The occurrence and influence on durability of wood-decaying and blue staining fungi in bark-beetle infested Norway spruce wood

The staining influence of iron (II) sulphate on Norway spruce wood The paper presents the results ofresearch on the colour change of Norway spruce (Picea abies L.) wood under the influence of iron (II) sulphatewater solution at three different concentrations (1%, 2%, 3%). The tests were perfomed wood showing defectstypical of coniferous wood. The aim was to determine the possibility of increasing the usefulness of wood withdefects (blue stain, reactive wood). Measurements of color parameters and their changes based on the CIELabcolor space were carried out. The influence of natural weathering on further staining effect was also determined.On the basis of the tests carried out, it was shown that iron (II) sulphate causes greying of Norway spruce (Piceaabies L.) wood and that the concentration of the solution does not have a major effect on color changes. The surfaceof the aged wood was clearly stained and darkened, with the greatest difference in the samples modified with a3% solution.

Comparing Norway spruce and silver fir regarding impact of bark wounds

ABSTRACTIn this study, mould and blue stain susceptibility, capillary water uptake (CWU) and microstructural properties of two thermo-hydro-treated (THT) birch plywood products A and B were investigated. Plywood A represented a THT industrial plywood glued with a phenol formaldehyde (PF) adhesive. Plywood B represented panels from THT veneers glued with a PF film. The THT regimes were (temperature, °C/time, min): 150/10, 150/50, 160/10 and 160/50. Both THT plywood products and untreated samples were resistant to mould and blue stain growth in 1 month of exposure in laboratory and outdoor conditions. A statistically significant correlation between fungal growth in laboratory and outdoor conditions for plywood products A and B was not found (P > .05). Artificial weathering of both plywood products provided adverse fungal growth results compared to the natural weathering test outdoors. The fungal growth on plywood A and B samples mutually strongly correlated (P < .05) only in the outdoor test. Plywood B samples demonstrated a much lower CWU than plywood A, obviously because of microstructural changes, including densification, and type of glue used. Lower CWU of THT plywood in comparison with untreated samples did not provide clear evidence on inhibition of fungal growth.

Scots pine (Pinus sylvestris L.) samples were vacuum pressure impregnated with quaternary ammonium (quat)-silicone micro-emulsion (<40 nm particle size), amino-silicone macro-emulsion (110 nm) and silicone macro-emulsion with alkyl modified side groups (740 nm). Quat-silicone micro-emulsion caused highest cell wall bulking (4.8%) and anti-swelling efficiency (21.8%) in wood when treated with 30% concentration of silicone in the treatment solution. All three formulations made wood hydrophobic which was evident from a capillary (longitudinal, tangential and radial) water uptake test. Amino-silicone macro-emulsion (10% silicone in treatment solution) resulted in strong resistance to blue stain attack with both pre-weathered and not pre-weathered wood samples. Signs of blue staining were more evident on the pre-weathered samples. Treatment with amino-silicone macro-emulsion (10% silicone in treatment solution) resulted in a certain resistance to mould growth on wood surfaces, whereas wood treated with the same concentration of quat-silicone micro-emulsion and alkyl-modified silicone macro-emulsion exhibited comparatively lower resistance.

Colonization by blue stain and brown rot fungi affects timber quality in distinct ways. Blue stain fungi cause discoloration without reducing wood properties, while brown rot fungi degrade wood tissues, resulting in brittleness and brown coloration. Given these chemical differences, we investigated whether near-infrared spectroscopy (NIRS) could distinguish between these fungal types. We hypothesized that early fungal attack would produce unique spectral signatures, allowing for rapid identification. Wood disc samples were collected from white spruce, lodgepole pine, and trembling aspen in Fox Creek, northwest Alberta, Canada, ca. 4 months after a wildfire. The trees were colonized by fungi associated with blue and brown sapwood discoloration and analyzed using NIRS. In white spruce, we found consistent and significant absorbance differences between blue- and brown-discolored sapwood across each 100 nm segment. In lodgepole pine, the most distinct differences occurred in the 1650–1750 nm, 2050–2150 nm, and 2350–2450 nm ranges. For trembling aspen, differences were evident across most 100 nm intervals, except 2150–2250 nm. Permutational multivariate analysis of variance (PERMANOVA) indicated greater spectral dissimilarity between fungal types in white spruce and trembling aspen, with less pronounced differences in lodgepole pine. Our findings suggest that NIRS can effectively classify fungal-discolored wood in white spruce and trembling aspen within the first year following wildfire. However, its application to lodgepole pine in the same timeframe may be less reliable.

In the present work, Norway spruce wood (Picea abies L.) was reacted with a commercial Trametes versicolor laccase in the presence of potassium iodide salt or the phenolic compounds thymol and isoeugenol to impart an antimicrobial property to the wood surface. In order to assess the efficacy of the wood treatment, a leaching of the iodinated and polymerized wood and two biotests including bacteria, a yeast, blue stain fungi, and wood decay fungi were performed. After laccase-catalyzed oxidation of the phenols, the antimicrobial effect was significantly reduced. In contrast, the enzymatic oxidation of iodide (I(-)) to iodine (I(2)) in the presence of wood led to an enhanced resistance of the wood surface against all microorganisms, even after exposure to leaching. The efficiency of the enzymatic wood iodination was comparable to that of a chemical wood preservative, VP 7/260a. The modification of the lignocellulose by the laccase-catalyzed iodination was assessed by the Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) technique. The intensities of the selected lignin-associated bands and carbohydrate reference bands were analyzed, and the results indicated a structural change in the lignin matrix. The results suggest that the laccase-catalyzed iodination of the wood surface presents an efficient and ecofriendly method for wood protection.

The permeability of Norway spruce wood can be reduced to 1–5% of that of green timber when dried, resulting in only slight radial penetration of chemical solutions. We investigated the penetration of the biocide 3-iodo-2-propynyl butylcarbamate, (IPBC) in Norway spruce and Scots pine sapwood when applied in a water-based coating system. Penetration of both untreated wood and specimens pretreated with the white-rot fungus Physisporinus vitreus was analyzed by the absence or presence of blue staining after incubation with Aureobasidiumpullulans and Sclerophoma pithyophila. The qualitative results were compared with quantitative data obtained by chemical analysis. It was assumed a pre-treatment with Physisporinus vitreus could make the surface of the substrate more porous and improve the penetration of fluid substances. All analytical investigations of the samples were done after an outdoor weathering period of 6 months. From a practical point of view the performance of the coated substrate is more relevant after a certain aging procedure then right after the application. The chemical measured uptake of IPBC for Scots pine was similar for all samples at the surface. The penetration depth was higher for those samples with a pre-treatment with Physisporinus vitreus. The colonization pattern of the samples by blue-stain fungi depended upon the pre-treatment but did not show a clear correlation between IPBC-content and staining. The cross-section of the samples with pre-treatment was completely stained, the cross-section of the samples without pre-treatment did show a distinctive blue stain-free zone. In Norway spruce, the chemical measured uptake of IPBC was similar for all samples at the surface independent of the pre-treatment. The penetration depth was higher for those samples with a pre-treatment with Physisporinus vitreus. But a clear visible colonization by blue-stain fungi was only observed for the samples with a pre-treatment with Physisporinus vitreus. The samples without pre-treatment were locally stained across the entire cross-section. As with the Scots pine, a clear correlation between IPBC-content and blue staining was not visible, following comparison of the samples with and without pre-treatment with Physisporinus vitreus. The results suggest that not only the presence of IPBC influences colonization by A.pullulans and S.pithyophila, but also a range of other factors in wood pre-treated with P. vitreus.

Under the moderate future greenhouse gas emissions scenario (RCP4.5), climate model simulations project that the annual mean temperature will increase in Europe by up to 2–3 °C by the middle of this century, compared to the end of the nineteenth century. The temperature increase is projected to be larger in Northern Europe than in Central and Southern Europe. The annual precipitation is projected to decrease in Southern Europe and increase in Northern and Central Europe. The projected changes in temperature and precipitation are expected to be higher in the winter than in the summer months. In Northern Europe, forest growth is generally projected to increase due to warmer and longer growing seasons. In southern Europe in particular, warmer and dryer summers are projected to decrease forest growth. Climate change is expected also to expose forests and forestry to multiple abiotic and biotic risks throughout Europe. The greatest abiotic risks to forests are caused by windstorms, drought, forest fires and extreme snow loading on trees. The warmer climate will also increase biotic risks to forests, such as damage caused by European spruce bark beetle (Ips typographus) outbreaks in Norway spruce (Picea abies) forests and wood decay by Heterobasidion spp. root rot in Norway spruce and Scots pine (Pinus sylvestris) forests. Different adaptation and risk management actions may be needed, depending on geographical region and time span, in order to maintain forest resilience, which is also important for climate change mitigation.

Bioincising of Norway spruce wood using wood inhabiting fungi

An extensive area of Norway spruce ( Picea abies (L.) Karst.) forests in the Šumava Mountains, Central Europe, has been affected by a massive bark beetle ( Ips typographus L.) outbreak since the mid-1990s. One part of the area was left without intervention and two types of intervention have been applied in other parts: (1) the classical forest approach, based on the logging of attacked trees and (2) “sanitation”, in which attacked trees were cut down, debarked, and left lying in the stand. The main goal of our research was to test the impact of nonintervention and both types of intervention on the regeneration of the Norway spruce forests. The Norway spruce forests influenced by natural disturbances (bark beetle outbreak and windfalls) regenerated very well if left without intervention. The bark beetle outbreaks and windfalls do not represent a threat to the long-term persistence of the forests. Clearcuts resulted in formation of pioneer stages with a postponed spruce regeneration. In sanitation plots, the reduction of both previous vegetation and tree regeneration was obvious. Generally, both interventions against bark beetle delayed the recovery of Norway spruce forests.

A current ongoing unprecedented outbreak of Ips typographus (L.) (Coleoptera, Curculionidae, Scolytinae) in the Białowieża Primeval Forest (BPF) has nearly eliminated Norway spruce (Picea abies L. Karst) as a major forest tree species there, since over 1 million trees have died. In this part of Europe, Norway spruce has grown for hundreds of years, previously accounting for 30% of forest species composition. The aim of this study was to evaluate 47 “Monuments of Nature” of Norway spruce as follows: (i) their current health status in the managed forests of Białowieża Forest District; (ii) possible causes and changes in their health during the last bark beetle outbreak; and (iii) potential losses from the gene pool. Our findings from ground and remote sensing inventories showed that only 12 out of 47 (25%) monumental trees protected by law survived until 2017 in the study area. The rest (75%) of the investigated trees had died. An analysis of meteorological data from Białowieża suggested that the beginning of the I. typographus outbreak in 2012 was associated with diminishing precipitation during growing seasons prior to this time and subsequent increases in annual temperature, coupled with heavy storms in 2017 toppling weakened trees. A comparison of old-growth “Monuments of Nature” spruce in the region (n = 47, average age 225 years) to seven reference spruce stands (n = 281, average age 132 years) revealed a loss of unique genetic features based on frequencies of eleven nuclear microsatellite loci. Although all studied populations had similar genetic background (FST(without NA) = 0.003 and no STRUCTURE clustering), all monumental spruce trees shared the highest parameters such as the mean observed and expected number of alleles per locus (Na = 15.909 and Ne = 7.656, respectively), mean allelic richness (AR(11) = 8.895), mean private alleles (Apriv = 0.909), and mean Shannon diversity index (I = 1.979) in comparison to the younger stands. Our results demonstrate that the loss of the old spruce trees will entail the loss of genetic variability of the Norway spruce population within the exceptionally valuable Białowieża Primeval Forest.

Wood coatings prolong the service life of wood-based products, but they are usually of synthetic origin. The aim of the present article is to reduce the fossil-based compounds in a commercial waterborne acrylic coating by CNC addition and to test its performance. The coatings were applied on European beech and Norway spruce wood in order to test durability against Gloeophyllum trabeum (brown wood rot) and Trametes versicolor (white wood rot). Artificial weathering and blue stain, contact angle, physical tests (adhesion, impact and scratch test), chemical (FTIR) and morpho-anatomical analysis (SEM) were carried out. CNC addition increased viscosity, limiting the spreading of the coating into wood pores as visible after SEM observation, which reduced coating adhesion on the substrate. CNC improved fungal resistance as seen by a reduced mass loss and FTIR spectroscopy thanks to crosslinks formation, which reduced water sorption as well. Color change was not significant, and, on the other hand, glossiness was reduced but resulted as more homogeneous than control. CNC addition gave good results also in blue stain protection. CNC improved scratch resistance, but no visible change to impact was registered. CNC has promising results in coatings depending on wood and fungal species and presence of further commercial additives (biocides).

Increased mortality rates in Scots pine (<i>Pinus sylvestris</i>) forests have recently been observed in the inner alpine Swiss Rhone valley. Drought, in combination with stand competition, mistletoe infections as well as nematode and insect infestations, appears to be the main factor for the decline. In focus of this study was the occurrence and role of fungal pathogens in the decline dynamics. Branches, stems and roots of 208 trees in five different crown transparency classes were collected and inspected for blue stain and fungal infections. Neither <i>Armillaria</i> species nor <i>Heterobasidon annosum s. str.</i> were detected, but blue stain was commonly observed. Visible blue stain increased with increasing crown transparency. Among the recently dead trees, 80% showed visible blue stain in the branches, 90% in the roots and 100% in the stems. In the crown transparency classes 2 and 3 (25–60% crown transparency), five of the 103 trees showed visible blue stain in the roots, one of 130 trees in the stem but none in the branches. Blue-stain fungi were isolated from all parts of the trees and from all crown transparency classes. Overall incidence of blue stain was highest in the roots and lowest in the branches. In class 2, roots of 60% of the trees were visibly blue-stained or developed blue stain in culture, but stems of only 24% and branches of 14% of the trees. In the roots <i>Leptographium</i> species, mostly <i>L. serpens</i>, dominated. From stems and branches, mainly <i>Ophiostoma</i> species were isolated. The positive relationship between the incidence of blue stain and crown transparency, in combination with the high infection levels of roots of fairly vigorous Scots pines, indicates the pathogenic potential of the blue-stain fungi. Hence, these fungi together with their insect vectors may well act as an important contributing factor involved in pine decline.

Forty paired plots were established from eastern Texas to Alabama to study root-infecting, blue-stain fungi in southern pine stands undergoing southern pine beetle (SPB) attack. Woody roots were sampled in plots undergoing recent or current attack by the SPB. Comparisons were made between occurrence of Leptographium spp. and related fungi and data on various characteristics of natural stands and plantations studied. Three fungal species, L. terebrantis, L. procerum, and Ophiostoma ips, along with unidentified Leptographium and Graphium species, were isolated from sampled roots. L. terebrantis was isolated more frequently from SPB-attacked plots (P < 0.001) than was either L. procerum or O. ips. More blue-stain fungal species and related genera were isolated from SPB-attacked plots than from control plots (P < 0.001). This also was true for combined isolation percentages of L. terebrantis, L. procerum, and O. ips (P = 0.03). Presence of blue-stain fungi also was associated with higher stand basal area in the control plots (P = 0.045). Isolation frequencies of O. ips and L. procerum, along with the combination of these fungal species with L. terebrantis, were logistically related to increasing stand basal area in the control plots (P = 0.02, 0.02, and 0.01, respectively). No logistic relationship was found for frequency of any of the three blue-stain species with respect to basal area in SPB-attacked plots. These results suggest blue stain fungi are important in the dynamics of susceptibility of southern pines to SPB attack.

SummaryPhlebiopsis gigantea, a white-rot fungus currently being tested in biological processing applications for the pulp and paper industry, was shown to effectively inhibit blue stain fungi in both laboratory and field trials. Inoculation of logs withP. giganteashortly after cutting resulted in up to 86% colonization of logs in the laboratory and 100% in field studies. Colonization of logs by blue stain fungi such asOphiostoma piliferumandO. piceaewas greatly reduced or completely inhibited with prior inoculation byP. gigantea. In field studies, blue stain fungi colonized up to 53% of the sapwood and stained as much as 31% of the sapwood in non-inoculated control logs in contrast to 4% colonization and 2% stain in treated logs. Logs inoculated withO. piliferum2 weeks prior to inoculation withP. giganteawere 88% colonized byO. piliferumand had 33% of the sapwood stained after 7 weeks, and 33% colonized and 18% stained after 29 weeks. Scanning electron micrographs ofP. giganteaandO. piliferumhyphae showedP. giganteaparasitizing the blue stain fungus.Phlebiopsis giganteawas shown penetrating and growing adjacent to collapsed and disintegrated blue stain hyphae.Phlebiopsis giganteaalso decolorized sapwood previously stained blue.