The nutritional status of the trees is an important indicator of the condition of the forest. It depends on site parameters such as soil properties and atmospheric nutrient inputs. The nutritional status of trees is an integral measurement within the Level II programme.

To determine the nutritional status, the chemical composition of fresh leaves or needles is analyzed and their mass is determined. In deciduous trees, leaves are sampled from the upper third of the tree crown in summer before leaf discoloration begins. For conifers, samples are taken in winter.

Different parameters help to determine whether a tree is experiencing nutrient deficiency or excess. Nutrient concentrations are measured in the samples for the main nutrients (nitrogen, phosphorus, potassium, magnesium, calcium and sulphur). The nutrient quantities are calculated as the product of leaf or needle mass and nutrient content. If the nutrient content is lower in a year in which the leaves or needles are larger, this may indicate a nutrient deficiency. Nutrient ratios, for example the ratio of nitrogen to phosphorus, provide information on whether the nutritional status is in balance.

At this time, the app is only available in German.

The app allows you to display and compare nutrient contents and concentrations of six main nutrients for four tree species. It also shows leaf or needle masses and nutrient ratios.

You can first select a target variable from the drop-down menu. Additional drop-down menus allow you to choose the tree species. Up to five combinations of tree species and nutrient can be selected at the same time. By resetting a tree species selection to “Tree Species” you can remove a combination from the plot. All selected combination underneath in the list will be turned off as well.

For coniferous trees, you can select the age of the needles. Current-year needles, which are formed in the spring of the measurement year, differ in nutrient content from needles formed in the previous spring or earlier. Besides comparing different years, the app enables comparisons of nutrients within the same tree species, the same nutrients across different tree species, or various other combinations.

The range of values displayed on the y-axis can be manually adjusted using a slider or, if the corresponding checkbox is selected, automatically adjusts to match the displayed values. Note that the y-axis can only be manually adjusted if the checkbox is not selected.