Biochar effects on early decomposition of standard litter in a European beech forest (northern Italy)

The release of biochar (BC) on forest soil is a strategy aimed at increasing carbon reserves and forest productivity. The effect of BC amendments on the decomposition of different quality litter is, however, poorly understood. With this study we investigate the effects of wood-derived BC applications on early decomposition in a European beech (Fagus sylvatica L.) forest through the burial of standard material, i.e. green tea and rooibos tea (high- and low-quality litter surrogates, respectively). Two main questions were addressed: 1) Do BC applications influence the decomposition of high- and low-quality standard litter and, if so, in what way? and 2) Does this effect (if measurable) depend on where the sample is placed with respect to the BC application layer? To test BC amendment effects, four application percentages were employed (0, 10, 20 and 100 %), after which standard litter mass loss was recorded. To investigate the effects of sample position, only three BC application percentages were used (0, 10 and 20 %), with teabags buried at three different depths - within the BC amended layer, between this layer and the unamended soil, and below the latter. Results show that early decomposition of high-quality standard litter was not influenced by BC applications, while a significant reduction in mass loss of low-quality standard litter was observed when the percentage of BC application was higher, specifically of litter within the 20 % and 100 % BC amended layers. Decomposition was also affected by sample position relative to the BC layer, exhibiting higher levels of mass loss when samples were placed within the BC amended layer. Overall, BC applications on beech forest soils not only seem to produce negligible effects on the early decomposition rate of high-quality standard litter, but such applications also seem to have the ability to reduce carbon loss following plant material degradation.