Impact of individual tree characteristics and neighbouring conditions on sap-flow in Acer saccharum : a multi-scale analysis

Details

Supervisors

Ponette, Quentin ; Messier Christian

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en gestion des forêts et des espaces naturels

Abstract

Maple syrup production is an important socio-economic activity for Quebec. Yet many uncertainties remain on how sap-flow in a maple tree is affected by neighbouring conditions and individual tree characteristics. Studies are important for providing producers with information pertinent to their decision making. In the Outaouais region of Quebec, 55 maple trees were selected, and sap was collected almost daily, to obtain the total volume of sap produced, the average sugar content per tree and the distribution of the sap volume during the season, from March until April of 2020. A subsample of 21 trees was selected to collect sap hourly, over a 6 day period during the season. Our study involves a multi-scale analysis, by combining hourly, daily and seasonal measurements. We found that variations in average sugar content among trees does not explain the variations in total sugar collected, and individual tree characteristics and neighbouring species have little impact, with the exception of the presence of conifer which is negatively related to sap sugar content. Among trees variation in sap volume was the most relevant parameter to explain total sugar collected. Neighbouring conditions did not seem to affect the sap volume collected. However, a higher volume was collected from trees experiencing more competition regardless of competitor species or abundance. This sap volume was also positively related to tree DBH, when relation to crown size and health was less clear. Yet both had an influence on the maximum hourly volume measured daily. This effect wasn’t observed from the start of the season, but appeared later in the season. Average sugar content was negatively correlated with the total volume. This effect was not consistent with other studies and might be due to the small size of our subsample. Light reaching the trunk had surprisingly no influence on the total volume of sap collected although an impact was found on seasonal distribution, since the flow-rate was higher in the early season. Further investigation is required to check if these observations are consistent from year to year and if similar results are obtained in other locations.