Redistribution of Soil Organic Carbon Triggered by Erosion at Field Scale Under Subhumid Climate, Hungary

Abstract

Soil organic carbon (SOC) has primary importance in terms of soil physics, fertility and even of climate change control. An intensively cultivated Cambisol was studied in order to quantify SOC redistribution under subhumid climate. One hundred soil samples were taken from the representative points of the solum along the slopes from the depth of 20-300 cm with a mean 1.2 % SOC content. They were measured by the simultaneous application of diffuse reflectance (240-1900 nm) and traditional physico-chemical methods in order to compare the results. On the basis of the results hierarchical cluster analyses were performed. The spatial pattern of the groups created were similar, and even though the classifications were not the same, diffuse reflectance has proven to be a suitable method for soil/sediment classification even within a given arable field. Both organic and inorganic carbon distribution was found a proper tool for estimations of past soil erosion process. Results show SOC enrichment on two sedimentary spots with different geomorphological positions. Soil organic matter compound also differs between the two spots due to selective deposition of the delivered organic matter. The components of low molecular weight reach the bottom of the slope and there can leach into the profile, while the more polymerised organic matter compounds are delivered and deposited even before, on a higher segment of the slope in an aggregated form. This spatial difference appears below the uppermost tilled soil layer as well; referring the lower efficiency of conventional ploughing tillage in spatial soil homogenisation.

A 300-year record of sedimentation in a small tilled catena in Hungary based on δ13C, δ15N, and C/N distribution

“…Many studies report data on SOC enrichment down-slope (Wang et al 2010;Farsang et al 2012). Szalai et al (2016) found SOC deposition spots on the toe-slope of the same research site. This suggests that beyond mass movement spatial heterogeneity of selective SOM deposition or mineralization may hardly affect local SOC contents.…”

“…1). Previous investigations demonstrated that this field site was representative of local cropland and suitable for historical soil erosion studies Szalai et al 2016). Moreover, landscapes with very similar properties and processes are widespread in Western and Central Europe, where soil erosion became serious due to forest clearance in historical times (Cerdan et al 2010).…”

“…The investigated catenas were individual erosion units without relevant external in-or outflow. Erosion rates were calculated by Szalai et al (2016) for the field, with a maximum of 3 mm year (loss of 1 m soil layer) at the most eroded spots, that resulted approximately 2 m sedimentation at the toe. Moreover, laboratory rainfall simulations identified sediment concentration values 6-50 g L ) that also underlined the high vulnerability of the site against sheet erosion.…”

“…These samples were gathered from representative layers of the solum with varying thickness. Detailed description of the sampling process is reported in Szalai et al (2016). In the present study, only 33 samples are investigated and discussed, including four soil profiles, and four additional samples from the uppermost tilled layer from the Regosol points (Fig.…”

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“…Previously, field scale erosional studies were done by Szalai et al (2016) and detailed aggregate related laboratory scale soil loss was also studied by Szabó et al (2015). The current study concentrates on erosional response of the soil in case of the slopes (2; 5; 12% steepness) and surface status (Table 1.)…”