| Co-Investigator(Kenkyū-buntansha) |
TAMURA Kenji University of Tsukuba, Institute of Applied Biochemistry, Associate Professor, 応用生物化学系, 助教授 (70211373)
KAMIJYO Takashi University of Tsukuba, Institute of Agriculture and Forestry, Assistant Professor, 農林学系, 講師 (10301079)
|
|---|
| Research Abstract |
This study aims to investigate the nutrients accumulation process in the initial soil formation process. Study field was Miyakejima Island where the vegetation and its primary succession is well documented and typical initial soil formation process from scoria of different age of deposition. The results obtained are as follows :
1) According to the soil survey on the scoria hills of 1983, 1962, 1940, 1974 and more than 1000 years, the development of soil profiles shows A/C profile up to 1874 with increasing the thickness of A horizon, classified as Immature Soils, while cambic Bhorizon is developed on the scoria hill of more than 100 years, classified as Brown Forest Soils.
2) Based on the analyses for particle size distribution, pH, water-soluble and exchangeable bases, total carbon and nitrogen, CEC, oxalate-extractable Al, Fe, Si, and clay mineral composition on the soil samples from each horizon of 5 representative soil profiles, the following characteristics of nutrient accumulation
… More
during the initial soil formation process from scoria.
(1) The fraction of more than 2 mm decreased, while sum of silt and clay fractions increased from 0.8 % to 48 %. And, accumulation process of soil organic matter is increased from 0.04 % to 9.15 % in the surface horizon. Moreover, nature of clay fractions is still amorphous, but the amount of oxalate-extractable Al+1/2Fe apparently increased. Due to these increases expressed as logarithm of the duration of time, CEC also increased from 0.64 to 21.75 cmolc/kg corresponding with the increase in water-soluble and exchangeable bases(Ca, Mg, K, Na) especially in the latter, which support the base saturation degree of nearly 100 % characteristic for this kind of soils studied in the early stage of soil formation.
(2) Available phosphorus and nitrate and ammonium ions extracted with water and 1N KCl also increased, showing the similar tendency with the increase in CEC.
From all results obtained above, it can be concluded that the rate of nutrition accumulation in the soils under the primary succession of about 1000 years (from bare land of scoria to climax of Castanopsis forest) is estimated for the first time in the world. Less
|
