A balanced nutrient supply is of great importance for the vitality and growth of trees. Without a balanced nutrient supply, trees can become more susceptible to pests, windthrow, or drought. The most important nutrients are nitrogen, phosphorus, potassium, calcium, magnesium and sulphur. Trace elements are also recorded on the Level II sites.

Various intensive forest environmental monitoring surveys record parameters that provide information about the nutrient cycle:

The availability of nutrients depends on their presence in the soil. Every ten years, soil samples are collected on the Level II sites, and chemical analyses are carried out using on subsamples from different depths.

Nutrients  in the soil solution are particularly important for plants and microorganisms. The nutrient concentrations in the soil solution of the subsoil can indicate the risk of leaching. The soil solution is continuously sampled.

Foliar nutrients are an important indicator of the vitality of trees. For this purpose, leaves or needles are taken from the upper part of the crown for chemical analyses.

When the leaves fall, nutrients return from the trees to the soil. This nutrient pathway is recorded on the Level II sites using litter traps.

Nutrients enter the forest through the air. The deposition is measured both within the forest and in open fields. In particular, nitrogen deposition has a significant impact on the condition of forest ecosystems.