The chemical analysis of freshly harvested leaves and needles (foliar analysis) shows the current nutritional status of trees. The repetition of these analyses over the years makes it possible to assess changes over time. These measurements provide important information for the assessment of forest health.
In particular, nutrient deficiencies and nutrient imbalances can be detected. While in deficiencies a nutrient is below a reference value, in imbalances the concentration of a particular nutrient is either too high or too low compared to that of another important nutrient.
Every other year, we harvest leaves and needles from the upper, sun-exposed third of the crown of 5 or 6 trees of the dominant tree species on all LWF sites. We then document the state of the leaves, weigh them, scan them to obtain the leaf area, and grind them for chemically analyses in the laboratory.