Characterization of Litter and Topsoil Under Different Vegetation Cover by Using a Chemometric Approach

Leaf litter conservation practices in forests can contribute to increasing CO2 storage in natural soils as organic matter; however, this process depends on the type of vegetation cover. This study, using different approaches, aimed to assess this process starting from the characteristics of three different types of litters and topsoil (0–5 cm depth) originating from chestnut, beech, and pine in various forest locations within the territory of Edolo (Camonica Valley, Central Italian Alps). Both labile (DOM) and recalcitrant (ROM) organic matter fractions were considered. Microbial degradation activity was strongly influenced by DOM (DOM vs. Respiration mg CO2 g−1 dry matter: r = 0.96), and NMR spectroscopy showed that aromatic C and polymethylene C in long-chain aliphatic structures (e.g., lipids, cutin) became more evident from litters to topsoils due to a concentration effect. Finally, chemometric elaboration of quantitative and qualitative data identified two principal component (PC) profiles, explaining 88% of the total variance, in which litter and the topsoil samples were spatially separated, indicating that significant changes occurred during the decomposition process. An Evolution Index (EI) calculated highlighted greater changes for chestnut (0.90) followed by pine (0.60) and beech (0.48), in agreement with chemical (degradation rates of 14.21%, 49.11%, and 48% for beech, chestnut, and pine litter, respectively) and spectroscopic data. Beech litter appears to be more efficient at conserving organic carbon. These findings underscore the importance of understanding litter characteristics for forest management, suggesting which species are most effective in promoting soil carbon storage.