Carbon Budgets Of Coniferous Plantations In Qianyanzhou Experimental Station, Jiangxi China

Plantations play important roles in terrestrial ecosystem in China. Qianyanzhou carbon fluxes observation station in Jiangxi Province, one of the typical hilly areas with red earth, is the only one for mixed coniferous plantation of ChinafluxNet including four for forests established in 2002. With the aid of eddy-covariance and biometric, this study aim at carbon budgets of coniferous plantations in Qianyanzhou which is composed of Pinus massoniana, Pinus elliottii and Cunninghamia lanceolata, and further discusses the environmental effects on CO2 echanges between atmosphere, vegetation and soil .Based on the biomass of P. massoniana, P. elliottii and C. lanceolata through felling sample trees with different diameters at breast height (DBH), their allometric growth equations were developed in Qianyanzhou. According to the number of trees with different DBHs in the plots, their biomass density and NPP ( Net Primary Productivity) are estimated, 85.159 t/hm2 and 6.306 t/(hm2·a) for P. massoniana, 109.990 t/hm2 and 9.09 t/(hm2·a) for P. elliottii, and 120.543 t/hm2 and 11.944 t/(hm2·a) for C. lanceolata. The biomass density of mixed coniferous forest which is composed of P. massoniana, P. elliottii and C. lanceolata with a mixture ratio of 49:48:3 for the whole area is 124.14 t/hm2 with 96.64 t/hm2 for trees, 14.808 t/hm2 for understory and 12.696 t/hm2 for litters. The mixed coniferous plantation's NPP is 8.905 t/(hm2·a) with 7.785 t/(hm2·a) for trees and 1.12 t/(hm2·a) for understory. The fallen items, including branches and leaves, contribute 5.367 t/(hm2·a) to litters every year.According to all tissues'carbon content measured by Finnigan Elemental Analyzer (Germany) and their biomass, the carbon contents of the four species are 0.5523 for P. massoniana, 0.5431 for P. elliottii, 0.5375 for C. lanceolata and 0.5115 for Schima superba. And these of the first three stands are the same as trees'. In mixed coniferous forest, carbon contents spatially decrease from trees, shrub to herb, with 0.5465 for trees, 0.5135 for shrub, 0.4954 for herb respectively. And carbon content rate of annual litter is 0.5529, higher than that of the undecomposed litters felling with 0.5280.Forest carbon density in Pinus massoniana stand, Pinus elliottii stand, and Cunninghamia lanceolata stand is 121.072, 139.77 and 160.108 t/hm2,and that in mixed coniferous forest is 130.3 t/hm2 with the ratio of below-ground to above-ground among 1.08~1.22. The annual carbon storage of coniferous forest involving all parts'contribution...