Effects of forest liming on soil processes

Abstract

On the basis of a field experiment in Norway spruce with acid irrigation and compensatory liming of the soil surface (H6glwald, S-Bavaria), liming effects are described as lime dissolution rate, transformation of carbonate buffer to exchange buffer, time required for deacidification of soil and drainage water, mobilization of Cu and Pb, changes in soil organisms, humus decomposition, and nitrogen turnover. It was shown that lime dissolution followed an exponentially decreasing curve. 4 t ha-l dolomitic lime were dissolved within 6 years. Additional acid irrigation of 4 kmol H + ha -1 yr -1 as sulphuric acid speeded up the lime dissolution to about 4 years. After dissolution of lime about 70% of Ca and about 30% of Mg, both originating from lime dissolution, are retained in the surface humus layer, loading the exchange buffer capacity there. Liming acted as a protection against acid irrigation but the extension of soil deacidification downwards proceeded slowly due to the high base neutralizing capacity of protonated functional groups of the organic matter. The main depth effect is caused by Mg translocation. A significant increase of organic Cu complexes occurred due to mobilization of water soluble humus decomposition products. The effect of liming on litter decomposing organisms is demonstrated with microorganisms, collembolae and earthworms regarding the abundance and the structure of dominance. It was shown that liming may induce unusually large changes in biocenoses of forest soils. The decay of surface humus accounted for 7.2 t ha-1 or 23% of the store within 7 years. Within the same time span, liming caused a loss of about 170 kg N ha -l or 14% of the store of the surface humus layer. The nitrate concentration in the drainage water thus increased by about 50 to 60 mg NO 3 L -1. Site-specific conditions are discussed, which produce such negative liming effects as increased nitrate concentration of seepage, humus decay and heavy metal mobilization. Redistribution of tree roots, induction of boron deficiency and root rot are also considered. It is indicated that liming may aggravate the increasing problem of nitrate contamination of forest ground water resources which is associated with deposition of atmogenous nitrogen compounds. Some recommendations are given regarding forest practice.

Experiences with liming in European countries - results of long-term experiments

“…Base saturation in the upper mineral soil was increased from 6% to 12% in Linz and from 3% to 5.5% in Pruem. Similar results were obtained by HILDEBRAND and SCHACK-KIRCHNER (1990) in soil column studies.Almost all surface liming experiments agree that these main positive effects on soil chemistry are restricted to a few cm depth of the profile, in most cases to the organic surface layer or the upper few cm of the top mineral soil (KREUTZER 1995). Only with very high dosages or after long times effects in deeper soil layers are reported (KREUTZER 1995;MARSCHNER et al 1989;MATZNER et al 1985; REI-TER et al 1986;WENZEL 1989).…”

“…In many studies the main effects of forest soil liming are found with respect to soil pH, cation exchange capacity and base saturation (HÜTTL 1989;KREUTZER 1995). In most cases these effects are restricted to the organic surface layer and the uppermost mineral soil (BEESE, MEIWES 1995;Fig.…”

“…This finding is mainly due to increased microbial acitivity, soil respiration and mineralization of soil organic matter (SOM; PERSSON et al 1991) and could result in a risk for further mineral soil acidification and pollution of ground and surface waters as well as for substantial losses of SOM stores from the soil. KREUTZER (1995) reported losses of up to 23% of total carbon and 13% of total nitrogen from the humus layer after liming (6.5-7 t C/ha and 170 kg N/ha, respectively). A major part of the carbon losses was contributed to increased respiration losses and release from the soil as CO 2 .…”

“…Only with very high dosages or after long times effects in deeper soil layers are reported (KREUTZER 1995;MARSCHNER et al 1989;MATZNER et al 1985; REI-TER et al 1986;WENZEL 1989).…”

“…In the Hoeglwald experiment the application of 4,000 kg/ha dolomitic lime increased pH in the organic surface layer from values of 2.8-3.5 to 3.5-6.5 (KREUTZER 1995).…”