Biomass production and carbon sequestration of a short-rotation forest with different poplar clones in northwest China.

Short Rotation Forestry (SRF) is of interest as producers of biomass for bio-energy, but also as carbon (C) sinks to mitigate CO emission. To investigate biomass production and C sequestration of SRF, ecosystem C stock (including C stored in tree biomass, litter and soil), NPP (net primary productivity), heterotrophic respiration (Rh) and NEP (net ecosystem productivity) of three poplar clone plantations were estimated by repeated field sampling in northwest China. Ecosystem C stock (105.62MgCha) was significantly lower in PB (P. balsamifera) stand than in PD (P. deltoids) and PE (P.×euramericana) stands (P<0.01). Biomass C stock was greatly affected by clone type (P<0.01), while significant difference in soil C stock was not detected. Averaged NPP was 8.80MgChayr across all clone stands, but the most productive clone of PD yielded up to 10.72MgChayr. NEP was found to be significantly different among the clone stands, increasing from 0.21MgChayr in PB to 6.77MgChayr in PD stand. With soil C outputs (Rh) being smaller than C sequestrations, the plantations all acted as C sinks, averagely absorbing 3.45MgCha during a year. Our results suggest that clone type is a main factor influencing C sequestration capacity of a plantation, along with determining the amount of biomass yield. The success of poplar plantations as a bio-energy resource largely depends on the selection of hybrid varieties.