Pedologist

To estimate the genetical period of the paleo-red soils based on tephrochronology, some tephra deposits overlying and/or underlying the paleo-red soils in Southern Kyushu were identified through the analysis of chemical composition of ferromagnetic minerals in them. The results obtained are as follows; 1) In Miyazaki Plain, Kakuto tephra (ca.340 ka) deposited between the paleo-red soil layer I and the pareo-red soil layer II in the profile of Higashibaru, and Ata-Torihama tephra (200-250 ka) was intercalated in the gravel bed under the paleo-red soil in profile of Nishi-azehara. 2) In Izumi Plain, Ata-Torihama tephra was intercalated in the gravel bed under the paleo-red soil in the profile of Obaru. 3) In Tanegashima, Kikai-Tozurahara tephra (90-95 ka) and Ata tephra (95-110 ka) covered the paleo-red soil in the profile of Tsubakiyama. These results suggest that the genesis of paleo-red soils began before 340 ka and lasted till 95-110 ka in Soutern Kyushu.

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Several chemical and mineralogical properties of volcanic ash samples erupted from the crater of Miyake island in the year of 2000 is as follows: 1. Clay contents and CEC values were much higher than those of volcanic ash samples from Sakurajima island and Mt. Usu. And smectite is present as observed for the volcanic ash samples from Mt. Usu. Therefore, it is suggested that volcanic ash samples are likely to contain secondary ashes previously weathered in crater as its major origin. 2. Both pH (H_2O) and pH (KCl) showed that the reaction of the ash sample is strongly acidic. It might be caused by the addition of large amounts of SO_2 gas from crater. 3. High amounts of exchangeable Al exist, and Al is assumed to be derived from the primary mineral dissolution with the decrease in pH. Almost all of the Ca^<2+> existed as water-soluble, and is present as gypsum.

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The bulk of water and material retention functions of soils is greatly dependent on the soil depth as well as state of pores and material retention ability of the horizons that constitutes the soil. However, the realization is difficult for investigating the soil depth to the deep layer by digging pit or boring, because considerable labor and costs are required, especially in mountains. In this paper, the relationship between soil depth and micro-topography and slope was investigated in detail in the mountains, and a practicable estimation method of soil depth was found. 1) On the 1:5,000 national large scale map, micro-topography is divided into broad ridge, verge of broad ridge, middle ridge, narrow ridge, break zone of ridge slope, straight slope, colluvial slope, mortar-shaped head hollow, head hollow, lower valley sides, valley floor, and valley plain by the shape of distribution pattern of contour lines of every 5 m. 2) Slope is divided in 25° or less and more than 25°. 3) By the combination of micro-topography class and slope class, soil depth (m) can be estimated at 0〜0.5, 0.5〜1,1〜2,2〜3, and above 3. 4) The mountain soils of the depth of 0〜0.5 m, 0.5〜1 m, and more than 1 m are the soil groupimgs of Terrestrial Regosols, Brown Forest soils, and Andosols, respectively in the Kozakura river basin. The estimation method is a case in the area covered with volcanic ash in the low mountains of the Tsukuba mountain range. It is desired that it accumulates the cases in the places of various conditions and establishes the comprehensive estimation method of soil depth.

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We directed our attention to the sizes of bordered pits on the surface of the transfusion tracheid phytoliths in and studied its difference among Pinus, Picea, and Abies. The sizes tended to increase in the order of Pinus (6.02 ± 0.42μm) > Picea (4.31 ± 0.49μm) > Abies (3.07 ± 0.33μm). The difference in average value was significant at 0.1% level. This suggests that we can assess the distribution and succession of northern conifers (Abies sachalinensis and Picea jezoensis var. jezoensis) by investigating the density of opal phytolith originating from transfusion tracheid cells and sizes of bordered pits on them. Though the sizes of bordered pits on the transfusion tracheid phytoliths did not differ largely among the conifers belonging to the same genus, there seemed to be a little difference among Picea glehnii, P. hitchensis, P. kaoraiensis, and P. jezoensis. Further study is nessessary to compare statistically. The size of bordered pits on the transfusion tracheid phytoliths using many individual Picea jezoensis var jezoensis and Abies sachalinensis.

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