Fire decreases soil enzyme activities and reorganizes microbially mediated nutrient cycles: A meta-analysis

The biogeochemical signature of fire shapes the functioning of many ecosystems. Fire changes nutrient cycles not only by volatilizing plant material, but also by altering organic matter decomposition, a process regulated by soil extracellular enzyme activities (EEAs). However, our understanding of fire effects on EEAs and their feedbacks to nutrient cycles is incomplete. We conducted a meta-analysis with 301 field studies and found that fire significantly decreased EEAs by similar to 20%-40%. Fire decreased EEAs by reducing soil microbial biomass and organic matter substrates. Soil nitrogen-acquiring EEA declined alongside decreasing available nitrogen, likely from fire-driven volatilization of nitrogen and decreased microbial activity. Fire decreased soil phosphorus-acquiring ERA but increased available phosphorus, likely from pyro-mineralization of organic phosphorus. These findings suggest that fire suppresses soil microbes and consumes their substrates, thereby slowing microbially mediated nutrient cycles (especially phosphorus) via decreased EEAs. These changes can become increasingly important as fire frequency and severity in many ecosystems continue to shift in response to global change.

Automated summary

The biogeochemical signature of fire affects the functioning of ecosystems by altering soil extracellular enzyme activities (EEAs) and nutrient cycles. Fire reduces EEAs by decreasing soil microbial biomass and organic matter substrates, resulting in a slower microbially mediated nutrient cycle, particularly for phosphorus. These effects may become increasingly important as fire frequency and severity continue to change in response to global change.