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Forest liming is a common measure to counteract soil acidification. In forest practice, lime is applied to the forest floor where it changes the chemical properties. However, little is known about the depth impact of liming and the depth translocation of lime components. To investigate the long-term impact of forest liming, several study plots have been established in the 1980s in Germany in stands with different site conditions. We analysed soil chemical data obtained during the last 28 years from 45 of the study plots. We examined the depth impact of liming and predicted the main factors responsible for the increase in Calcium (Ca) and Magnesium (Mg) stocks after liming in the mineral soil using multiple linear regression analyses (MLR). Stocks of Ca and Mg as well as base saturation (BS) showed a strong depth gradient with significant differences between limed and control plots down to 40 cm of the mineral soil. About 65–70 % of applied Ca and Mg were recovered in the forest floor and the upper 40 cm of the mineral soil. BS in 0–40 cm increased by a mean of 11 %. MLR models could explain 48–74 % of the variation in mean changes of Ca and Mg in 0–10, 10–20 and 20–40 cm soil depth when soil and climate variables, amount of applied lime and years after liming are included in the model. After testing the model robustness with a cross-validating procedure, we concluded that these models might be applied to many regions in Central Europe with comparable soil and climate conditions and thus, have widespread application.

In a forest stand lime is commonly applied to the forest floor to neutralize acidity and to improve buffering capacity of soil by the addition of carbonate and other anions of weak acids. This is expected to cause major chemical changes in the forest floor. In this study, different liming materials, equivalent to 60 kmol c Ca 2+ +Mg 2+ ha −1 , were applied to the forest floor of a spruce stand. The limes were dolomite, mixtures of dolomite and calcite or chalk, and silicate industrial slag lime (‘Huttenkalk’) of varying particle size combinations. Two years after lime application, salt extractable Ca 2+ and Mg 2+ was measured in the forest floor using a sequential percolation method. This method allowed the assessment of Ca 2+ +Mg 2+ present on exchange sites by distinguishing between the amounts released upon dissolution of residual, undissolved liming material. In all cases there were major changes in exchangeable content of Ca 2+ and Mg 2+ in the L+F layer, whereas changes in the H layer were small. Differences in the effects of liming materials on the litter layer were attributed to their texture, the contents of Ca 2+ and Mg 2+ and the associated anion (carbonate or silicate). High content of exchangeable Ca 2+ and Mg 2+ was observed in the forest floor when liming materials were of high Ca and Mg content and of fine texture. The sum of exchangeable Ca 2+ +Mg 2+ in the forest floor increased from 7 kmol c ha −1 (control) to 17–26 kmol c ha −1 after liming and accounted for 15.5–31.5% of Ca+Mg applied. This increase in exchangeable Ca 2+ and Mg 2+ of L+F layer indicates large amounts of lime may be required to ameliorate mineral soil at depth, and that the content of these cations will partly determine future lime requirement of the spruce stands.

Lime and wood ash may be useful to improve acidic forest soils. A field experiment was conducted in a pine stand on a sandy podzol at Fuhrberg, Germany, which involved an application of dolomitic lime (3 t ha-1) with three replications or wood ash (4.8 t ha-1) without replications on the forest floor. During the 2 yr study period, lime affected the soil solution composition only slightly. Ash had a marked effect on solution chemistry of the mineral soil at 10 cm and the pH values dropped temporarily from 3.7 to 3.1. Nineteen months after the treatments, exchangeable calcium in the organic layer and mineral soil increased by 222 (lime addition) or 411 kg ha-1 (ash addition) and exchangeable magnesium increased by 101 (lime addition) or 39 kg ha-1 (ash addition). After ash addition, no marked change in heavy metal content was found below 4 cm of the organic layer. In the ash treatment, the potassium concentration of the 1-yr-old pine needles increased from 5.6 to 5.9 g kg-1. This study suggests that ash fro...