Carbon content of soil fractions varies with season, rainfall, and soil fertility across a lowland tropical moist forest gradient

Divergent changes of carbon and nitrogen in the density fractions of soil organic matter after revegetation in the Tengger Desert, north China

“…Alternatively, increased plant productivity with the succession of vegetation depleted soil N (Li et al, 2018). The fLF had the highest OC and N concentrations whereas the HF had the lowest (Figure 3), which corresponded to previous studies and was mainly due to the HF being dominated by minerals (Golchin et al, 1994; Li et al, 2012; Llorente et al, 2010), and indicating an increasing degree of SOM decomposition (Dietterich et al, 2021; Golchin et al, 1994). The OC and N contained in the oLF were also higher than those in the HF, which can be ascribed to the higher intensity of physical protection through aggregation in the oLF (Llorente et al, 2010; Six et al, 2002).…”

“…This difference was attributed to an increase in low‐quality litter, which contributed to the formation of the fLF owing to its low decomposability (Sonsri et al, 2022). The variation patterns of the oLF were similar to those of the fLF in this study (Figure 3), mainly because the oLF stemmed from the fLF, thereby the processes that control the mass and the OC and N in the fLF would affect the oLF (Dietterich et al, 2021). At the sites, the OC in each fraction changed faster than N (Figures 3–5).…”

“…Importantly, communities with higher diversity in older sites would produce more complex OC compounds, increasing the C:N ratio (Dale et al, 2015; Dietterich et al, 2021). In addition, soil metabolism might be increasingly limited by nutrients apart from OC, which may increase the C:N ratio over time (Dietterich et al, 2021). The C:N ratio decreased with increasing density of the fractions (Figure 3).…”

“…We ascribed this to a reduction in high-quality litter (low C:N) and utilization of N by plants (Berendse et al, 1998;Grüneberg et al, 2013). Importantly, communities with higher diversity in older sites would produce more complex OC compounds, increasing the C:N ratio (Dale et al, 2015;Dietterich et al, 2021). In addition, soil metabolism might be increasingly limited by nutrients apart from OC, which may increase the C:N ratio over time (Dietterich et al, 2021).…”

“…Furthermore, organics produced during decomposition, such as carbohydrates, proteins, and polyphenols resulted in the formation of stabilized soil structures, especially aggregates (Burns et al, 2013;Strickland & Rousk, 2010). The declined percentage of OC and N in HF was primarily attributed to the increasing proportion of LF and increasing degree of SOM decomposition (Dietterich et al, 2021;Golchin et al, 1994), suggesting that revegetation contributed to OC and N sequestration by increasing the allocation of OC and N in LF but decreasing their allocation in HF (Yang et al, 2023).…”