Tree height

[mmcgrath]

Looking at some PFTs in Europe, it's not clear that the allometric relationships are correct. These were originally derived from forest inventory results. However, the parameters for PFT7, for example, suggest that trees will only be 25 meters tall if they have a diameter of one meter. Trees in the boreal zone will never have a diameter of one meter, but it's not uncommon to see trees that are 18-20 meters tall. Therefore, perhaps the tree height in the model is too small. This could be checked, as it would likely have an impact on the coupling.

PFT6 was also flagged for checking.

[luyssaert]

In r7478 the pipe_tune2 parameters are adjusted to get reasonable heights when the trees reach a 30 cm diameter. One consequence of taller trees could be that the diameter growth will slow down (higher trees for a given diameter require more biomass for a given diameter).

[luyssaert]

The current approach assumes that unmanaged forests are always at an RDI of 1. This is not case and especially not in the young stages of the forest. Even in mature stages and RDI of 1 is rarely reached and old unmanaged forests have been observed to have an RDI of 0.9 or less (Luyssaert et al 2011). To accomodate the increase in RDI of unmananged stands, two parameters were added (unmanaged_alpha_rdi and unmanaged_beta_rdi). The rdi is calculated as alpha + qm_dia + beta. Nmax is reduced by the RDI. This approach has a considerable effect on the height growth of the evergreen PFTs. The effect on the deciduous PFTs is smaller but the parameters for these PFTs (especially PFT6) are not yet satisfying. These changes are committed in r7549 and r7592.