No significant differences in soil organic carbon contents along a chronosequence of shrub willow biomass crop fields

Shrub willow biomass crops (SWBC) have been developed and promoted for widespread deployment in northeastern and mid-western US as well as in Europe. There are concerns that the production system could reduce the soil organic carbon (SOC) over time due to soil disturbances and repeated three-year harvest cycles. This study assesses changes in SOC beneath shrub willow (Salix x dasyclados [SV1]) biomass crops utilizing a 0, 5, 12, 14, and 19-year old SWBC fields. The sites' management history was similar, suggesting uniform SOC contents prior to plantation establishment. SOC contents were analyzed by total (i.e. 45cm) and by layer (i.e. 0-15cm, 16-30cm, and 31-45cm) across different ages. Mean SOC contents to 45cm depth ranged from 175 to 188Mg ha^-1, and showed no statistically significantly differences across ages (p=0.15) and no interaction between age and depth (p=0.19). SOC contents differed significantly with soil depth when averaged across ages (p<0.0001). Statistical analysis of SOC contents by layer, however, showed that SOC contents in the upper 15cm depth were significantly different (p<0.001). Linear contrasts of mean SOC contents for the 0-15cm depth revealed that the 0-year old was significantly different compared with the 5, 12, 14, and 19-year old SWBC.