The plant hydrodynamic approach represents a recent advancement to land
surface modeling, in which stomatal conductance responds to water
availability in the xylem rather than in the soil. To provide a
realistic representation of tree hydrodynamics, hydrodynamic models must
resolve processes at the level of a single modelled tree, and then scale
the resulting fluxes to the canopy and land surface. While this
tree-to-canopy scaling is trivial in a homogeneous canopy, mixed-species
canopies require careful representation of the species properties and a
scaling approach that results in a realistic description of both the
canopy and individual-tree hydrodynamics, as well as leaf-level fluxes
from the canopy and their forcing. Here, we outline advantages and
pitfalls of three commonly used approaches for representing
mixed-species forests in land surface models, and present a new
framework for scaling vegetation characteristics and fluxes in
mixed-species forests. The new formulation scales fluxes from the tree-
to canopy-level in an energy- and mass-conservative way and allows for a
consistent multi-species canopy description for hydrodynamic models.