Abstract

COUTEAUX, Marie-Madeleine; HERVE, Dominique  and  BECK, Stephan. Decomposition of plant litter and roots in a long fallow system (Bolivian Altiplano). Ecología en Bolivia [online]. 2006, vol.41, n.3, pp.85-102. ISSN 1605-2528.

The fallow agriculture system is based on the fact that after depletion of soil organic matter due to cultivation, the soil can recover its initial level of fertility by leaving the fields for a long fallow period. During this period, the soil organic matter stock will be reconstituted by the inputs of the residues of the natural vegetation succession. The decomposition of 12 kinds of plant material (different organs and species) from a young three-years old and an old eight-years old fallow was studied in the semiarid Bolivian puna (Patacamaya, South of La Paz, 3,800 m asl.) by incubating litterbags over one or two years in field conditions. A PCA ordinated the initial litter quality in three groups: (i) the grass shoots, (ii) the leaves and stems of non-grass plants, and (iii) the roots. The lignin content was higher in the plants of the old fallow. The plant materials that decomposed the slowest were the grasses and the roots, and it is assumed that these plant materials are the main source to recover the SOM (Soil organic matter) lost during the cultivation period. Mass loss of leaves of shrubs “tola” (Baccharis incarum) reached about 60% during the first three months. This high decomposition rate was mainly due to non-structural compound content (NS). Models were proposed for predicting decomposition rate and first year mass loss.

Keywords : Fallow system; Soil organic matter; Litter quality; Decomposition.

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