Abstract
Abstract Key message Self-thinning lines are species- and climate-specific, and they should be used when assessing the capacity of different forest stands to increase biomass/carbon storage. Context The capacity of forests to store carbon can help to mitigate the effects of atmospheric CO2 rise and climate change. The self-thinning relationship (average size measure ∼ stand density) has been used to identify the potential capacity of biomass storage at a given density and to evaluate the effect of stand management on stored carbon. Here, a study that shows how the self-thinning line varies with species and climate is presented. Aims Our main objective is thus testing whether species identity and climate affect the self-thinning line and therefore the potential amount of carbon stored in living biomass. Methods The Ecological and Forest Inventory of Catalonia was used to calculate the self-thinning lines of four common coniferous species in Catalonia, NE Iberian Peninsula (Pinus halepensis, Pinus nigra, Pinus sylvestris and Pinus uncinata). Quadratic mean diameter at breast height was chosen as the average size measure. The self-thinning lines were used to predict the potential diameter at a given density and study the effect of environmental variability. Results Species-specific self-thinning lines were obtained. The self-thinning exponent was consistent with the predicted values of −3/2 and −4/3 for mass-based scaling for all species except P. sylvestris. Species identity and climatic variability within species affected self-thinning line parameters. Conclusion Self-thinning lines are species-specific and are affected by climatic conditions. These relationships can be used to refine predictions of the capacity of different forest stands to increase biomass/carbon storage.
Highlights
Forests store approximately 45 % of terrestrial carbon, constitute around 50 % of terrestrial primary production and can sequester large amounts of carbon annually (Bonan 2008; Pan et al 2011) and mitigate the rise of atmospheric CO2 and global warming
The four studied pine species are abundant in the study area, but they occupy very different areas in Catalonia (Barbero et al 1998): Pinus halepensis is only present in Mediterranean coastal zones (1400 m) in the Pyrenees
The STL slopes of P. sylvestris was significantly steeper than the range of expected values, whereas P. uncinata, P. nigra and P. halepensis did not show significant differences (Fig. 3)
Summary
Forests store approximately 45 % of terrestrial carbon, constitute around 50 % of terrestrial primary production and can sequester large amounts of carbon annually (Bonan 2008; Pan et al 2011) and mitigate the rise of atmospheric CO2 and global warming. Carbon sequestration is high in young, secondary forests, which dominate many areas in the temperate zone (Bonan 2008; Pan et al 2011). In secondary forests, developing trees accumulate mass, in the stem. While growing taller and bigger, trees in secondary forests may compete strongly for available. Under conditions of limited resource availability, weaker trees may become suppressed and die. In other words, such forests will gradually be dominated by fewer larger trees
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