Abstract:

【Objective】Litter regression can affect the soil carbon and nitrogen cycle, which is an important process of sustainable management and soil fertility maintenance in Chinese fir(Cunninghamia lanceolata)plantations. The changes in soil carbon content, nitrogen content, and enzyme activity under the treatment of adding C. lanceolata and Schima superba litter were analyzed to provide the basis for nature-approximating transformation and stand management of C. lanceolata plantations.【Method】In the present study, 30-year-old C. lanceolata plantation soil was treated with C. lanceolata litter (S), S. superba litter (M), and a mixture of C. lanceolata and S. superba litter (mixed at a m (S):m (M)=5:1, SM). After 60 days of incubation, the content of ammonium nitrogen ( {\mathrm{NH}}_4^{+}-N), nitrate nitrogen ( {\mathrm{NO}}_3^{-}-N), soil organic carbon (SOC), water soluble organic carbon (WSOC), hydrochloric acid hydrolyzed organic carbon (HHOC), alkaline-hydrolyzable organic carbon (AHOC), recalcitrant organic carbon (ROC), and enzyme activities (β-glucosidase(GC); β-N-acetylglucosaminidase(NAG); polyphenol oxidase(PPO); and leucine aminopeptidase(LAP)) in the soil were measured in the different treatments. The relationship among soil carbon content, nitrogen content, and enzyme activity in different treatments was analyzed, and the effects of different litter on soil carbon content, nitrogen content, and enzyme activity in C. lanceolata plantations were evaluated.【Result】The degree of humification in the soil treated with mixed litter was increased compared to the soils treated with either litter alone. In the single litter treatment, the degree of humification with S. superba treatment was low, and the proportion of soil recalcitrant organic carbon (ROC) was relatively higher. After 15 and 30 days of incubation, the soil GC, NAG and PPO enzyme activities with C. lanceolata litter were significantly higher than those with S. superba litter. The decomposition of mixed litter significantly improved soil GC and NAG enzyme activities. The results of redundancy analysis and correlation analysis showed that soil AHOC content was significantly positively correlated with soil GC enzyme activity. NAG enzyme activity was positively correlated with soil WSOC content and negatively correlated with {\mathrm{NH}}_4^{+}-N content, while PPO enzyme activity was negatively correlated with {\mathrm{NO}}_3^{-}-N content and positively correlated with ROC and HHOC contents (P<0.01).【Conclusion】The addition of different litters significantly affects the soil carbon content, nitrogen content, and enzyme activity in C. lanceolata plantations. Compared to the addition of S. superba litter, the addition of C. lanceolata litter results in a higher soil humification degree, as well as higher enzyme activities related to the carbon and nitrogen cycle. Further, the addition of both C. lanceolata and S. superba litter is more beneficial in improving the degree of soil humification, soil carbon invertase activity, and nitrogen invertase activity compared to the addition of either litter alone, thus ultimately benefitting the soil carbon and nitrogen cycle of C. lanceolata plantations.

Key words: Cunninghamia lanceolate plantation, litter decomposition, carbon content, nitrogen content, soil enzyme