Converting Abandoned Agricultural Lands to Intensive Hybrid Poplar Plantations: Effects on Soil Organic Carbon Stocks

ABSTRACT Intensively managed fast‐growing plantations can provide a significant portion of the world's wood biomass and preserve natural or extensively managed forest ecosystems by limiting harvesting pressure and associated disturbances. However, the establishment of plantations should not be at the expense of soil organic carbon stocks, and their potential as a carbon source or sink may depend on their initial stocks prior to planting. The choice of plantation sites is therefore crucial in minimizing losses or allowing the accumulation of carbon from a hybrid poplar plantation. The aim of our study was to determine the impact of afforestation with fast‐growing hybrid poplars on soil carbon stocks of sites of different origins: Abandoned agricultural land (AAL) with a herbaceous vegetation cover; shrubby AAL; and logged (previously forested) sites. Our results showed that 15 years post‐afforestation, previously forested sites where fast‐growing hybrid poplar plantations were established had lower soil organic carbon stocks than their non‐afforested equivalents and than other plantations established on AALs, while plantations on AALs had similar soil organic carbon stocks to their non‐afforested counterparts. AALs would therefore appear to be the preferred establishment site for taking advantage of the high yield of hybrid poplars while preserving soil carbon stocks.