Carbon Allocation/Transportation in ECOPHYS

The carbon allocation / transportation model in ECOPHYS is used to determine the proportion of photosynthate exported from a leaf and the pattern of photosynthate allocation from th leaf to various growth centers within the plant.

Ecophys uses an emprical model based on carbon allocation matrices, created from poplar studies performed by Dr. Jud Isebrands. Using this strategy, recently mature and mature leaves will export some or all of their photosynthate to the various growth centers based on their Leaf Plastochron Index (LPI).

There is also a constant allocation strategy (see Guan, 2002). This means that each specific source leaf sends carbon downward to the bottom of the main trunk with each unit length of internode receiving an equal amount of carbon. This helps to avoid non-monotonicity, where an internode further along a branch has a larger diameter then the one previuos to it.

This transportation model is a source-sink model.

Sources - Leaves

Sinks - Branches, Leaves, Trunk, Roots

After Bud Set

After bud set hybrid poplars and aspen change their allocation strategy to prepare for the dormant season. Gradually, most of the photosynthate that would normally be sent upward, will now be sent downward instead.

The following chart shows the shift in transportation that happens after bud-set on a branch. Ten days after the shift starts, 80% of what would normally be sent upward, will now go downward.