Nitrogen deposition changed the N status of forest ecosystems and nitrate leaching below the rooting zone is used to indicate forests as N saturated. The use of different definitions implies that the N states of ecosystems are not fully described by N saturation. We used input-output matter balances and stratify 41 forests into systems being in the Steady State and those being in a Transient State. Forests in the Steady State lose nitrate if the input exceeds the plant increment. Of the forests in the Steady State, some grow on base rich soils with a mull humus type and a high N pool in the mineral soil indicating that they are naturally enriched with nitrogen (n=5). Other forests in the Steady State grow on base poor soils with moder/mor humus and were naturally N limited (n=9). They became N enriched by anthropogenic N deposition. Forests in the Transient State accumulate or release N. Of the forests in the Transient State losing nitrate by seepage water are classified by the process of humus degradation (n=3) (Degradation Type). Forests at the Transient State which accumulate N are either at the beginning of soil development (Aggrading Type) or are limited in N (Accumulation Type). Forests accumulate N from N deposition either by increasing N content or by increasing forest floor mass. The German data indicated that some forests of the Accumulation Type are fare away from equilibrium between input and output and has a C/N ratio >25 (n=10). Other forests of the Accumulation Type had higher nitrate losses but still accumulating N despite a C/N ratio <25 (n=14). These forest are assumed to accumulate deposited nitrogen by increasing forest floor mass which up to know has not been considered to be an important process.