Table 3_Alfalfa fields with different stand ages alters soil inorganic nitrogen dynamics through shifts in nitrogen-cycling functional genes across growth stages.xlsx

The abundances of genes involved in nitrification, denitrification, and nitrate reduction also varied with stand age and showed growth-stage-specific patterns. Growth stage explained a greater proportion of variation in nitrogen-cycling gene profiles than stand age, although stand age was also significantly associated with these profiles. The relationships between functional genes and soil inorganic nitrogen varied among growth stages.

SEM analysis suggested that growth stage was the primary factor associated with variation in nitrogen-cycling gene groups. Nitrification-related genes were positively correlated with soil inorganic nitrogen, whereas nitrate reduction-related genes showed negative correlations.</p>Conclusion<p>Overall, the 4-year alfalfa field exhibited the highest observed soil inorganic nitrogen concentrations, while this pattern was less evident in the 7-year field.

These findings indicate that soil nitrogen status and nitrogen-cycling functional genes vary jointly with alfalfa stand age and growth stage. Nitrogen-cycling functional genes may serve as potential indicators of soil nitrogen status, although further experimental studies are needed to verify these relationships.</p>