Seasonal variation and fire effects on CH4, N2O and CO2 exchange in savanna soils of northern Australia

Livesley, S, Grover, S, Hutley, L, Jamali, H, Butterbach-Bahl, K, Fest, B, Beringer, J and Arndt, S 2011, 'Seasonal variation and fire effects on CH4, N2O and CO2 exchange in savanna soils of northern Australia', Agricultural and Forest Meteorology, vol. 151, no. 11, pp. 1440-1452.

Document type: Journal Article
Collection: Journal Articles

Title Seasonal variation and fire effects on CH4, N2O and CO2 exchange in savanna soils of northern Australia
Author(s) Livesley, S
Grover, S
Hutley, L
Jamali, H
Butterbach-Bahl, K
Fest, B
Beringer, J
Arndt, S
Year 2011
Journal name Agricultural and Forest Meteorology
Volume number 151
Issue number 11
Start page 1440
End page 1452
Total pages 13
Publisher Elsevier BV
Abstract Tropical savanna ecosystems are a major contributor to global CO2, CH4 and N2O greenhouse gas exchange. Savanna fire events represent large, discrete C emissions but the importance of ongoing soil-atmosphere gas exchange is less well understood. Seasonal rainfall and fire events are likely to impact upon savanna soil microbial processes involved in N2O and CH4 exchange. We measured soil CO2, CH4 and N2O fluxes in savanna woodland (Eucalyptus tetrodonta/Eucalyptus miniata trees above sorghum grass) at Howard Springs, Australia over a 16 month period from October 2007 to January 2009 using manual chambers and a field-based gas chromatograph connected to automated chambers. The effect of fire on soil gas exchange was investigated through two controlled burns and protected unburnt areas. Fire is a frequent natural and management action in these savanna (every 1-2 years). There was no seasonal change and no fire effect upon soil N2O exchange. Soil N2O fluxes were very low, generally between -1.0 and 1.0 mu g N m(-2) h(-1), and often below the minimum detection limit. There was an increase in soil NH4+ in the months after the 2008 fire event, but no change in soil NO3-. There was considerable nitrification in the early wet season but minimal nitrification at all other times. Savanna soil was generally a net CH4 sink that equated to between -2.0 and -1.6 kg CH4 ha(-1) y(-1) with no clear seasonal pattern in response to changing soil moisture conditions. Irrigation in the dry season significantly reduced soil gas diffusion and as a consequence soil CH4 uptake. There were short periods of soil CH4 emission, up to 20 mu g C m(-2) h(-1), likely to have been caused by termite activity in, or beneath, automated chambers. Soil CO2 fluxes showed a strong bimodal seasonal pattern, increasing fivefold from the dry into the wet season. Soil moisture showed a weak relationship with soil CH4 fluxes, but a much stronger relationship with soil CO2 fluxes, explaining up to 70% of the var
Subject Earth Sciences not elsewhere classified
Keyword(s) Carbon dioxide
Nitrous oxide
Savanna woodland
Soil gas diffusion
DOI - identifier 10.1016/j.agrformet.2011.02.001
Copyright notice © 2011 Elsevier BV. All rights reserved.
ISSN 0168-1923
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