PARENT SESSION
Poster Session 23: Soil Ecology
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Relating nitrogen dynamics to carbon stabilization in calcium and nitrogen amended soils.

Brewer, Elizabeth¹, Morris, Sherri¹, Paul, Eldor², Robertson, G. ³, ¹ Bradley University, Peoria, IL, USA² Colorado State University, Fort Collins, CO, USA³ Michigan State University, East Lansing, MI, USA

ABSTRACT- Management strategies that use afforestation as a short-term strategy for mitigation of anthropogenically elevated atmospheric CO₂ require a better understanding of the impacts of N on C stabilization in soils. Changes in N availability alter stabilization of organic matter through changes in microbial community structure, mineralization rates, decreased production of lignin degrading enzymes and abiotic incorporation. The goal of our research was to examine impacts of N and Ca on N turnover in a C poor, previously afforested system. Field plots were established in an afforested red pine stand. Treatments included control, addition of CaCl₂, addition of NH₄NO₃, and additions of CaCl₂ and NH₄NO₃. Each treatment was also incorporated with litter to a depth of 20 cm. Incubations for N mineralization were established on soils collected one year after amendment to evaluate changes in C and N pools. Incubations were also established using soil from our field site but amended in the laboratory. Field N mineralization rates were lowest in Ca treatments after 70 days of incubation. Laboratory Ca treatments were also lower than other treatments although only at 180 days, but had significantly lower nitrification rates than other treatments through day 120. The decrease in N mineralization, which represents decreased turnover of organic matter for mineral N, suggests sequestration. This is supported by analysis of C pools, which show increases in total and resistant C pool sizes with addition of CaCl₂ and litter incorporation. Surprisingly, N additions had little impact on N cycling parameters measured initially or after 1 year. This suggests our system was limited by something other than N and it may be worthwhile to consider other amendments that might stimulate changes in nutrient dynamics and alter C sequestration rates. Overall, our study supports the hypothesis that Ca and N amendments increase soil C sequestration.

Key words: Soil Carbon, Calcium, Afforestation, Nitrogen