中国南亚热带不同造林模式碳汇林土壤碳、氮、磷的积累及化学计量特征

Characteristics of soil carbon, nitrogen, phosphorus accumulation and their ecological stoichiometry in Chinese subtropical forest under different afforestation patterns

碳汇林的固碳效益十分显著,是实现“碳中和”的主要碳增汇途径之一,在研究南亚热带地区不同造林模式碳汇林土壤碳汇的同时,研究碳汇林土壤氮、磷储量及土壤碳、氮、磷的生态化学计量特征,能够为不同造林模式碳汇林的土壤碳、氮、磷储量的评估提供科学依据。采取单因素随机区组设计,选择立地条件基本一致的研究区和4种造林模式(新造林、封山育林、补植套种、更新改造)的碳汇林,分析了不同造林模式土壤有机碳(SOC)、全氮(TN)、全磷(TP)的含量、储量、生态化学计量比,以及微生物生物量碳(MBC)的变化特征。结果表明,不同造林模式碳汇林的土壤理化性质,碳氮磷储量、化学计量比及微生物生物量碳含量差异显著,且土壤碳氮磷储量随土壤深度增加而减少,表现出明显的垂直变化特征。4种造林模式下碳氮比(C/N)介于11.11—17.86,碳磷比(C/P)介于17.00—242.59,氮磷比(N/P)介于1.18—15.99之间,在0—60 cm土层上均以更新改造模式林最低,封山育林模式下C/P和N/P均显著高于其他造林模式。土壤SOC与TN、N/P呈极显著正相关关系,土壤TN与C/P呈极显著正相关关系。综合来看,封山育林模式土壤的碳、氮含量和储量最高,而磷含量最低,说明封山育林模式更有利于土壤碳、氮的累积,而后期表现出土壤磷的缺乏,可能会限制封山育林模式碳汇林后期的碳汇功能。更新改造模式碳汇林的土壤养分限制少,后期碳汇潜力较大。

Carbon sink forests is one of the effective ways to achieve "carbon neutrality". Besides soil carbon(C) sink, soil nitrogen(N), phosphorus(P) stocks and stoichiometry were investigated under different afforestation patterns, which provides the theoretical basis for estimating soil nutrition stocks. A single-factor randomized block design was used to investigate C, N, and P contents, stocks, their stoichiometric characteristics and soil microbial biomass carbon in soils with different soil depths under four afforestation patterns including new afforestation, closed mountain afforestation, replanting, and regeneration. The results showed that the storage of soil C, N, and P decreased with soil depth. The range of soil C/N, C/P and N/P under the four afforestation patterns were 11.11—17.86, 17.00—242.59 and 1.18—15.99, respectively. Soil C/P and N/P under closed mountain afforestation were significantly higher than the other afforestation patterns, while regeneration pattern showed the lowest. The soil C was positively correlated to soil N and N/P, soil N was positively correlated with C/P. In summary, the content and stock of soil C and N were the highest under closed mountain afforestation, while phosphorus content was the lowest, indicating that the closed mountain afforestation is an effective afforestation to promote the accumulation of soil carbon and nitrogen. However, the capacity of soil carbon sink under closed mountain afforestation may be weakened by soil phosphorus limitation. Regeneration pattern has less nutrition limitation, which has great potential to sequestration carbon.