Does the invasive weed S. chamaejasma chamaejasme L. alter grassland soil fungal communities?

Stellera chamaejasma has become the most problematic weed in China's grasslands. Allelochemicals from its roots may alter soil fungal communities enhancing its competitive nature. On two adjacent areas, one invaded by Stellera chamaejasma the other a control , vegetation cover was recorded and soil samples were taken to 20 cm depth. Soil samples were analysed for a range of physiochemical parameters and their fungal communities characterised by DNA sequencing. The two sites were compared and relationships within the invaded site between Stellera chamaejasma and soil indices investigated. There was a clear separation between control and invaded site fungal communities, although this difference accounted for a relatively small proportion of the overall variation. Communities on the invaded site had a lower diversity and reduced relative abundance of AMF, but a greater abundance of pathogenic fungi. The invaded soils also had lower reserves of N and P, and of organic matter. dbRDA analyses indicated that soil organic content was the factor most strongly linked to site differences in fungal communities. Within the invaded site, variations in several soil parameters were linked to fungal communities, but links to Stellera chamaejasma indices were weak by comparison. This study indicates that lower fertility soils may be more susceptible to invasion and that any direct effect of bioactive chemicals on fungal communities in general, as opposed to particular functional groups, is limited.