Nitrogen retention patterns and their controlling factors in an alpine meadow: implications for carbon sequestration

X. L. Xu (1) , H. Ouyang (1) , G. M. Cao (2)

1 Key Laboratory of Ecosystem Network Observation and Modelling
2 Northwest Plateau Institute of Biology

We hypothesized that the patterns of NO₃^? and NH₄⁺ retention are different over short-term scales while they are similar over long-term scales in alpine meadows and that abiotic and biotic factors might be responsible for their different patterns over short-term scales. In order to test the hypotheses, a ¹⁵N-labeled experiment was conducted in an alpine meadow in the Qinghai-Tibet Plateau over four years. Our results showed that ¹⁵NO₃^? and ¹⁵NH₄⁺ retention was distinctly different within two months, and even one year after tracer additions. The long-term retention of ¹⁵N at the whole-plot level did not differ significantly between ¹⁵NH₄⁺ and ¹⁵NO₃^? treatments, and averaged 50% after four years. Higher soil temperature or soil organic carbon concentration enhanced ¹⁵NH₄⁺ retention, but significantly reduced ¹⁵NO₃^? retention in the soil within two months following tracer additions. Soil moisture significantly affected ¹⁵N recovered in soil organic matter and microbial biomass as well as aboveground parts, but had no significant effects on ¹⁵N recovered in roots. These findings have important ecological implications with regard to the consequences of deposited nitrogen because of the possible difference in the fate of NH₄⁺ vs. NO₃^? in alpine meadow ecosystems.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]; Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

X. L. Xu, H. Ouyang, G. M. Cao. Nitrogen retention patterns and their controlling factors in an alpine meadow: implications for carbon sequestration. Biogeosciences Discussions, 2007, 4 (4), pp.2641-2665. ⟨hal-00297911⟩