Wpływ wybranych czynników na zawartość składników mineralnych w soku brzozy brodawkowatej (Betula pendula Roth)

The aim of this study was to determine the content of selected minerals in silver birch sap, and to examine whether the tree thickness (DBH), the obtained daily volume of sap and the date of collection have an impact on their content. The study was carried out in central−eastern Poland, in the Garwolin Forest District, in a stand with a dominant share of silver birch at the age of 65, which grows on a moist mixed broadleaved forest habitat type. Sap from the selected trees was taken after 24 hours of leakage, four times, at weekly intervals. In each case, the daily sap volume was measured and the content of zinc, copper, and manganese was determined. As a result, no effect of tree diameter on the content of the studied elements was found. However, a negative relationship was stated between copper content and daily sap volume. Moreover, birch sap was characterized by increasing concentration of zinc and copper over time. The obtained results of the determination of the content of minerals in birch sap testify to the fact that it is characterized by high nutritional value. However, the large variability in its composition means that in order to obtain such benefits it is necessary to combine sap taken from as many trees as possible, while sap collected from only one tree may have a negligible nutritional value.