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 and cosmetics industries.
The potential increase in birch sap use prompts to undertake research on both the principles of its collection and the impact of various factors on its use possibility and 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 approx. 100 years, in a fresh broadleaved forest habitat. On each of the 6 selected trees, 4 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 hours 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 compounds), refractometric index (proving the approximate content of sugars), pH and the percent of dry matter.
The average daily volume of collected sap was 1.026 dm3/24h (the highest in the N direction - 1.397 dm3/24h, while the lowest in W - 880,58 dm3/24h, but the statistical analysis did not confirm the significance of this statement). Similar trend was observed concerning refractometric index (N: 0.74°Brix; W: 0.62°Brix; avg: 0.7°Brix, also not statistically proved). In other cases, the variability was small and multidirectional (for example: electrolytic conductivity: S – 654 µS/cm, N – 531 µS/cm, avg. – 577 µS/cm; pH: E- 5.6, W – 4.9, avg. – 5.3). This may mean that the location of the hole on the tree stump is of no practical importance for commercial sap harvesting. The obtained results may be important in the case of developing the principles of commercial collecting of birch sap.
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