Ground bryophytes regulate net soil carbon efflux: evidence from two subalpine ecosystems on the east edge of the Tibet Plateau

Background and aims Given the broad distribution of bryophytes and their prominence in alpine and high latitude ecosystems, to generate a better understanding of how bryophyte communities influence soil CO2 efflux is essential for increasing our comprehension of the global C cycle. Methods We measured CO2 efflux from bryophyte-covered and bryophyte-removed soil surface in two subalpine ecosystems: a conifer dominated forest and an ericaceous dominated shrubland, on the east edge of Tibetan Plateau. In addition, soil temperature (Tsoil), soil water content (SWC), total soil organic C (SOC), dissolved organic C (DOC) and microbial community structure were measured as possible drivers of the bryophyte-effects. Results Bryophyte removal resulted in reduced floor (bryophyte + soil) and mineral soil CO2 efflux, SOC, DOC, microbial biomass C (MBC) and phospholipid fatty acid (PLFA) concentrations, and caused a change in soil microbial community in the two ecosystems. The higher soil CO2 emissions from the bryophyte-covered, relative to the bare soil, was not caused by the changes in Tsoil and SWC, rather, it was consistent with the higher SOC, DOC, MBC and/or the PLFAs contents in the plots with bryophytes. Conclusion Our results highlight bryophytes are regulators of soil C efflux in subalpine ecosystems. Incorporating the effects of bryophytes will help improve the accuracy of current ecosystem C cycling models.