applied sciences Article Long Term Effects of Forest Liming on the Acid-Base Budget Martin Greve 1,* , Joachim Block 1, Gebhard Schüler 1 and Willy Werner 2 1 Research Institute for Forest Ecology and Forestry (Rhineland-Palatinate), Hauptstrasse 16, 67705 Trippstadt, Germany;
[email protected] (J.B.);
[email protected] (G.S.) 2 Department of Geobotany, Regional and Environmental Sciences, Trier University, Behringstraße 21, 54296 Trier, Germany;
[email protected] * Correspondence:
[email protected] Abstract: In Rhineland-Palatinate (Germany), a high percentage of the forest area is located on poor soils with low buffering capacity. Extensive liming applications were performed to compensate for the negative consequences of acid deposition. In 1988, three experimental sites with untreated control plots and different liming treatments were established in coniferous stands to investigate the effectiveness of liming on acidification and its effect on forest ecosystems. Measuring deposition and seepage waters for 24 years allowed for calculating long-term acid-base budgets. The original approach was expanded by data from a detailed sampling of the forest stand and mineral weathering rates. Without liming, the acid load exceeded the buffer capacity by base cation release from silicate weathering during the whole observation period. As a result, there was a high release of aluminum. After liming seepage water output of organic anions, nitrate and sulfate increased in some cases, leading to a higher acid load. However, the carbonates of dolomitic limestone compensated for a higher acid load, resulting in less aluminum released compared to the control plots. Until sulfate output by seepage water declines and nitrogen emissions are reduced, liming and restricted biomass harvesting are required for forest stands on base poor soils to prevent further acidification, decline of nutrient stocks, and the destruction of clay minerals.