Physical fractions of organic matter and mineralizable soil carbon in forest fragments of the Atlantic Forest

Abstract

This study determined the physical granulometric fractionation evaluated the mineralizable carbon within and around forest fragments of the Atlantic Forest biome located in the state of Paraná. Soil samples were collected at three three internal points of the fragments: the edge (E), the half radius (HR) and the center (CF); and one point in no-tillage system (NTS) areas around the fragments, in four replicates. The contents of total organic carbon (TOC), particulate fraction carbon (C-POM) and mineral fraction (C-MOM) were determined, and the %POM and %MOM and the stocks of POM (StockPOM) and MOM (StockMOM) were calculated, in addition to the indices: carbon stock index (CSI), lability (L), lability index (LI) and carbon management index (CMI), also evaluating CO2 emission, daily and accumulated. The highest TOC levels were observed in the CF point. The highest C-POM contents were observed in the E and CF points of fragment 1, in the CF point of fragment 2, and the highest C-MOM contents were expressed in the CF points of both fragments. CMI showed a distinct pattern among the fragments. The NTS areas showed lower C-CO2 emissions, with 39.8% and 28.3% less total emission compared to CF. The results of physical granulometric fractionation show the CF point favors the quality of SOM and the mineralizable carbon analysis indicated that the conversion of native areas into NTS compromises soil microbial activity.

Influence of land use and occupation on the chemical and physical fractions of organic matter in cultivated and native areas in the Atlantic Forest biome

“…L is considered an excellent indicator of soil quality, being obtained through the ratio between POM and MOM fractions, and values closer to 1.00 suggest balance between these fractions (Benbi et al, 2015). Similar results were obtained by Schiavo et al (2011) in the state of Mato Grosso do Sul and Rosset et al (2019) and Ozório et al (2020) in the state of Paraná, both comparing managed and native areas. Except for the PP area, it was observed that for the other areas evaluated, the L of the SOM decreased according to the depth, especially in the area of NTS (Table 4).…”

“…From the analyses of C of FA, HA and HUM, the values of alkaline extract (AE) (AE = HA+FA) and the ratios of HA/FA and AE/HUM were calculated to verify the humification processes of the SOM. In addition, the C stocks of the humic fractions were calculated according to the equivalent mass method (Reis et al, 2018;Ozório et al, 2020). The physicalgranulometric fractions of the MOS were determined according to the method of Cambardella and Elliott (1992), obtaining the particulate organic matter (POM) and mineral organic matter (C-MOM).…”

“…The physicalgranulometric fractions of the MOS were determined according to the method of Cambardella and Elliott (1992), obtaining the particulate organic matter (POM) and mineral organic matter (C-MOM). Subsequently, C stocks of particulate organic matter (StockC-POM) and mineral organic matter (StockC-MOM) were calculated following the equivalent mass method (Reis et al, 2018;Ozório et al, 2020). Then, the following indices were calculated to evaluate the quality of the soil organic fraction: carbon stock index (CSI), lability of SOM (L), lability index (LI) and carbon management index (CMI) according to Blair et al (1995).…”

“…The NTS area had intermediate levels in the layers of 0.00-0.05 m and 0.05-0.10 m, with 9.26 g kg -1 and 8.51 g kg -1 , respectively. The highest levels of C-MOM (Table 4) are mainly related to the higher levels of TOC in these areas (Table 3), added to non-revolving, and to the contribution of POM stabilization over time, where the labile fraction of C becomes the most recalcitrant fraction, with consequent stabilization of the SOM over time (Ozório et al, 2020).…”

Impact of Different Use Systems on Total and Mineralizable Organic Carbon in a Sandy Soil

“…The Sd was determined by the methodology described by Claessen (1997). The TOC content was determined by oxidation of organic matter by potassium dichromate in a sulfuric medium under heating and titrated with ammoniacal ferrous sulfate (Yeomans;Bremner, 1988), with subsequent calculation of the StockC according to the equivalent mass method (Reis et al, 2018;Ozório et al, 2020).…”