Ecosystem carbon accumulation following fallow farmland afforestation with red pine in southern Quebec

Abstract

We assessed the organic C stocks and inferred their changes in vegetation biomass, forest floor, and soil using a 50 year chronosequence of red pine ( Pinus resinosa Ait.) plantations established on postagricultural fields in southern Quebec, Canada. The data come from soil and tree field surveys carried out in the 1970s in 348 sites. Organic C concentrations were usually measured in three major mineral soil horizons; for the remaining soil horizons, they were estimated using pedotransfer functions. The effect of soil order, drainage, and texture was analysed. Over 22 years, organic C accumulation rates (Mg C·ha–1·year–1) were 1.66 ± 0.03 in vegetation biomass, 0.56 ± 0.07 in forest floor, 0.86 ± 0.47 in loamy soils (0–100 cm), and  –0.18 ± 0.24 in sandy soils (0–100 cm). The greater rate of C accumulation in loamy soils was due to the contribution of the 30–100 cm subsoil layer. The overall net accumulation of organic C in these plantation ecosystems was estimated to 51.4 ± 4.8 Mg C·ha–1at 22 years. Soils of these plantations acted as a C sink in the first two decades, particularly in loamy soils compared with sandy soils, with no major differences among soil order or drainage.