Carbon sequestration in willow (Salix spp.) plantations on former arable land estimated by repeated field sampling and C budget calculation

There was a discrepancy between SOC sequestration rates from soil sampling and C budget calculation, −2.1-1.0 and 0.15-0.45 Mg ha−1 y−1, respectively. Mineralization of old organic material from previous land-use and input to SOC from understory vegetation were not included in the calculations, which may explain part of the differences. The importance of understory litter in C budgets for young plantations was apparent, as it comprised 24-80% of aboveground litter C.