Carbon density in managed coast redwood stands: implications for forest carbon estimation

Carbon sequestration and wood volume production will be major objectives of future forestry projects. Optimization of these two objectives will require a better understanding of how management regimes affect stand average wood density and carbon fraction. Two contrasting coast redwood (Sequoia sempervirens) sites were chosen for analysis of volume growth rates and tree stem carbon sequestration rates under two management systems-even-aged and multiaged-each with various treatments. A young plantation showed high volume increment and stem carbon sequestration rates in all treatments with the highest in the control plots. Control plots in the plantation had peak periodic volume increment of 75.6 m(3) ha(-1) year(-1) and a maximum stem carbon sequestration rate of 16.08 tonnes C ha(-1) year(-1). The multiaged stand in contrast had the lowest volume and carbon increment in the control plots at 11.97 m(3) ha(-1) year(-1) and 2.40 tonnes C ha(-1) year(-1), respectively. In both the management systems, significant differences were observed in the carbon fraction (mass carbon per unit mass dry wood) of heartwood (HW) and sapwood (SW) at 0.5385 and 0.5293, respectively, implying that increasing the ratio of HW to SW will result in higher average carbon fractions. Carbon density varied between management regimes with the highest values occurring in the multiaged stand indicating the potential for enhancement of carbon sequestration through silvicultural prescriptions. Utilization of standard carbon accounting practices resulted in a systematic underestimate of stand-level carbon stocks for both systems studied of 26 per cent in the even-aged stand and 27 per cent in the multiaged stand.