We examined the impacts of warming, nitrogen (N) addition and suppression of arbuscular mycorrhizal fungi (AMF) on soil bacterial and fungal richness and community composition in a field experiment. AMF root colonization and the concentration of an AMF-specific phospholipid fatty acid (PLFA) were significantly reduced after the application of the fungicide benomyl as a soil drench. Warming and N addition had no independent effects but interactively decreased soil fungal richness, while warming, N addition and AMF suppression together reduced soil bacterial richness. Soil bacterial and fungal species diversity was lower with AMF suppression, indicating that AMF suppression have negative effect on microbial diversity. Warming and N addition decreased the net loss of plant species and the plant species richness, respectively. AMF suppression reduced plant species richness and the net gain of plant species but enhanced the net loss of plant species. Structural equation modeling (SEM) demonstrated that the soil bacterial community responded to the increased soil temperature (ST) induced by warming and the increased soil available N (AN) induced by N addition through changes in AMF colonization and plant species richness; ST directly affected the bacterial community, but AN affected both the soil bacterial and fungal communities via AMF colonization. In addition, higher mycorrhizal colonization increased the plant species richness by increasing the net gains in plant species under warming and N addition.
IMPORTANCE
Arbuscular mycorrhizal fungi (AMF) can influence the composition and diversity of plant communities. Previous studies have shown that climate warming and N deposition reduce the effectiveness of AMF. However, how AMF affects soil bacterial and fungal communities under these global change drivers are still poorly understood. A 4-year field study revealed that AMF suppression decreased bacterial and fungal diversity irrespective of warming or N addition, while AMF suppression interacted with warming or N addition to reduce bacterial and fungal richness. In addition, bacterial and fungal community compositions were determined by mycorrhizal colonization which was regulated by soil AN and ST. These results suggest that AMF suppression can aggravate the severe losses to native soil microbial diversity and functioning caused by global changes and thus AMF plays a vital role in maintaining belowground ecosystem stability in the future.
Studies on the arbuscular mycorrhizal fungal association in the plant species of theerthamalai hills, western ghats of dharmapuri district tamilnadu, india