Spatial variability of soil CO2 emission in a sugarcane area characterized by secondary information

Abstract

Soil CO 2 emission (FCO2) is governed by the inherent properties of the soil, such as bulk density (BD). Mapping of FCO2 allows the evaluation and identification of areas with different accumulation potential of carbon. However, FCO2 mapping over larger areas is not feasible due to the period required for evaluation. This study aimed to assess the quality of FCO2 spatial estimates using values of BD as secondary information. FCO2 and BD were evaluated on a regular sampling grid of 60 m × 60 m comprising 141 points, which was established on a sugarcane area. Four scenarios were defined according to the proportion of the number of sampling points of FCO2 to those of BD. For these scenarios, 67 (F67), 87 (F87), 107 (F107) and 127 (F127) FCO2 sampling points were used in addition to 127 BD sampling points used as supplementary information. The use of additional information from the BD provided an increase in the accuracy of the estimates only in the F107, F67 and F87 scenarios, respectively. The F87 scenario, with the approximate ratio between the FCO2 and BD of 1.00:1.50, presented the best relative improvement in the quality of estimates, thereby indicating that the BD should be sampled at a density 1.5 time greater than that applied for the FCO2. This procedure avoided problems related to the high temporal variability associated with FCO2, which enabled the mapping of this variable to be elaborated in large areas.

Characterization of potential CO2 emissions in agricultural areas using magnetic susceptibility

“…The Gaussian model was the best fit to the fCO 2 × MS ADS cross semivariogram, while other values of MS SAND and MS CLAY were not correlated with fCO 2 , which is indicated by the absence of spatial dependence (pure nugget effect). However, even this study had shown spatial correlation between MS ADS and fCO 2 , isotropic models were found for all properties studied, which can be verified in studies conducted by Teixeira et al (2013) and Bicalho et al (2014). However, these results differ from studies conducted by Bahia et al (2014).…”

“…), and the high soil compaction represented by a bulk density average of 1.50 ± 0.01 g cm −3 as was noted by Teixeira et al (2013), could be an explanation for the low average emission. The fCO 2 coefficient of variation (CV) was 57 %, which is typical for this property (La Scala et al, 2000).…”

“…Thus, compartments with higher MS SAND and MS CLAY will show greater pore spaces, which might favor an easier gas exit, resulting in higher fCO 2 rates. Teixeira et al (2013), who studied spatial estimates of fCO 2 through soil density, found lower range values (18.95 to 21.37 m) and degrees of spatial dependence (0.07 to 0.17) for cross semivariograms of fCO 2 × soil density. This suggests that MS ADS may have greater potential for the production of spatial estimates of fCO 2 relative to soil bulk density, as well as being a technique which is faster, easy to handle and low-cost for the examination of larger field areas.…”

“…to evaluation (Teixeira et al, 2013). Larger scale eddy covariance and associated plume methodologies assume that the source strength is constant, a feature that has already been demonstrated to be heterogeneous.…”

24-h variation in soil respiration after a long dry season in a Sudano-Sahelian region

“…Several studies have been conducted on SR (Teixeira et al, 2013;Liang et al, 2014). In particular, they have shed light the diel variability of SR, i.e.…”