This study was conducted for the purpose of determining some properties and distribution of soils present in Kali Gandaki valley located in Cental Nepal, which was climatologically divided into 6 zones : humid subtropical, humid temperate, subhumid temperate, semiarid temperate and arid temperate from the south to the north and subalpine zone with elevations ranging from 3000 to 4000 m. The results obtained showed a considerably clear variation in some soil properties and soil distribution brought about by the differences in climatic conditions. 1) The pH value and carbonate-C content increased with increasing aridity from the humid sutropical zone to the arid temperate zone. 2) The organic carbon content and the CEC of surface horizons increased from the humid tropical to the humid and subhumid temperate and then decreased from the arid temperate to the semiarid temperate. The pattern of changes with respect to climate was also observed for the exchangeable base or NH_4OAc (pH 7)-extractable base content except for Na. 3) The C/N ratios of the surface horizons were higher in the semiarid temperate and in one part of the arid temperate region than in the other zones. 4) The base saturation generally increased from the humid subtropical to the subhumid temperate through the humid temperate, though a significantly high base saturation was observed in one part of the humid temperate zone. 5) The properties of the soil in the subalpine region were nearly the same as those of the humid temperate soils. 6) With regard to classification of the soils in each region, Dystric Cambisols in the humid temperate and in one part of the humid subtropical zone, Haplic Phaeozems in the subhumid temperate and in one part of the humid subtropical zone, Calcic Chernozems in the semiarid temperate, and Calcic Regosols in the arid temperate were recognized. The soil in the subalpine zone presumably belonged to Dystric Cambiosols.

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This study was carried out for the purpose of elucidating a sequence of soil organic matter using evidences obtained on organic matter accumulation and humus composition in Kali Gandaki valley located in central Nepal. The area is divided into six different climatic regions : humid subtropical, humid temperate, subhumid temperate, semiarid temperate and arid temperate from the north to the south, and subalpine with elevations ranging from 3000 to 4000 m. The results obtained showed a considerably clear transition in some properties of soil organic matter caused by the climatic differences. 1) The accumulation of organic carbon in mineral soil horizons was highest (180-219 ton/ha) in the humid temperate region and decreased in the order of humid temperate ≧ subhumid temperate (165 ton/ha, except for the AC soil) > subalpine (110-173 ton/ha) ≧ semiarid temperate (75-146 ton/ha) ≧ humid subtropical (69-116 ton/ha) > arid temperate (16-79 ton/ha). Changes in the total nitrogen accumulation as influenced by the climate were basically similar to those of the organic carbon accumulation. The ratio of the accumulated amount of C to N in each soil profile varied from 10 to 18, and was higher (16-18) in the semiarid or arid temperate region because of the slower rate of organic matter decomposition caused by the aridity. 2) The ratio of extracted humic fractions (humic and fulvic acids) to the accumulated organic carbon in each soil profile (C_E/C_T) ranged mostly between 50 to 52% and was slightly lower in the humid subtropical zone (43.8%, except for No. 2) and in the semiarid temperate zone (47%}. This indicates that the extraction of humic fraction is more difficult in highly humified and relatively fresh organic matter than in moderately decomposed one. The Ch/Cf ratio showed a tendency to decrease with depth in most soil profiles. The ratio of accumulated humic acid to fulvic acid in each profile was highest (1.39-1.65) in the subhumid temperate followed by the semiarid temperate region (0.94-1.03), ranging between 0.35 to 0.84 in the soils belonging to the other climatic regions. The significant correlation obtained between the Ch/Cf ratio and the NH_4OAc (pH 7)-extractable Ca in A or A_1 horizon suggested that the formation of humic acid is accelerated when the exchangeable Ca content of the soil is high. The types of humic acid obtained from samples, except for those in the 0-5 or 0-10 cm horizons, were Rp, P-B, P-A, and A in the arid to semiarid temperate, subhumid temperate and subalpine, humid temperate and humid subtropical, respectively. It is obvious that the wamer and the more humid the climatic condition of the region in which the soil is present, the higher is the degree of humification of the humic acid. This may suggest the intensity of soil organic matter decomposition by micro-organisms is closely related to the humification of humic acids. The Pg (green fraction of humic acid) content was higher in the deeper parts of most soil profiles, and was higher in the subhumid temperate (400-470 kg/ha) and the subalpine (184-439 kg/ha) than in the other regions. The alkaline to weak alkaline soils of the arid to semiarid temperate regions contained no Pg fraction. The conditions for Pg production are presumed to exist in acidic soils in the humid temperate region.

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Successive sinking of the Lake Biwa and uplifting of the Suzuka Mountains have caused the formation of several fans along the Echi River. Older fans are transformed into elevated terraces, while the recent fan covers the alluvial plain. Soil profiles are poly-genetic in this situation. Intermittent superposition of different soil surfaces (abbreviated as SS) have occurred in the course of deposition and erosion cycles. Six different soil surfaces have been distinguished and described. The oldest soil surface SS6 remains on the high terrace. The diagnostic feature is Torahan (tiger-mottled) layer, which is resting on deep gravel beds of Plio-Pleistocene formation. SS5 is located extensively on the middle terrace. The diagnostic layer is red-yellow-colored compact clay with developed cutan and manganese mottles. SS5 abuts the recent fan at the lower margin. SS4 is located on the low terrace, and has layers of dull yellow-brown to grayish color. This is derived from the reworked material of SS5. SS3 is derived from the admixture of aeolian volcanic ash, and has developed into Kuroboku (Ando soil) and Loam (smeary, weathered volcanic ash deposit). SS2 is derived from the reworked material of SS3. SS1 covers the recent flood plain. It has gray and gley soil layers. Representative soil stratigraphy on older fans are: SS6, SS5, SS2/SS5, and SS2/SS3/SS5. The recent fan has that of SS1 and SS1/SS3. Two analytical items are significant in indicating the parent material and weathering sequence. Clay mineralogical composition of the soils inherits the nature of parent material, and thus enables us to distinguish the parent material and their distribution: weathered gravel beds of the high terrace, Kobiwako (Old Lake Biwa) deposits and recent fluvial deposits. Free sesquioxides of iron and aluminium which are extracted by Tamma A solution and Dithionite-Citrate-Bicarbonate solution indicate the coinciding weathering sequence of soil material with successively older soil surfaces.

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Plant opal analysis was carried out on soils derived from volcanic ashes at the foots of Mt. Fuji and Mt. Amagi, central Honshu, to reveal previous vegetations and clarify soil-vegetation relationships. The Fuji soils derived from basaltic ashes (younger than about 2,700 y. B. P.), were collected from a Brown Forest soil (No. 1) and a Black (Kuroboku) soil (No. 2) belonging to the cool temperate zone. The Amagi soils were Brown Forest soils (Nos. 3 and 5) and a Black (Kuroboku) soil (No. 4), which were developed from dacitic ashes (younger than about 2,900 y. B. P.). The soil (No. 3) was in the cool temperate zone. On the contrary, the soils (Nos. 4 and 5) were in the warm temperate zone. 1) Plant opal assemblage of Black (Kuroboku) soils (Nos. 2 and 4) was characterized by the dominance of non-Bambusoid, Panicoid and Festucoid phytoliths. Brown Foresn soils (Nos. 1 and 3) were doninated by Bambusoid, mainly, from Sasa and jigsaw pazzle shaped phytolith originated from a deciduous broad leaf tree, Fagus crenata. In a Brown Forest soil (No. 5), Y-shaped phytolith of evergreen oak origin was much more abundant than in the other soils. 2) The present plant opal composition suggests that the Black (Kuroboku) soils, the Brown Forest soils in the cool temperate zone, and the Brown Forest soils in the warm temperate zone have respectively been formed under the vegetation of grass, Fagus crenata forest with Sasa, and evergeen oak forest. This implies that vegetations are able to exert respective and signficant influence upon soils developed from similar parent materials in lithology and age under similar climatic conditions.

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