Effects of elevated CO2 and cutting frequency on the productivity and herbage quality of a semi-natural grassland

Autor: Catherine Picon-Cochard, Jean Michel Besle, Jean-François Soussana, Florence Teyssonneyre
Přispěvatelé: UR 0874 Unité de recherche Agronomie de Clermont, Institut National de la Recherche Agronomique (INRA)-Environnement et Agronomie (E.A.)-Ecologie des Forêts, Prairies et milieux Aquatiques (EFPA), Institut National de la Recherche Agronomique (INRA)-Unité de recherche Agronomie de Clermont (URAC), Unité de recherche Agronomie de Clermont (URAC), Institut National de la Recherche Agronomique (INRA), Unité de Recherches sur les Herbivores (URH)
Rok vydání: 2004
Předmět:
Zdroj: European Journal of Agronomy
European Journal of Agronomy, Elsevier, 2004, 20, pp.363-377. ⟨10.1016/S1161-0301(03)00040-6⟩
ISSN: 1161-0301
DOI: 10.1016/s1161-0301(03)00040-6
Popis: Monoliths of a fertile, although N limited, C 3 grassland community were subjected (or not) to an atmospheric CO 2 enrichment (600 μmol mol −1 ), owing to the Mini-FACE system from August 1998 to June 2001, at two contrasting cutting frequencies (3 and 6 cuts per year). The present study reports the effects of elevated CO 2 on the above-ground productivity and on the herbage quality. Elevated CO 2 did not affect the dry matter (DM) yield of the swards in 1999. In 2000, the second year, there was a positive CO 2 effect (+26%) both on the DM and on the nitrogen yields (+30%). With the frequently cut monoliths, the DM of the legume component of the sward was strongly increased by elevated CO 2 . This effect became also significant in July 2000 for the low cutting frequency treatment. These results are in good agreement with the concept of an increased legume development and symbiotic N 2 fixation triggered by an increased ecosystem scale demand of N under elevated CO 2 . At a low cutting frequency, the DM of the forbs was strongly increased in elevated compared with ambient CO 2 . This increased development of the forbs apparently led to a competitive decline of the grasses. Therefore, the total DM yield response to CO 2 was smaller at a low (+15%) compared with a high (+36%) cutting frequency in 2000. An increase in the water soluble sugar content of the bulk forage under elevated CO 2 and a corresponding decline in cell wall contents (NDF) were observed. In June 1999, the decline in NDF was correlated with an increased in-vitro DM digestibility. The forage quality was also indirectly affected by elevated CO 2 through changes in leaf:stem ratio and in botanical composition. At a low cutting frequency, the increased forb content favoured the herbage quality because of a higher digestibility of the forb shoots and, indirectly, through the reduction in the mass of the grass stems. These results emphasise the role of species dynamics for elevated CO 2 impacts on semi-natural grassland productivity and herbage quality.
Databáze: OpenAIRE
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