Relações entre os atributos do solo e as frações orgânicas do carbono em ambientes de pastagens e floresta no norte de Rondônia

Abstract

The rate of change in soil carbon stocks of large areas of forests will suffer from future transformations in vegetation cover or from disorderly land use, as well as climate change and CO2 increases. As for social and environmental importance, carbon and its dynamics are directly involved in the 0.1% of greenhouse gases present in the atmosphere, which despite being low are quite harmful, justifying its study. Thus, this work aims to study the dynamics and assimilation of carbon and its impacts on environmental conservation in the soils of the Amazon region, and to analyze the dynamics of the spatial distribution of the different forms of carbon present in different environments, pastures and forest. The study was carried out in the municipality of Porto Velho, in the União Bandeirantes- Rondônia district, under the geographical coordinates latitude 9º 45' 32'' S and longitude 64º 31' 39'' W. A grid of 90x50 m was established with regular spacing of 10 m between sampling points, within the areas of Mombasa, brachiaria and forest The soils were sampled at the grid crossing points, under depths of 0.00-0.10 m and 0.10-0.20 m, making up a total of 60 sample points in each area in the form of a lump and a volumetric ring, totaling 120 samples per area and 360 samples in all. From the volumetric ring and the lump, the physical and chemical attributes and the organic fractions of carbon were determined. For the granulometric fractionation of organic carbon (CO), approximately 20g of soil and 60 mL of sodium hexametaphosphate solution (5g L-1) were used to determine the carbon associated with minerals (COam) and particulate organic carbon (COp). After obtaining and processing the data, they were first analyzed using descriptive statistics and the means were compared using the Tukey test at 5% probability to verify the differences and similarities between environments. For the behavioral study of the spatial distribution of carbon forms in the soil, a geostatistical analysis was performed. Based on the geostatistical parameters, the kriging maps of the variables were generated, and to verify the intra and inter dependency relationships of the attributes between the environments, principal component analyzes were performed, arising from the multivariate and geostatistical analysis. Geostatistics proved that the substitution of the forest area for the management area associated with the relief caused changes in the dynamics of the distribution and behavior of soil carbon variables. For the environments that were studied, it was observed that the brachiaria did not have as much differentiation in relation to the forest area, being less influenced in comparison to the mombasa pasture. The values of particulate organic carbon (COp) with greater focus were found in the forest area, where it increases in depth. There is a relationship between organic carbon (CO) and concentrations of organic carbon associated with minerals (COam) in a way that they are related to the increase or decrease of these rates