Temperature sensitivity of soil organic matter mineralization decreases with long‐term N fertilization: Evidence from four Q 10 estimation approaches

Abstract

Abstract Climate warming and anthropogenic nitrogen (N) loads are two major global change components interactively affecting carbon cycling. However, the effects of N forms and amounts on temperature sensitivity (Q 10 ) of soil organic matter (SOM) mineralization remain incomplete. With this goal, soil was sampled after 23 years of mineral and (or) organic N fertilization, and then incubated for one year at 10, 20, and 30°C. For the first time, we compared four approaches (Equal time, Equal C, 1‐C pool, and 2‐C pool model) to evaluate the Q 10 of SOM mineralization. All approaches showed that the Q 10 decreased by more than one third with N fertilization compared to unfertilized control at low temperatures. The '1‐C pool model' was not adequate for Q 10 estimation with various C availability. The Q 10 estimated by '2‐C pool model' was strongly depended on incubation duration. The 'Equal C' approach was more powerful for separating SOM pools and it revealed the decreased Q 10 of the recalcitrant pool at high N rates. The impact of N fertilization on Q 10 was more evident at high N than at low N. Notably, the Q 10 decreased more by mineral N compared to organic fertilizers (~60% vs. ~40% decreased in Q 10 ) at 10–20 o C. The added benefit of N fertilization in protecting SOM under climate warming was demonstrated by decreased Q 10 . Such one‐third reduction of temperature sensitivity by N fertilization is large enough to be considered in predictions of global SOM stocks under warming and anthropogenic N loads.