Carbon and nitrogen dynamics in tropical ecosystems following fire

Aim: Tropical ecosystems have grown increasingly prone to fire over the last century. However, no consensus has yet emerged regarding the effects of fire disturbances on tropical biogeochemical cycles. Location: Tropics. Time period: 1960–2018. Major taxa studied: Tropical ecosystems: Above- and below-ground carbon (C) and nitrogen (N) dynamics. Methods: We analysed the impacts of fire on C and N dynamics in tropical ecosystems through a meta-analysis of 1,420 observations from 87 studies. Results: Fire reduced both above- and below-ground C and N pools, with greater reductions above- than below-ground. Fire decreased soil total carbon (TC), total nitrogen (TN) and nitrate nitrogen ((Formula presented.)) and increased ammonium nitrogen ((Formula presented.)) in surface mineral soil layers but did not affect those in deep layers. Fire decreased TC and TN in savanna but did not affect those in tropical dry and moist forests. Fire did not affect (Formula presented.) and (Formula presented.) in savanna because of non-significant responses of N mineralization rate (N_min) to fire. Conversely, fire increased (Formula presented.) and decreased (Formula presented.) in tropical dry forest, but did not affect (Formula presented.) and increased (Formula presented.) in tropical moist forest owing to thermal decomposition of soil organic N and increased soil nitrification, respectively. Moreover, (Formula presented.) declined and (Formula presented.) increased initially and then decreased with time after fire. Above- and below-ground response variables to prescribed fire were mediated largely by fire frequency and experimental duration, respectively. Main conclusions: Our results suggest a high vulnerability of the above-ground C and N pools to fire, whereas the biogeochemical cycles below-ground are of high complexity. Fire effects on below-ground C and N pools, which are highly uncertain and vegetation specific, should be investigated further.