Abstract:
In order to reveal effects of short-term nitrogen (N) addition on stoichiometrical characteristics of C, N, and P in soils, which can provide a basis for guidance of N management in
Cunninghamia lanceolata plantations, two Chinese fir plantations with different ages, i.e., 11 and 18 years old, were used as models to study responses of stoichiometrical characteristics of C, N, and P in soils to N addition. In each plantation, we randomly set 9 plots with an area of 400 m
2 in each plot. Three regimes of N addition, i.e., control (CK, 0 g/(m
2·a)), low-nitrogen (LN, 5 g/(m
2·a)) and high-nitrogen (HN, 10 g/(m
2·a)), were deployed in each
C. lanceolata plantation. Every N regime included 3 replicated plots. From April to November in 2019, NH
4NO
3 as additional N source was sprayed in the plots monthly. In both growing season and non-growing season, soils in two layer depths (0−20 cm and 20−40 cm) were sampled. Soil properties including contents of available inorganic N, total organic C (SOC), total N, and total P, and their stoichiometrical ratio were analyzed to determine the impact of short-term N addition on stoichiometrical characteristics of C, N, and P in soils. N addition increased N-NO
3− content in soils of both
C. lanceolata plantations, and induced accumulation of N-NO
3− in soils with the increase of N addition. The increase of N-NO
3− in soils of 11 years plantation was more significant than that of 18 years plantation under the corresponding N regime. Under N addition, concentrations of SOC, N, and P in soils of both
C. lanceolata plantations increased to varying degrees. Such increases in upper layer soil depth (0−20 cm) were more obvious than those in deeper layer soil depth (20−40 cm). There was no significant alteration in stoichiometrical ratio of C, N, and P under short-term N addition in both plantations, which was affected by season and soil layer depth significantly. Available N nutrients and soil stoichiometrical characteristics of C, N, and P were more responsive in 11 years
C. lanceolata plantation under short-term N addition, when compared to those in 18 years
C. lanceolata plantation.