Dynamic Characteristics of Forest Carbon Storage and Carbon Density in Hunan Province

Distribution and dynamics of carbon storage and carbon density were examined in forest vegetation in Hunan Province of China,based on four forest inventories during 1983-2009( 1983-1987,1990-1995,2003-2004,and2009). Inventory data consisted of biomass expansion factors and carbon concentration of existing forest types in this region.The results showed that the arboreal forests were carbon sinks with a value of 66. 40 x 10~6 t C from 1987 to 2009. The highest carbon sink was in broad-leaved forests( 48.43x10~6t C),followed by Chinese fir plantations( 9.54 x 10~6 t C) and pine forests( 6.68 x 10~6 t C). All age-group forests exhibited carbon sinks,except mature forests. The middle-aged forests had the highest value for carbon sinks. Carbon density increased 5. 65 t C / hm~2 in arboreal forests during the four forest inventory periods. Carbon density increased by 4. 75,4. 09,and 0. 83 t C / hm~2 in young,middle-aged,and near mature arboreal forests,respectively,whereas it declined by 6.87 and 13.88 t C / hm~2 in mature and over-mature arboreal forests,respectively. Carbon sinks were 41.01 x 106 and 25.39 x 10~6 t C in natural forests and man-made plantations,respectively.Carbon density increased 7.19 and 4.91 t C / hm~2 in natural and plantation forests. The total carbon sink was 84.87 x 10~6 t C in forest vegetation( including open forests). The arboreal and bamboo forests accounted for 78.24% and 33.31% of total carbon sinks,respectively. Carbon density increased 6.24 t C / hm~2 in forest vegetation. Carbon storage changed in various types of forest vegetation due to change in forested areas. Our results suggested that carbon sequestration ability is considerably high in the arboreal forest vegetation in the Hunan Province. In particular,the natural forests contribute substantially to carbon storage and sequestration in Hunan forests.