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Soil profile research and analyses of soil physical and chemical properties were conducted for the soils under Hinoki (Chamaecyparis obtuse) plantation and broad-leaved forest in the basin of Tsuzura River in Shimanto Town, Kochi Prefecture, Japan. The soil under Hinoki plantation had no O horizon and contained large number of gravels in upper part of the profile, which was suggested that the soil under Hinoki plantation was influenced hardly by soil erosion. Total carbon and nitrogen content and CEC in the topsoil under Hinoki plantation were lower than those under broad-leaved forest. Macro-porosity was higher and micro-porosity was lower in topsoil and subsoil under Hinoki plantation than those under broad-leaved forest. There was high correlation between micro-porosity and liquid phase rate. As making thin section from the topsoil, soil micro-morphology in each soil was observed with polarizing microscope. Soil particles mainly existed to form peds in broad-leaved forest. On the other hand, in soil under Hinoki plantation, the amount of peds was comparatively small, and micro-structure consisted of peds and single grains. Crumbs in the soil under broad-leaved forest were aggregate of minute peds, which contained many small voids, while crumbs in the soil under Hinoki plantation were compact with low amounts of small interaggregate voids. It was supposed that such differences of quantity and quality of peds between the soils under Hinoki plantation and broad-leaved forest caused differences of soil physical properties.

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The relationships between the vertical distribution of charred plants and the humus composition or the carbon storage in the soil profile of a cumulative Andisol were investigated using 44 soil samples collected from surface and buried horizons. (1) The fraction of less than specific gravity 1.6g cm^<-3>, which was isolated after HCl-HF treatment of the soil samples, was mainly composed of charred plants. (2) The proportion of the amounts of charred plants (CO) to the amount of total organic matter (TO) ranged from 5.15 to 12.4% in 15 soil samples. (3) The vertical distribution pattern of the CO was similar to that of the TO, the amount of humic acid or the amount of fulvic acid. However, their changes were not constantly related to the elapse of soil age. (4) The CO was highly correlated with the sum of the amounts of NaOH-extractable humic acid (a_1) and fulvic acid (b_1) and the amounts of Na_4P_2O_7-extractable humic acid (a_2) and fulvic acid (b_2), the a_1+a_2, the b_1+b_2, the a_1+b_1, the a_1 and the b_1 (r≧0.860). (5) It was assumed that in the cumulative Andisol studied, charred plants contributed to the formation of Type A humic and fulvic acids as well as the carbon storage.

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To gain a fundamental understanding about the relationship between the distribution of charred plant residues and the humus composition in chernozemic soils, 15 soil samples were collected from Kazakhstan, Ukraine, and Hungry. Total organic C (TOC) content of whole soil ranged from 16.2 to 61.4g C kg^<-1> whole soil, and the organic C content of the fraction (mainly charred plant residues) of less than specific gravity 1.6g cm^<-3> (CPC) varied from 0.657 to 3.96g C kg^<-1> whole soil, except for 2 samples. The percentage contribution of the CPC to the TOC ranged from 2.16 to 9.29% and was 4% or more in 7 out of 15 soil samples. In all soils, the amounts of Type A humic acids exceeded greatly those of fulvic acids. The CPC was highly correlated (r>0.770) with the TOC, amounts of humic and fulvic acids, and the color coefficient of humic acid. The ^<13>C nuclear magnetic resonance spectra of selected humic acids showed that the relative contents of the aromatic-C were the highest among carbon species and that the aromaticity values ranged from 0.464 to 0.742. It is assumed that in the chernozemic soils, charred plant residues contribute to the formation of Type A humic acid and fulvic acid as one of the constituents of soil organic matter, as in the case of Japanese Andosols.

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The most commonly used method to extract sulfate ion (SO_4^<2->) from soils is probably the method by Soil Science Society of America (SSSA). However, the SSSA method appeared to be not directly applicable for volcanic ash soils. In the present study, we extracted SO_4^<2-> with calcium dihydrogen phosphate solution, based on the SSSA method from two soils derived from greywacke and volcanic ash, Typic Haplic Brown Forest soils and Typic Brown Kuroboku soils, respectively. It was shown that the 5 times extraction was capable to extract almost all of the SO_4^<2-> present in soils. Compared with the amount of SO_4^<2-> extracted with SSSA method, 5 times sequential extraction showed higher amount of SO_4^<2->. And different correlations were obtained between these two amounts extracted from the soils of volcanic ash and greywacke, suggesting that the SSSA method underestimated the total SO_4^<2-> present in volcanic ash soils. Moreover, the SSSA method did not reach reaction equilibrium as to the shaking time and the ratio of soil/solution. Instead, newly proposed condition of 4 hour shaking and the soil to solution ratio of 1:100 was good enough to reach equilibrium, and the amounts of SO_4^<2-> extracted under this condition were almost same as those of the 5 times sequential extraction, irrespective of the difference in parent materials.

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