Nitrogen IsotopesRadiometric DatingCarbon IsotopesHistory, AncientNitrogenHairIsotopesIsotope LabelingNitrogen FixationDietNitrogen CycleOxygen IsotopesNitrogen CompoundsBlood Urea NitrogenNitrogen DioxideEcosystemReactive Nitrogen SpeciesCarbonSoilNitrogen OxidesPII Nitrogen Regulatory ProteinsAtmosphereIsopoda