High-Density Poplar SRC Accumulates More Soil Organic Carbon Than Very-High-Density SRC

Short rotation coppice (SRC) systems play an important role in producing renewable energy and contributing to soil organic carbon storage while providing potential mitigation for climate change. Our chronosequence study assessed the influence of 6 years of high-density (H) and very-high-density (VH) SRCs on soil organic carbon (SOC) accumulation in an alluvial area of Piedmont (Italy) by investigating the effects of agronomic management (fertilization, irrigation, fertilization and irrigation, no treatment) using a spatial survey approach. A first sampling was performed at 40 points to characterize the variability of the initial SOC and other soil properties; 6 years after, a total of 80 samplings were carried out to verify changes in SOC. A mixed effect model procedure was used to evaluate the impact of 6 years of SRC and agronomic management on SOC, testing for autocorrelation among the model residuals. The results showed: (i) a higher accumulation potential of H-SRC (0.076 kg m−2 year−1) compared to VH-SRC (0.037 kg m−2 year−1); ii) a significant positive influence of the initial SOC value and of fertilization associated with irrigation on the SOC sequestration; (iii) the importance of considering spatial variability at sites with high particle-size diversity in evaluating the SOC changes.