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Technischen Universitat Munchen (2011)

Nitrogen turnover in steppe soils of Inner Mongolia as affected by sheep grazing

Wu, Honghui

Titre : Nitrogen turnover in steppe soils of Inner Mongolia as affected by sheep grazing

Auteur : Wu, Honghui

Université de soutenance : Technischen Universitat Munchen

Grade : Doktors der Naturwissenschaften 2011

Résumé
An evaluation of nitrogen (N) turnover in grazed steppes of Inner Mongolia showed that the freeze-thaw process is the key period to understand the whole-year N cycling which produces approximately 50% inorganic N. Grazing effects were mostly pronounced in the spring freeze thaw period by decreasing the temperature and soil moisture. Net N mineralization did not provide insight into dynamics of actual (gross) N turnover while gross nitrification exceeded gross ammonification at the annual scale. Grazing reduced both plant and microbial N acquisition but increased nitrification and nitrate accumulation and thus negatively affected potential ecosystem N retention. Heavy grazing increased CO2 production significantly and net mineralization in bulk soils, however, moderate grazing exhibited no significant effects. A reduction of current stocking rates is recommended to establish sustainable summer grazing in Inner Mongolia

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