Eleonora Bonifacio, Senior pedologist
Soils form in a very long time from a parent rock, and their characteristics depend on the vegetation and climate that are or were present during their development. Soil science, or more precisely pedology, studies soil development through the observation in the field of soil morphology, which is then followed by several types of analytical determinations: from soil chemistry and soil mineralogy, to soil physics and soil micromorphology.
A pedologist can recognize in the field if a soil has been disturbed, if a previously existent soil surface was buried or if a soil has developed under sharply different climatic or environmental conditions. Present days soils are an archive of the past, a past which is often much older than any human or biotic trace.
We were in the field at the Kobiotsuka Kofun in August, but unfortunately, deep field investigations were not possible and thus we had to rely more than we wanted on lab analyses.
We spent several days at Prof. Toshio Nozaka’s lab where, with his help, we analysed the elemental composition of the soils of the Kofun.
During soil development, specific trends for each group of chemical elements from top to bottom layers are expected and deviations from the expected trends indicate disturbances, such as soil truncation or burial by sediments. Thanks to prof. Suzuki Shigeyuki, we prepared the samples for the mineralogical analyses and brought them to Italy, where in addition other soil analyses were performed.
The vertical trend in soil organic matter and in phosphorus contents were irregular with depth and that was really interesting: an organic matter “rich” soil layer is now present at a certain depth in all soils along the trench.
What is that? An ancient soil surface that was buried during mound construction? A naturally organic matter enriched layer as those found in humid conifer forest soils? Only a soil scientist can answer these questions, through a careful examination of the whole soil profile….
More time has to be spent on the Kofun to fully understand its history, but we are sure that the soils will show us the way. Hopefully in August 2020!