A study on mechanisms of aggregate collapse after cutting

为了阐明森林土壤采伐后团粒崩塌的机理，采用土壤培养实验的方法，研究了土壤微生物的溶蚀作用和活化作用对森林土壤团粒崩塌的影响。虽然在树种和骨料大小上存在一定的差异，但在干湿条件下骨料崩塌较为明显，说明骨料发生了滑坡崩塌。不同树种间的崩塌程度无显著差异。另一方面，骨料对熟化的稳定性受骨料粒度的影响，粒度大的骨料对熟化的稳定性更高。从骨料样品的总碳和总氮的测定结果来看，认为影响骨料滑塌稳定性的主要因素是水分对骨料的渗透速率，而不是有机质含量。对于微生物活化团聚体的崩解，在30℃的培养过程中，土壤微生物的活性高于15℃，在30℃的培养过程中团聚体崩解明显。由于累积值与聚集指数呈负相关，微生物活性积分值与聚集指数呈负相关，因此可以认为团聚体崩塌受土壤微生物活性的影响。但由于全碳、全氮变化趋势不明显，有机质分解与团聚体崩塌的关系尚不明确。因此，定量地表明，团聚体崩塌是由土壤微生物的松弛和活化引起的。

In order to clarify about mechanisms of aggregate collapse in forest soil after cutting, aggregate collapse by slaking or activation of soil microorganisms were investigated by means of soil incubation experiments. Although there were some differences in tree species or aggregate sizes, aggregate collapse was notable in dry-wet conditions, so it showed that aggregates were collapsed by slaking. There were not striking differences in degree of collapse between tree species. On the other hand, stability of aggregate to slaking was influenced by aggregate size, and large size aggregates had higher stability to slaking. And from the measurement results of total carbon and total nitrogen of aggregate samples, it was considered that stability of aggregate to slaking was influenced by the permeate rate of water into aggregates rather than contents of organic maters. For the collapse of aggregate by activation of microorganisms, it was recognized that activity of soil microorganisms is higher in samples incubated at 30C° than 15C° through the incubation period, and aggregate collapse was notable at 30 C°. Since negative correlations were recognized between accumulation values and aggregation index, and between integral values of raicrobial activities and aggregation index, it was considered that collapse of aggregate was influenced by activity of soil microorganisms. But it was not accomplished to clarify the relation between decomposition of organic matter and aggregate collapse, since there were not clear tendencies in changes of total carbon and total nitrogen. Consequently, it was indicated quantitatively that aggregate collapse was occurred by slaking and activation of soil microorganisms.