Abstract
The aim of this study was to determine the effect of the age of trees, daily sap volume as well as the term of tapping birch sap collected in the forest environment on the content of selected minerals (zinc, copper and manganese) and heavy metals (lead, nickel, chromium and cadmium). The study was performed on material taken from two stands (aged 34 and 84 years) in a moist broadleaved forest habitat with a dominant share of silver birch (Betula pendula Roth).The research results confirmed the presence of both nutritional essential minerals and hazardous heavy metals in the birch sap. At the same time, the content of minerals and heavy metals was found to be very variable and the differences between their concentrations, recorded on the same day of collecting in several trees of the same age group, can be even several dozen times higher. Depending on the examined elements, the factors influencing their content vary. The age of the trees determines only the manganese content; daily sap volume significantly affects the content of manganese and copper, and date of collection differentiates the content of zinc, lead, nickel and cadmium.The results may be interesting in the context of developing procedures for collecting birch sap for the purpose of obtaining raw material with beneficial nutritional values and a high level of health safety. For this reason, our recommendation for guaranteeing the health safety and high nutritional value of birch sap is to combine batches of raw material taken from as many trees as possible, and at the same time to publicize the fact that collecting birch sap from just one single tree may result in a raw material that is both dangerous and has no nutritional benefits.
Highlights
The use of non-wood forest resources, which for centuries was only a spontaneous human activity, is of historical significance today [1,2,3,4]
The most frequently harvested forest resources primarily include mushrooms, forest fruits and medicinal plants [9,10]. Their value sometimes exceeds the importance of wood production, and harvesting is indicated as an opportunity to diversify the income of forest owners [11,12], especially in the face of climate change and the resulting consequences for forest management [13]. It is in this context that new opportunities for non-wood forest use are sought through research and the promotion and formalisation of new or currently forgotten forest resources [14]
The aim of this study was to determine the effect of the age of trees, daily sap volume and date of sap collection from silver birch trees growing in a forest environment on the content of Selected features of silver birch tree sap selected minerals and heavy metals
Summary
The use of non-wood forest resources, which for centuries was only a spontaneous human activity, is of historical significance today [1,2,3,4]. The most frequently harvested forest resources primarily include mushrooms, forest fruits and medicinal plants [9,10] Their value sometimes exceeds the importance of wood production, and harvesting is indicated as an opportunity to diversify the income of forest owners [11,12], especially in the face of climate change and the resulting consequences for forest management [13]. 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 [15,16,17] The popularity of this forest product observed today is due to the unique role of birch trees in the culture and beliefs of the region [18,19], and, and above all, to numerous ethnographic studies discussing the old traditional uses of birch sap as medicine product and a source of nutritional benefits [20,21,22]
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