Does grazing mediate soil carbon and nitrogen accumulation beneath C(4), perennial grasses along an environmental gradient?

azote biologie du sol biomasa biomass biomasse bouteloua carbon carbone carbono cycling environment environnement fertilidad del suelo grassland soils grazing medio ambiente nitrogen panicum pastoreo plant animal relations relaciones planta animal relation plante animal schizachyrium scoparium soil biology soil fertility soil organic matter sol d'herbages suelo de praderas