the Cerrado - Urochloa decumbens and Urochloa umidicola. We hope, with this study, to quantify the expansion rates of the two invasive species in response to fire and, thus, provide subsidies for control actions.