Quartzitic Caves with guano at the Serra do Ibitipoca State Park (MG) - Brazil: key nutrient hotspots in the soils and adjacent forests

Little is known about the role of guano from quartzite caves in forming biodiverse plant communities in the surrounding areas due to direct or indirect nutrient and energy inputs. This study investigates four caves in the Quartzite Endokarst of Ibitipoca State Park (PEI), Brazil, by analyzing surface soils from the cave interior to surrounding forests. We evaluated the following hypotheses: (i) guano deposits modify the cave floor and influence external plant communities; (ii) there is a nutrient gradient from the cave interior to its surroundings, linked to guano deposition and redistribution; (iii) forest communities near the caves rely on nutrient cycling from guano to achieve greater biomass and structural complexity. Results confirmed a significant incremental effect of macro and micronutrients in the studied caves, with notable variability between interior and exterior environments and between forested areas and more distant soils. This nutrient input profoundly alters soil morphology and physico-chemical properties through long-term cumulative processes. Many trees and shrubs in these forested areas are larger than their counterparts in the adjacent Rupestrian Quartzite Complex. Although both birds and bats are abundant in these caves, the insectivorous diet of these animals complicates the differentiation of their roles in guano deposition. Further studies using precise biogeochemical markers are needed to clarify the distinct contributions of birds and bats and the temporal dynamics of this phenomenon. Ultimately, this biogenic input creates nutrient-rich oases in an otherwise oligotrophic environment.