Diurnal dynamics of CH₄, CO₂and N₂O fluxes in the saline-alkaline soils of the Yellow River Delta, China

Abstract

Salt-affected soils are extensively present and constitute about 7% of total land surface. However, our knowledge about greenhouse gas (GHG) turnover between the atmosphere and the saline soils is very limited. In order to evaluate the potential of GHG consumption in saline soils, we measured gas fluxes of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) from the soil surface to the atmosphere under saline-alkaline mudflat and various community types in the Yellow River Delta in China. In general, the emissions of GHG of different ecosystems showed a unique peak diurnal pattern, with the peak at 13:00 h and the lowest value at 07:00 h. The CH 4 and N 2 O emission of different ecosystems followed the order: saline-alkaline mudflat . T. chinensis . S. salsa . P. australis, while the CO 2 emission followed the order: T. chinensis . P. australis . S. salsa . saline-alkaline mudflat. On the whole, saline-alkaline mudflat and different vegetations acted as CO 2 and N 2 O source in spring, while saline-alkaline mudflat and P. australis communities acted as CH 4 source and CH 4 sink, respectively. However, T. chinensis and S. salsa communities acted as CH 4 sink before 12:00 h and CH 4 source after 12:00 h. Although measurements of the CO 2 , CH 4 and N 2 O fluxes were taken simultaneously, CH 4 and N 2 O fluxes were strongly correlated with soil moisture, temperature and electrical conductivity, while no significant correlation was found between CO 2 flux with above environmental factors. These results probably suggest that factors other than soil temperature, moisture and salinity exerted a larger impact on fluxes than on CH 4 and N 2 O release and/or that there were not enough samples for CO 2 flux measurements because of its higher spatial and temporal variability.

Co-effects of salinity and moisture on CO2 and N2O emissions of laboratory-incubated salt-affected soils from different vegetation types

“…Since vegetation plays an important role in regulating the temporal and spatial variations of soil respiration by controlling a variety of environmental variables (Barba et al, 2013;Han et al, 2014;Jenkins and Adams, 2010). Zhang et al (2013Zhang et al ( , 2015 and Song et al (2013) investigated GHG production of saline soils in above-mentioned three vegetation communities and in bare land with no vegetation cover in situ. They found that temporal variations of GHG emissions were related to the interactions of abiotic factors, such as soil water content and electrical conductivity, while spatial variations were mainly affected by the vegetation composition at spatial scale.…”

CO2 and N2O Emissions from Spring Maize Soil under Alternate Irrigation between Saline Water and Groundwater in Hetao Irrigation District of Inner Mongolia, China

“…The main processes that produced CO 2 from soil are soil respiration with autotrophic (root) and heterotrophic (microbial) activity [11]. In the present study, CO 2 emission from spring maize soil was mainly the product of soil respiration and maize respiration.…”

“…In literature, some researchers focused on the interaction of GHG emissions and salt from soil or water [10,11,12]. Yang, et al [13] studied the saline-alkaline soil and found that, when compared with low saline-alkaline soil, high saline-alkaline soil significantly increased Global Warming Potential (GWP) by raising N 2 O emission and reducing CH 4 uptake.…”