Leaf litter decomposition exhibits home-field advantage at organic nitrogen-dominated sites and away-field advantage at inorganic nitrogen-dominated sites

Abstract

Soil organic nitrogen (N) and inorganic N function as important plant N sources, both of which dominate at contrasting sites; however, little is known about how the shift from soil organic to inorganic N dominance influences litter decomposition. We conducted a 3-year experiment with Solidago canadensis subject to three treatments: organic N dominance, inorganic N dominance, and co-dominance by both. Building on this experiment, we performed a reciprocal leaf litter transplant experiment, determined leaf transcription, leaf mechanical and chemical traits, soil microbes and abiotic properties, and linked the associations among variables via structural equation modelling. Leaf litter decomposed faster on home soil relative to away soil when soil organic N dominated but slower on home soil when soil inorganic N dominated, and this opposing pattern was linked to the changes in leaf mechanical and chemical traits and microbial decomposers. The shift in soil N relative dominance elicited transcriptional up- and down-regulation, mainly associating with leaf chemical but not mechanical traits. Microbial decomposers were more important than potential litter quality in controlling for leaf decomposition, and bacterial decomposers outweighed fungal decomposers at early stages. Our findings provide evidence that leaf litter decomposition could shift from home-field advantage at organic N-dominated sites to away-field advantage at inorganic N-dominated sites, and highlight the key role of soil N relative dominance in reshaping carbon and nutrient cycling at local landscapes.