Nitrous oxide emissions from different land uses affected by managements on the Qinghai-Tibetan Plateau

Abstract We evaluated the N 2 O emissions from four land use types (a native alpine meadow with winter grazing (NAM), an abandoned pasture (APL), a perennial Elymus nutans Griseb . pasture (PEN) and an annual Avena sativa L. pasture (AAS)) with and without three management practices (nitrogen (N) fertilizer, sheep manure and no tillage (NT)) in a Gelic Cambisol soil underlying an alpine meadow on the Qinghai-Tibetan Plateau in 2009 and 2010. Our results show that, compared with NAM, APL had significantly higher cumulative-average seasonal N 2 O emissions. Converting unmanaged APL to PEN or AAS significantly increased cumulative-average seasonal N 2 O emissions by 35% and 75%, respectively. Sheep manure and N fertilizer application significantly increased N 2 O emissions due to increased soil inorganic N concentration. The effect of sheep manure addition on N 2 O emissions was lower than that of N fertilizer. For AAS, tillage significantly decreased the effect of sheep manure application on N 2 O emissions. Compared with tillage, NT significantly decreased N 2 O emissions from AAS. Therefore, our results suggest that cultivating natural grassland would increase N 2 O emissions, and fertilizer application would amplify the magnitude of emissions, whereas NT could mitigate the fertilizer impact on N 2 O emission. Furthermore, the structural equation analysis revealed that land use change affected N 2 O emissions directly by influencing the number of plant species and soil characteristics. There were two different underlying mechanisms regulating N 2 O emissions in response to N fertilizer and sheep manure addition.