Carbon fixation estimation for the main plantation forest species in the red soil hilly region of southern-central Jiangxi Province, China

Using field survey data from the sixth inventory of forest in Jiangxi Province and calculating the relationship between forest biomass and carbon storage from this,we estimated total forest biomass and carbon storage for the three major plantation forest species,Pinus massoniana,Cunninghamia lanceolata,and Pinus elliottii,in the red soil hilly region of southern-central Jiangxi Province.We also analyzed the relationship between carbon density and age for these forest species,using logistic equations,and described the spatiotemporal dynamics of forest biomass and carbon storage between 1985 and 2003 in the study area. In this study,we used three methods of biomass expansion factor,biomass organ distribution and parameter fitting,to estimate carbon density.Qianyanzhou Experimental Station was chosen to compare these three corresponding results.The result obtained from parameter fitting was found to be the best way of calculating forest biomass and carbon storage on a regional scale.Increasing sample size would increase reliability of results. The following conclusions were obtained from this study.In 2003,total stand area of the three forest species was 31.04×104 hm2;total biomass was 22.20 Tg;vegetation carbon storage was 13.07 Tg C;and average carbon density was 42.36 t C/hm2.Carbon storage by different forest types in descending order was: Pinus massoniana,Pinus elliottii and Cunninghamia lanceolata.Carbon storage by age group in descending order was middle stand forests,young stand forests,near-mature stand forests,mature stand forests.Storage of carbon by plantation forests was 1.89 times higher than by natural forests.Pinus massoniana and Cunninghamia lanceolata forests were the main natural forest carbon sinks,while Pinus elliottii forests were the main plantation carbon sinks.Carbon density of the three species increased each year and increased 8.58 tC / hm2 during the study period;this was 1.66 times higher than in 1985.Forest carbon storage was 4.91,11.41,and 13.07 Tg C in 1985,1994,and 2003,respectively.Average amount of carbon fixation was 0.45 Tg C/a per year.Stand area enlarged from 15.54 × 104 hm2 in 1985 to 30.30×104 hm2 in 1994.The carbon density of the three species was higher in the east and west of Taihe County and lower in the middle.It was higher in the east and north of Xingguo County than in the middle.Average carbon density was highest at 700 to 900 m altitude and 25 to 35° slope.Overall,carbon density of forest vegetation increased with increasing altitude and slope. Afforestation projects contributed significantly to the increase in carbon storage in the red soil hilly region of Jiangxi Province.Understanding the growth patterns of the three species was important for calculation of biomass and carbon storage in these plantation ecosystems,and was crucial for forest management.Reasonable forest management may improve the carbon sequestration capacity of forest ecosystems.Further study should focus on the carbon reservoirs provided by other species and the soil in order to estimate the carbon fixation potential of the whole forest ecosystem.