Although there is a considerable understanding of individual plant growth processes such as photosynthesis and translocation, knowledge about carbon partitioning at whole plant level is still scarce(Genard et al. 2008). Increasing resource supply tends to increase partitioning to aboveground biomass production and decreases partitioning of belowground biomass (Litton et al. 2007). However, there has been a long-standing debate about whether production increases in response to improved resource availability (water and nutrients), or is due to shifts in allocation (Coyle and Coleman 2005). On the one hand it has been claimed that the observed shifts from below to above ground biomass are a cause of increased stem growth with intensive management (Misra et al. 1998) while on the other hand, some authors defend the view that shifts in allocation induced by irrigation and fertilization are largely due to accelerated development (Coleman et al. 2004; Coyle and Coleman 2005). The data collected in the stone pine irrigation and fertilization trial referred to in Task 2, will provide new information to help resolve this controversy. In addition, it will be extremely interesting to find out more about this issue in a species where nut yield is likely to be a major factor influencing carbon allocation.
Intraspecific competition under different availabilities of water and nutrients has been already analyzed for Eucalyptus globulus in Portugal (Reed and Tome 1998; Tome et al. 1994) and for Pinus taeda in the US (Jokela et al. 2004). The PINEA Project intends to look at intraspecific competition in stone pine through its consequences both at individual and stand level. The trial will be established in stone pine stands where competition between trees through their roots is already intense, as was shown during the preparatory studies carried out when several soil pits were opened and soil profiles were analyzed. Individual-tree size frequency distribution and size variability, the relationship between mean annual relative growth rate and social status of the tree and percentage survival will be examined in each treatment.