[Effect of Stimulated N Deposition on N2O Emission from a Stipa krylovii Steppe in Inner Mongolia, China].

ABSTRACT

With fast development of industry, agriculture and society, very high N deposition occurs in China. N deposition has exceeded 3 g · (m² · a)⁻¹ in some areas of temperate steppes, which is a significant part of the Eurasia grassland, but may possibly be sensitive to N deposition. To study the effect of N deposition on N cycling in typical temperate steppe, N2O emissions were measured in a Stipa krylovii steppe in Inner Mongolia for a whole year. A field control experiment of simulated N deposition (by NaNO3 addition) was also carried out at 6 dose levels, CK (control), N2 [2 g · (m² · a)⁻¹], N5 [5 g · (m² · a)⁻¹], N10 [10 g · (m² · a)⁻¹], N25 [25 g · (m² · a)⁻¹], and N50 [50 g · (m² · a)⁻¹]. The results showed that the natural N2O-N emission flux was 0.10 g · (m² · a)⁻¹, accounting for about 3% of the total N deposition, and much depended on soil water content and soil temperature under ambient N deposition. In addition, enhanced N deposition might significantly increase N2O emission, especially at very high N doses (N25 and N50 treatments). The annual N2 0 emission flux showed a linear relationship with the N addition. Greater attention should therefore be paid to the relatively high N2O emission in the typical temperate steppe in China.