Abstract
In order to predict and mitigate future climate change, it is essential to understand plant-mediated effects of elevated CO 2 (eCO 2) and O 3 (eO 3) on N-cycling, including N 2O emissions. This is of particular interest for agroecosystems, since N-cycling and N 2O emissions are responsive to adaptive management. We investigated the interaction of soil moisture content with eCO 2 and eO 3 on potential N 2O emissions from SoyFACE during a 28-day laboratory incubation experiment. We also assessed field N 2O fluxes during 2 soybean-growing seasons. In addition, we sought to link previously observed changes in soybean growth and production to belowground processes over a longer time scale by analyzing changes in natural abundance stable isotope ratios of soil N (δ 15N). This method relies on the concept that soil δ 15N can only change when inputs or outputs with an isotope signature different from that of soil N are altered. We found no major effects of eCO 2 and eO 3 on laboratory and field measured N 2O emissions. Natural abundance isotope analyses suggested, however, a decrease in belowground allocation of biologically fixed N in combination with decreased total gaseous N loss by eCO 2, resulting in a tighter N cycle in the longer-term. In contrast, the isotope data suggested an increase in belowground allocation of biologically fixed N under eO 3, leading to increased gaseous N loss, most likely in the form of N 2. Given that effects of eCO 2 and eO 3 on N pools and instantaneous transformation rates in surface soil layers of this agroecosystem have been minimal, our results illustrate the importance of evaluating longer-term changes in N turnover rates. We conclude that eCO 2 decelerates whereas eO 3 accelerates N-cycling in the longer-term, but feedback through changed N 2O emissions is not occurring in this soybean system.
Original language | English (US) |
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Pages (from-to) | 104-114 |
Number of pages | 11 |
Journal | Soil Biology and Biochemistry |
Volume | 51 |
DOIs | |
State | Published - Aug 2012 |
Keywords
- Agroecosystem
- Climate change
- Greenhouse gases
- N-budget
- Natural abundance stable isotopes
- Nitrous oxide
- Soybean
ASJC Scopus subject areas
- Microbiology
- Soil Science