N mineralization data

We combined field and laboratory analyses to assess how biocrusts influence N inputs, turnover, and shrub uptake in a representative semiarid shrubland dominated by <i>Artemisia ordosica</i> on the Chinese Loess Plateau. Our results showed that biocrusts significantly enhanced N fixation potential across 0–20 cm, as indicated by elevated <i>nifH</i> gene abundance of cyanobacteria (0–10 cm) and heterotrophic diazotrophs (10–20 cm). Biocrusts also increased soil inorganic N pools and accelerated net ammonification, nitrification, and N mineralization throughout the growing season, especially in summer, by increasing the supply of labile C and N substrates and enhancing N-cycling enzyme activities. These processes were strongly regulated by the interaction between soil moisture and temperature, with biocrusts amplifying their coupling effect. Moreover, biocrusts slightly reduced the temperature sensitivity of soil N mineralization under shrub canopy. Notably, shrub-biocrusts patches exhibited higher shrub leaf N content and more depleted δ¹⁵N values than shrub patches, indicating that biocrusts enhanced plant N uptake and increased reliance on biologically fixed N.