Soil greenhouse gas fluxes from different tree species on Taihang Mountain, North China
The objectives of this study were to investigate seasonal variation of greenhouse gas fluxes from soils on sites dominated by plantation ( Robinia pseudoacacia, Punica granatum, and Ziziphus jujube) and natural regenerated forests ( Vitex negundo var. heterophylla, Leptodermis oblonga, and Bothriochloa ischcemum), and to identify how tree species, litter exclusion, and soil properties (soil temperature, soil moisture, soil organic carbon, total N, soil bulk density, and soil pH) explained the temporal and spatial variation in soil greenhouse gas fluxes. Fluxes of greenhouse gases were measured using static chamber and gas chromatography techniques. Six static chambers were randomly installed in each tree species. Three chambers were randomly designated to measure the impacts of surface litter exclusion, and the remaining three were used as a control. Field measurements were conducted biweekly from May 2010 to April 2012. Soil CO 2 emissions from all tree species were significantly affected by soil temperature, soil moisture, and their interaction. Driven by the seasonality of temperature and precipitation, soil CO 2 emissions demonstrated a clear seasonal pattern, with fluxes significantly higher during the rainy season than during the dry season. Soil CH 4 and N 2O fluxes were not significantly correlated with soil temperature, soil moisture, or their interaction, and no significant seasonal differences were detected. Soil organic carbon and total N were significantly positively correlated with CO 2 and N 2O fluxes. Soil bulk density was significantly negatively correlated with CO 2 and N 2O fluxes. Soil pH was not correlated with CO 2 and N 2O emissions. Soil CH 4 fluxes did not display pronounced dependency on soil organic carbon, total N, soil bulk density, and soil pH. Removal of surface litter significantly decreased in CO 2 emissions and CH 4 uptakes. Soils in six tree species acted as sinks for atmospheric CH 4. With the exception of Ziziphus jujube, soils in all tree species acted as sinks for atmospheric N 2O. Tree species had a significant effect on CO 2 and N 2O releases but not on CH 4 uptake. The lower net global warming potential in natural regenerated vegetation suggested that natural regenerated vegetation were more desirable plant species in reducing global warming.