Study on the nutrient accumulation process during the initial soil formation Process

本研究旨在研究土壤形成初期的养分积累过程。研究区域为宫崎岛，那里的植被及其初级演替得到了很好的记录，并具有典型的不同沉积年龄的渣土初始成土过程。结果表明：1)根据1983、1962、1940、1974和1000多年的土壤调查资料，土壤剖面的发育表现为A/C剖面至1874年随A层厚度的增加而增加，属于未成熟土，而荒漠土层发育于100年以上的渣土丘陵区，属于棕森林土。营养积累…的以下特征(1)大于2 mm的粒级减少，而粉粒和粘粒的总和从0.8%增加到48%。表层土壤有机质积累过程由0.04%增加到9.15%。此外，粘土组分的性质仍然是无定形的，但草酸盐萃取物Al+1/2Fe的量明显增加。由于这些以时间的对数表示的增长，CEC也从0.64增加到21.75cmolc/kg，与水溶性和交换性盐基(Ca、Mg、K、Na)的增加相对应，尤其是后者，这支持了土壤形成早期所研究的这类土壤近100%的碱基饱和度。(2)水和1N KCl提取的有效磷、硝酸盐和铵离子也增加了，表现出与CEC增加的相似趋势。结果表明，在世界上首次估算了从荒漠荒地到栎林顶峰1000年左右的初级演替过程中土壤养分的积累速率。较少

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