Land use legacy footprint in Mediterranean forest soils: An infrared spectroscopy approach

Chemical properties of forest soils can strongly influence this compartment vulnerability to climate change effects. Past human activities can play a major role in structuring soil chemical properties. In the Mediterranean region, abandonment of terrace agriculture since 1860 induced the coexistence of forests with different ages. Here, soil chemical signature (SCS) was compared between very recent, recent and ancient forests using Fourier Transform InfraRed (FTIR) spectroscopy and other chemical properties (total C and N, CaCO 3 percentages). Land Use Legacy (LUL) effects were analysed depending on soil depths and on contrasted climate conditions (humid vs subhumid Mediterranean climates). Statistic treatments, Linear Mixed-Effect and Anova COMmon DIMension models, were used to highlight the influence of depth’s soil, climate and LUL effects. Interestingly, the soil depth did not influence LUL effect on soil spectra. The effect of climate, LUL and their interactions were observed on the SCS. Higher available N was observed in soils from ancient forests than in soils from very recent forests. Moreover, mineral fraction discriminated soils with different LUL (very recent vs recent and ancient forests) and this depended on climate. Under subhumid climate, soils from very recent forests were indeed negatively correlated with the mineral fraction, while under humid climate, they were positively correlated to it. Finally, a recovery of soils chemical properties was observed in recent forests under humid climate, while under subhumid climate, SCS of post agricultural forests was different from that of ancient forests.