SFU mathematicians crack the mysteries of the maple tree

An SFU study has unlocked some new evidence regarding how maple trees produce such a large quantity of sap — and the implications of these findings could mean big things for the maple syrup industry.

The study, led by SFU mathematician John Stockie with colleagues Isabell Graf and Maurizio Ceseri, looks into the subject of tree sap exudation (excretion) in sugar maples.

The research was developed to find a more concrete answer to why these particular trees continued to produce a lucrative amount of sap even in a leafless state during the winter months.

The prevalent theory of the secretion of tree sap attributes exudation to the physical processes of osmosis and freeze-thaw cycles, which involve the buildup of gas in sap cells during freezing and results in the release of gas and expansion of the sap as it thaws. However, these models have led to their fair share of unanswered questions and head-scratching over the years.

Hoping to close the gap of uncertainty, Stockie and his team designed the first mathematical model of sap exudation as means of resolving the bewilderment linked to the strange case of maple exudation.

Stockie justified the need for a mathematical model: “Typically what happens with problems like this — with many different physical mechanisms coupled together and interacting — people have ideas for what could be going on, but the physics is so complex that it’s very difficult to fasten on the correct solution unless you get into the math.”

SFU mathematicians worked first on modelling the mechanics of sap exudation on a cellular level, to understand all the processes that were going on. They then scaled up the cellular processes to arrive at a simpler string of equations, which the computer could then go on to solve.

A year later, Stockie and his team discovered three new physical mechanisms that were essential components in tree sap secretion. Additionally, they discovered a connection between exudation and freeze-induced embolism, which causes blockages in sap flow and further damage to the tree itself.

Stockie argued that the model could be greatly helpful to the maple syrup industry. It would, he said, aid in the optimization of sap harvests for syrup producers, and help foresee the potential impacts of climate change on sap yields.

For Stockie, though, these findings are only the beginning to unlocking more unanswered questions in the study of sap harvest. He hopes to further pursue this topic over the next two years and continue to unlock more secrets into our beloved national treasure, maple syrup.