The mechanistic simulations of chemical processes in forest soils require estimates of uptake and release rates of nutrients from trees, as well as rates of microbial transformations of organic matter, chemical weathering and solute transport within the soil profile. Among the processes that affect the chemistry of forest soils chemical inorganic equilibrium processes are best understood. An appropriate presentation of microbiological processes is lacking. Further uncertainty is introduced by simplistic approaches to estimate nutrient uptake by trees and rates of chemical rock weathering. Parameters for processes are derived from studies conducted at different spatial or temporal scales and therefore, may not always be consistent. Since kinetics cannot often be adequately modeled, many processes are described assuming steady-state conditions. Moreover most European temperate forests are in a successional transition phase and considerably off chemical steady-state. Reasons are disturbances due to natural disasters (e.g., wild-fires) and anthropogenic impacts (e.g., litter raking, acidic emmissions and management practices). Changing intensities of anthropogenic land-use and silvicultural methods affect the chemical status of soils for decades. A major constraint to modeling is the inability to properly account for long-term patterns that arise from the longevity of forests. Results of simulation models are rather suitable to establish the boundaries of the status of soil chemistry under defined environmental conditions. Models often fail to accurately describe soil chemistry at particular locations and times.