Forest soil conditions in the CONECOFOR Permanent Monitoring Plots and in the Level I Network in Italy

The study of forest health is not complete without an assessment of soil condition. Forest soils were monitored in 20 Italian sites in the CONECOFOR programme with different pedological and climatic conditions, the Permanent Monitoring Plots (PMPs). The main objective was the evaluation of the effect of acid depositions on soils and nutrient availability. The FAO classification was applied to all the CONECOFOR soils. Other analyses were carried out on the organic layer and on four mineral layers. Although the number of sites is too small for this monitoring to be considered wholly representative of the state of Italian forest soils, the analyses yield some general information. In addition, a smaller number of determinations were carried out on a higher number of soils (70 soils in the first level monitoring programme (FLP), including the twenty PMPs). Results show that no soils have pH <3 and few soils have pH between 3.0-3.5 (measured in CaCl2 solution). Furthermore, the soils with low pH values are naturally acid, due to the parent material. The parameters that provide information on the sensitivity of soil to acidification, such as base saturation and the sum of exchangeable base cations in the mineral layers, as well as the amount of total K, Ca and Mg in the organic layer, show that there are hardly any soils in poor health. A high proportion of Italian soils have a lower content of organic matter than other European soils, due to Mediterranean climatic conditions; these are very different from those in central and northern Europe, which represent the majority of the European soils monitored. The availability of nutrients (particularly nitrogen and phosphorus) is on the whole sufficient. The results of the determinations of the FLP programme confirm the evaluations expressed for the PMPs, but provide more information, for example regarding the C/N ratio in the different soil layers: several anomalous sites, where the C/N ratio is higher in the surface mineral layer than in the organic layer, were found in this programme, but not in CONECOFOR.