Dynamics and its Control of Soils in Tropical Monsoon Regions

我们研究了热带季风区的土壤，主要是分布在泰国的土壤，重点是被认为是热带地区最易退化的土壤类型之一的“Ultisols”土壤。认为热带地区的生态脆弱性主要是由于这些地区土壤的退化所致。为了阐明退化机制所涉及的基本概念，首先，我们必须在更大程度上努力选择土壤采样地点，其中土壤类型从土壤发生学的角度来看应该是相同的，但在人类管理方面是不同的，即“耕种的和未耕种的”。其次，我们从土壤性质和作物根系形态的角度对土壤退化机制进行了研究，结果在1988年、1989年和1990年分别采集了30个、41个和1990年的土壤样品，其中大部分来自于土壤类型为Ultisols的地区。此外，对这些土壤样品进行了物理、化学、微生物和根系形态特征的分析，以探讨土壤退化的可能机制。

We have studied the soils in the tropical monsoon regions, mainly the soils distributed in Thailand emphasizing soils classified as "Ultisols" which has been considered to be one of the most degradable soil types in the tropical regions. The ecological fragility in the tropics were considered mainly due to the degrability of the soils in these regions. For elucidating the basic concept involved in the degradation mechanism, firstly, we had to spend our effort to a greater extent in selecting sites for the soil sampling where the type of soil should be identical from the viewpoint of the soil genesis but different in human management as "Cultivated vs Uncultivated". Secondly, we have tried to investigate from the viewpoint of soil properties and crop root morphology which might be involved with the degradation mechanisms of soil.As a result we succeeded in collecting 30 soil samples in 1988, 41 in 1989 and in 1990 mostly from areas of the Ultisols soil type. Furthermore, these soil samples were analyzed for the physical, chemical, microbiological and root morphological properties in order to investigate th possible mechanisms involved in the soil degradation.