Humus forms in each layer of forest soils were examined for organic matter composition, humus composition, elementary composition and nitrogen transformation using brown forest soils in Chubu district of Japan. The results obtained are summarized as follows. 1) The L, F and H layers and A horizons of several forest soils were fractionated physically. The L layers were mainly composed of Lf_1 (fresh litter) or Lf_2 (decomposed to some extent, > 2mm) and Lf_3 (decomposed, > 2mm). Fifty to ninety percent of the F layers were Ff_1 (> 2 mm) or Ef_2 (1-2 mm), crushed organic particle fractions. Ffty to eighty percent of the H layers was Hf_6 (< 0.1 mm, precipitate after dispersing in water overnight). A large portion of plant remains in the A horizons originated from roots at various stages of decay. 2) The physical fractions of each layer of the A0 horizon were analysed for the organic matter composition by the modified WAKSMAN's method. The amount of lignin and protein increased with the progress of decomposition of organic matter in A_0 horizons, while the total amounts of each extract benzeneethanol extract and hot water extract, except for the HCl extract, and the amounts of sugar and starch, phenolic substances, hemicellulose and pectin, and cellulose decreased. Sugars and starch comprised only a small portion of the hot water extract, and polyphenolic substances comparable to sugars and starch were also found in the extract. Hemicellulose and pectin accounted for only about one-half of the HCl extract. 3) The physical fractions of each layer and horizon were examined for humus composition by the KUMADA's method. Most of the humic acids from plant residual fractions of A_0 horizons belonged to the Rp type. The humic acids form the L layers showed a tannin-like character which disappeared in the F layers, and humic acids from the fine particle fractions of the H layers contained Pg fractions. The humic acids from A horizon belonged to the P or B type and contained Pg fractions. 4) On the changes in elementary composition with decomposition and humification of organic matter, the change in C/N ratio was the most obvious compared to the others. The decomposition process of organic matter within A_0 horizons can be divided into two stages based on the changes in C and N content, the first stage from the L to F or F-H layer and the second from the F or F-H to H or H-A layer. The C/N ratios of mineral horizons were lower in moderately moist type (B_D) than in dry type (B_A, B_B) soils. It was specially pointed out that Hf_7 and Hf_8, fine particle and water-soluble fractions from H layers, respectively, were fairly different materials from the other fractions, and were suspected to play an important role in soil formation. 5) The samples of each layer and horizon from the 29 brown forest soils were examined for nitrogen mineralization by determining the inorganic nitrogen during 20 week's incubation at 30℃. The higher the NT (total nitrogen) level of the sample, the greater the content of N_I (total inorganic nitrogen) was. Both the N_I level and the nitrogen mineralization rates (N_I/N_T×100) showed a tendency to increase with decreasing the C/N ratio from the L layer to the F or F-H layer, and thereafter decreased with increasing depth. Most of the N_I existed as NH_4-N in the majority of the samples except that remarkable nitrification was observed in the F, F-H, H, H-A layers and A horizon from some moderately moist type soil with the vegetation of Cryptomeris japonica or brood-leaf tree. In the samples where much NO_3-N was generated, ammonification and nitrification took place alternately. The mineral horizons of the moderately moist type soils were distinguished from those of the dry type soils by their higher NI levels and higher values of the NO_3-N/N_I ratio.

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Generally, the essential clay mineral of the volcanic ash soils is characterized by a predominance of allophane, imogolite, halloysite, and gibbsite. The 14Å minerals also are, however, extensively identified in the volcanic ash soils, but there is a divergence of opinion as to their origin. The occurrence of 14Å minerals in the volcanic ash soils in the Honshu and Hokkaido districts of Japan is considered to have relations with a snowfall. The 14Å minerals in these areas are probably provided as an ice nuclei of snow from eolian dusts in the atmosphere, which are dominantly originated from China. The eolian dusts may directly fall on the ground in the Kyushu district. From the amounts of eolian dusts in the palaeosols and peat soils, the accumulation rates of eolian dusts in last glacial intervals and Holocene are estimated to be 2.1〜3.3 and 0.11〜0.80 g/cm^2/1,000 yr, respectively. The clay mineral of eolian dusts is characterized by a predominance of 14Å minerals, illite, kaolinite, and quartz. The 14Å minerals are dominant in montrnorillonite, vermiculite, and intergrades, and their contents depend on the degree of weathering. The composition of crystalline clay minerals in the volcanic ash soils resembles nearly to that of Chinese loess, eolian dusts, and the North Pacific marine sediments, although the latter contains much more illite than the 14Å minerals in comparison with the former. Probably the dominating weathering sequence of eolian dusts deposited in the soils is considered to be as follows : [chemical formula] From these results, the contribution of eolian dusts is primarily reflected in the 14Å minerals, illite, kaolinite, and quartz in the volcanic ash soils in Japan.

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The Republic of Korea (Korea), a southern part of the Korean Peninsula extending almost directly southward from northern China, has the total land area of 98,478km^2 of which 67% is covered by forest and 22.7% is being cultivated. The environmental characteristics of Korea vary from south to north. It has a hot, wet summer and a cold, dry winter. The distribution of forest vegetation can be divided into five categories : warm-temperate evergreen lucidophyll forest, warm-temperate deciduous broadleaf forest (southern subzone and northern subzone), cool-temperate deciduous broadleaf forest, and subarctic coniferous forest. The general landscape of Korea is mountaineous or hilly. Granites and Gneises of the late Archeozoic era cover almost the surface geology The reconnaissance soil survey was finished between 1965 and 1967 and the detailed soil survey has been continuing since 1964. The reconnaissance soil maps with scales of 1 : 250,000 and 1 : 50,000 were published. The detailed soil maps of 135 regions where the survey was finished (with scale of 1: 25,000) and the the official soil series descriptions were published, too. Pedological and agricultural characteristics of Red and Yellow colored soils, rice soils and volcanic ash soils in Korea were described. The Red and Yellow colored soils occupy nine percent, and the rice soils occupy twelve percent of the total land area of Korea. The volcanic ash soils are distributed mainly on Jeju island and only a little on Ulleung island. Low inherent fertility characterized by low organic matter content and low cation exchange capacity is one common property of soils in Korea. Progresses of soil researches carried out by Korean researchers were reviewed. Utilization of the land and rice production were also described.

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