Grazing history effects on above-and below-ground litter decomposition and nutrient cycling in two co-occurring grasses

• Autores: Semmartin, María; Garibaldi, Lucas Alejandro; Chaneton, Enrique J.
• Año de publicación: 2007
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Flooding Pampa; Grassland; Herbivory; Nitrogen; Phosphorus; Roots
• Institución: Universidad Nacional de Río Negro

Fil: Semmartin, María. Universidad de Buenos Aires (UBA). Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas vinculadas a la Agricultura (IFEVA); Argentina.
Fil: Garibaldi, Lucas Alejandro. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio Ecotono; Argentina.
Fil: Chaneton, Enrique J. Universidad de Buenos Aires (UBA). Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas vinculadas a la Agricultura (IFEVA); Argentina.
Fil: Chaneton, Enrique J. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Argentina.
Fil: Garibaldi, Lucas Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Semmartin, María. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Argentina.
Large herbivores may alter carbon and nutrient cycling in soil by changing above- and below-ground litter decomposition dynamics. Grazing effects may reflect changes in plant allocation patterns, and thus litter quality, or the site conditions for decomposition, but the relative roles of these broad mechanisms have rarely been tested. We examined plant and soil mediated effects of grazing history on litter mass loss and nutrient release in two grazing-tolerant grasses, Lolium multiflorum and Paspalum dilatatum, in a humid pampa grassland, Argentina. Shoot and root litters produced in a common garden by conspecific plants collected from grazed and ungrazed sites were incubated under both grazing conditions. We found that grazing history effects on litter decomposition were stronger for shoot than for root material. Root mass loss was neither affected by litter origin nor incubation site, although roots from the grazed origin immobilised more nutrients. Plants from the grazed site produced shoots with higher cell soluble contents and lower lignin:N ratios. Grazing effects mediated by shoot litter origin depended on the species, and were less apparent than incubation site effects. Lolium shoots from the grazed site decomposed and released nutrients faster, whereas Paspalum shoots from the grazed site retained more nutrient than their respective counterparts from the ungrazed site. Such divergent, species-specific dynamics did not translate into consistent differences in soil mineral N beneath decomposing litters. Indeed, shoot mass loss and nutrient release were generally faster in the grazed grassland, where soil N availability was higher. Our results show that grazing influenced nutrient cycling by modifying litter breakdown within species as well as the soil environment for decomposition. They also indicate that grazing effects on decomposition are likely to involve aerial litter pools rather than the more recalcitrant root compartment.