Field and microcosms decomposition dynamics of European beech leaf litter: Influence of climate, plant material and soil with focus on N and Mn

Leaf litter decomposition is one of the key phenomena in forest ecology. The patterns and trends of decomposition are related to the complex interaction of climate, soil biota and litter quality. The decay dynamics for the European beech are well-known for middle Europe, but lesser investigated in the Mediterranean area. In this study, we investigated mass loss and nutrient dynamics, especially nitrogen and manganese, in two Mediterranean beech forest located in northern and southern Italy. We used a litterbag experiment with leaves of each forest incubated in their own area of origin and vice versa. Moreover, we also used microcosms to follow early stages of decomposition under controlled conditions. The aims of this study were to investigate the role of climate and soil/litter quality at the different stages of decomposition and assess the response of diverse soils to changes in temperature and humidity. The results showed a faster field decomposition for the southern (warmer) site compared to the northern (colder) site, whereas under stable conditions in microcosms this trend reversed, implying different microbial adaptations to climate. Moreover, changes in temperature and humidity triggered complex microbial response during litter decay. Additionally, whereas our results showed trends of nitrogen concentration comparable to previous studies, the role of manganese in decomposition was very relevant even from the early stages. Noticeably, manganese was generally lower in both sites compared to middle Europe, but it was higher in the northern site than in the southern one. Manganese concentration, however, strongly increased for those leaves that had a lower initial content in all conditions, giving evidence of a strong mobilization of this nutrient and its essential role for decomposition in Mediterranean beech forests.