Grazzing affects above- but not below-ground C compartments in grasslands of central Argentina.

VAIERETTI, MARÍA VICTORIA; CONTI, GEORGINA; POCA, MARÍA; HUYGENS, DRIES; BERTONE, GUSTAVO; CINGOLANI, ANA MARÍA; PÉREZ-HARGUINDEGUY NATALIA

Encuentro; Digging Deeper: Research challenges in plant-soil interactions; 2013

British Ecological Society

Grazers affect soil organic carbon (SOC) inputs directly, by altering plant production, but also indirectly through their impact on plant community composition. We evaluated the effect of different grazing intensities and associated changes in aboveground plant biomass on mountain grassland SOC stocks. We selected vegetation patches associated with high, intermediate and low grazing use (lawns, open tussock and closed tussock, respectively). We measured plant biomass and leaf litter quantity and quality, in situ leaf litter decomposition, and SOC contents until 15 cm depth. Litter quantity was dramatically reduced under high grazing pressure while litter quality was enhanced. In situ decomposition was not related to grazing pressure, being highest at both extremes of the grazing gradient. Unexpectedly, SOC did not change across patches, in spite of significant grazing effects on aboveground C pools. We suggest that the lack of differences in SOC between grassland patches could be explained by an overarching influence of root dynamics on SOC patterns. Specifically, roots may show compensatory growth or be unresponsive to grazing for which root biomass may have opposite patterns to that of aboveground vegetation.