Inventaris van de toestand van de bosbodem in het Vlaamse Gewest

In order to evaluate the role of the soil in relation to the pollution load in forest ecosystems, a transnational inventory of the forest soil condition is carried out in Europe.
This article deals with the Flemish part of this survey. Following topics are con¬sidered: samplingdesign, parameters and analysis methods, presentation and discussion of the results of the inventory in the 16 x 16 km grid in Flanders(level I of the EU).
The first inventory shows that the soil is chemically poor in most of the 10 Flemish sample plots(low pH values, low cation exchange capacity and base saturation). 80 % of the plots show veryacid soils (pHcaci2 - 3.5 in the mineral layers 0-5 cm and 5-10 cm). The base saturation in themineral layer 5-20 cm is low to extremely low in 70 % of the plots. In the 0-5 cm layer highervalues are recorded. In 30 % of the plots the cation exchange capacity is below 3 meq/100 g in allthe sampled mineral soil layers .
70 % of the plots show a humus layer of the mor type. Large stocks of carbon, nitrogen and othermacronutrients are immobilized in a thick organic layer and are not directly available for the treesand the accompanying vegetation. This humus accumulation can lead to an interruption of the nutrient cycle.
The chemical poverty of the sandy soils is partly caused by the parent material. However the results of the survey indicate a soil degradation, in which acidi¬fying deposition might be involved. Deposition measurements in the Flemish Region show that throughfall water isconsiderably enriched with pollutants. A further decrease of the available nutrients in the soil maylead to deficiencies, which may damage the trees. High nitrogen depositions may lead to adistur¬bance of the nutrient balance, physiological malfunctions, reduced frost and droughtresistance and a general decrease of the resistance against damaging factors.
The execution of a second inventory will result in a better understanding of the evolution and the influence of natural and anthropogenic factors on soil processes.