Restoration goals: Insights from antiquity and dynamics of forest–savanna mosaics in Central India during the Holocene

Forest-savanna mosaics are important for biodiversity, but the savannas in these mosaics are often considered degraded forests due to low tree cover, and are thus targeted for tree planting. Yet, these mosaics may be naturally bistable systems, wherein disturbance regimes such as fire and herbivory create alternative stable states of forest and savanna. Globally, forest-savanna mosaics have been present from pre-historic times and map to regions with high biodiversity today. Here, we conduct a meta-analysis of paleo-ecological studies in Central India-a highly biodiverse forest-savanna mosaic landscape threatened by tree plantations today-to understand the spatiotemporal antiquity and dynamics of the mosaics across this region. We find that alternate states of low and high tree cover have been present in Central India since the early Holocene and that the tree cover is explained by the interaction of mean annual precipitation (MAP) and the disturbance regime of fire. We find no statistical evidence for bimodality or hysteresis-conditions that are required for alternative stable states-although patterns suggestive of alternative stable states are present. Further, in contradiction to the hypothesis of high and low tree cover states being stable, this system transitions between alternate states of high and low tree cover at time periods ranging from ~40 to 220 years. Switching back and forth between alternate states is significantly more frequent in sites with higher richness of fire-resistant tree taxa. Our historical data thus lend support to the idea that low tree cover regimes have been created or maintained through interactions between climatic conditions and disturbance regimes such as fire, and that tree cover can increase when either of these factors changes. The study further suggests that restoration should focus on maintaining the ability to switch between low and high tree cover rather than increasing tree cover in Central India.