The coupled loss of carbon and nutrients during disturbance events is a well-documented pattern across ecosystems and thought to be critical in limiting ecosystem recovery. However, the short-term response of an ecosystem to a single disturbance event is not always predictive of the long-term response to repeated disturbance events. Of particular concern is whether compensatory responses dampen nutrient losses or positive feedbacks emerge to accelerate disturbance-induced nutrient limitation over time.
Here, we focus on the long-term effect of fire on carbon and nutrient cycling. We synthesize data from 47 sites worldwide to evaluate how fire alters nitrogen and other nutrients, what mechanisms regulate the effect of fire, and whether fire-plant-soil interactions create either a compensatory response or accelerating feedback.
Results/Conclusions
Frequent burning on average resulted in coupled declines in total soil carbon and nitrogen, but the effect depended on the length of fire frequency alterations, plant community composition, and climate.
Analyses of the plant community revealed that frequent burning selected for species adapted to low nitrogen conditions, but not always for nitrogen-fixing legumes, resulting in the assembly of plant species with functional traits that further contribute to slow nutrient cycling. In contrast, nutrient stoichiometry of individual species remained unchanged, suggesting fire-plant-soil feedbacks likely emerge through community filtering.
Vegetation model simulations revealed that fire-driven nitrogen losses significantly suppress net-primary productivity. Moreover, the relative effects are surprisingly constant across ecosystems, suggesting a general role for fire-driven nitrogen losses to constrain productivity. These results raise fundamental questions about the role of fire-driven nutrient losses in the evolution of species strategies, and their role in determining the stability of ecosystems.