In a study published in Soil Biology & Biochemistry, ZOU Yuanchun and his graduate student DUAN Xun from Northeast Institute of Geography and Agroecology of the Chinese Academy of Sciences found that wetland plant roots significantly enriched Fe(III) and organically complexed Fe oxides (Fe_p) in rhizosphere soil through radial oxygen loss and rhizodeposition, and Fe(III) could protected OC through adsorption and co-precipitation.

The researchers explored coupled relationship among Fe, C and FeRB in the rhizospheres and bulk soils of two typical plants (Calamagrostis angustifolia, Carex lasiocarpa) in the freshwater wetlands of Northeast China using in situ rhizoboxes.  

Each rhizobox was divided into one root chamber and two side chambers. Each side chamber was divided into the inner, middle and outer bulk soil parts by two 2.5 mm thick plexiglass sheets. The wetland plant roots were restricted so as to only grow in the root chamber.  

Considering the rhizosphere effect was most significant at their mature timing, the researchers measured the soil and microbial indexes by soil geochemical analyses, 16s RNA high-throughput sequencing and fourier transform infrared spectrometer after 100 d of cultivation when each rhizobox was filled with roots. 

The results showed that wetland plant roots did influence the coupled Fe-C microbial transformations and Fe-bound organic carbon was 3–5 fold greater in rhizosphere soil than bulk soils. This study highlighted the role of plant roots and identified the conserving hotspot of iron-bound organic carbon in wetland rhizosphere.