Temperature sensitivity of termites determines global wood decay rates

Animals, such as termites, have largely been overlooked as global-scale drivers of biogeochemical cycles1,2, despite site-specific findings3,4. Deadwood turnover, an important component of the carbon cycle, is driven by multiple decay agents. Studies have focused on temperate systems5,6, where microbes dominate decay7. Microbial decay is sensitive to temperature, typically doubling per 10°C increase (decay effective Q10 = ~2)8–10. Termites are important decayers in tropical systems3,11–13 and differ from microbes in their population dynamics, dispersal, and substrate discovery14–16, meaning their climate sensitivities also differ. Using a network of 133 sites spanning 6 continents, we report the first global field-based quantification of temperature and precipitation sensitivities for termites and microbes, providing novel understandings of their response to changing climates. Temperature sensitivity of microbial decay was within previous estimates. Termite discovery and consumption were both much more sensitive to temperature (decay effective Q10 = 6.53), leading to striking differences in deadwood turnover in areas with and without termites. Termite impacts were greatest in tropical seasonal forests and savannas and subtropical deserts. With tropicalization17 (i.e., warming shifts to a tropical climate), the termite contribution to global wood decay will increase as more of the earth’s surface becomes accessible to termites.

Enzymatic Activities, Characteristics of Wood-Decay and Wood Substrate Specificity within Genera of Some Wood-Rotting Basidiomycetes from Cameroon and Tropical Africa

A total of 72 species of wood-rotting Basidiomycetes belonging to 40 genera, 13 families and 5 orders, were investigated in this study of which 46 for the first time as far as type of wood-rot is concerned. 61 of the 72 cause white rot (W) representing 84.72 % of the total and 11 cause brown rot (B) or just 15.27 %, confirming the predominance already known of white rot (W) on brown rot (B) as shown in other studies. Results recorded show that even though most species belonging to same genera display the same type of rot (W or B), species of some few other genera were found to rather display different types of rot (W and B) in species within the same genera. Other results show that when determining the type of wood-rot caused by some species of fungi, in case of negative (-) test using tincture of guaiac which is known as the key test to determine the type of rot, syringaldazine must also be used as a differential test before concluding whether the species is a white (W) or brown rot (B) fungus. The level of activity of tyrosinase and peroxidase shows important variations between species of some genera, whereby some species of a given genus show varying potential level (+, ++, +++, ++++) of activities of these two enzymes, whereas other species of the same genus show no sign (-) of activity of the same enzymes. Therefore, our results led to the conclusion that the presence (+, ++, +++, ++++) or absence (-) of activity of peroxidase and tyrosinase can from now onwards also be used as an enzyme linked taxonomic criteria to distinguish between species of some genera. About detection of laccases activity, if a negative (-) result occurs during detection test in a wood-rotting fungus using syringaldazine, α-naphtol must also be used as a differential test before concluding on whether the species produces laccases or not. Based on the overall results recorded in the detection of enzymes activities, it appears necessary to use, where indicated, several substrates with different chemical sensitivities to detect the existence of an enzyme and its potential activity level in a fungal species. Additionally, preliminary lists of wood-decay fungi with potentially strong (+++, ++++) capacity to produce different types of polyphenol oxidases potentially usable in paper making industries, wastewater treatment and soil remediation, are provided. With regard to the study of substrate specificity which aimed at finding out the existence or not of a specificity between polyporales and tree wood species on which they grow, the first results recorded on a limited number of trees investigated led to the preliminary conclusion that, although some few tree species may serve as hosts for only a single species of polyporales, there is rather a greater tendency of finding several species growing on different species of wood as well as the same species of wood hosting several species of polyporales. These field observations led to the remark that a much larger inventory including a greater number of tree species in various tropical ecosystems is necessary in order to come out with a final conclusion.

Bjerkandera carnegieae comb. nov. (Phanerochaetaceae, Polyporales) a wood-decay polypore of cactus

Poria carnegieae was described from Arizona growing on the woody ribs of the saguaro cactus, Carnegiea gigantea, and was transferred to Ceriporiopsis due to morphological evidence. Posterior phylogenetic studies showed a relationship of Poria carnegieae with Bjerkandera. New sequence data and morphologic evidence are presented to support the transfer of Ceriporiopsis carnegieae to Bjerkandera.

Applying Electrical Impedance Tomography Techniques for Detection of Decay Inside Trees

Trees play a critical role in creating green spaces in public areas such as streets, parks, schools,offices. Over time, the trees often get pests and diseases, and then rotten trees can break. To care for andconserve the trees, it is necessary to determine the condition inside the trunk, especially the possibility ofhaving a hollow or not. Wood decay, modifications of moisture and ion content, density due to biotic andabiotic stress agents of water extremity, salinity, and infection strongly change (di-) electrical propertiesof wood. Hence, we propose to use electrical impedance tomography to detect the change in electricalproperties inside the trees that can link to wood decay. In electrical impedance tomography, an array ofelectrodes is attached around the tree trunk, and small alternating currents are injected via these electrodes,so the resulting voltages are measured. Processing the data, we can construct the spatial distribution ofimpedance (or resistivity) of the object. In this work, we will present the preliminary results of our groupresearch. We will show theoretical forward modeling results, followed by laboratory experiments and realdata application. The results illustrate that electrical impedance tomography can be useful to define severaldecay scenarios inside the trees.

Decadal Variations of Wood Decay Hazard and El Niño Southern Oscillation Phases in Iran

The intensive use of wood resources is a challenging subject around the world due to urbanization, population growth, and the biodegradability of wooden materials. The study of the climatic conditions and their effects on biotic wood degradation can provide a track of trends of wood decay and decomposition at regional and global scales to predict the upcoming responses. Thus, it yields an overview for decision-makers and managers to create a precise guideline for the protection of wooden structures and prolonged service life of wooden products. This study aimed at investigating the decay hazard in Iran, its decadal changes, and how it is affected by different phases of the El Niño Southern Oscillation (ENSO). Therefore, the risk for fungal decay of wood was estimated based on the Scheffer Climate Index (SCI) at 100 meteorological stations located in Iran, for the period 1987–2019 (separately for first, second, and third decade as decadal analysis). Subsequently, SCI value trends were analyzed using the Mann–Kendall and Sen’s slope method. Finally, the relationship between SCI and climatic parameters (temperature and precipitation) was explored. Generally, the SCI fluctuated between 2 and 75 across the region. The decay risk was ranked as low in most parts, but moderate in the northern part of the country along the Caspian Sea coastlines. Decadal analysis demonstrated that the highest mean SCI values took more place in the third decade (58% of stations) and the lowest mean SCI values in the second decade (71% of stations). Furthermore, the highest and the lowest SCI values occurred at 70 and 66% of stations in El Niño and Neutral phase, respectively. Trend analysis of SCI values showed that large parts of several provinces (i.e., Markazi, Tehran, Alborz, Qazvin, Zanjan, Ardebil, East Azarbayjan, West Azarbayjan, Kurdestan, Kermanshah, and Ilam) exhibited a significantly increasing decay hazard with a mean SCI of 2.9 during the period of 33 years. An analysis of causative factors (climatic parameters) for these changes revealed that all the meteorological stations experienced a significant increase in temperature while the number of days with more than 0.25 mm precipitation increased at some stations but decreased at others. However, in summary, the SCI increased over time. Hence, in this study, the effect of precipitation on SCI was confirmed to be greater than the temperature. Analysis of the results shows that the correlation between the SCI and ENSO was positive in most of the stations. Moreover, the results of spectral coherent analysis of SCI and ENSO in different climates of Iran showed that the maximum values of SCI do not correspond to the maximum values of ENSO and are associated with lag time. Therefore, the extreme values of the SCI values cannot be interpreted solely on the basis of the ENSO.

Collection and Characterization of Wood Decay Fungal Strains for Developing Pure Mycelium Mats

Wood decay fungi (WDF) seem to be particularly suitable for developing myco-materials due to their mycelial texture, ease of cultivation, and lack of sporification. This study focused on a collection of WDF strains that were later used to develop mycelium mats of leather-like materials. Twenty-one WDF strains were chosen based on the color, homogeneity, and consistency of the mycelia. The growth rate of each strain was measured. To improve the consistency and thickness of the mats, an exclusive method (newly patented) was developed. The obtained materials and the corresponding pure mycelia grown in liquid culture were analyzed by both thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) to evaluate the principal components and texture. TGA provided a semi-quantitative indication on the mycelia and mat composition, but it was hardly able to discriminate differences in the production process (liquid culture versus patented method). SEM provided keen insight on the mycelial microstructure as well as that of the mat without considering the composition; however, it was able to determine the hyphae and porosity dimensions. Although not exhaustive, TGA and SEM are complementary methods that can be used to characterize fungal strains based on their desirable features for various applications in bio-based materials. Taking all of the results into account, the Fomitopsis iberica strain seems to be the most suitable for the development of leather-like materials.

Damage risk assessment of building materials with moisture hysteresis

Heat and Moisture Transfer (HMT) simulations are used to evaluate moisture related damage risks in building envelopes. HMT simulations are commonly performed accepting the hypothesis of not considering the moisture hysteresis of materials. The results of HMT simulation of a timber wall with hysteresis are presented, and compared to the results of three simplified models, showing the effects of hysteresis on the simulation results and on the assessment of the risk of decay. Moisture content is the most influenced variable, while temperature and relative humidity are slightly affected. The wood decay risk analysis is performed using the simplified 20% moisture content rule. Similar temperature values and relative humidity values are calculated as simplified models, while the moisture content annual average values have differences up to 2.3%. The wood decay risk obtained with the simplified models could be overestimated if the simulation is performed using the desorption curve, while it could be underestimated with the adsorption curve. The best approximation is obtained with the mean sorption curve, while the desorption curve and the adsorption curve could be used to calculate the upper and lower boundary of the moisture contents respectively.

Decay detection of constructional softwoods using machine olfaction

Fungal decomposition of wood severely affects the soundness of timber constructions. The diagnosis of wood decay requires direct observations or sampling by skilled experts. Wood decay often occurs in obscure spaces, including the enclosed inner spaces of walls or under the floor. In this study, we examined the ability of machine olfaction to detect odors of fungi grown on common construction softwoods to provide a novel diagnostic method for wood construction soundness. The combination of a simple device equipped with semiconductor gas sensors (gas sensor array) and multivariate analysis discriminated a fungi-related odor from control odor without instrumental analysis (e.g., gas chromatography). This method is often referred to as machine olfaction or electronic nose. We measured the odor of wood test pieces that were infected with Fomitopsis palustris or Trametes versicolor and sound test pieces using a gas sensor array. The sensor responses of the specimens showed different patterns between the inoculated and control samples. Each specimen class formed independent groups in a principal component score plot, almost regardless of wood species, fungal species, or cultivation period. This method provides a new decay diagnosis method that is cost-effective and easy to operate.

Analysis of pigments and damages for the 19th century White-robed Water-moon Avalokitesvara Painting in Gongju Magoksa Temple, Republic of Korea

The White-Robed Water-Moon Avalokiteshvara painting displayed on the rear wall of Daegwangbojeon (main hall) in Magoksa temple, is one of the representative Buddhist paintings in the late nineteenth century of Korea, and a valuable resource for understanding the coloring techniques and characteristics of Buddhist paintings in terms of expression and description in landscape painting. In this painting, the contours and colored surface remain undamaged, but blistering and exfoliation appear on some pigment layers. Furthermore, the partial decomposition of wooden materials due to wood-decay fungi and insect damage were found on the rear wall requiring proper treatment for long-term conservation. As the results of chromaticity and P-XRF analysis regarding the color pigment layer of the painting, the pigments were classified into ten types. The results suggest that the colors other than blue, green, yellow, red, black, and white were prepared by mixing two or more pigments. The types of pigments according to colors, were determined as traditional pigments with azurite; emerald green or clinoatacamite; 0 massicot; minium or hematite; Chinese ink; and kaolin, white lead, and gypsum, respectively. Violet and pink colors were assumed to have been prepared by mixing white with blue and red. In most of these pigments, small amounts of synthetic compositions from the modern era were detected at many points.