Temperature and Moisture Effects on Nitrification Rates in Tropical Rain-Forest Soils
Lutz Breuera,
Ralf Kieseb and
Klaus Butterbach-Bahl*,b
a Dep. of Natural Resource Management, Heinrich-Buff-Ring 26-32, Justus-Liebig University Gießen, D-35392 Gießen, Germany
b Fraunhofer Institute for Atmospheric Environmental Research (IFU), Div. Biosphere/Atmosphere Exchange, Dep. of Soil Microbiology, Kreuzeckbahnstr.19, D-82467 Garmisch-Partenkirchen, Germany
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Fig. 1. Experimental setup for the determination of gross nitrification rates in intact soil cores using the Barometric Process separation technique (BaPS). Three intact gas-tight sealed chambers containing soil cores were incubated in a water bath at constant temperatures. Determination of O2 and CO2 was performed by gas chromatography. Pressure sensors inside the soil cores recorded pressure changes constantly.
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Fig. 2. Effect of temperature on gross nitrification rates (± standard error [SE]) and N2O-emission rates (±SE) for soil cores taken from the different field sites during the dry season in 1997. All experiments were performed in triplicate. Values for gross nitrification rates and N2O emissions marked with the same letter are not significantly different (P > 0.10).
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Fig. 3. Effect of temperature on gross nitrification rates (± standard error [SE]) and N2O-emission rates (±SE) for soil cores taken from the different field sites during the wet season in 1998. All experiments were performed in triplicate. Values for gross nitrification rates and N2O emissions marked with the same letter are not significantly different (P > 0.10).
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Fig. 4. Gross nitrification rates as a function of temperature for the tropical-forest soils in Australia. Data pooled across sites and seasons. [•]: gross nitrification rate ± standard error (SE), N = 9; [] linear regression: y = -12.0 + 1.17 x; r2 = 0.865, p < 0.001; [------] 95% confidence limit of the linear regression line.
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Fig. 5. Changes in gross nitrification rates (± standard error [SE]) and N2O-emission rates (±SE) resulting from simulated precipitation (0–5 mm) and increased water-filled pore space (WFPS) (%) for intact soil cores (N = 3) taken from the different field sites. Precipitation was applied in 1-mm steps. Values for gross nitrification rates and N2O-emissions marked with the same letter are not significantly different (P > 0.10). NA represents not available.
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Fig. 6. Changes in gross nitrification rates (± standard error [SE]) and N2O-emission rates (±SE) on simulated precipitation [0–17 mm] and increased water-filled pore space (WFPS) (%) for intact soil cores (N = 3) taken from the different field sites. Precipitation was applied in 3-, 4-, 5-, and 6-mm steps. Values for gross nitrification rates and N2O emissions marked with the same letter are not significantly different (P > 0.10). ND represents not detected.
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Fig. 7. Correlation between gross nitrification rates as determined in the lab on intact soil cores and N2O-emission rates as observed in the field for the three different tropical rain forest sites on the Atherton Tablelands, Queensland, Australia. [] regression line; [------] 95% confidence band.
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Copyright © 2002 by the Soil Science Society of America.
