恢复方式对东北东部森林土壤碳氮磷计量特征的影响

Effects of restoration approaches on forest soil carbon, nitrogen and phosphorus stoichiometry in eastern Northeast China

土壤生态化学计量是土壤肥力和植物养分状况的重要指标,探索森林的恢复方式对土壤生态化学计量特征的影响,可为准确评价生态系统物质循环过程对干扰和恢复的响应提供理论依据和数据支撑。该研究比较测定了东北东部山区人工恢复的3种针阔混交林和天然恢复的4种落叶阔叶林的土壤、凋落物和枯落物的碳(C)、氮(N)和磷(P)含量,以及土壤pH、土壤密度等理化性质。结果显示:人工针阔混交林和天然落叶阔叶林的土壤C、N和P含量均随着土壤深度的增加而降低。各林分类型的O(有机质)层土壤C、N和P含量的波动范围分别为53.78–90.59、5.02–7.83和0.75–0.91g·kg^(-1)。人工针阔混交林O层土壤的C和N含量显著低于天然落叶阔叶林,而人工针阔混交林A(腐殖质)和B(淀积)层土壤的C、N和P含量均高于天然落叶阔叶林。人工针阔混交林O层土壤的C密度显著低于天然阔叶林。土壤C:N、C:P和N:P的波动范围为10.08–12.53、43.97–135.52和4.56–11.64;O层土壤的C:N在两种恢复方式的森林间无显著差异,人工针阔混交林O和A层土壤的C:P和N:P显著低于天然落叶阔叶林。土壤各层次的C和N含量均存在显著的正相关关系(R2范围0.40–0.76)。除C:N以外,恢复方式、土壤发生层及其二者交互作用对土壤C、N、P含量、密度和计量比均存在显著影响。土壤密度和凋落物C含量显著影响土壤C、N和P含量。这些结果表明,通过人工恢复方式增加针叶树种的比重,使表层土壤的C、N含量降低,导致表层土壤的碳固持量减弱;但是对C:N无显著影响,表现出相对稳定的土壤C、N计量特征。

Aims Soil ecological stoichiometry is an important indicator of soil fertility and plant nutrient status.Investigating impacts of restoration approaches on forest soil ecological stoichiometry characteristics provides a theoretical foundation and data support for accurately assessing responses of the ecosystem material cycling processes to disturbance and restoration efforts.Methods This study compared the forest soil stoichiometry from two forest restoration approaches,i.e.,artificial(RG)and natural regenerations(TR)that included three coniferous or broadleaf mixed stands and four deciduous broadleaf stands,respectively,in eastern Northeast China.The carbon(C),nitrogen(N),and phosphorus(P)contents of both soil by horizons,litterfall and litter were determined,as well as the soil properties such as pH and bulk density.Important findings The results showed that soil C,N,and P contents decreased with the soil depth in the RG and TR.The soil C,N and P contents of the O(organic)horizon varied from 53.78 to 90.59 g·kg^(-1),5.02 to 7.83 g·kg^(-1),and 0.75 to 0.91 g·kg^(-1) in all the stands,respectively.The soil C and N contents of the RG were significantly lower than those of the TR in the O horizon,while the soil C,N and P contents of the RG were higher than those of the TR in the A(humus)and B(illuvial)horizons.The soil C density of the O horizon in the RG was significantly lower than that in the TR.The C:N,C:P,and N:P varied from 10.08 to 12.53,43.97 to 135.52,and 4.56 to 11.64 in all the stands,respectively.The C:N of the O horizon had no significant difference between RG and TR,but the C:P and N:P of the O and A horizons in the RG were significantly lower than those in the TR.There was a significant positive correlation between C and N contents in all soil horizons(R2 ranged from 0.40 to 0.76).Except for C:N,restoration approaches,soil horizons and their interaction had significant effects on the content,density and stoichiometry of C,N and P in soil.Soil bulk density and litterfall C content significantly affected soil C,N and P contents.These findings suggest that increasing the proportion of coniferous species by reforestation reduced the content of C and N in the topsoil,which decreased the carbon sequestration accordingly.However,restoration approaches had no significant effect on the C:N,featuring a relatively stable carbon and nitrogen stoichiometry.