| Budget Amount *help |
¥4,000,000 (Direct Cost: ¥4,000,000)
Fiscal Year 2002: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2001: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2000: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
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.
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