LITTER FALL AND LITTER DECOMPOSITION IN A FOREST OF THE PARQUE-CHAQUENO-ARGENTINO

Amounts of litter produced by four species in a native forest in the P arque Chaqueno Argentino were registered monthly during a year. The sp ecies selected were Espina Corona (Gleditsia amorphoides (Griseb.) Tau b), Gauyabi (Patagonula americana L.), Mora (Chlorophora tinctoria (L. ) Gaud.) and Urunday (Astronium balansae Engl.). Espina Corona stands presented the highest contribution in total dry matter (13.5 kg ha(-1) ); following in importance is Mora with 11.3 kg ha(-1) Guayaibi with 9 .8 kg ha(-1) and Urunday with 8.8 kg ha(-1). Mora leaves accounted for 8.3% of its total litter followed by Espina Corona with 8.1%, Guayaib i with 3.8% and Urunday with 2.8%. The rate of decomposition leaf litt er was estimated according to the Olson model (single exponential). Th e species which presented the greatest average annual decomposition ra te was Mora with k = 0,28, significantly different (P less than or equ al to 0.05) to Espina Corona with k = 0.16, and significantly differen t (P less than or equal to 0.05) to the third group composed by Urunda y (k = 0.08) and Guayaibi (k = 0.04). Espina Corona, Guayaibi and Urun day experimental data suggest that the dynamics of litter decompositio n may be better described by a double exponential model with a fast de composable fraction and a more resistant one. Mora leaf litter followe d a different pattern, fitting to the single exponential model. From t he present study it may be concluded that a more active biogeochemical cycle can be established for Mora followed by Espina Corona, Urunday and Guayaibi, given that, a greater decomposition rate means less time of nutrient retention by the litter. (C) 1998 Elsevier Science B.V.