Arbuscular mycorrhizal fungi (AMF) are ubiquitous, form associations with roots of over 80% land plant species, and obtain carbon from their host plants in return for mineral nutrients. Soil contains more organic carbon than the atmosphere and global vegetation combined. A small change in soil organic carbon may critically affect air CO2 and the climate. Plants allocate up to 20% of their photosynthates to AMF hyphae and their exudates, which can enhance soil carbon decomposition through stimulating decomposition of other soil microbes (i.e., the priming effect) and increasing plant nutrient acquisition from the decomposing organic matter. Climate change components such as warming and ozone can exert significant impacts on mycorrhizal functioning and ecosystem processes through altering plant and microbial growth. However, few field experiments so far have been conducted to assess the relative effect of AMF removal of N and AMF supply of labile carbon to saprotrophs on soil organic carbon decomposition under warming and elevated ozone conditions.
We initiated a field experiment to assess how AMF affect organic carbon decomposition under warming and ozone conditions. The objectives of this study were to: (1) examine effects of warming and ozone on AMF, and (2) assess the effect of the resulting alteration in AMF on soil carbon decomposition under warming and ozone conditions. Results from this study would advance our understanding of the mechanisms that govern organic carbon decomposition under elevated
Results/Conclusions
Our results showed that ozone significantly increased the AMF infection of soybean roots. Elevated temperature tended to increase the AMF infection of roots, but the effect was not significant. The presence of both roots and AMF significantly increased soil organic carbon decomposition. Elevated ozone, not warming, significantly stimulated soil organic carbon decomposition. However, the combination of warming and elevated ozone significantly enhanced organic carbon decomposition. Together, these findings suggest that elevated temperature and ozone may stimulate terrestrial ecosystem carbon cycling by increasing organic carbon decomposition in the rhizosphere and the mycorhizosphere.