Bavarian State Institute of Forestry
Section Soil and Climate
Phone: +49 (8161) / 71 - 4945
Fax: +49 (8161) / 71 - 4971
With liming, comparisons with human medicine are unavoidable since lime works like a strong medication on the soils and forests. Medications often have risks and side effects. Patients are to be informed of this before their use.
|Fig. 1: With a diagnosis from clear symptoms and/or a needle analysis there is no doubt about the necessity of a treatment. A dose of lime in such cases is extremely advisable (Picture: M. Hertel).|
Liming can be understood as a form of therapy for sick soils and forests. As a result, clear reactions in the treated forests are intended and are most always achieved. If the liming is seen as a medical treatment, the question arises if the therapy is associated with more advantages than risks for the patient.
When liming the forest, it is important the check the necessity of the treatment and see if the advantages outweigh the disadvantages. This is because the measures:
Lime in the forest is not simply a harmless household remedy that only presents advantages and usefulness.
The use of lime in the forest is primarily comprised of three goals:
|Fig. 2: A liming backdrop for the forested area in Bavaria (LWF 2010/2013 excerpt): The green areas do not require liming. Liming could be considered useful on the red areas. Sites that can be excluded from liming include nutrient rich sites, proximity to water, wet and dry sites plus sites with exposed bedrock and boulders.|
An application of lime should always be viewed against the backdrop of the entire nutrient balance of the forest. Through tree species selection and the principles of admixture, the soil can be "browsed" to exhaustion by the roots of various trees in its entire depth. It is thus important, that the nutrients that are taken up from the subsoil are delivered to the topsoil through litterfall and harvest residues (i.e. slash). Forest trees have the capability to sustainably improve their own sites over centuries through their own "waste production". This should not be impaired, for example, through excessive harvests or other types of usage. It is decisive to care for and maintain the nutrient and water storage characteristics of the humus layer in our forests. Liming is only considered a supportive remedy when the nutrient balance of the forest is impaired to such an extent that the danger of malnutrition and deficiency could arise. The goal of near to nature forestry primarily remains the concept of self-regulation. This concept entails the incorporation of site appropriate and mixed tree species with a high proportion of broadleaves, the securement of the long-term capability of natural regeneration and the utilization of harvest operations that are gentle on the soil. Liming in Bavaria is only encouraged after consideration of the soil condition and nutrient situation on critical sites. This ensures that no negative effects on the ecosystem arise as a result of the application of lime.
In human medicine the clinical endpoint is the condition that is to be reached through a medical treatment. As a result, measureable and clearly defined criteria are determined.
Which clinical endpoint is sought for by liming? Should the pH value after the treatment measure 4,5 or 5,65? Is a mull humus form desired or will a moder suffice? Should the soil have many or just a few earthworms? And what does "many" or "just a few" mean? Are stands with satisfactory levels of nutrition with out deficiencies enough or is there an ambition to maximize growth? Should the level of base saturation be fifteen percent or is ten percent acceptable? What is a "good" soil condition? The original condition from around 1000 AD with minimal anthropogenic influence, the highly altered historical condition after the overexploitation of the modern era around 1900, the once more modified condition through acid rain after 1980 or the presently varied condition after liming measure?
The protection against damage, disadvantages and influences from conducting soil protection measures is defined in federal soil protection laws in Germany. In a managed forest the main soil function is to serve as a site for utilization through agriculture and forestry. The core issue is to determine how the usage is influenced through destructive changes to the soil: Can the trees grow and thrive as expected from forest landowners and forestry officials under the given soil condition? Or do these people have to intervene in a regulatory manner? Questions about soil protection in the forest are: Should soil functions be ensured and restored beyond those that simply serve as "a site for production"? Should the waterways downstream also be taken into consideration? Is the soil as the basis of life and habitat for humans, animals, plants and soil organisms in danger?
It is time to make a consensus about the endpoints that are to be achieved and to build a consensus about the level of quality the forest soil should have and how this can be achieved. In natural systems like the forest every last endpoint doesn't have to be realized and every condition doesn't have to be optimized. Ultimately it is the diversity of rich and poor soils, of fast and slow growing forests and of wild and tamed nature that makes our forest environment so exciting. Liming the forest isn't a question of natural science, but rather a societal and political question.