We studied a dystric, laxic Leptic Cambisol site (900 m2) stocked with Norway spruce in the Nationalpark Bayerischer Wald. Soil samples were taken at the nodes of a rectangular grid with distances of 5 m and a nested sampling scheme with a sampling distance of 0.2 m. Comparison of the HF-soluble and the non-soluble OC stocks showed that only the HF-soluble OC stock exhibited a spatial pattern. In contrast, the non-soluble OC stocks were characterized by a pure nugget effect. HF-soluble stocks of neutral sugars were significantly spatially correlated with the pH and the amount of oxalate extractable iron and aluminum oxides in both horizons. Comparison of the spatial variability of the different OC species of the HF-soluble OC showed an increasing spatial variability in the order aryl C < carboxyl C < alkyl C < O/N-alkyl C.
Our results indicate that the spatial variability of OC stocks is mainly due to the spatial variability of the HF-soluble OC stocks. Different spatial distribution patterns of different OC species indicate different stabilization mechanisms.