IFEVA   02662
INSTITUTO DE INVESTIGACIONES FISIOLOGICAS Y ECOLOGICAS VINCULADAS A LA AGRICULTURA
Unidad Ejecutora - UE
artículos
Título:
Grazing-induced changes in plant composition affect litter quality and nutrient cycling in Flooding Pampa grasslands
Autor/es:
GARIBALDI, L.A.; SEMMARTIN, M.; CHANETON, E.J.
Revista:
OECOLOGIA
Editorial:
Springer
Referencias:
Año: 2006 vol. 151 p. 650 - 662
ISSN:
0029-8549
Resumen:
Changes in plant community composition induced by vertebrate grazers have been found to either accelerate or slow C and nutrient cycling in soil. This variation may re X ect the di V erential e V ects of grazing-promoted (G+)plant species on overall litter quality and decomposition processes.Further,site conditions associated with prior grazing history are expected to influence litter decay and nutrient turn-over.We studied how grazing-induced changes in plant life forms and species identity modi W ed the quality of litter inputs to soil,decomposition rate and nutrient release in a flooding Pampa grassland,Argentina. Litter from G+forbs and grasses (two species each) and grazing-reduced (G ¡)grasses (two species)was incubated in long-term grazed and ungrazed sites.G+species,overall,showed higher rates of decomposition and N and P release from litter.However,this pattern was primarily driven by the low-growing,high litter-quality forbs included among G+species.Forbs decomposed and released nutrients faster than either G+or G ¡grasses.While no  onsistent di V erences between G+ and G- grasses were observed,patterns of grass litter decay and nutrient release responded with interspecific differences in phenology and photosynthetic pathway. Litter decomposition,N release and soil N availability were higher in the grazed site,irrespective of species litter type. Our results contradict the notion that grazing, by reducing more palatable species and promoting less palatable ones, should decrease nutrient cycling from litter. Plant tissue quality and palatability may not unequivocally link patterns of grazing resistance and litter  decomposability within a community, especially where grazing causes major shifts in life form composition.Thus, plant functional groups defined by species ’ "responses " to grazing may only partially overlap with functional groups based on species effects on C and nutrient cycling. X ect the di V erential e V ects of grazing-promoted (G+)plant species on overall litter quality and decomposition processes.Further, site conditions associated with prior grazing history are expected to influence litter decay and nutrient turn-over.We studied how grazing-induced changes in plant life forms and species identity modi W ed the quality of litter inputs to soil,decomposition rate and nutrient release in a flooding Pampa grassland,Argentina. Litter from G+forbs and grasses (two species each) and grazing-reduced (G ¡)grasses (two species)was incubated in long-term grazed and ungrazed sites.G+species,overall,showed higher rates of decomposition and N and P release from litter.However,this pattern was primarily driven by the low-growing,high litter-quality forbs included among G+species.Forbs decomposed and released nutrients faster than either G+or G ¡grasses.While no  onsistent di V erences between G+ and G- grasses were observed,patterns of grass litter decay and nutrient release responded with interspecific differences in phenology and photosynthetic pathway. Litter decomposition,N release and soil N availability were higher in the grazed site,irrespective of species litter type. Our results contradict the notion that grazing, by reducing more palatable species and promoting less palatable ones, should decrease nutrient cycling from litter. Plant tissue quality and palatability may not unequivocally link patterns of grazing resistance and litter  decomposability within a community, especially where grazing causes major shifts in life form composition.Thus, plant functional groups defined by species ’ "responses " to grazing may only partially overlap with functional groups based on species effects on C and nutrient cycling. X ect the di V erential e V ects of grazing-promoted (G+)plant species on overall litter quality and decomposition processes.Further, site conditions associated with prior grazing history are expected to influence litter decay and nutrient turn-over.We studied how grazing-induced changes in plant life forms and species identity modi W ed the quality of litter inputs to soil,decomposition rate and nutrient release in a flooding Pampa grassland,Argentina. Litter from G+forbs and grasses (two species each) and grazing-reduced (G ¡)grasses (two species)was incubated in long-term grazed and ungrazed sites.G+species,overall,showed higher rates of decomposition and N and P release from litter.However,this pattern was primarily driven by the low-growing,high litter-quality forbs included among G+species.Forbs decomposed and released nutrients faster than either G+or G ¡grasses.While no  onsistent di V erences between G+ and G- grasses were observed,patterns of grass litter decay and nutrient release responded with interspecific differences in phenology and photosynthetic pathway. Litter decomposition,N release and soil N availability were higher in the grazed site,irrespective of species litter type. Our results contradict the notion that grazing, by reducing more palatable species and promoting less palatable ones, should decrease nutrient cycling from litter. Plant tissue quality and palatability may not unequivocally link patterns of grazing resistance and litter  decomposability within a community, especially where grazing causes major shifts in life form composition.Thus, plant functional groups defined by species ’ "responses " to grazing may only partially overlap with functional groups based on species effects on C and nutrient cycling.