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Aboveground dead wood has a range of important ecological functions, including carbon (C) storage. According to the Intergovernmental Panel on Climate Change guidelines for National Greenhouse Gas Inventories established on the basis of the United Nations Framework Convention on Climate Change and the Kyoto Protocol, Lithuania is encouraged to quantify C pools in forests, including C in living biomass, soil and dead wood. The aim of this study was to assess species-specific dead wood density (DWD) and carbon content (CC) per decay class for Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst.), silver birch or downy birch (Betula pendula Roth or Betula pubescens Ehrh.), European aspen (Populus tremula L.), grey alder (Alnus incana (L.) Moench), black alder (Alnus glutinosa (L.) Gaertn.), common oak (Quercus robur L.) and European ash (Fraxinus excelsior L.), as the main representative hemiboreal forest tree species. The study findings revealed that mean DWD significantly decreased, while mean CC slightly increased during the wood decomposition process, which led to carbon density (CD) reduction over five decay classes. The mean CC showed little variation among the eight tree species and ranged between 47 and 54%. The lower CDs in the dead wood of decay classes 1 and 2 were more associated with coniferous than deciduous species. The estimated CD significantly decreased in all species with increasing decay class. Dead wood at decay class 5 of Scots pine, silver or downy birch, European ash and common oak had the highest CD, followed by Norway spruce and grey alder, and the lowest CDs were obtained for European aspen and black alder.

The European beech (Fagus sylvatica L.) is a competitive and shade-tolerant species, with its natural regeneration in closed-canopy stands affected by a number of variables. The study aimed to identify factors related to beech regeneration by focusing on two main questions: (1) can we identify environmental and stand structural characteristics that promote beech regeneration or indicate suitable conditions for regeneration under closed canopy conditions, and (2) do environmental and stand structural characteristics favorable for beech regeneration differ among the ontogeny of seedlings and saplings? To answer these questions, we sampled four beech-dominated forest complexes in northern and southern Poland. Study plots were established in sites with varying overstory composition, including beech-dominated, mixed, and conifer-dominated stands. In the analyzed forest complexes, regeneration consisted mostly of beech seedlings and saplings with admixture of shade tolerant or intermediate light-tolerant species—Norway spruce (Picea abies (L.) Karst.), silver fir (Abies alba Mill.), hornbeam (Carpinus betulus L.), and sycamore maple (Acer pseudoplatanus L.). The average density of beech regeneration was 9047, 10,305, 5198 and 8972 trees ha−1 in forest complexes 1, 2, 3 and 4, respectively; however, the inter-plot variation of the regeneration density was high. Beech regeneration occurrence were determined by stand structural characteristics. Beech regeneration decreases as stand density increases and increases with stand basal area and the percentage of beech in the dominant canopy layer. The ecological prerequisites favorable for beech regeneration abundance differ with the ontogeny of seedlings and saplings—the smallest seedlings regeneration was determined by stand structural variables to a greater extent, while more advanced regeneration abundance was also associated with light-demanding species regeneration abundance. Under closed canopy conditions, beech regeneration abundance was weakly influenced by intra/interspecific competition from surrounding vegetation; however, canopy openings may increase it, therefore, competition aspects should be taken into account in the selection of forest management practices.

Due to the effect of butt rot, Norway spruce crown defoliation has increased, and the proportion of healthy trees has decreased; butt rot acts as a predisposing factor for the decline of spruce. The exact contribution of butt rot in influencing the health and vitality of Norway spruce is still unclear. Previous studies have mostly evaluated the effect of butt rot on the radial increment in Norway spruce, as an indicator of the productivity and vitality of the tree. To our knowledge, no study has evaluated the influence of butt rot on the crown condition of Norway spruce; previous studies mainly determined the incidence and frequency of butt rot based on external signs (crown parameters). In this paper, we performed a comparison of the average crown defoliation among decayed and non-decayed Norway spruce trees within three single Norway spruce stands. We addressed the following questions: did the average Norway spruce crown defoliation differ among decayed and non-decayed trees? Did butt rot predispose, initiate, or contribute to the Norway spruce decline process? Results revealed that the average crown defoliation was higher among decayed trees in all three assessed stands. Among the decayed Norway spruce trees, the proportion of trees with defoliation class 0 (crown defoliation from 0 to 10%) was considerably low and that of trees with defoliation class 2 (crown defoliation from 26 to 60%) was much greater compared to that in non-decayed trees. The study was able to verify the assumption that as per Manion’s tree decline concept, butt rot acts as a predisposing factor for the decline of Norway spruce because of a non-lethal effect. This study provides meaningful knowledge about the influence of butt rot on the crown condition of Norway spruce and contributes to a better understanding of the impact of disease on spruce vitality.

We assess the influence of edaphic, climatic, stand structure and individual tree (stump diameter) factors on incidence of Norway spruce (Picea abies (L.) H. Karst.) butt rot. The data used in the study come from 97 stands, originated from natural regeneration, which were clear-cut. The age of the stands varied between 71 and 130 years old. The climate continentality, site fertility, hydrotop (site humidity index), part of Norway spruce in the stand, stand stocking level (density index) and stump diameter were selected as the factors related with frequency of decay. The study material revealed that selected variables explain 34% of Norway spruce butt rot incidence in Lithuanian forests. Site fertility and stand age influence on butt rot incidence was weak. Higher incidence was related with low stand density, low site humidity (dry sites) and higher part of Norway spruce in stand. More frequent damages were recorded on higher diameter stumps. Our results showed longitudinal distribution of decay incidence in Lithuania—the frequency of decay increasing from West (coast) to East (continent).

This study observed the genotypic variation among Scots pine (Pinus sylvestris L.) half-sib families&rsquo, susceptibility to Heterobasidion annosum. Scots pine susceptibility was tested in 12 half-sib families by inoculating them with four different H. annosum strains. At two, six, and ten months after the inoculations, the susceptibility indicators (incidence rate, pathogen spread, and mortality rate) were compared and the total phenolic compounds (TPC) in the inoculated and control groups determined using the Folin&ndash, Ciocalteu method. Among half-sib families, significant differences were found for seedling mortality (range: 1.3%&ndash, 21.2%), however, the differences in incidence rate (range: 54%&ndash, 77%) and pathogen spread (range: 24&ndash, 53 mm) were not significant. The incidence rate among half-sib families correlated positively and significantly (r = 0.72, p &lt, 0.05) with the mortality rate, while the pathogen spread correlated negatively with mortality, although the correlation was not significant (r = &minus, 0.29, p &gt, 0.05). The TPC comparison with susceptibility indicators showed that the half-sib families with lower susceptibility were characterized by the ability to increase TPC after inoculation compared to the control group. This tendency was most apparent in stems and roots six and two months after inoculation, respectively. Correlation analyses revealed that higher TPC in stems six months after inoculation determined a lower incidence rate (r = &minus, 0.32, p &lt, 0.05), while higher Change in concentration of total phenolic compounds (TPC&Delta, ) indicated a lower pathogen spread (r = &minus, 0.60, p &lt, 0.05). The lowest incidence of the pathogen was determined in half-sib families with the highest TPC&Delta, in the roots two months after inoculation. The lower susceptibility of Scots pine half-sib families is based on a combination of enhanced constitutive and inducible phenolic defense mechanisms. The data may facilitate the selection of Scots pine half-sib families with low susceptibility for breeding programs and forest management strategies.