Abstract
BackgroundForest restoration has been considered an effective method to increase soil organic carbon (SOC), whereas it remains unclear whether long-term forest restoration will continuously increase SOC. Such large uncertainties may be mainly due to the limited knowledge on how soil microorganisms will contribute to SOC accumulation over time.MethodsWe simultaneously documented SOC, total phospholipid fatty acids (PLFAs), and amino sugars (AS) content across a forest restoration gradient with average stand ages of 14, 49, 70, and > 90 years in southern China.ResultsThe SOC and AS continuously increased with stand age. The ratio of fungal PLFAs to bacterial PLFAs showed no change with stand age, while the ratio of fungal AS to bacterial AS significantly increased. The total microbial residue-carbon (AS-C) accounted for 0.95–1.66 % in SOC across all forest restoration stages, with significantly higher in fungal residue-C (0.68–1.19 %) than bacterial residue-C (0.05–0.11 %). Furthermore, the contribution of total AS-C to SOC was positively correlated with clay content at 0–10 cm soil layer but negatively related to clay content at 10–20 cm soil layer.ConclusionsThese findings highlight the significant contribution of AS-C to SOC accumulation along forest restoration stages, with divergent contributions from fungal residues and bacterial residues. Soil clay content with stand age significantly affects the divergent contributions of AS-C to SOC at two different soil layers.
Highlights
Forest restoration has been considered an effective method to increase soil organic carbon (SOC), whereas it remains unclear whether long-term forest restoration will continuously increase SOC
Soil pH, soil bulk density (BD), and soil clay content changed with soil layer and forest restoration stage (Table 2, P < 0.05)
Soil clay content showed a trend of initial increase, decline in both soil layers following forest restoration (Table 2), with the lowest value in F14 (4.14 and 5.53 % in topsoil and subsoil, respectively) and the highest value in F70 (16.27 and 17.28 % in topsoil and subsoil, respectively)
Summary
Forest restoration has been considered an effective method to increase soil organic carbon (SOC), whereas it remains unclear whether long-term forest restoration will continuously increase SOC. Such large uncertainties may be mainly due to the limited knowledge on how soil microorganisms will contribute to SOC accumulation over time. Forest restoration or reforestation is considered an effective land-based climate mitigation strategy through carbon (C) sequestration in both plant biomass and soil (Lal 2003; Laganière et al 2010). Our knowledge is very limited in accurately predicting the C sequestration potential of restored forests (Wieder et al 2018)
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