Scholarly record

A NATIONAL-SCALE ASSESSMENT OF THE TOPSOIL CLAY CONTENT MAP OF ROMANIA DERIVED FROM THE LUCAS SURVEY

Ruxandra VINTILA

Abstract

The clay consists of the tiniest particles of soil, which have a considerable amount of physical and chemical activity with influence on water and nutrient cycles, observable over several scales. Therefore, the Global Soil Map Project (GSM) has included clay content among the key properties estimated across the world at 100 m resolution. Subsequently, in 2015 the Joint Research Centre (JRC) of the European Commission produced a clay content map of the soil uppermost layer (called пїЅtopsoilпїЅ), converging towards the GSM specifications. JRC produced this raster map at 500 m resolution, in the coordinate system ETRS89-LAEA, recommended by the INSPIRE Directive for spatial analysis. The JRC map contains values estimated - based on point soil data measured in the field during the LUCAS-2009 survey of EUROSTAT- using advanced statistical methods and environmental covariates relevant to soil forming processes. The present paper addresses the need for feedback on/validation of this JRC map. It proposes a general method for comparing continuous raster maps at medium-coarse resolutions to other spatial datasets, in case there are no sufficient data for applying geostatistical techniques. The paper shows the results of the method application for the JRC topsoil clay content map (952,065 cells at 500m resolution within Romania), obtained due to the reference/legacy data existing across the territory of Romania. For this purpose, the main reference information on topsoil clay content comes from the vector soil map SIGSTAR-200k, which has national coverage and the most suitable available granularity for evaluating the content of the above JRC map. The comparison method opted for the preservation of the reference information on topsoil clay content during the mathematical processing. Accordingly, the soil map SIGSTAR-200k was transformed into the coordinate system ETRS89-LAEA. Afterwards, data derived from the JRC map (e.g., as area-weighted average) were ingested by the SIGSTAR-200k polygons having been intersected, so the main comparison phase could take place. An additional comparison used legacy statistical information on topsoil clay content for the main soil types in Romania, estimated thanks to 2735 soil profiles selected from the "PROFISOL" database.

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DOI resolver: doi.org/10.5593/sgem2017/23/s11.044

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