Aporte de serrapilheira, fauna edáfica e taxa de decomposição em áreas de floresta secundária no Município de Pinheiral, RJ

Abstract

This work had as objective to evaluate the port of the litter material, the soil fauna and the decomposition rate of the litter in two semidecidual estacional forest areas, on secondary succession, being these: Forest of Medium Status (FMS) and Forest of Advanced Status (FAS), located in Pinheiral county, Rio de Janeiro, Brazil. For evaluation of it, arrives in port it of litter had been installed 20 conical collectors in the beginning of the 1998 year of random form inside of the two areas. The plant material was collected seasonally until of March, 2002. After the collection the material was dried in a oven (65°C ± 5) and separated in leaves, branches, flowers, fruits, rinds and others. After that, the material was triturated and it was made the quantification of the macro and micronutrients. The soil fauna was collected with the aid of a metallic collector in number of 10 samples for area. The extraction of the soil and the litter organisms was made by Berlese-Tülgreen funnels, per 15 days. The animals then had been stored in glasses contend salicylic acid, and later separated and identified. The evaluation of the decomposition rate was made with litter bags, that had been made use random form on the forest floor. Three composed evaluations with 3 repetitions had been carried through. After collected, them to litter bags they had been led to the laboratory dried in an oven of forced air circulation (65°C ± 5) and weighed in 0.01 g analytical scale of precision. The FMS area presented greater variation with relation to it arrives in port of litter former material (LFM) of that the FAS area, to the long one of the study. In the FMS area the biggest value of 13.14 ton ha-1 arrived in port LFM per year and the 9.40 ton ha-1 minor per year. In the FAS area the biggest value was of 10.94 ton ha-1 per year and the 10.72 ton ha-1 was the minest of the year. The occurrence of the El Niño phenomenon in the summers of 2000 and 2002, could has had an influenced in the depositional dynamics of the two areas, being that in the FMS area this influence was stronger. Differences between areas and stations were not observed in relation of the nutrients chemical composition in the arrived port material (LFM). The 6 taxonomic groups of bigger occurrence in the study, amongst the 34 identified groups, had been Formicidae (40,12 %), Homoptera (17,43 %), Diptera (17,20 %), Coleoptera (6,70 %), Trichoptera (3,29 %), Hymenoptera (3,16 %), that together they add 87,9 % of the total number of collected individuals. These data point to a low speed of the litter degradation which could be explained by the small ratios. During the study it was observed bigger presence of the individuals in the litter in detriment to the soil in the FMS area. The evaluations of the decomposition rate indicate that this process occurs in a slow way, being observed values of remaining mass between 83 % in the FMS area and 58 % in the FAS area, for the first evaluation. In the second evaluation the remaining values of mass had been lesser, 61 % for FMS area and 65 % for the FAS area. For the third evaluation the percentile minors of remaining material 37 % in the FMS area and 32 % in the FAS area had been observed. In all the evaluations the exponential function was the one that better described the decomposition speed, being that it was observed the best correlations between the variable in the last evaluation.