Spatial variability structure of soil CO2 emission and soil attributes in a sugarcane area

Abstract

Soil CO2 emission (FCO2) is influenced by chemical, physical and biological factors that affect the production of CO2 in the soil and its transport to the atmosphere. FCO2 varies in time and space depending on environmental conditions, including the management of the agricultural area. The aim of this study was to investigate the spatial variability structure of FCO2 and soil attributes in a mechanically harvested sugarcane area (green harvest) using fractal dimension (DF) derived from isotropic variograms at different scales (fractograms). FCO2 showed an overall average of 1.51μmol CO2m−2s−1 and correlated significantly (P<0.05) with soil physical attributes, such as soil bulk density, air-filled pore space, macroporosity and microporosity. Topologically significant DF values were obtained from the characterization of FCO2 at medium and large scales (above 20m), with values of 2.92 and 2.90, respectively. The variations in DF with scales indicate that the spatial variability structure of FCO2 was similar to that observed for soil temperature and total pore volume and was the inverse of that observed for other soil attributes, such as soil moisture, soil bulk density, microporosity, air-filled pore space, silt and clay content, pH, available phosphorus and the sum of bases. Thus, the spatial variability structure of FCO2 presented a significant relationship with the spatial variability structure for most soil attributes, indicating the possibility of using fractograms as a tool to better describe the spatial dependence of variables along the scale.