Over the past decade, Koelreuteria paniclata was introduced in manganese mine wastelands in central southern China as a suitable plant species in order to remove metals from the contaminated soils. In this study, we examined changes in biomass and carbon storage in 3 K. paniclata plantations at 3-, 5-and 9-year old stands in a Mn mining wasteland. We measured biomass and carbon concentrations in various plant organs and soil depths and estimated total carbon storage in the forests to gain an understanding of the dynamics of biomass and carbon in the plantation ecosystems since phytoremediation.
The result showed that: (1) The different tree organs biomass, total tree biomass increased with aged stands, and the proportion of stem biomass in the total tree biomass increased with increasing of stand ages. The biomass in undertorey layer increased with aging stands with dominant component of herbaceous vegetation; (2) The carbon content ranged from 0.51 gC/g to 0.53 gC/g, in overstorey layer and was higher than that in understorey layer. The carbon content in soil layer ranged from 0.01 gC/g to 0.03gC/g, and significant differences of carbon content were found at the same soil depth in different aged stands; (3) The biomass carbon storage was 1.66、18.32 and 49.87 t/hm² in 3-,5-and 9-year old plantations, respectively. The stem was a dominant component of the tree biomass carbon storage, which accounted for the larger part of the total biomass carbon storage, from 27.71% at 3-year old stands to 43.43% at 9-year old stands; (4) The total carbon storage was 77.76、101.63 and 149.86 t/hm² in 3-,5-and 9-year old K. paniclata plantation ecosystems respectively. The carbon storage in soils ranged from 76.09 t/hm² to 99.93 t/hm², which accounted for 66.68%-97.85% of the total carbon in the ecosystems. The carbon storage in litter layer ranged from 0.01 to 0.04 t/hm², which accounted for 0.001%-0.02% of the total carbon storage in the plantation ecosystems. (5) The carbon storage in vegetation layer ranged from 1.67 to 49.89 t/hm² in the aging stands, accounting for 2.15% to 33.29% of the total carbon storage in these forested ecosystems. The carbon storage in different components of the aged K. paniclata plantation ecosystems was in order as soil layer > vegetation layer > litter layer. Our results may provide scientific references for sustainable forest resources management and carbon sink forest development in vegetation restoration of mining wastelands.