Soil aeration - the key factor of oak decline?

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it is a „complex disease . This result can hardly be falsified because of its fuzziness. A significant contribution of pathogenic fungi is not without controversy, because the primary pathogenicity is not proven (Johnsson, 2004). Our starting point is the research of Gaertig et al. (2002) who found that on a spatial integration level of 28 oak stands in Baden-Wuerttemberg the symptoms of oak health are significantly correlated with soil aeration. Large-scale changes of soil structure in oak stands during the last decades can be attributed to the mechanization of logging (Vossbrink and Horn, 2004) as well as to a decrease of earthworm activity in acidified soils. In the proposed project we want to establish a relationship between roots and aerationrelevant parameters in a three-dimensional space. This laborious procedure is necessary because the soil-air access is highly heterogeneous and by this way forms a three-dimensional pattern. This makes one-dimensional models inefficient. By modelling the soil air access in a three-dimensional space we want to test the aeration hypothesis. Important indicators of rooting are clustering of fine roots, necrosis, or space discrimination. By assessing simultaneously soil-chemical and soil-physical parameters in the same spatial resolution, alternative hypotheses can be tested. As modelling tools point statistics, non parametric regression (GAM), and a three dimensional solution of the instationary gas-diffusion equation will be used.