A Research on Mechanism of Decomposition and Reduction of Organic Soil Accompanying Root-matting in Rhizosphere of Reed

随着芦苇在根际的生长，人们观察到它们的根茎和根向四面八方扩散，取代土壤，形成根垫。研究了植根过程中有机土壤的分解还原机理。采用富营养化湖泊疏浚土壤的4个试验盆，每盆移植30株从种子中发芽的芦苇，用T/R比（地上部分与地下部分的干重比）表示芦苇地上部分和地下部分的增长规律。结果表明，该比值随土壤有机碳的减少有较大的相关性变化。芦苇床土壤有机质的上升和下降可以用有机质供给和细菌有机分解的质量平衡模型来表示。土壤有机质的供给主要是随光合产物从地面部分向地下部分的运输和储存而渗出，随地下部分的分解而释放。即使在不种植芦苇的情况下，土壤中的细菌有机分解也在好氧条件下发生。然而，随着芦苇的种植，从地面部分向根区扩散供应引起了微生物有机分解。在较老的芦苇中，有机还原在春季出芽时变得容易发生，因为分解的质量高于有机质的供应。提出了通过控制刈割时间促进土壤有机质分解，同时抑制土壤部分有机质供给的技术发展的可能性。

With growth in the rhizosphere of reeds, it has been observed that their rhizomes and roots are spread around in all directions and replace the soil, the root-matting. The mechanism of decomposition and reduction of the organic soil accompanying the root-matting was studied. Four experimental pots in which contained the soil dredged from an eutrophic lake were used, and 30 reeds which budded from a seed were transplanted and were grown in the every pot.The pattern of the increase in a ground part and an underground part of the reeds was able to be expressed using the T/R ratio which is a dry weight ratio of a ground part to an underground part. It was suggested that relevance had quite a few change of this T/R ratio with the pattern of a reduction of the organic carbon in soil.The rise and fall of the organic matter in the reed-bed soil could be expressed with the mass balance model consisted of the organic supply and the bacterial organic decomposition. The organic matter was supplied by exudation into the soil accompanying transportation and storage of the photosynthetic products from a ground part to an underground part, and by release accompanying decomposition of an underground part. Bacterial organic decomposition took place under the aerobic condition in soil even without planting the reeds. However, diffusion-supply from a ground part to the root area with planting the reeds raised a microbial organic decomposition.At older aged reeds, organic reduction was shown to become easy to take place at the time of budding in spring, because that the decomposition stood high rather than supply of organic matter in quality. Moreover, it was suggested the possibility of development of the technique of promoting organic matter decomposition in soil by control of mowing time, while suppressing the organic matter supply from a ground part.