Dissertations and Theses

Structure of spatial and temporal variability of CO2 emission and soil attributes characterized by fractal dimension in sugarcane area.

Author: Elton da Silva Bicalho

Keywords: anisotropy, fractogram, isotropy, soil respiration.

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Summary

The soil CO2 emission (FCO2) is influenced by physical, chemical and biological processes that affect the production of CO2 in the soil and its transport to the atmosphere, varying in time and space depending on the environmental conditions and the management agricultural area. The objective of this study was to investigate the correlation between the patterns of spatial and temporal variability of FCO2 and soil attributes in the sugarcane area under a cane management system, using fractal dimension (DF), derived from isotropic and anisotropic variograms at different spatial scales. The experimental area consisted of a regular 60 × 60 m mesh containing 141 spaced points at minimum distances ranging from 0.5 to 10 m. The CO2 emission, temperature and soil moisture were evaluated during 7 days, and the physical and chemical attributes of the soil were determined in a depth of 0.0 to 0.1 m. The average FCO2 ranged from 1.26 to 1.77 μmol m-2 s-1 over the days, with temporal dependence on the mean and long scales, in ranges over 20 m. In spite of the isotropic behavior observed for FCO2, its DF values, calculated for different directions, showed greater temporal variability in the direction parallel to the planting line, indicating the influence of the management practices adopted in the area. The spatial variability of FCO2 was better evidenced in the mean (20 to 30 m) and long (40 to 60 m) scales, with its structure of variability, characterized by the fractogram, correlating significantly with the majority of soil attributes and presenting behavior similar to that observed for soil temperature and total pore volume. In addition, the fractograms allowed to observe the spatial and temporal dependence behavior of FCO2 and other soil attributes along the scales, directions and days of study, as well as their homogeneity and heterogeneity patterns.