Temperature and Moisture Effects on Nitrification Rates in Tropical Rain-Forest Soils
2002
Breuer, Lutz | Kiese, Ralf | Butterbach-Bahl, Klaus
Intact soil cores from three tropical rainforest sites on the Atherton Tablelands, Australia, were sampled at different hygric seasons to determine the effects of soil temperature and soil moisture on gross nitrification using the barometric process separation technique (BaPS). Parameterization experiments revealed that gross nitrification was positively correlated to increases in soil temperature, but negatively correlated to increased rates of water-filled pore space (WFPS) because of simulated rainfall. Pronounced seasonal variations of gross nitrification rates were observed at all three sites with lowest values during the dry season (1.9–9.7 mg NH⁺ ₄-N m⁻² h⁻¹) and highest values during the transition period between dry to wet season (14.8–27.6 mg NH⁺ ₄-N m⁻² h⁻¹). Highest nitrification activities were found for two sites characterized by a narrow C/N ratio and a high total C content in the mineral soil, whereas the site with a wider C/N ratio and lower C content in the soil showed significantly lower nitrification rates. Gross nitrification was positively correlated to in situ N₂O-emission rates indicating that nitrification is a key regulating process of N₂O-production and emission in these tropical soils.
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