Mixed Plantations Induce More Soil Macroaggregate Formation and Facilitate Soil Nitrogen Accumulation

Nitrogen plays a crucial role in limiting plant growth and determining net primary productivity forest ecosystems. However, variations influencing factors of soil nitrogen distribution on the aggregate scale pure mixed Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations remain unclear. This study aimed to explore how composition, geometric mean diameter (GMD), weight (MWD), total (TN), acidolyzable (TAN), available (AN), nonacidolyzable (AIN), amino acid (AAN), nitrate (NO3−-N), cidolyzable ammonia (AMN), unknown-acidolyzable (HUN), sugar (ASN), ammonium (NH4+-N) contents stocks varied with size (>2, 1–2, 0.25–1, <0.25 mm) stand type [Chinese Michelia macclurei Dandy (CF + MM), Mytilaria laosensis Lecomte ML) stands (CF)] 0–20 20–40 cm depth. Soil N content different types decreased as increased, whereas stock exhibited opposite trend. In contrast CF soil, MM ML displayed significant increase MWD, GMD, aggregate-associated TN, AN, NO3−-N, NH4+-N, AIN, AAN, ASN, AMN stocks, especially soil. Organic was more sensitive response than mineral N. Redundancy analysis Pearson’s correlation indicated that 0.25–1 mm proportion main controlling factor for storage. Overall, this contributed significantly promotion sustainable use resources reference information scientific management development forests.