BOOK OF ABSTRACTS 173 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Friday, 28 August 2026 / Hall C Travel Awardee Presentations energies calibrated to 99% clay dispersion, yielding the free-light (FLF), occluded-light (OLF), and heavy (mineralassociated organic carbon, MAOC) fractions. Carbon concentrations were determined by EA-IRMS, and stocks were calculated from soil bulk density. Withinfield-pair contrasts were tested with linear mixed-effects models. In the Horticultural-PV, bulk SOC stocks were 26.9 to 31.6% lower beneath panels than at matched control positions, with an area-integrated bulk SOC stock deficit of 19.1% (−11.23 Mg C ha⁻¹). All three fractions (FLF, OLF, and MAOC) were lower in Agri PV than in the paired control. Within the Agri-PV field, FLF and OLF also showed an opposing spatial pattern between UP and GAP positions. FLF was depleted in UP positions, whereas OLF was relatively enriched, a pattern that was absent in the paired control and therefore suggests panel induced microenvironmental drivers rather than background variability. In the Crops-PV, area-integrated bulk SOC stock remained close to control (−1.4%, −0.81 Mg C ha⁻¹, non-significant). Within the Agri-PV field, FLF and OLF showed contrasting spatial patterns. FLF was consistently higher beneath panels, significantly so in the center and east subzones, whereas OLF was generally enriched in gaps, particularly in the west and east. MAOC showed little evidence of systematic UP–GAP redistribution, although a localized/marginal decrease beneath panels was observed in the center. Within these two field pairs, AgriPV did not affect SOC uniformly rather system architecture appeared to reorganize functional carbon pools, with the Horticultural-PV associated with both lower bulk SOC and altered fraction-level partitioning, and the Crops-PV associated with fraction-level redistribution but near-conventional bulk SOC. Because each Agri-PV system was paired with a single control field and no pre-installation baseline data were available, inference is restricted to within-field-pair contrasts rather than to generalizable Agri-PV effects. The findings nonetheless indicate that bulk SOC monitoring alone may overlook early-stage shifts in carbon stabilization under Agri-PV, and that spatially explicit, fraction-resolved sampling is needed to support soil-carbon-informed evaluation of Agri-PV deployment. Acknowledgement This work was supported by the Bioeconomy Science Center (BioSC) project “SoilCE-PV”, funded by the Ministry of Culture and Science of North Rhine-Westphalia within the NRW Strategieprojekt BioSC (No. 005-20120107).
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