20 Jun 2023
 | 20 Jun 2023
Status: this preprint is currently under review for the journal BG.

Identifying landscape hot and cold spots of soil GHG fluxes by combining field measurements and remote sensing data

Elizabeth Gachibu Wangari, Ricky Mwangada Mwanake, Tobias Houska, David Kraus, Gretchen Maria Gettel, Ralf Kiese, Lutz Breuer, and Klaus Butterbach-Bahl

Abstract. Upscaling chamber measurements of soil greenhouse gas (GHG) fluxes from points to landscape scales remain challenging due to high variability of fluxes in space and time. This study measured GHG fluxes and soil parameters at selected point locations (n=268), thereby implementing a stratified sampling approach on a mixed land-use landscape (~5.8 km2). Based on these field-based measurements and remotely-sensed data on landscape and vegetation properties, we used Random Forest models to predict GHG fluxes at a landscape scale (1 m resolution) in summer and autumn. The results showed improved GHG flux prediction performance when combining field-measured soil parameters with remotely-sensed data. Available satellite data products from Sentinel-2 on vegetation cover and water content played a more significant role than attributes derived from a digital elevation model, possibly due to their ability to capture both spatial and seasonal changes of ecosystem parameters within the landscape. Similar seasonal patterns of higher soil/ecosystem respiration (SR/ER-CO2) and nitrous oxide (N2O) fluxes in summer and higher methane (CH4) uptake in autumn were observed in both the measured and predicted landscape fluxes. Based on the upscaled fluxes, we also assessed the contribution of hot spots to total landscape fluxes. The identified emission hot spots occupied a small landscape area (7 to 16 %) but accounted for up to 42 % of the landscape GHG fluxes. Our study showed that combining remotely-sensed data with chamber measurements and soil properties is a promising approach for identifying spatial patterns and hot spots of GHG fluxes across heterogeneous landscapes. Such information may be used to inform targeted mitigation strategies at landscape-scale.

Elizabeth Gachibu Wangari et al.

Status: open (until 01 Oct 2023)

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  • CC1: 'Comment on bg-2023-99', David Pelster, 04 Aug 2023 reply
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Elizabeth Gachibu Wangari et al.

Elizabeth Gachibu Wangari et al.


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Short summary
Agricultural landscapes act as sinks or sources of the greenhouse gases (GHG) CO2, CH4 or N2O. Fluxes of these GHGs between ecosystems and the atmosphere are controlled by various physico-chemical and biological processes. Therefore, fluxes depend on environmental conditions such as moisture, temperature, or soil parameters, which results in large spatial and temporal variations of GHG fluxes. Here we describe an example how this variation may be studied and analysed.