Removal of <scp>N</scp>‐fixing vs. <scp>non‐N</scp>‐fixing herbs in postfire chaparral: Competition and contributions to soil N and C cycling

Abstract As climate change increases fire frequency in Mediterranean‐type shrublands, it is essential to understand the links between common postfire plant assemblages and soil nitrogen (N) carbon (C) cycling during succession. In California chaparral, periodic removes shrub cover, deposits ammonium (NH 4 + ‐N) on soils, allows herbaceous dominate for 3–5 years. Herbs influence biogeochemistry through several mechanisms, including nutrient uptake, litter decomposition, rhizodeposition. Controlled experimental removal of select groups from wild can demonstrate interactions how traits belowground processes. a two‐year herb‐removal experiment, we investigated impact N‐fixing non‐N‐fixing herbs N C cycling. Treatments were (1) all herbs, (2) only species, (3) (4) no herbs. high‐N environments, N‐fixers predicted compete poorly against neighbors. doubled abundance when non‐N‐fixers removed, but unaffected by N‐fixer removal. Two years after fire, no‐herbs plots had lowest microbial respiration rates, total accumulated lower than all‐herb plots. treatments, no‐herb plots, elevated mineral concentrations, net mineralization, nitrification second year experiment. Our findings underscore importance fire‐following retention organic matter accumulation. A combination both maximized N, although accumulation TC TN was not significantly higher non‐N‐fixer Results demonstrated key role accumulating communities retaining N. Elevated availability two may contribute long‐term recovery shrubs, even are longer dominant. Future investigations should also consider magnitude with different herb functional groups, along species‐specific contribution