Spatial properties affecting the sensitivity of soil water dissolved organic carbon long-term median concentrations and trends

Katarzyna Sawicka; Joanna M Clark; Elena Vanguelova; Don T Monteith; Andrew J Wade

doi:10.1016/j.scitotenv.2021.146670

Spatial properties affecting the sensitivity of soil water dissolved organic carbon long-term median concentrations and trends

Sci Total Environ. 2021 Aug 1:780:146670. doi: 10.1016/j.scitotenv.2021.146670. Epub 2021 Mar 23.

Authors

Katarzyna Sawicka¹, Joanna M Clark², Elena Vanguelova³, Don T Monteith⁴, Andrew J Wade²

Affiliations

¹ Soil Research Centre, Department of Geography and Environmental Science, University of Reading, Reading RG6 6DW, UK; UK Centre for Ecology & Hydrology, Environment Centre Wales, Deiniol Road, Bangor LL57 2UW, UK; Environmental Science Group, Wageningen University, PO Box 47, 6700 AA Wageningen, the Netherlands. Electronic address: katwic55@ceh.ac.uk.
² Soil Research Centre, Department of Geography and Environmental Science, University of Reading, Reading RG6 6DW, UK.
³ Centre for Ecosystems, Society and Biosecurity, Forest Research, Alice Holt Lodge, Farnham, Surrey GU10 4LH, UK.
⁴ Environmental Change Network, UK Centre for Ecology and Hydrology, Lancaster Environment Centre, Bailrigg, Lancaster LA1 4AP, UK.

PMID: 34030324
DOI: 10.1016/j.scitotenv.2021.146670

Abstract

It is increasingly clear that increases in dissolved organic carbon in upland waters in recent decades have often been dominated by acid deposition, but reasons for substantial variation in rates of change remain unclear. This paper focuses on the extent to which spatial properties, such as variation in soil properties, atmospheric deposition and climate, affect the sensitivity of DOC concentrations in soil water. The purpose is to i) examine evidence for differences in site average concentrations and trends in soil water DOC between sites with contrasting ecosystem properties, i.e. vegetation cover and soil type, and ii) identify the wider combination of site characteristics that best explain variation in these DOC metrics between sites. We collated soil water and deposition chemistry, soil chemistry and meteorological data from 15 long-term UK monitoring sites (1992-2010) covering a range of soils, vegetation, climate and acid deposition levels. Mineral soils under forests showed the greatest range of long-term mean DOC concentrations and trends. Regression analysis indicated that acid and sea-salt deposition, and soil sensitivity to acidification were the factors most strongly associated with spatial variation in mean DOC concentrations. Spatial variation in DOC trends were best explained by Al saturation and water flux. Overall, the sensitivity of DOC release from soil to changes in pollutant deposition could be related to the type of vegetation cover and soils chemistry properties, such as Al saturation, divalent base cation content and hydrological regime. The identification of the ecosystem properties that appear most influential in modifying DOC production and responses to long-term drivers, helps elucidate potential mechanistic explanations for differences in DOC dynamics across seemingly similar ecosystems, and points to the importance of DOC mobility in regulating its dynamics.

Keywords: Acidification recovery; Dissolved organic carbon; Ecosystem properties; Effective rainfall; Soil aluminium saturation; Soil solution chemistry.