Could Soil Acidity Enhance Sequestration of Organic Carbon in Soils?
On the basis of field and laboratory measurements of the dynamics of soil organic matter (SOM) in Japan, Thailand, Indonesia, Kazakhstan, and Ukraine having different soil pH levels, we postulate that soil acidity plays an important role in the accumulation of SOM through two processes. Firstly, the amount of potentially mineralizable C (C 0) in the acid soils of Kalimantan or light-fraction C in the Japanese acid soils often increased drastically. Hence, it seems that high soil acidity can enhance the accumulation of organic materials in surface soils by decreasing the soil microbial activities for SOM decomposition. Secondly, field measurements of C flux in various soils under forest showed that the internal leaching of dissolved organic carbon (DOC) from litter layers or surface soils increased under low pH conditions, typically for Humods in Japan and Udults in Kalimantan. This indicates a downward movement of DOC in acid soils that increases the tendency of the subsoils to accumulate SOM as organo-mineral complexes. It is concluded that high soil acidity can enhance the storage level of soil organic materials in the form of readily mineralizable organic materials in the surface soils and by organo-mineral complexes formed in subsoils as a result of accelerated leaching of DOC from the O horizon.
KeywordsDecomposition Dissolved organic carbon Organic matter Soil acidity
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