Monday, November 13, 2006

Carbon Monoxide Uptake Kinetics in Unamended and Long-Term Nitrogen Amended Temperate Forest Soils.

Alvarus S.K. Chan, AgCert International, 1901 S. Harbour City Blvd. Suite 400, Melbourne, FL 32901 and Paul A. Steudler, The Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543.

The impact of nitrogen (N) additions to the dynamics of carbon monoxide (CO) consumption in temperate forest soils is poorly understood.  To explore the consequences of long-term N additions on atmospheric CO consumption in soils, we measured soil CO profiles, potential rates of CO consumption and uptake kinetics in temperate hardwood and pine soils.  N-amended plots received 50 and 150 kg N/ha/y for more than 15 years.  CO concentrations in the soil profiles were above atmospheric levels in the high N plots of both stands suggesting that in these soils the balance between consumption and production may sometimes be shifted.  Highest potential rates of CO consumption were measured in the organic horizons and decreased with depth.  CO consumption increased in all but one depth of the hardwood N amended plots while in the pine N amended plots CO consumption decreased in all depths.  CO enzyme affinities increased with depth in the soil profiles of both control plots.  However, enzyme affinities in the most active soil depths (organic and 0-5 cm) decreased in response to addition of low levels N in both stands suggesting an adaptation by the microbial community to N inputs.  The response to high levels of N was mixed between stands.  Enzyme affinities dramatically increased in these two depths in the hardwood stand.  In the pine stand, affinities decreased in the organic horizon, but increased slightly in the 0-5 cm mineral soil.  These findings indicate that long-term addition of N either by fertilization or deposition may alter the size, composition and/or physiology of the community of CO consumers so that their ability to act as a sink for atmospheric CO changes.  These changes could have a substantial effect on the lifetime of greenhouse gases such as Methane (CH4) and therefore the future of Earth’s climate.