Abstract Riparian corridors are key components of the global nitrogen (N) cycle, acting as potential nitrate (NO 3 − ) sinks within landscapes. To better understand the factors driving NO 3 − cycling, we compiled 808 observations of soil moisture, temperature, inorganic N content and net nitrification (NN) rates from 174 riparian sites and used them to build a process‐based model that explored how NN varied as a function of gross nitrification (GN), gross NO 3 − consumption (GC), and their sensitivity to environmental conditions. The empirical data set showed substantial variation in NN across biomes, with rates spanning two orders of magnitude between arctic (median: 0.006 mg N kg −1 d −1 ) and both mediterranean and tropical regions (median: 0.65 mg N kg −1 d −1 ). Globally, soil moisture and temperature together explained 51% of the variation in NN, with soil moisture emerging as the dominant control. Model simulations also revealed that the optimal moisture was lower for GN (WFPS = 60%) than for GC (WFPS = 79%). As a result, saturated soils enhanced NO 3 − buffering potential (i.e., high GC/GN), whereas intermediate moisture levels favored NO 3 − accumulation (i.e., high NN). Finally, GN and GC simulations varied considerably among biomes, reflecting differences in climatic regimes and influencing the potential NO 3 − sink or source behavior of riparian soils. Overall, these findings offer a means to forecast global trends of riparian N cycling and their capacity to mitigate NO 3 − pollution under current and future climatic conditions.
Lupon et al. (Sun,) studied this question.