Natural Nitrogen—15 Abundance of Ammonium Nitrogen and Fixed Ammonium in Soils
摘要
The present article deals with the natural nitrogen-15 abundance of ammonium nitrogen and fixed ammonium in different soils.Variations in the natural ^15N abundance of ammonium nitrogen mineralized in soils under anaerobic incubation condition were related to soil pH.The δ ^15N of mineralizable N in acid soils was lower but that in neutral and calcareous soils was higher compared with the δ ^15N of total N in the soils.A variation tendence was also found in the δ ^15N of amino-acid N in the hydrolysates of soils.The natural ^15N abundance of fixed ammonium was higher than that of total N in most surface soils and other soil horizons,indicating that the increase of δ ^15N in the soil borizons beneath subsurface horizon of some forest soils and acid paddy soils was related to the higher δ ^15N value of fixed ammonium in the soil.