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

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

Jornada; BES Plant-Soil-Ecosystems Group meeting; 2013

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 in mountain grasslands SOC stocks (through changes in aboveground plant biomass). We selected vegetation patches associated with high, intermediate and low grazing use (lawns, open tussock and closed tussock, respectively). We measured plant biomass quantity and quality, in situ litter decomposition, and SOC at 15 cm depth. Litter quantity was dramatically reduced under high grazing pressure while litter quality was enhanced. In situ decomposition was not related with grazing pressure, being highest at both extremes of the grazing gradient. Unexpectedly, SOC did not change across patches. Grazing effects on aboveground C pools were not reflected in the SOC pool at 15 cm depth in the grasslands studied. We propose that grazing may be affecting only superficial C stocks. Alternatively, root biomass response to grazing may be behind the lack of differences in SOC. Roots may show compensatory growth, and root litter patterns may dilute that of aboveground vegetation. Besides, roots could be not responding to grazing, and root litter input may be determining SOC pattern.