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Humplík P., Čermák P., Žid T. (2016). Electrical impedance tomography for decay diagnostics of Norway spruce (Picea abies): possibilities and opportunities. Silva Fennica vol. 50 no. 1 article id 1341. 13 p. Highlights• Statistical parameters of EIT datasets with values of electrical resistance of heartwood are possible to employ in refining heartwood rot diagnostics.• Sapwood proportion is decreasing as the proportion of decay on the radial cut expands.• Using EIT datasets and sapwood proportion, trees with rot can be split into two groups as per proportion of decay: [< 35%] and [> 35%]. AbstractThe paper aimed at testing the potential of refining tree rot diagnostics carried out by means of electrical impedance tomography (EIT). Examined was the use of EIT datasets with electrical resistance values and sapwood proportion determined on the basis of tomograms. Making use of datasets with resistance values in EIT rot diagnostics is not a default method, although datasets stay unaffected by a fixed colour scale and subsequent subjective evaluation unlike tomograms. Tomography measurement was carried out for 27 individuals of Norway spruce (Picea abies [L.] Karst.) in two stands north-east of Brno, Czech Republic. Once felled down, radial cut-outs were sampled at the measurement site and used for localising rot and determining the extent of the area of decay. The results were subsequently compared with tomograms. EIT datasets containing values of electrical resistance found by measuring were statistically processed and compared with the extent of rot area identified within the cuts. Sapwood proportion values were also detected using the tomograms. The baseline assumption that sapwood proportion decreases as the rot area in the radial cut expands was confirmed. In trees with rot percentage to 35% approximately, sapwood proportion was exceeding 30% except one tree. In trees with rot percentage exceeding 35%, sapwood proportion was below 30%. On the basis of interpreted datasets, the trees can be split into three characteristic groups that correspond to the occurrence, extent and nature of the rot.

Abstract:The research was conducted in selected spruce stands of the Silesian Beskids aged over 70 at altitudes from 403 m a.s.l. to 794 m a.s.l. in 2008. The samples were taken and processed in compliance with standard dendrochronological methodology. Tree rings were measured and the treering curves were synchronized using the PAST4 application. The age trend was removed in the ARSTAN application and the climatic influences were modelled in the DendroClim application. The regional standard tree-ring chronology shows an obvious decrease in the radial increment from the beginning of the 1970s to the mid-1990s. The gradual increase in radial increment which followed in the second half of the 1990s was interrupted in 2000, 2003, and 2006. Most of the years with the decreased radial increment have been confirmed by the analysis of significant negative years. The radial increment statistically significantly correlates with the precipitation in July and September of the previous year, precipitation in June of the year in question and precipitation during the vegetation period. Moreover, the growth of spruce is statistically significantly affected by temperatures in October of the previous year and March of the year in question. Additionally, the paper includes habitual monitoring of trees and the volume of salvage cutting in these districts. The condition of the habit of trees and the development of salvage cuttings agree with the hypothesis about strong stress load or its considerable increase in 2003 and the following years.

Climatic parameters are the main environmental factors affecting tree growth. The main aim of the presented study was to determine whether different oak species growing under contrasting environmental conditions show different sensitivity to climatic parameters. Four oak stands with Quercus robur, Quercus petraea, Quercus polycarpa and Quercus dalechampii growing in the same area were evaluated. Standard dendrochronological methods were used for sample preparation, ring width measurements, cross-dating, chronology development, and the assessment of growth-climate response patterns. Although the species grew under different environmental conditions, their local tree-ring chronologies are highly correlated. The radial growth responses to climatic parameters differ slightly, but the response depends more on local site conditions than on the oak species. At the same time, the strongest correlations between radial growth and climatic parameters were identical among species and sites. The amount of water available in the soil was the main climate-dependent factor limiting radial growth. Approximately since the 1990s, the distribution of rainfalls within the growing season has changed at the expense of spring precipitation. The significance of relative soil moisture content during spring for oak growth increased and the significance of summer values decreased.

Research on the influence of temperatures and precipitation on radial increment was carried out in spruce stands over ninety years old in the surroundings of Anenský vrch in the Orlické hory Mts. at altitudes over 800 m above sea level. To model diameter increment in dependence on climatic conditions, the standard tree-ring and correlation analysis together with the analysis of negative pointer years were used. The diameter increment has a statistically significant correlation with temperatures in July of each year in question. The growth of spruce is also affected to a statistically significant degree by precipitation in July of the previous year and by precipitation in February and March of the year in question. The standard tree-ring chronology shows an obvious decrease in radial increments starting at the beginning of the 1970s and ending at the end of the 1980s. The lowest increments were recorded for 1974, 1980, 1984 and 1986. These years with low increments were also confirmed by the analysis of negative pointer years. In the following period there is an increase in increments, with slight decreases in 1996 and 2000, which, however, according to the analysis of negative pointer years do not demonstrate any significant reduction of increments. Another decrease was recorded starting in 2003 and this lasted until the studied period, i.e. 2007. The current condition of spruce stands is certainly the result of more stressors but it appears that with the current air pollution load the climatic conditions are the factor determining the resulting effect of the synergic influence of the stressors on the stands.