PARENT SESSION
Poster Session #26: Soil Ecology I.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Plant species and rhizosphere community effects on soil carbon cycling processes .

DRINKWATER, LAURIE^*,1, ¹ Cornell University, Ithaca, NY

ABSTRACT- Significant differences exist among plant species in terms of root characteristics and rhizosphere community composition. Although it is recognized that differences in belowground characteristics will influence C and N cycling process, little is know about the extent of these effects. The goal of this experiment was to investigate how plant species differences at the rhizosphere scale impact soil organic C (SOC) pools. An experiment was initiated to compare the fate of belowground C inputs from six plant species commonly found in managed ecosystems, including N-fixers and non N-fixers. Additional treatments involved inoculating plants with Trichoderma harzianum, a rhizosphere fungus that is used as a biocontrol agent. All plant species studied were C₃ plants and had ¹³C signatures in the range of -25 to -27. The experimental field had been under a corn monoculture for 50+ years, and as a result, the ¹³C signature of SOC pools with faster turnover times were shifted by the corn signature, which is close to -12. Soil samples were collected prior to planting and at reproductive maturity. Natural abundance of ¹²C/¹³C was determined for SOC fractions in order to track the fate of belowground C inputs. There were significant plant species differences in both the quantity and biochemical composition of belowground inputs as well as in the fate of root-derived C among labile SOC fractions.

KEY WORDS: carbon cycling, rhizosphere, plant species effects, labile organic matter pools