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Yellowing of part or the whole canopy of chestnut trees was observed during the summer of 2014 in the areas of Tenno, Pranzo and Drena in Trentino, where chestnut cultivation is traditional on the lateral moraine deposit in a context of a prevalent limestone lithological substrate. Symptoms were observed on chestnut trees of different ages, either grafted or not, scattered or in stripes along the maximum slope. Investigations were carried out in the form of field surveys, chemical and molecular analyses of soil and leaves and greenhouse trials, to assess the damage evolution and its causes. No known pathogens emerged during the field surveys, and laboratory tests excluded the presence of phytoplasma infections. A comparison of yellow and asymptomatic leaves evidenced significant deficiencies of manganese (Mn) and iron (Fe) in the yellow leaves, though the level of the two nutrients was the same in the soil below green and yellowed trees. Experimental run-off trials in the greenhouse reproduced the foliage damage with a continuous basic water regime; open-field fertilizations with Mn and Fe led to a slightly recovery on the part of some treated leaves, thus confirming the hypothesis of a probable, sudden deficiency of the mentioned microelements. A possible explanation of this phenomenon could be, on one side, the high precipitation level of 2014, and, on the other side, the previous outbreaks of the Asian chestnut gall wasp, that had reduced foliage volume and thus the organic substance in the soil. The natural recovery from symptoms was clearly visible in trees after four years in a context of normal rainfall regime and increasing organic acid in the soil, after effective biological control of wasp. Even if related to a particular and rare geological condition, this is the first description of Mn deficiency in Castanea sativa.

To describe the decay stage of coarse woody debris (CWD) a five decay-class system has been introduced and it is currently the most commonly applied. This system is based on visual, geometric and tactile features of the wood in the field; however, a detailed chemical characterization is often missing. Furthermore, the driving mechanisms (particularly substrate quality vs. environmental conditions) of deadwood decay are controversially discussed. Consequently, we investigated how typical major and minor chemical parameters of wood were correlated with the decay stage. The decomposition patterns of Norway spruce (Picea abies (L.) Karst) and European larch (Larix decidua Mill.) CWD of an Alpine setting were analyzed, and how the chemical and physical parameters were affected by the substrate and environmental conditions was checked. Two altitudinal sequences, having a different exposure (north- vs. south-facing sites), were sampled. We measured main biochemical compounds (lignin and cellulose), physical properties (density and water content), element concentrations (C, N, P, K, Ca, Mg, Fe, Mn), and the carbon isotopic signature (δ13C) of living trees and CWD at five decomposition stages (decay classes). Most investigated wood physico-chemical parameters such as wood density, water content, lignin and cellulose and even minor constituents (N, Ca, Mg, P, Fe, Mn) correlated well to the five decay-class system. Some important components, such as the carbon concentration and δ13C, did not vary with increasing decomposition. Our hypothesis that the different substrate should be traceable during CWD decay had to be rejected, although some statistically significant chemical differences between larch and spruce were measured in the living trees. The chosen tree species were probably not different enough to be chemically traceable in the CWD. Already in decay class 1, these differences were zeroed. The site conditions (expressed by the different altitudes and exposure) influenced only some of the investigated parameters, namely lignin, the δ13C isotopic ratio and nutrients such as P, Ca and K.