Soil carbon responses to prescribed burning, nitrogen addition, and their interactions in a Mediterranean shrubland

Abstract

Understanding the effects of prescribed burning management practices in combination with anthropogenic nitrogen (N) deposition on soil carbon (C) storage capacity is of crucial importance in Mediterranean mountain shrublands. To address this issue, an experiment was conducted to assess the effects of prescribed burning (Burn, B / No Burn, NB), N additions (0, 15, and 50 kg N·ha⁻¹·year⁻¹, N0, N15, N50) and their interactive effects on various soil parameters in a shrubland located in the mountain range of Madrid over 2-year period. The results of the study confirmed that both low-intensity prescribed burning and short-term N additions did not alter the C stocks in the soil and floor shrubs. Furthermore, the combination of these two factors did not lead to an increase in soil C accumulation. However, the prescribed fire treatment caused divergent responses in soil parameters and fluxes. Specifically, it caused transient changes including decreased soil respiration (Rs), alterations in the soil microbial community, increased soil water content, temperature, and soil pH, and changes in NH₄, NH₃, and available P. Moreover, the cumulative amount of N added gradually depressed Rs, and microbial biomass. Additionally, the interaction between prescribed burning and N fertilisation did not modify the effects associated with fire. The findings indicate that prescribed burning, as implemented in the experiment, can be effectively employed in Mediterranean shrublands, as it did not significantly affect soil C storage under both current and future N deposition scenarios.