Impacts of a large-scale reforestation program on carbon storage dynamics in Guangdong, China

In the early 1980s, the province of Guangdong, China implemented a 10-year, large-scale reforestation program to counter environment degradation as a result of rapid economic development. Quantification of the contribution of this forest restoration program to carbon storage will provide critical information and guidance for designing future forest restoration and management strategies at the provincial level.The Guangdong Provincial Forest Inventory Database, together with our field sampling data was used to estimate carbon storage dynamics over the 10-year period of 1994–2003 for key restoration forest types as well as OBPA (open forest, bamboo forest, production forest and ambient trees). Various layers of forests were considered in calculating carbon storage: tree layers, understory vegetation and litterfall layers for the key forest types and bamboo forests; tree layers and litterfall layers for production forests; and only tree layers for open forest and ambient trees.Our results show that over the 10-year period, the reforestation program has increased total carbon storage by 41.67 Tg and forest carbon density by 1.58 Mg C ha−1. Carbon storage in tree layers was the greatest among all layers studied. Carbon storage in litterfall and understory layers amounted to approximately 38%–44% of the total carbon storage, demonstrating that litterfall and understory layers can not be neglected in estimating regional forest vegetation carbon storage in the sub-tropical forests. It was determined that coniferous forests provided the greatest contribution to total carbon, followed by broadleaved forests, OBPA, and mixed coniferous and broadleaved forests in decreasing order of magnitude. Among all key forest types, stands of P. massoniana had the greatest amount of carbon storage (from 59.65 to 65.87Tg) while Albizia falcataria (Linn.) Fosberg forest stands had the lowest (from 0.05 to 0.37 Tg). Over the 10-year period, carbon storage pools in maturescent forests, mature forests and post-mature forests were on the increasing trend, while those in young forests and middle-aged forests were declining and relatively stable, respectively. Our analysis also shows that the carbon accumulation rate in broadleaved forests (0.19–1.36 Mg ha−1 year−1) was the highest among the key forest types in Guangdong, which has important implications for selection of future forest restoration species.