Litter decomposition at two forest sites in the Italian Alps: a field study

We studied in situ litter decomposition at a subalpine (1737 ma.s.l.) and a submontane (570 m) long-term monitoring forest site in the Italian Alps in the period 2000-2003 and 10 years later (2010-2013). Litter bags filled with site-specific (pine needles) and standard (cellulose) litter were exposed in autumn 2000 and 2010 on the soil surface. Cellulose was additionally exposed in litter bags buried at 2 cm soil depth to monitor the effect of soil microclimate. Decomposition rates were calculated after 1, 2, and 3 years of exposition from litter mass loss. Mass loss of litter exposed on soil surface was significantly affected by the site (altitude) and the litter type, while the decade of exposition (2000-2003, 2010-2013) had no significant impact. Litter decomposition was significantly lower at the site at the higher altitude, which was related to the colder climate, and pine needles were decomposed to a significantly lower extent than surface-exposed cellulose. Decomposition of cellulose buried in soil was neither influenced by the decade nor by the site. Cellulose mass loss was higher in soil than on soil surface, which is attributed to the favorable soil microclimate conditions in soil. The better adaptation of the soil population at the submontane site compared to that at the site at the higher altitude for accelerated degradation of easily decomposable compounds (cellulose) was confirmed by a laboratory study.