Changes of the organic carbon content and stability of soil aggregates affected by soil bacterial community after afforestation

Effects of land use change on organic carbon dynamics associated with soil aggregate fractions on the Loess Plateau, China

“…Our calculations showed that the increases in OC stock within mesoaggregate fractions were primarily due to increases in the proportions of these fractions but less to the changes in mesoaggregate‐associated OC content (Figure ). Prior works in the same area reported a relatively higher recovery of soil structure and faster increase in larger aggregate proportions after afforestation (Wei, Li, et al, ; Zhao et al, ), indicating that OC accumulation relies on a well‐developed soil structure. Six et al () also further demonstrated that the enhancement of larger aggregates acts as a ‘wet nurse’ in the formation of microaggregates and corresponding accumulation of OC within them.…”

“…In the present study, we observed significant increases in the proportions of macroaggregates (>2 mm) and mesoaggregates (2–0.25 mm) and in the values of MWD and GMD after the conversion of FL into AL42yr, CK42yr, and RP42yr (Table , Figure ), indicating that revegetation of abandoned FL improves soil structure, that is because tillage disrupts aggregates by bringing subsurface soil to the surface where it is more exposed not only to dry–wet cycles but also to freeze–thaw cycles and to the mechanical shock of rainfall (Beare, Coleman, Pohlad, & Wright, ; Denef, Six, Paustian, & Merckx, ). On the contrary, when tillage is suppressed in FL, plant residues accumulate on the surface as mulch (Han et al, ; Six et al, ), resulting in an accrual of SOM (Cheng, Xiang, Xue, An, & Darboux, ; Razafimbelo et al, ), and the increase in relative dominance of fungi in soil may promote greater enmeshment of soil particles by fungal hypha and the formation of aggregates (Six et al, ; Tisdall, Smith, & Rengasamy, ; Zhao et al, ). Thus, soils excluded from disturbance are prone to physical restoration, which increases the reaggregation of around the SOM (Blanco‐Canqui & Lal, ).…”

“…Moreover, the F1 and F2 values (Figure 3) is more exposed not only to dry-wet cycles but also to freeze-thaw cycles and to the mechanical shock of rainfall (Beare, Coleman, Pohlad, & Wright, 1993;Denef, Six, Paustian, & Merckx, 2001). On the contrary, when tillage is suppressed in FL, plant residues accumulate on the surface as mulch Six et al, 2000), resulting in an accrual of SOM (Cheng, Xiang, Xue, An, & Darboux, 2015;Razafimbelo et al, 2008), and the increase in relative dominance of fungi in soil may promote greater enmeshment of soil particles by fungal hypha and the formation of aggregates Tisdall, Smith, & Rengasamy, 1997;Zhao et al, 2018). Thus, soils excluded from disturbance are prone to physical restoration, which increases the reaggregation of around the SOM (Blanco-Canqui & Lal, 2004 In our study, the favorable effects of revegetation on soil structure improvement varied with soil depth (Table 3 and Figure 1).…”

“…Because the uppermost layer receives the input of fresh organic matter directly, which stimulates microbial activities thereby generating more organic by-products, such as polysaccharides, that play an important role in aggregates' formation and structure stability (Briedis et al, 2012; Garcia-Franco, FIGURE 2 Correlations between the content and stock of organic carbon associated with aggregates, proportion of aggregates, and organic carbon stock in bulk soils Martinez-Mena, Goberna, & Albaladejo, 2015;Martins, Corá, Jorge, & Marcelo, 2009;Six et al, 2004). In addition, the effect of soil structure improvement depends on land use type (Gelaw et al, 2015;Zhao et al, 2018). In our study, the highest macroaggregate and mesoaggregate amounts and MWD and GMD values were observed under RP42yr with a lower C:N ratio of plant residues (Table S4),…”

Effect of Tillage Treatment on the Diversity of Soil Arbuscular Mycorrhizal Fungal and Soil Aggregate-Associated Carbon Content

“…In addition, soil aggregate stability and SOC are important indicators of soil quality and environmental sustainability in agro-ecosystems. Firstly, the decomposition and transformation of SOC are affected by aggregation construction (Zhang et al, 2008; Zhao et al, 2015, 2018). It has been reported that stable aggregates can physically prevent SOC against rapid decomposition (Sun et al, 2018).…”