MODELING RECENT AND HISTORIC SOIL DATA FROM THE ROTHAMSTED-EXPERIMENTAL-STATION, UK USING SAFE

Historic soil data from 1883, 1906, 1964 and new data from 1991 from the Geesecroft Wilderness Experiment at Rothamsted Experimental Station, UK, was used as a test of the dynamic biogeochemical model SAFE in a situation where the available data can be used to confine the model completely. The test indicated that the model is capable of predicting the observed changes over time in soil chemistry, without calibration. This suggests that the model formulation and choice of significant processes are quantitatively correct. The model application at Rothamsted shows that deposition of acidity because of sulphur and nitrogen emissions during the last 110 years, is the major cause of soil acidification in Geesecroft Wilderness. Natural afforestation of the site has also contributed with a significant but smaller amount of acidity input to the soil. Acidification has caused a possibly irreversible decrease in the cation exchange capacity of the soil because of weathering of clay minerals.