Land-use disturbance changes the nitrogen cycle by altering trajectories of forest recovery

Land-use disturbance alters nitrogen (N) cycling in ecosystems, but the mechanisms driving long-term changes remain unclear. We examined how historical disturbance shapes long-term N cycling in a temperate forest across a hillslope gradient. We found that increasing disturbance intensity promoted symbiotic N fixation (SNF) during early succession, which facilitated later dominance by arbuscular mycorrhizal (AM) trees. This shift indirectly enhanced N transformation rates, mineralization, nitrification, and denitrification, increased ammonium and nitrate pool sizes, and elevated microbial gene abundances (e.g., amoA, nirK, nirS, nosZ) by raising soil pH. Our findings suggest that N-fixing trees can generate biogeochemical priority effects that shape recovery trajectories for decades, providing a mechanism through which land-use disturbance exerts long-term influence on ecosystem processes.