To evaluate the efficacy of agricultural interventions in restoring soil carbon stocks under UVA stress, we monitored SOC fractions throughout the 32 day incubation. Contrary to the significant carbon loss observed in the control (CK), all management practices maintained consistently higher SOC levels (p < 0.05, Figure 1f). By the end of the experiment, the SOC content in the FA, Mulch, and Mulch-FA treatments increased by approximately 8.98%, 5.35%, and 18.77%, respectively, relative to the CK, respectively. In addition, these practices regulated distinct carbon pools (Figures 1g, h and S1a, b). FA treatment significantly promoted the accumulation of MAOC, matching a decrease in POC content (p < 0.05; Figure 1g). By providing labile, aromatically enriched substrates, FA alleviated metabolic limitation and reduced microbial dependency on recalcitrant organic matter degradation─a substrate priming effect that facilitates mineral adsorption. (43,44) Conversely, Mulch significantly elevated POC concentration but lost some MAOC (p < 0.05; Figure 1g, h). By physically blocking UV radiation and maintaining soil moisture, mulching lowered the maintenance energy costs associated with desiccation and DNA repair, thereby favoring the structural stabilization of POC via enhanced EPS production. (45) Notably, as the incubation proceeded, the combined Mulch-FA treatment maintained or promoted the accumulation of both POC and MAOC in soils (Figure 1g, h). By simultaneously mitigating photobiological stress (via Mulch) and relieving resource constraints (via FA), this combined approach effectively decouples the trade-off between POC protection and MAOC preservation, enabling the concurrent restoration of both carbon pools even under high-intensity radiation. (46) Detailed temporal dynamics and absolute concentration changes of SOC fractions across all sampling points are provided in the Supporting Information Text 5 (Figure S1).
To evaluate the efficacy of agricultural interventions in restoring soil carbon stocks under UVA stress, we monitored SOC fractions throughout the 32 day incubation. Contrary to the significant carbon loss observed in the control (CK), all management practices maintained consistently higher SOC levels (p < 0.05, Figure 1f). By the end of the experiment, the SOC content in the FA, Mulch, and Mulch-FA treatments increased by approximately 8.98%, 5.35%, and 18.77%, respectively, relative to the CK, respectively. In addition, these practices regulated distinct carbon pools (Figures 1g, h and S1a, b). FA treatment significantly promoted the accumulation of MAOC, matching a decrease in POC content (p < 0.05; Figure 1g). By providing labile, aromatically enriched substrates, FA alleviated metabolic limitation and reduced microbial dependency on recalcitrant organic matter degradation─a substrate priming effect that facilitates mineral adsorption. (43,44) Conversely, Mulch significantly elevated POC concentration but lost some MAOC (p < 0.05; Figure 1g, h). By physically blocking UV radiation and maintaining soil moisture, mulching lowered the maintenance energy costs associated with desiccation and DNA repair, thereby favoring the structural stabilization of POC via enhanced EPS production. (45) Notably, as the incubation proceeded, the combined Mulch-FA treatment maintained or promoted the accumulation of both POC and MAOC in soils (Figure 1g, h). By simultaneously mitigating photobiological stress (via Mulch) and relieving resource constraints (via FA), this combined approach effectively decouples the trade-off between POC protection and MAOC preservation, enabling the concurrent restoration of both carbon pools even under high-intensity radiation. (46) Detailed temporal dynamics and absolute concentration changes of SOC fractions across all sampling points are provided in the Supporting Information Text 5 (Figure S1).
