Labile forms of carbon and soil aggregates

Abstract

Tobiašová E., Barančíková G., Gömöryová E., Makovníková J., Skalský R., Halas J., Koco Š., Tarasovičová Z., Takáč J., Špaňo M. Soil organic matter (SOM) plays an important role in the soil aggregation and vice versa, its incorporation into the soil aggregates is one of the mechanisms of soil organic carbon stabilization. In this study the influence of labile carbon fractions on the fractions of dry-sieved (DSA) and wet-sieved (WSA) macro-aggregates and the relationship between the content of total organic carbon (TOC) and its labile fractions in the soil and in the fractions of macro-aggregates were determined. The experiment included six soil types (Eutric Fluvisol, Mollic Fluvisol, Haplic Chernozem, Haplic Luvisol, Eutric Cambisol, Rendzic Leptosol) in four ecosystems (forest, meadow, urban, and agro-ecosystem). In the case of DSA, the contents of labile fractions of carbon, in particular cold water extractable organic carbon (CWEOC) and hot water extractable organic carbon (HWEOC), had a higher impact on the proportions of larger fractions of macro-aggregates (3-7 mm), while in the case of WSA, the impact of labile fractions of carbon, mainly labile carbon (C L ) oxidizable with KMnO 4 , was higher on the proportions of smaller fractions of aggregates (0.25-1 mm). The WSA size fraction of 0.5-1 mm seems an important indicator of changes in the ecosystems and its amounts were in a negative correlation with C L (r = -0.317; P < 0.05) and HWEOC (r = -0.356; P < 0.05). In the WSA and DSA size fractions 0.5-1 mm, the highest variability in the contents of TOC and C L was recorded in the forest ecosystem > meadow ecosystem > urban ecosystem > agro-ecosystem. The higher were the inputs of organic substances into the soil, the greater was the variability in their incorporation into the soil aggregates. The influence of the content of TOC and its labile forms on their contents in the DSA and WSA was different, and the contents of TOC and C L in the aggregates were more significantly affected by the C L content than by water soluble carbon. In the case of WSA fractions, their carbon content was more affected in the 1-2 mm than in 0.5-1 mm fraction.

Effects of Biochar on Soil Aggregation and Distribution of Organic Carbon Fractions in Aggregates

“…Therefore, stable MaAs would also contain some additional organic matter (Figure 6d). Tobiašová et al [35] indicated the similar outcomes with our results by evaluating LOC (WEOC and ROC) in the aggregate with different sizes. Based on our results, the RSOC seems to be transformed into MBC fraction obviously in MaAs and MeAs, 2021, 9, 1431 which implied that the susceptible fresh OM might be occluded during formation process of larger aggregates.…”

Soil microbial biomass and oxy-hydroxides contribute to aggregate stability and size distribution under different land uses in the Central Andes

“…These increases in HWC, microbial biomass and respiration potential were correlated to the soil organic matter content, which was 37% higher under Eucalyptus compared to potato and fallow land uses (Coca-Salazar et al 2021a). Moreover, the absence of soil physical perturbation (Eucalyptus soils are not managed after seedling plantation) could also favour the formation of new aggregates and the binding of the already existing free macroaggregates, microaggregates and silt + clay (Tisdall and Oades 1982;Tobiašová et al 2016). The observed higher soil aggregate stability in water under Eucalyptus is also generally explained by higher soil C content (Wei et al 2006) and a more active microbial community, which is considered to be the consequence of successful afforestation (Caravaca et al 2002).…”

“…Understanding the link between soil C, microorganisms and soil aggregates under different land uses is essential to shed light on the consequences of modifications in soil structure for soil organic matter dynamics and the potential resulting effects on nutrient availability and biogeochemical cycles. Indeed, increased relative abundance of mega-and macroaggregates indicate higher labile carbon content, soil porosity, oxygen diffusion, water infiltration, root penetration and decreased risk of erosion (Whalen and Chang 2002;Pagliai et al 2004;Tobiašová et al 2016). Higher abundance of mega-and macroaggregates is thus generally linked to increased rates of biological processes and higher nutrient availability (Cai et al 2016).…”

“…Different land uses strongly influence both soil organic C and microbial activity (Li et al 2020;Vazquez et al 2020). For example, in agricultural land uses, tillage may lead to the breakdown of macro-and megaaggregates (Whalen and Chang 2002;Tobiašová et al 2016), and increased decomposition, leading to a depletion of labile C with a subsequent decrease in microbial biomass and microbial activity (e.g. C respiration and N mineralisation).…”

Long-term Use of Balanced and Integrated Nutrient Management Improved Soil Aggregation and Carbon Stabilization in a Maize-wheat Cropping Sequence

“…Tobiašová [46] similarly conducted a study on labile carbon content in different aggregate sizes and results revealed that macro-aggregates having size 0.25-1 mm had a maximum fraction of labile C especially labile C oxidizable with KMnO4. The aggregate fraction of size 0.5-1 mm was in a negative correlation with labile C fraction and appears to be a crucial indicator of changes in the ecosystems.…”