Sap volume and sugar concentration
of ice damaged sugar maples

A multi-year study was initiated soon after the ice storm to evaluate sap production and recovery of damaged sugar maples. At a site near the Uihlein Field Station, trees were categorized by four levels of crown damage (percent crown loss). Sap volume yield and sap sugar concentration data were collected on an individual tap basis during 1998, 1999, 2000 and 2001. Each damage category had 10 taps.

Results
Relative volume differences among classes were consistent during the first 2 study years. Relative sap volume increased significantly for Class 4 (51%-75% crown loss) during the third year, suggesting the trees with heavy crown loss are recovering. Sap sugar concentration among crown loss classes and by years expressed only small differences.

2001 Update
Although deep snow and poor sap runs resulted in much smaller volumes in 2001, the relative proportions of sap volume yields to the crown damage classes were consistent with that of previous years. In general, trees in the 11-25% damage class showed the highest increase in amounts of sap volume and sugar content in the four years of study, as high as an average of 17.5 gallons of sap per tap at 2.6% Brix in 2000.

This could suggest that a small amount of crown loss could be stimulating, an effect similar to that encouraged by proper pruning. However, the trees that experienced crown loss by the ice storm received ragged wounds, not the clean cuts produced by proper pruning. It is also uncertain at this time how the damage sites caused by loss of branches will heal over time.

Relative sap volumes among classes remained consistent for the first two years but the more severely damage classes increased over the last two years of the study. This suggests that after two growing seasons trees in the 51-75 percent crown loss class are showing recovery. Sap sugar concentration differences between the crown class categories have remained insignificant although expected slight overall differences between years have taken place. All of the trees selected for the study in 1998 remain productive at this time.

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Support was provided by: Cornell University, College of Agriculture and Life Sciences;
South Meadow Farms (provided study site).