Stand development affects soil properties, nitrogen (N) dynamics, and soil microbial community composition, but the question remains whether differences in N mineralization rates are mirrored by the abundance of relevant functional genes. In this study, we used the ¹⁵N pool-dilution method to estimate N mineralization (i.e., ammonification and nitrification) rates across a Chinese fir (Cunninghamia lanceolata) chronosequence, with stands aged 7, 16, 29, 36, and >80 years. Gene copy numbers of bacteria (16S rRNA), fungi (ITS), ammonia-oxidizing archaea (AOA) and bacteria (AOB) (amoA), denitrifiers (nirS, nirK), N₂ fixers (nifH) and organic N decomposers (chiA) were quantified by qPCR. Gross ammonification and nitrification rates increased linearly with stand age in the topsoil (0–5 cm depth) and were strongly positively correlated with the abundance of the bacterial 16S rRNA gene and AOA amoA, respectively. Higher net nitrification but lower NO₃⁻ immobilization rates in older stands (32 and > 80 years) drove higher N availability for vegetation than in young stands (7 years). Older stands also had higher rates of NH₄⁺ consumption than younger stands due to the increased fungal ITS abundance and higher microbial biomass N (MBN), and AOA amoA was more abundant and active than AOB amoA due to the more acid conditions characteristic of mature forests. Redundancy analysis showed that functional gene abundance was strongly affected by soil properties such as pH, NH₄⁺-N content, and MBN. We also found that microbial N storage potential was lower, and the NO₃⁻-N leaching and gaseous N loss potential were higher in older stands than in younger stands. Collectively, stand developmental stage gave rise to the observed spatial gradient of gross ammonification and nitrification rates by altering the abundance of microbial functional genes, which affected plantation productivity via its modulation of the supply of bioavailable N.

林分发育影响土壤性质、氮 (N) 动态和土壤微生物群落组成，但问题仍然是氮矿化速率的差异是否反映了相关功能基因的丰度。在这项研究中，我们使用¹⁵ N池稀释法来估算杉木（Cunninghamia lanceolata）树龄7、16、29、36和>80年的氮矿化（即氨化和硝化）速率。 。细菌 ( 16S rRNA )、真菌 ( ITS )、氨氧化古菌 (AOA) 和细菌 (AOB) ( amoA )、反硝化菌 ( nirS、nirK )、N ₂固定菌 ( nifH )和有机氮分解菌 ( chiA )的基因拷贝数）通过 qPCR 进行定量。总氨化率和硝化率随着表土（0-5厘米深度）的林龄线性增加，并且分别与细菌16S rRNA基因和AOA amo A的丰度呈强正相关。老林分（32年和> 80年）的净硝化作用较高，但NO ₃ ^-固定率较低，导致植被的氮利用率高于年轻林分（7年）。由于真菌ITS丰度增加和微生物生物量 N (MBN)较高，较老的林分也比年轻的林分具有更高的 NH ₄ ⁺消耗率，并且由于成熟林分的酸性条件特征更强， AOA amoA比 AOB amoA更加丰富和活跃。森林。冗余分析表明，功能基因丰度受pH、NH ₄ ⁺ -N 含量和MBN 等土壤性质的强烈影响。我们还发现，较年轻的林分，微生物氮储存潜力较低，NO ₃ ^{- -N 淋溶和气态氮损失潜力较高。}总的来说，林分发育阶段通过改变微生物功能基因的丰度，产生了观察到的总氨化和硝化速率的空间梯度，这通过调节生物可利用氮的供应来影响种植园生产力。