Simulation of soil chemistry and nutrient availability in a forested ecosytem of southern Quebec. Part II. Application of the SAFE model

The dynamic soil model SAFE was calibrated and validated in a small hardwood forest of southern Quebec as a function of its ability to reproduce current soil chemistry and similar pre-industrial soil conditions despite the difference in forest history. SAFE was relatively accurate for reproducing soil chemistry, but comparison of pre-industrial soil conditions between unburned and burned stands casts doubt as to its applicability at sites where specific processes may be involved in nutrient cycling, e.g. the immobilization of N by microbes. Simulated soil chemistry in the unburned zone reinforced the conclusions of a few historical studies which support the hypothesis that acid-sensitive forest sites of northeastern USA underwent significant acidification when major inputs of acidity from the atmosphere occurred, i.e. during the 1930-1980 time span. Model projections in the mineral soil suggest that a new steady-state should be reached in the 21st century assuming no harvest, but that this equilibrium is broken if timber harvesting is done. Model output also suggests that cation nutrient deficiencies could occur in the long-term, but future Al phytotoxic responses are unlikely to occur due to a relatively high projected pH. Finally, it was demonstrated that the time-series files of nutrient cycling should be prepared with care as they can be the source of some abnormalities in model calibration. (C) 2002 Elsevier Science Ltd. All rights reserved.