Tree influence on soil biological activity: what can be inferred from the optical examination of humus profiles?

Keiko Mori (1) , Nicolas Bernier (2) , Takashi Kosaki (3) , Jean-François Ponge (2, 4)

1 Laboratory of Soil Science
2 Mécanismes adaptatifs : des organismes aux communautés
3 Laboratory of Terrestrial Ecosystems Management
4 MAOAC - Mécanismes adaptatifs : des organismes aux communautés

Humus forms may vary in different forest stands, but the local influence of trees upon soil microbial and faunal activities is still imperfectly known. Optical methods could help to discern processes of litter transformation and formation of organo-mineral assemblages, allowing a better diagnostic of tree influences upon humus-soil development. The microstratification of humus was studied under a beech (Fagus crenata), a mixed oak forest (Quercus crispula and Quercus serrata), and a cedar (Cryptomeria japonica) plantation. The three sites are located in Kyoto (Japan), and share similar environmental conditions. Litter decomposition rates and soil fauna were also investigated. At the beech site, which had the thickest 0 horizon, the main process was the gradual fragmentation of litter. This process, together with shallow root and weak fungal development, gave rise to a stable sandwich-like structure in the 0 horizon. In contrast, the oak site showed a two-step transformation of litter. Initially, litter decomposition was triggered by the activity of white rot fungi, and the discarded litter decayed much more slowly thereafter. The cedar site exhibited a sharp vertical delineation between upper thick Oe horizon developed since plantation time and a relict A horizon. The optical method thus demonstrated differences in soil biological activities and litter transformation patterns under the three sites.

Mots clés: Humus form; Micromorphology; Soil fauna; Litter transformation; Humus form

Domaines: Science des sols

Keiko Mori, Nicolas Bernier, Takashi Kosaki, Jean-François Ponge. Tree influence on soil biological activity: what can be inferred from the optical examination of humus profiles?. European Journal of Soil Biology, 2009, 45 (4), pp.290-300. ⟨10.1016/j.ejsobi.2009.05.001⟩. ⟨hal-00494621⟩