PARENT SESSION
Friday, August 11, 8:00-11:30 am
COS 105 - Nutrient cycling
Chickasaw, Mezzanine Level, Cook Convention Center
Presiders: D Bryant
Plant organic matter deposition into fast and slow cycling soil pools.
Maul, Jude*,1, Drinkwater, Laurie1, 1 Cornell University, Ithaca, NY, USA
ABSTRACT- We tracked plant derived organic carbon into fast and slow cycling soil organic matter (OM) pools using stable isotope techniques. We utilized an agroecosystem with a long history of C4 plants as a contrasting soil OM background, into it we planted 15 C3 plant species to study deposition of OM over three years. Free particulate organic matter (fPOM), is exposed to decomposers in the soil and decomposes rapidly, on the order of days. Occluded particulate organic matter (oPOM) is protected within soil aggregates and unavailable to soil decomposers, it is metabolized slowly in the time frame of months. Evidence suggests organic matter deposition into oPOM pools may have stabilizing affects on very slow cycling soil OM pools that cycle in years or decades. We compared 15 herbaceous agricultural plant species with regards to the annual contribution of plant organic matter to fast (fPOM) or slowly cycling (oPOM) soil pools. Measurements of POM pool sizes, DOC, microbial biomass, root length density and microbial community structure (TRFLP) were determined for all plant treatments. We found positive relationships between fPOM pool size and total root length density. Grasses such as Itialian ryegrass (L. perenne), Reeds canary grass (P. arundinacea), and Corn (Zea maize) tended to have the largest fPOM pools. The mechanism of plant contribution to the oPOM pool appears to be more complex in nature with no single variable able to strongly predict pools sizes. Interactions between plant, microbial and edaphic variables all contributed to description of soil oPOM dynamics.
Key words: Organic matter cycling, Agricultural plants, Soil Biogeochemistry