Decomposition and nutrient dynamic of leaf litter and roots from palatable and unpalatable grasses in a semi-arid grassland

A field experiment was conducted in a temperate semi-arid grassland of central Argentina to test the hypothesis that decomposition of and nutrient release from leaf litter and roots are faster in Poa ligularis and Stipa clarazii (high-nutrient, palatable grasses) than in S. tenuissima (low-nutrient, unpalatable grass). Leaf litter and roots of each species were incubated in 0.35 mm mesh bags for 21 months at their source sites. Leaf litter decomposition was faster (P < 0.01) in the palatable than in the unpalatable species and, on average, root decomposition was faster (P < 0.01) in S. clarazii than in P. ligularis and S. tenuissima. At the end of the incubation period nitrogen (N) and phosphorus (P) release from the leaf litter was higher (P < 0.01) in the palatable than in the unpalatable species, whereas there was no difference (P > 0.05) among species in N and P release from the roots. The results on leaf litter support the hypothesis that decomposition and nutrient release are faster in the palatable than in the unpalatable grasses, whereas the results on roots did not support this hypothesis. Moreover, since below-ground production represents the major input of new soil organic matter in the system, the N and P dynamics of roots suggest a low capacity to immobilize nutrients in both palatable and unpalatable grasses. (C) 2001 Elsevier Science B.V. All rights reserved.