CONICET | Buscador de Institutos y Recursos Humanos

Litter decomposition has been widely studied for individual plant species, and has contributed to our understanding of the control of different litter qualities on carbon and nutrient cycling in forest ecosystems. However, in most natural ecosystems, the integrated effect of litterfall from different species generates litter mixtures when reaching the soil surface. The objectives of the present study were to determine the effects of 1) mixing litter from different assemblages of litter types and 2) to evaluate the decomposition of individual species within a mixture. We conducted our experiment in a Nothofagus mixed forest in Patagonia, Argentina. We collected leaf litter from the four dominant tree species: Nothofagus dombeyi, N. nervosa, N. obliqua and N. pumilio. Litterbags containing all combinations of 1, 2, 3, or 4 different species (15 treatments) were placed randomly in five blocks in the forest floor. After one year, species decomposing alone significantly differed in their decomposition rate (P<0.05), with N. nervosa been the slowest litter (0.20 yr-1) and N. pumilio the fastest (0.39 yr-1). We also found that litter in mixtures decomposed significantly slower after 270 days (P<0.05) of incubation than was predicted based on the average decomposition of the component species decomposing alone. Furthermore, N. nervosa litter decomposed significantly slower when it is surrounded by other species, while N. dombeyi did not respond to mixture effects. Finally, litter richness did not have an effect on decomposition. Our results suggest that litter decomposition of mixture of species could not be predicted based on our knowledge of individual species? decomposition, as a given litter species could significantly change in the presence of litter from other co-occurring species.