凋落物与蚯蚓对杨树人工林土壤团聚体分布及其碳氮含量的影响

【目的】研究凋落物与蚯蚓对杨树人工林土壤团聚体的分布及不同粒径团聚体中C和N含量的影响,为改善杨树人工林土壤质量提供参考。【方法】以东台滨海杨树人工林为研究对象,采用随机区组法设置野外固定试验样地,共设置6个不同处理,即对照(CK)、杨树凋落叶表施(T1)、杨树凋落叶混施(T2)、接种蚯蚓(T3)、杨树凋落叶表施+接种蚯蚓(T4)、杨树凋落叶混施+接种蚯蚓(T5)。每种处理设置4个重复样地。按照粒径的不同对土壤中的团聚体进行分级,测定每种粒径团聚体中的有机碳和全氮含量,同时以平均质量直径(MWD)作为指标来考察土壤团聚体稳定性。【结果】不同粒径水稳性土壤团聚体中的有机碳含量一般随着粒径的增大而提高。杨树凋落叶混施+接种蚯蚓(T5)比杨树凋落叶表施+接种蚯蚓(T4)更能提高团聚体中的有机碳含量。在接种蚯蚓后,杨树凋落叶无论是表施还是混施均使得各粒径团聚体的有机碳含量有所提高。对比同一处理不同粒径团聚体全氮含量,粒径为≥0.250~2.000 mm团聚体的全氮含量普遍要高于其他粒径团聚体的,而粒径<0.053 mm团聚体的全氮含量相对最低。【结论】接种蚯蚓可以提高杨树人工林土壤团聚体中的全氮含量,同时杨树凋落叶混施比表施能更有效提高土壤团聚体中的全氮含量;接种蚯蚓加速了杨树人工林土壤有机质的腐殖化过程,使得土壤有机质的分解速率加快。相比杨树凋落叶表施处理,杨树凋落叶混施处理会加快土壤有机质的腐殖化过程。

Effects of litterfalls and earthworms on distribution of soil aggregates and carbon and nitrogen content in poplar plantations

【Objective】We aimed to study the effects of litterfalls and earthworms on the distribution of soil aggregates and the contents of carbon and nitrogen in aggregates of different particle sizes, and to reveal the distribution of soil aggregates and the changes of organic carbon and total nitrogen in aggregates. 【Method】 We set up the field fixed experimental plots using a random block experimental design in a poplar plantation located along the coast of Dongtai City, Jiangsu Province, China. A total of six different treatments were used, namely, a control treatment (CK), a poplar leaf litter surface application treatment (T1), a poplar leaf litter mixed application treatment (T2), an earthworm inoculation only treatment (T3), a poplar leaf litter surface application and inoculated with the earthworm treatment (T4), and a poplar leaf litter mixed application and inoculated with the earthworm treatment (T5). Four replicate plots were set for each treatment. According to the different particle sizes, the aggregates in the soil were graded, and the organic carbon and total nitrogen content of each particle size aggregate were determined. At the same time, the mean of weight diameter (MWD) was used as an indicator of the stability of the aggregates. 【Result】The organic carbon content of water-stable aggregates with different particle sizes generally increased with particle sizes. The organic carbon content of aggregates increased more in the T5 group than that in the T4 group. Furthermore, both the surface application and the mixture application of poplar leaf litter can increase the organic carbon content of aggregates with different particle sizes. Compared with the total nitrogen content of different particle size aggregates in the same treatment, the total nitrogen content of aggregates with particle sizes of ≥0.250-2.000 mm is generally higher than those of the other particles, while the total nitrogen content of aggregates with a particle size of ﹤0.053 mm was the lowest. 【Conclusion】The earthworm inoculation could improve the total nitrogen content of soil aggregates in the poplar plantation, and the mixed application of poplar leaf litter could improve the total nitrogen content of soil aggregates more effectively than the surface application. This study also showed that the earthworm inoculation accelerated the humification process of the soil organic matter in a poplar plantation and accelerated the decomposition rate of soil organic matter. In addition, compared with the surface application of poplar leaf litter, the mixed application of poplar leaf litter will also accelerate the humification rate and the decomposition of the soil organic matter.