Elevated CO2 and O3 alter soil nitrogen transformations beneath trembling aspen, paper birch, and sugar maple
Document Type
Article
Publication Date
12-2006
Department
College of Forest Resources and Environmental Science
Abstract
Nitrogen cycling in northern temperate forest ecosystems could change under increasing atmospheric CO2 and tropospheric O3 as a result of quantitative and qualitative changes in plant litter production. At the Aspen Free Air CO2-O3 Enrichment (FACE) experiment, we previously found that greater substrate inputs to soil under elevated CO 2 did not alter gross N transformation rates in the first 3 years of the experiment. We hypothesized that greater litter production under elevated CO2 would eventually cause greater gross N transformation rates and that CO2 effects would be nullified by elevated O3. Following our original study, we continued measurement of gross N transformation rates for an additional four years. From 1999 to 2003, gross N mineralization doubled, N immobilization increased 4-fold, but changes in microbial biomass N and soil total N were not detected. We observed year-to-year variation in N transformation rates, which peaked during a period of foliar insect damage. Elevated CO2 caused equivalent increases in gross rates of N mineralization (+34%) and NH 4+ immobilization (+36%). These results indicate greater rates of N turnover under elevated CO 2, but do not indicate a negative feedback between elevated CO 2 and soil N availability. Elevated O3 decreased gross N mineralization (-16%) and had no effect on NH 4+ immobilization, indicating reduced N availability under elevated O3. The effects of CO2 and O3 on N mineralization rates were mainly related to changes in litter production, whereas effects on N immobilization were likely influenced by changes in litter chemistry and production. Our findings also indicate that concomitant increases in atmospheric CO2 and O3 could lead to a negative feedback on N availability.
Publication Title
Ecosystems
Recommended Citation
Holmes, W.,
Zak, D.,
Pregitzer, K.,
&
King, J.
(2006).
Elevated CO2 and O3 alter soil nitrogen transformations beneath trembling aspen, paper birch, and sugar maple.
Ecosystems,
9(8), 1354-1363.
http://doi.org/10.1007/s10021-006-0163-5
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p/4792