Behind the stones - Soil memories of Medieval terraces in Monti Lucretili, Central Italy

Agricultural terraces are labor-intensive to build and maintain but often serve as key productive areas due to their potential for irrigation and enhanced soil depth in challenging terrains worldwide. However, their cultural and historical significance as records of past events is often overlooked, despite historical terraces being potential hotspots of soil memory because of intensive human-environment interactions.

The terraced landscape of Monti Lucretili in Central Italy was selected to apply the soil memory framework to agricultural terraces. This area has long been used for pastoral and agricultural practices and is likely culturally connected to the Medieval castle of Montefalco. A multi-scalar approach is being applied, from landscape to molecular level, through a set of high-resolution techniques. Six limestone-wall bench terrace soils were described in the field (WRB, 2022), with undisturbed blocks collected for soil micromorphology and bulk samples for phytoliths, geochemistry, lipids, and sedaDNA analyses. For dating the features, bulk sediment samples were collected and subjected to optically stimulated luminescence (OSL) profiling in the field using a portable luminescence reader, and subsequent OSL dating in the laboratory.

Preliminary results suggest that five of the studied terrace walls in Monti Lucretili were constructed near karstic dissolution holes where vertic and proto-vertic soil properties are buried by the wall stones and younger terrace sediments. In contrast, the closest terrace to the castle of Montefalco lacks buried clayey horizons, with the karstic hole filled with chert artifacts. This possibly indicates early land management strategies that eroded the paleo-Vertisol. The terrace soils often include gravels and rocks from both slope processes and artifacts (mainly cherts and bricks). Vitric properties are also present, along with poorly-weathered pyroxenes, indicating volcanic deposits stratigraphically correlated to the first stages of the terrace construction.

Furthermore, finer stratifications and bioturbation (with crumb structures) in the superficial horizons are identified, which might indicate the period of terrace abandonment. The OSL profiling in the field showed net signal intensities displaying similar trends for each terrace soil, with normal signal-depth progression. This indicates the gradual burying of the materials behind the terrace walls and might be related to minimum historical plowing.