# Sugar Maple and Red Maple Face-Off: Which Produces More and Sweeter Sap?
## 4 Discussion
### Sugar Content and Physicochemical Characteristics of Sap  
Sugar maple and red maple showed a similar temporal pattern in soluble sugar content during the sap season. Our analyses indicated that the degree Brix varied similarly between the two species, closely mirroring the sucrose concentration. These results confirmed previous studies showing that sucrose represents 96 to 99% of the solid fraction of sugars in the sap of maple [14; 31]. Another study showed that the sugar content (i.e., the degree Brix) of sap in sugar maple ranged between 2 and 2.5 [11]. Our results ranged between 2.6 and 4.0 \({}^{\circ}\)Brix. This difference may be attributed to the site, which is located at the northern limit of maple distribution, and characterized by colder temperature and more acid soils [32; 33]. The Brix for sugar maple and red maple followed a similar pattern throughout the sugar season, indicating a similar sucrose concentration in the two species. Both species demonstrated a relatively stable sucrose concentration, with a slight decrease toward the end of the sap season, which may be due to an increased bacterial activity associated with the rising temperatures in spring [28; 31; 34; 35]. The trend in sugars is linked to the metabolism of the trees during growth reactivation [36]. A decrease in the sucrose concentration at the end of the season could be associated with microbiological activity within the sap throughout the growing season [37; 38]. In our case, the concentrations of glucose and fructose were always below the detection limit, except for one sample of sugar maple obtained on the last day of harvesting, where the amount of glucose and fructose slightly exceeded the detection limit. Previous studies reported a higher sugar content in sugar maple compared to red maple [11; 39]. However, we were unable to detect differences in sugar concentrations between the two species, which may be explained by site characteristics and the methods of data collection. Previous studies collected the sap using micropipette aspiration for two days in early April or from the pipe system [39]. Our method involved daily sap sampling throughout thewhole season, providing a more comprehensive and quasi-continuous description of sap characteristics over the whole sugar season. Our analyses revealed similar fluctuations in osmolality between the two species, which could be explained by the common physiological processes involved in sap exudation. This measurement indicates the concentration of dissolved compounds in the sap, such as sugar content (mainly sucrose), organic acids, and mineral ions. To our knowledge, this is the first time that osmolality has been described for maple. When comparing the osmolarity to the total concentration of dissolved solids, as determined using refracometry, or to the sucrose concentration determined using the enzymatic method, a very high correlation is observed. This is clearly explained by the dominance of sucrose in the sample, which accounts for between 96% and 99% of the dry matter in the sap [14]. The integration of osmolality in sap monitoring could lead to a better understanding of how maple trees manage their water balance and adapt to fluctuating environmental conditions [40,41]. Also, pH had similar seasonal pattern between the two species, characterized by neutral values at the beginning of the season, slightly decreasing to 6 toward the end of sap production. The pH available in the literature (ranging from 3.9 to 7.9) concerned sap from stands including both sugar maple and red maple [14,31], while specific information on the pH of maple species is lacking. By integrating the pH, we can obtain new information on the microbiological activity within sap throughout the season. Specifically, by monitoring the evolution of sap pH, we can track the microbial evolution of the sap, which will ultimately impact the maple syrup quality [34].