Rhizosphere processes such as rhizosphere and microbial respiration produce belowground CO₂ representing approximately 35 to 350 fold of atmospheric condition. High dissolved CO₂ in soil water promotes soil acidification enhancing soil-mineral (carbonate or silicate) weathering process and controlling dissolved organic carbon (DOC) adsorption on soil-mineral surface. However, surprisingly little is known about the contribution of soil CO₂ to carbon and dissolved silica (DSi) generation in the saltmarsh. This study pinpoint the feedback of soil CO₂ gradients coupling with various rainfall regimes on carbon and nutrient export from the saltmarsh soil to the leachate water. Using the soil columns approach by manipulating three different soil CO₂ conditions and precipitation gradients coupled with water chemistry analysis, we found that the effect of elevated CO₂ on inorganic carbon (as total alkalinity or TA) showed logarithmic behavior and the magnitude increased up to 2.9 fold. While, the precipitation gradients showed a linear relationship with TA and the magnitude was highly pronounced with 3.3 fold. Furthermore, both elevated CO₂ and precipitation posed a significant increase of the DSi production with the same observable behavior as TA. However, elevated soil CO₂ did not significantly affect DOC mobilization. Together, our findings help explain that soil containing high CO₂ plays a role in the generation of TA and DSi. It also provides the direct link between the role of rhizosphere processes and enrichment of carbon and nutrient export in saltmarsh soil.   

Primary Presenter: Panunporn Tutiyasarn, University of Hamburg (panunporn.tutiyasarn@uni-hamburg.de)

Authors:

Gibran Mujalli, University of Hamburg  (gibran.romero.mujalli@uni-hamburg.de)

Jens Hartmann, University of Hamburg  (jens.hartmann@uni-hamburg.de)