Short-term impacts of prescribed fire on C, N, and P dynamics in a subtropical rangeland

Background and aims Prescribed fire is a common management practice in native rangelands that can result in significant losses of C, N, and P from plant and soil. This study evaluated the short-term, fire-induced changes in C, N, and P stocks in subtropical native rangelands in Florida, USA. Methods Changes in C, N, and P stocks were quantified in aboveground biomass and soil (0-20 cm depth) in locations within native rangelands dominated by either saw-palmetto ( Serenoa repens Bartr.; Saw-palmetto) or grasses (mixed C 4 grasses; Grass). Results Prescribed fire had no impact on soil temperature below 2.5 cm, but peak temperature at soil surface was greater in Saw-palmetto than Grass areas. Despite greater pre-fire aboveground biomass in Saw-palmetto (1115 g m −2 ) vs. Grass (689 g m −2 ), no difference in post-fire net loss (−660 g m −2 ) was observed between vegetation types. This occurred because 97% of biomass in Grass was combusted during fire vs. 65% in Saw-palmetto dominated areas. Similar responses were observed for aboveground C and P stocks. Fire-induced N loss was greater in Saw-palmetto (−6 g N m −2 ) than grass (−2.7 g N m −2 ). Soil C, N, and P stocks were not affected by prescribed fire. This was likely due to limited effects of prescribed fire on soil temperature. Although fire had no effect on soil respiration, ash addition increased soil potentially mineralizable C by 11%. Conclusion Prescribed fire reduces C, N, and P stocks in aboveground vegetation, but limited impacts are expected to occur in soil pools.