Plant diversity–mediated variation in root exudates regulates anaerobic nitrogen transformations in soil

Plants can regulate soil biogeochemical processes via root exudates, yet how exudate quantity and composition influence soil nitrogen (N) transformations remains unclear.

We conducted complementary pot and microcosm experiments across gradients of plant species, phylogenetic and functional group diversity to examine effects of root exudates on anaerobic N transformation processes in soils, including dissimilatory nitrate reduction to ammonium (DNRA), denitrification and anaerobic ammonium oxidation (anammox).

Results showed that both rhizosphere metabolite and root exudate chemodiversity increased with multidimensional plant diversity, with phylogenetic diversity explaining more variance than species or functional group diversity. Carbohydrates and organic acids had stronger effects on N transformation processes than amino acids, with shikimic acid and sucrose identified as key components influencing DNRA and denitrification rates. Notably, higher exudate carbon (C) content significantly enhanced DNRA and denitrification, whereas exudate chemodiversity negatively correlated with these two processes but positively associated with anammox. Additionally, both exudate C content and chemodiversity directly or indirectly affected soil N transformations through changes in soil N availability, rather than microbial communities.

Synthesis . These findings advance the mechanistic understanding of how plant diversity–mediated variation in root exudate quantity and composition regulates soil N cycling, highlighting its pivotal role in shaping ecosystem nutrient dynamics.