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Simulating N2O emission from Kobresia humilis Serg. alpine meadow on Tibetan Plateau with the DNDC model

100%

Du Y., Cui X., Cao G., Zhao X., Yang G.

Polish Journal of Ecology

2011

tom 59

nr 3

Field me asured N2O emissions in two years were used to parameterize and validate a process-based model, DNDC, for an alpine Kobresia humilis meadow on the Tibetan Plateau in China. Although this model failed to capture the N2O fluxes in some time periods in the spring or autumn, the modeled results showed overall a good performance in terms of simulating the seasonal variation of N2O fluxes and quantifying the annual total emissions. The relative deviation on the annual basis was about 12.4% and –15.9% for the two years, respectively. The modeled data showed that nitrification contributed about 53% of total N2O production, slightly higher than denitrification. The modeled fluxes were sensitive to soil organic content (SOC), pH, and temperature, but less sensitive to variation of precipitation, soil ammonium and nitrate contents. Further mo difications for the model were suggested to focus on the process of soil freezing and thawing as well as the crop growth sub-model that would improve the model’s performance for quantifying N2O emission from the alpine meadow.

Contribution of the vegetation layers in the nitrous oxide emission from Alpine Kobresia humulis Serg. meadow ecosystem on the Tibetan Plateau

100%

Du Y., Cao G., Deng Y., Sun G., Cui X.

Polish Journal of Ecology

2010

tom 58

nr 1

Nitrous oxide (N₂O) was one of the major atmospheric greenhouse gases. Its budget was poorly understood in alpine meadow, a dominant vegetation type on the Tibetan Plateau. To characterize a Kobresia humilis meadow on the plateau, N₂O emission rates were monitored from June 2003 to June 2006 in the study area located at 3280 m a.s.l. Nine plots with 1 m × 1 m each were divided into three treatments, i.e. intact herbaceous community (HCK), removal of aboveground plant biomass (CBK), and removal of both above and belowground plant biomass (BSK), to estimate contribution of plants, r hizosphere and bulk soil to the total N₂O emission. N₂O emission from plant aboveground biomass was calculated by flux difference between HCK and CBK, denoted as F (HCK-CBK), from rhizosphere by F (CBK-BSK), and from bulk soil was the flux in BSK treatment. Static chambers (height 50 cm, area 0.5 × 0.5 m²) were used for gas collection. N₂O emission rate was significantly correlated with soil temperature at 5 cm depth in both HCK and BSK (P <0.001). Both treatments demonstrated a seasonal peak rate in growing season and minimum rate in dormancy period. The mean emission rates in the three years were 39.7±2.9 and 30.6±2.5 μg m⁻² h⁻¹ in HCK and BSK, respectively, with the former significantly higher than the latter (P <0.05). In CBK, however, the emission rate did not show consistent correlation with soil temperature, especially in growing season. Its three-year mean emission rate was 36.2±3.3 μg m⁻² h⁻¹. In the K. humilis meadow, bulk soil contributed much more than plants and rhizosphere. The mean emission rate was 3.5±2.9, 5.7±3.8, and 30.6±2.5 μg m⁻² h⁻¹ (P <0.001) from plants, rhizosphere and bulk soil, and these accounted for 9, 14 and 77%, separately. Our results implied that N₂O emission rate decreased little with grazing as indicated by the difference between HCK and CBK in K. humilis meadow (P <0.05). N₂O emission from alpine meadow could not be ignored in addressing regional greenhouse gases budget on the Tibetan Plateau, considering the vast area and much higher radiative forcing of N₂O.

Ograniczanie wyników

2 Polish Journal of Ecology

2 Cao G.

2 Cui X.

2 Du Y.

1 Deng Y.

1 Sun G.

1 Yang G.

1 Zhao X.

1 2011

1 2010

Wyniki wyszukiwania

Simulating N2O emission from Kobresia humilis Serg. alpine meadow on Tibetan Plateau with the DNDC model

Contribution of the vegetation layers in the nitrous oxide emission from Alpine Kobresia humulis Serg. meadow ecosystem on the Tibetan Plateau