Carbon Dynamics of a Young White Pine Plantation Forest

English Abstract:

This study assesses the effects of seasonal and annual climate variability on the growth and carbon dynamics of a temperate white pine (Pinus strobus L.) plantation established in 2002 in southern Ontario, using CO₂ fluxes measured by the eddy covariance technique. It is rare to have continuous long-term flux measurements in a young forest since its planting. The plantation became a carbon sink after 4 years of its establishment. Drought events resulted in reduction in net ecosystem productivity (NEP). In 2005, an early growing season drought and heatwave caused the stand to become a net carbon source. Water use efficiency consistently increased over the study period with a mean value of 3.0 g C uptake per kg of water loss in 2013. Quantum yield, α (0.01 to 0.07) and maximum photosynthetic capacity, A_max (4.0 to 25.1 µmol m^-2s^-1) increased steadily as the size and density of the canopy increased over the stand age. A linear stepwise regression analysis found that growing season mean soil water content, photosynthetically active radiation and soil temperature explained 67% of the variability in NEP. This study will be a significant contribution to our understanding of the carbon dynamics of young plantation forests and their environmental controls. It will also help to determine how young plantation forests may be affected by climate variability and extreme weather events.