Studies on Soil Organic Matter Dynamics and Their Application for Sustainable Agriculture in Humid Tropics

本研究对湿热带土壤有机质（SOM）动态进行了研究，取得了以下主要成果：1）通过对土壤温度、湿度等环境条件的监测，确定了控制土壤有机质动态的主要参数。这些区域包括：日本天然林、印度尼西亚不同成土母质的天然林、泰国北方克伦人的流动农田和休闲林、泰国东北部的桑迪农田和泰国不同的家庭花园。2）为了优化区域作物轮作系统以减缓SOC耗竭，利用地理统计学技术分析了泰国东北部桑迪农田土壤有机质动态的时空变化。土壤有机碳、氮含量、土壤颗粒大小分布及其它相关指标存在明显的空间变异 关于我们 特性.土壤有机质动态和土壤侵蚀被假定为所观察到的土壤性质的异质性背后的驱动力。研究结果还表明，地统计学方法可以在区域尺度上模拟土壤有机质的动态变化，并考虑到土壤资源的空间异质性。3）确定了不同地区土壤有机质动态变化的土壤相关参数。东加里曼丹省轮作农田的碳、氮动态受土壤酸度的影响。土壤的火山源性质（或倍半氧化物的无定形性质）也强烈地控制着不同土壤中有机质的动态。4）因此，即使在潮湿的亚洲的有限地区，有机质的分解速率也有很大的差异，这不仅取决于气候条件，还取决于与颗粒大小和/或无定形特征有关的土壤性质，后者反映了气候（即，土壤的有机质分解速率）。例如，冷）和地质（i.例如，火山成因）条件。土壤酸度通过不同的途径影响土壤碳通量，即通过改变分解速率常数和分解同化的分解比，或形成向下迁移的DOC。其中一些条件是潮湿热带地区特有的。因此，在建立适用于湿热带生态系统的土壤有机质动态模型时，应充分考虑这些条件。少

The main results obtained in the present study, in which soil organic matter (SOM) dynamics in humid tropics were investigated, are listed below:1) In situ SOM dynamics were measured together with detailed monitoring on environmental conditions such as soil temperature and moisture, and parameters that primarily control the SOM dynamics in various regions of humid tropics were determined. The regions included: Japanese natural forests, Indonesia natural forest with different soil parent materials, shifting cropland fields and fallow forests used by Karen people in northern Thailand, sandy cropland in Northeast Thailand, and different home gardens in Indonesia.2) To optimize regional crop rotation systems for mitigating SOC depletion, spatial and temporal variation of the SOM dynamics was analyzed using a giostatistics technique in sandy croplands in Northeast Thailand. A clear spatial variation was observed for organic C and N soil content, particle size distribution, and other related … More properties. The SOM dynamics and soil erosion were postulated to be driving forces behind the observed heterogeneity in soil properties. The results also indicated that the methodology of geostatistics were useful to simulate SOM dynamics in a regional scale considering spatial heterogeneity of soil resources according to topography.3) Soil-related parameters controlling SOM dynamics were determined in different regions of humid tropics. The C and N dynamics in the shifting cropping fields in East Kalimantan were influenced by the degree of soil acidity. The volcanic-derived properties of soils (or amorphic properties of sesquioxides) also strongly controlled SOM dynamics in different soils investigated.4) Thus the decomposition rates of SOM varied widely even in the limited areas of humid Asia, depending not only on climatic conditions but also on soil properties relating to particle size and/or amorphous characteristics, the latter of which reflects both the climatic (i. e., cool) and geological (i. e., volcanic origin) conditions. Soil acidity can affect C fluxes in different ways; that is, through changing decomposition rate constant and splitting ratio for decomposition to assimilation, or forming DOC that migrates to downward in soil profiles. Some of these conditions are specific for humid tropics. Therefore, these conditions should be taken into account to establish SOM dynamics model that could actually be applied to ecosystems in humid tropics. Less