Long–term consequences of plant–soil feedback in fire-main-tained grasslands and savannas

Anita Simha , Gaurav Kandlikar

Woody encroachment into grasslands and savannas is widespread and has wide-rangingconsequences. Past work suggests that positive feedbacks are a common feature of woodyencroachment, and emerging evidence points to the importance of soil microbes in this process.For example, many encroaching plants associate with N-fixing bacteria or ectomycorrhizal fungi,while herbaceous plants often accumulate self-limiting microbes. However, projecting the long-term consequences of plant-soil feedbacks in natural systems that are simultaneously shaped bydisturbances like fire remains a challenge. We developed a mathematical framework for predictingmicrobial impacts on vegetation dynamics in fire-maintained grasslands and parameterized thismodel with data from a meta-analysis. We find that plant-soil feedbacks necessitate especiallyfrequent fire to maintain grassy communities and restrict the recovery of grass after woodyencroachment. In all, our model points to the importance of belowground processes in drivingwoody encroachment and the urgent need for empirical data testing this process.