Radicular Biomass and Organic Carbon of the Soil in Forest Formations in the Southern Amazonian Mesoregion

Abstract

The soils of the Amazon region, despite being under one of the densest forests in the world, are mostly characterized by the low availability of nutrients, with litter being the main route of nutrient entry. The objective of this study was to quantify the biomass of fine roots in the dry and rainy seasons of the year, including the organic carbon of the soil, and to compare the results in different study environments. The study was carried out in environments of native forest and reforestation aged over 20 years, located in the municipality of Humaitá – AM state. To assess the root biomass, collections were carried out in two periods of the year: dry and rainy seasons. In each of the study areas, five trenches, 0.40 m deep by 0.40 m wide, were dug manually at depths of 0-5, 5-15, and 15-30 cm. For the organic carbon analysis, soil samples were collected in the form of clods at the same depths. The production of root biomass in the native forest environment occurred more intensely in the rainy season, reaching values of 8.19 t. ha-1, greater than 3.57 t. ha-1 found in reforestation. The density as a function of the soil volume showed that the highest concentration is found in the first 5 centimeters of depth, differing significantly in the 5-15 and 15-30 cm layers for native forest area. The organic carbon of the soil showed significance between the dry and rainy seasons for the natural forest environments and reforestation with genipap.

Accumulation and decomposition of cultural residues of Theobroma grandiflorum, Paullinia cupana, Bixa orellana and forest in the southern region of Amazonas

“…Regarding the decomposition of litter in the Amazon, works developed by Freire et al (2020) in studies of decomposition in 'terra firme' environments in Western Amazon; Pereira et al (2016) evaluating litter and nutrients in 'terra firme' tropical forest in the Amazon basin, as well as Bello et al (2021) who studied decomposition in reforestation and forest systems found that the leaf fraction contributes the most to returning nutrients to the soil. For Tonin et al (2017) the climatic components (high temperature and high atmospheric humidity) of the Amazon assume a determining role in the decomposition of the litter, enabling the development of vegetation without Fertilization and liming were not performed on the areas during the entire growing season.…”