Carbon respiration of a forest soil and its relation to the litter fall

The objectives of this work were: a) to evaluate C respiration as an index of the microbiological activity in the soil with the different dominant species of the site, and b) to relate this variable with the weight loss of the leaves as a result of decomposition of the different species throughout the year. The study was conducted in a subtropical native forest (27-28° S lat., 56-60° W long.) located in Chaco, Argentina, during 1996/97. The arboreal species selected were: espina corona [ Gleditsia amorphoides (Griseb.) Taub], guayaibí ( Patagonula americana L.), mora [ Chlorophora tinctoria (L.) Gaud.] and urunday ( Astronium balansae Engl.). The litter bag technique was used in order to register the weight loss in the field of each selected species. Simultaneously a soil sample under each bag was taken to determine the C respiration. Every three months, at the beginning of each season, one bag per species and a sample of the soil under the bag were collected at random. In each case, the weight loss of the leaf material and the CO 2 released by the soil samples were determined. They had seasonal fluctuations with the highest values in autumn and spring and differed in the soil under the four species, being linked to the quality of the soil residue. Regarding the weight loss, it was determined to be greatest for the mora, followed by espina corona, urunday and guayaibí. Inasmuch as the species had different chemical compositions, the decomposition patterns were different. The C respiration correlated significantly with the leaf weight loss during the first trimester, as a consequence of the mineralization of the more labile compounds