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Recherches sur les écosystèmes des réserves biologiques de la forêt de Fontainebleau. VI. Influence tardive du clairiérage sur les humus

The long-term influence of glading on the soil humus types appears related to their nature and to the herbaceous layer they may support. In the mull, with a conspicuous herb layer, a decrease in the easily decomposable substrates follows an early increase in organic matter content and biological activity. However, the in situ mineralization is still more active the C/N ratio clearly lower than under timber tree forest and the pH higher: the humus is clearly improved. In the moder, where the herb layer long remains discrete, the establishment of glades has led early to a reduction in the rate of organic matter and of the decomposable substrates as well as in the biological activity. In the absence of a conspicuous herb layer the evolution continues slowly alike. The development of Calamagrostis epigeios, which may take place after a couple of years, avoids the increase in C/N ratio and ensures the preservation of the metabolizable nitrogen stock, yet activates the mineralization of this element.

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