Rhizospheric carbon cycling: The implications of community structure

Background/Question/Methods

One of the major ways that plants interact with belowground communities is via the exudation of simple carbon compounds. The exudation of these compounds can lead to changes in soil microbial communities, often altering both activity and composition. Additionally, such compounds are presumed to be responsible for as much as 30% of heterotrophic soil respiration. However, our understanding of how changes in the quantity and quality of these exudates mediate carbon cycling and the role that communities play in mediating these processes is only beginning to be explored.

Here, I present a synopsis of recent research, which examines how change in exudate inputs can influence community structure and activity. Additionally, I will examine how inclusion of other soil organisms might elucidate a more complete picture of the role root exudates play in rhizospheric carbon cycling.

Results/Conclusions

Results thus far indicate that the quantity, quality, and composition of exudates play an important role in shaping both soil microbial community structure and function. I have found, using a lab-based microcosm approach, that organic acids often lead to the most marked change in microbial community function. This indicates that exudates have the potential to directly influence soil microbial communities. Pairing field studies and stable isotope methods, I have shown that the whole belowground communities, particularly predatory mites, mediate the cycling of dominant exudates. Together these findings indicate that the role of exudates in carbon cycling is likely very dynamic.

In conclusion, the interplay between exudates, belowground communities, and carbon cycling is complex. However, understanding the interplay between microbial community composition and the rest of the belowground community (particularly its trophic structure) may prove informative with regards to rhizospheric carbon cycling.