Estudo da serapilheira, biomassa radicular e variáveis do solo: uma abordagem socioambiental na Amazônia

Abstract

The production of burlap is essential for the permanence and continuity of the forests. The present study sought to quantify the production of serapilheira, the rate of decomposition, the root biomass and soil variables in native forest environments and reforestation in the Southern mesoregion amazonense. For the evaluation of the production of burlap, ten tapered collectors were randomly installed in each study area. The collections were made monthly in the period from April 2018 to March 2019. After each collection was carried out the sorting of the leaves, branches, reproductive material (flowers, seeds and fruits) and miscellaneous (rest of the material), were placed in air circulation greenhouse at 65 C, for 48 hours, then weighed on a precision balance for the evaluation of the contribution of each fraction. The estimation of the rate of decomposition of the burlap was made by the analysis of mass loss usingif litter bags, being randomly distributed 64 litter bags with 10 grams of foliar material that predominated in the composition of the burlap in each study area. For the assessment of the root biomass (≤ 2 mm), the trenches were opened, where a distance was adopted from the base of the plant of approximately 80 m, collecting samples with the aid of a steel cylinder 10 cm high and 7 cm diameter, at depths of 0.00-0.05, 0.05-0.15 and 0.15-0.30 cm, thus constituting three repetitions per depth per area. The samples were subjected to manual washing in running water until total removal of the soil, using a set of sieves overlapped with meshes of 2mm, 1mm and 500 micrometers respectively, after effective root washing (≤ 2 mm), they were taken into circulation for 72 hours. For soil analysis deformed and undefended soil samples were collected at three different depths, 0.00-0.05 cm; 0.05-0.15 cm and 0.15-0.30 cm; pH and organic carbon analyses were performed. The production of serapilheira did not present any significant difference between the study areas. Among the fractions of the serapilheira, the leaf fraction contributed the most, reaching the highest percentage in the year of 72.1% for the environment of reforestation with teak (Tectona grandis) RET. The decomposition of the burlap occurred more quickly (0,0025 g-1day) for the reforestation environment with jenipapo (Genipa americana L.) REJ, and it took 277,26 days to decompose half of the foliar material. The greatest quantity of biomass of fine roots, adding up the three depths of the soil was found in the environments of native forest (FN), with 8191,50 kg ha-1, corresponding to the rainy period, decreasing as the depth increases, with higher found value of root density of 8,1997 g-dm-3, in the layer of 0-5 cm, for (FN), corresponding to the rainy period. The soil’s organic carbon (COS) ranged from 19.47 g kg-1 (FN) to 14.62 g kg-1 (RET) for collection in January.