Spatio-temporal variation in soil derived nitrous oxide emissions under sugarcane

Abstract

Nitrous oxide (N 2O) is a significant greenhouse gas with a global warming potential that is 300 times than that of carbon dioxide. Soil derived N 2O emissions usually display a high degree of spatial and temporal variability because of their dependence on soil chemical and physical properties, and climate dependent environmental factors. However, there is little research that incorporates spatial dependence in the estimation of N 2O emissions allowing for environmental factors in the same model. This study aims to examine the impact of two environmental factors (soil temperature and soil moisture) on N 2O emissions and explore the spatial structure of N 2O in the sub-tropical South East Queensland region of Australia. The replicated data on N 2O emissions and soil properties were collected at a typical sugarcane land site covering 25 uniform grid points across 3600 m 2 between October 2007 and September 2008. A Bayesian conditional autoregressive (CAR) model was used to model spatial dependence. Results showed that soil moisture and soil temperature appeared to have substantially different effects on N 2O emissions after taking spatial dependence into account in the four seasons. There was a substantial variation in the spatial distribution of N 2O emission in the different seasons. The high N 2O emission regions were accompanied by high uncertainty and changed in varying seasons in this study site. Spatial CAR models might be more plausible to elucidate and account for the uncertainty arising from unclear variables and spatial variability in the assessment of N 2O emissions in soils, and more accurately identify relationships with key environmental factors and help to reduce the uncertainty of the soil parameters.