Higher early concentrations

[Mean_Oscar]

Is it common for the first sap out of a tree to be significantly higher Brix than it will be even 3 days later?

[DRoseum]

Yes - btw, Ohio state is doing a study this year on brix levels throughout the season.

[DrTimPerkins]

Is it common for the first sap out of a tree to be significantly higher Brix than it will be even 3 days later?

Yes. Sap sugar content is quite dynamic over a sap run, over a season, and from season-to-season. Quite well known phenomenon.

https://mapleresearch.org/pub/mn2020sapsugar/

Also, see Figure 6.1 on page 6-3 of the North American Maple Syrup Producers Manual https://mapleresearch.org/pub/manual/

In general, sap sugar concentration (SSC) is low in winter, rises in the early-spring, then falls again. Depending on when you tap, it may appear to be high early on, then drop over the season, with some excursions brief upward periodically after a freeze, but the general trend is downward during the spring sap run.

Trees vary considerably based upon both genetics and environment. The heritability of high SSC isn't particularly strong, so there is no guarantee that a tree from a high SSC mother will be itself high in sugar, but it will have a slight tendency to be that way. However trees do tend to rank pretty much the same from one season to the next, so a tree that is high in sugar relative to its neighbors will tend to be high relative to its neighbors each year and vice versa.

Trees that are dominant or codominant (large) with big crowns tend to have higher SSC and higher sap yields (stronger growth=wider rings), largely due to less competition for light (the "fuel" for photosynthesis).