Insights into ECOSSE modelling of soil organic carbon at site scale from Irish grassland sites and a French grazed experimental plot

<p></p><p>The work provides insights into soil organic carbon (SOC) modelling procedures associated with different management practices for Irish grassland sites selected from two large soil databases (LUCAS-2009 _[1]and Teagasc-SIS _[2]) and a single treatment-plot&#160; from France &#160;(paddock of a long- term grassland-experiment) _[3]. Modelling of SOC was done at site scale using &#8220;Model to Estimate Carbon in Organic Soils -Sequestration and Emissions&#8221; (ECOSSE) 6.2b version of the model in site-specific mode _[4]. The selection of Irish sites and the Irish model input-parameters followed procedures explained in Premrov et al. (2020) _[5]. As explained in Premrov et al. (2020) _[5], special attention was given to model SOC-input data because the preliminary findings showed high sensitivity of model predictions to the initial SOC-inputs _[5]. Initial SOC-inputs for Irish sites were extracted from the Irish soil NSDB-database _[8]because of lack of data at that time. The preliminary SOC modelling results from Irish sites [RMSE >36%; 84 sites (out of total 95 pre-selected LUCAS and SIS sites after excluding 11 potential outliers _[7])]indicated that further work is needed on obtaining initial SOC-input data. The new LUCAS-2015 _[6] soil-point data in combination with older LUCAS-2009 _[1] data provide opportunities to resolve this issue, which is currently work in progress. Considering that Irish sites were selected from large soil-databases that lacked detailed site-specific information (i.e. stocking rates and fertilisation-data could be obtained only in general form), the treatment-plot from France _[3] was also simulated to gain further insights into the ECOSSE SOC modelling at site/point-scale. This work confirmed the importance of using appropriate conversion-factor when applying stocking rates as a proxy for the manure-inputs (as an alternative for grazing _[7]). Further insights included the importance of assessing the modelled SOC &#8216;trends&#8217; over time, and its comparison with observed ones _[7].</p><p>&#160;</p><p><strong>Acknowledgements</strong></p><p>SOLUM project is funded under the Irish EPA Research programme 2014-2020. Thanks go to Dr Jo Smith (University of Aberdeen, Scotland) for ECOSSE-model and to all who provided data or advice/support, among others, Teagasc-SIS, Ireland; &#160;French national-observatory SOERE ACBB, a part of ANAEE-F French national infrastructure, and Dr Katja Klumpp (INRAe, France).</p><p>&#160;</p><p><strong>Literature</strong></p><p>&#160;</p><p>[1] JRC (2018). LUCAS-2009, ESDAC. JRC. EC.</p><p>[2] Teagasc, (2018) Irish Soil Information System (SIS). Teagasc, EPA, Ireland.</p><p>[3] SOERE ACBB (2020) http://www.soere-acbb.com/</p><p>[4] Smith, J., et al. (2010). ECOSSE. User Manual.</p><p>[5] Premrov, A., et al. (2020). Insights into modelling of soil organic carbon from Irish grassland sites using ECOSSE model. EGU2020-8090. doi.org/10.5194/egusphere-egu2020-18940; (CC-BY-4).</p><p>[6] JRC (2020). LUCAS 2015, ESDAC. JRC. EC.</p><p>[7] Saunders, M. et al. (draft-report 2020) SOLUM. EPA Research Report. 2016-CCRP-MS.40.</p><p>[8] EPA (2007). National Soils Database (NSDB). Environmental Protection Agency, Ireland.</p>