Tree species' effects on litter decomposition in a natural forest mosaic in Patagonia, Argentina

VIVANCO, L. Y A. T. AUSTIN

Montréal, Canada

Congreso; Ecological Society of America 90th Annual Meeting; 2005

Ecological Society of America

Understanding the effects of plant species on belowground processes is critical in order to evaluate the consequences of vegetation changes that are ocurring globally as a result of human activities. Many of the effects of vegetation on soil properties, particularly in long-lived ecosystems, develops over long periods of time. The existence of a natural undisturbed forest of mixed species allows to evaluate not only the effect of individual species but also the effect of plant species diversity on belowground proceses. We conducted an experiment to examine the effect of identity and diversity of tree species on litter decomposition in a mixed Nothofagus (southern beech) forest (40°S, 71°W), in Patagonia, Argentina. Our experimental plot was defined as the triangular area below the intersection of the canopies of three trees. The one-species treatment included triangles composed of three trees of a single species of N.dombeyi, N.obliqua, or N.nervosa, while the mixed-species triangles consisted in the intersections of the three different Nothofagus species. We placed litterbags with N.dombeyi, N.obliqua, N.nervosa litter and mixed litter of the three species within all these triangles and estimated the decomposition rate (k) after one year of incubation. Decomposition rates were significantly different between litter types (P<0.001). In the mixed-species triangles decomposition rate (yr-1) was 0.28 for N.dombeyi litter, 0.24 for N. obliqua litter, 0.16 for N.nervosa litter and 0.20 for mixed species litter. Triangle effects were also significant (P<0.01), with mixed species litter decomposing slower in N.nervosa triangles (0.17 yr-1) than in the other triangles (average 0.21 yr-1). Interaction between litter type x triangle were significant (P<0.001) showing specificity for litter decomposition, that is, decomposition proceeded faster when litter originated from the same species as the tree triangle. These results suggest that tree species, in addition to intrinsic differences in litter quality that affect decomposition, may create species-specific relationships with the decomposer community that result in faster in-situ decomposition.