Wild boar grubbing affects soil carbon quantity and fractions under native, reforested and planted vegetation

The wild boar (Sus scrofa L.) grazing represents one of the main disturb for soil and plants in Mediterranean ecosystems. The wild boar grubbing activity of soil mixing is recognizable by disturbance of topsoil layer and modification in main characteristics as decomposition rates, hydrological connectivity, species richness and diversity. These effects depend on grazing pressure and plant cover that shows a different ability to adapt and recover. For these reasons, to shed light on the impact of wild boar activity on soil quality and C dynamics in different Mediterranean ecosystems, i.e. olive grove, managed pine forest, low and high maquis ranging from coastal areas to hilly grounds, were studied. We evaluated the physical, chemical and biological characteristics of soils under different vegetation, with and without the impact of wild boar in “Cilento, Vallo di Diano e Alburni” National Park (Southern Italy). We focused on soil C amount, carbon compounds (carboxyl-C, phenol-C, aryl-C, O-alkyl-C, methoxyl-C, and alkyl-C) and specific labile C fractions (Soluble C, Microbial and Fungal C). The results showed that wild boar overgrazing induced an increase in the soil C and N content and a significant reduction in its soluble fraction, regardless of plant cover. The maquis grubbed soils showed an increase in microbial respiration and mineralisation rate related to the improvement of resource availability and soil aeration stimulating the microbial community, and in particular the bacterial component. In the grubbed soil of pine forests, bacterial biomass as well as the microbial respiration and mineralization seemed to be inhibited. Similarly, a reduced resource utilization of microbial community was found in the grubbed soil of olive grove where an increase in microbial carbon was also detected. The effects of grubbing activities on edaphic com- munity in pine forest and olive grove soils likely revealed a previous stress condition.