Temporal variations and distribution of carbon stocks in aboveground biomass of radiata pine and maritime pine pure stands under different silvicultural alternatives

In recent years there has been considerable interest in evaluating carbon budgets in forests because of the importance of these ecosystems as carbon sources and sinks. Quantifying forest net primary production (NPP) is critical to understanding the global carbon cycle because forests are responsible for a large portion of the total terrestrial NPP The present study provides information about the temporal and spatial dynamics of carbon (C) stored in aboveground tree biomass in even-aged, pure stands of maritime pine and radiata pine managed under different silvicultural regimes in northwest Spain. Carbon budgets (storage calculations) for tree biomass provide useful information for characterizing forests as important C sinks and allow assessment of the potential effects of harvesting and logging residue management on forest C status. Stand dynamic growth models were used to estimate the amount of C accumulated in the remaining stand and the amount removed in thinning treatments throughout the whole rotation. For radiata pine, carbon sequestration in total aboveground tree biomass at stand level in the whole rotation (thinnings and clear-cutting at 30 years) ranged from 3.4 Mg ha(-1) per year (the lowest initial stocking density, the worst site quality and 35% of thinning intensity) to 5.9 Mg ha(-1) per year (the highest initial stocking density, the best site quality and 15% of thinning intensity). For maritime pine, the amount of tree biomass at stand level was significantly lower than in radiata pine stands, and mean annual carbon storage ranged from 2.3 to 4.6 Mg ha(-1) per year for the same rotation length. The total aboveground and stem wood biomass C pools in these stands can be increased by increasing the rotation age and site quality and decreasing thinning intensity. Selection of the best site qualities, reduction of the thinning intensity and perhaps extension of the rotation length are therefore possible strategies for sustainable management of pine stands in Spain when the main objective is biomass production and C sequestration. (c) 2006 Elsevier B.V All rights reserved.