Selected Physical Parameters and Daily Volume of Silver Birch Sap Collected from the Cardinal Directions of the Tree Trunk

Abstract

The collection, sale, and processing of non-wood forest products are becoming a significant factor in stimulating regional development and improving the economic situation, especially of poor rural communities. The fashion for a healthy lifestyle is also conducive to the growth of interest in such goods. Among them, birch sap is indicated as one of the most promising non-wood forest resources of central Europe, with very wide possibilities of its practical use, e.g., in the food, pharmaceutical, and cosmetics industries. The potential increase in birch sap commercial use prompts research on both the principles of its collection and the impact of various factors on its quality. In this presentation, we decided to investigate how the daily volume and selected sap parameters change depending on the location of the holes in relation to the cardinal directions. The research was conducted in April 2018, in the eastern part of Poland, in a stand with a dominant share of silver birch (Betula pendula Roth) at the age of approximately 100 years, in a fresh broadleaved forest habitat. On each of the six selected trees, four holes were drilled at a height of 1 m, positioned according to the cardinal directions (N-E-S-W). Sap was collected twice, one week apart, always after 24 h of leak. In each case, the daily volume of the obtained sap was determined, and then the selected properties of the sap were tested: electrolytic conductivity (proving, among others, the content of pro-health minerals), refractometric index (proving the approximate content of sugar), pH, and the percent of dry matter. As a result of the research, it was found that the location of boreholes in the tree trunk in relation to the cardinal directions (N-E-S-W) does not affect the efficiency of the birch sap leak intensity or other tested physical sap properties: refraction, pH value, and percentage of dry matter. However, a slight effect on the electrolytic conductivity was found. Therefore, it can be summarized that the cardinal directions do not affect the usefulness of the sap for the production of birch syrup, but may affect a nutritional value.