Plants harbour a wide range of leaf‐feeding insects whose survival and fitness are influenced by both energy‐rich molecules and phytochemicals in the host foliage. Yet, how leaf host chemical ...diversity and insect microbiota—key factors in ecological and physiological processes—impact insect nutrition and fitness are still poorly understood.
To study the effects of leaf metabolic composition on insect herbivory resistance and performance, we fed the larvae of the specialist herbivory Tortrix viridana with leaves of susceptible and resistant Quercus robur trees that are characterized by contrasting metabolomes. We analysed the larval performance and mortality, the metabolomes in plant leaves, and in the insects' saliva and faeces by non‐targeted metabolomics. Using chemometrics, mass difference network analysis and metabarcoding, we show the metabolome changes and chemical reactions associated with the different diets as well as their impact on insect fitness and gut microbiota.
In the saliva and faeces of larvae, plant secondary metabolites (e.g. flavonoids) persisted more the insect digestion while compounds from primary metabolism were more depleted. In addition, metabolic reactions within the larvae indicated different degradation pathways used on the two plant metabolic types (syn. metabotypes), including sulfation and sulfonation. We show that feeding insects with resistant oak leaves, enriched in secondary metabolites and depleted in primary metabolites, impaired insect performance and mortality. Although the insects' gut microbiota was slightly different upon the contrasting diets, overall, it was fairly stable. Despite the impact of host chemicals on herbivores, larvae were generally highly efficient in nutrient assimilation (feed conversion ratios of 3.3–3.6) and able to minimize plant defences (78% of secondary metabolites were converted, broken down or sequestrated).
The comparison of the oak metabotypes showed how the foliar composition of resistant oaks affected insect fitness by influencing their digestion. Herbivores feeding on resistant oaks were less efficient due to their lower ability to metabolize and detoxify higher levels of host phytochemicals, whereas those on susceptible oaks were more efficient as they could degrade the host metabolome. This study highlights the importance of the oak leaf chemical composition to insect digestion and fitness of a specialized herbivore.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
We overview the recent development of oak dendrochronology in Europe related to archaeology and art-history. Tree-ring series of European oaks (
Quercus robur and
Q. petraea) have provided a reliable ...framework for chronometric dating and reconstruction of past climate and environment. To date, long oak chronologies cover almost the entire Holocene, up to 8480 BC and the network over the entire area in which the two oaks grow is being improved. We present the main characteristics of oak ring series and discuss the latest methodological advances in defining the calendar year in which the tree-rings were formed and in interpreting such dating in terms of the age of a wooden object. Dendrochronology has established itself as a standard dating tool and has been applied in a wide variety of (pre-)historical studies. Archaeological wood, historical buildings, works of art (such as panel paintings and sculptures) have been successfully investigated. Recent advances in dendro-provenancing have helped to obtain more information on the timber trade in the past. Information on past forest structures, silviculture and timber use have become available through scrutinizing historical and contemporary ring-width patterns.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In 1980 Ernst Hollstein published his Central European Oak Chronology, which covers a period from 724 BCE to 1974 CE. Besides a later correction of the end date of the sampling site chronologies ...Kirnsulzbach (Germany) and Gustavsburg (Germany) this master chronology has since not been changed and still remains one of the most important bases for dendrochronological dating in western Germany. It stands out in so far as it provides comprehensive graphical findspot series for each individual sampled site and year to year growth values for eight regional sub-chronologies in addition to the combined Central European reference curve.
Particularly due to the fact of Hollstein’s chronology being publicly available, it has frequently been criticized for its insufficient data to bridge the Late Antiquity between 350 and 400 CE with only three sampling sites (tomb near Beerlegem, Belgium; tomb inside of Cologne Cathedral, Germany; subfossil trees near Broichweiden, Germany) and that these site chronologies cover those decades with inadequate correlation coefficients. With regard to recent statistical threshold values for crossdating, Hollstein’s Late Antiquity bridging needs to be reconsidered.
Therefore, in a combined effort, the dendrochronological laboratories at Rheinisches Landesmuseum Trier (RLM), the University of Cologne and Albert-Ludwigs-University Freiburg re-evaluated Hollstein’s findings for Late Antiquity by including the respective dendrochronological examinations conducted in Rhineland-Palatinate, North Rhine-Westphalia and north-eastern France during the past 40 years. A total of 62 site chronologies were compiled to establish a new Late Antiquity chronology. Thirteen of these site chronologies could be used to support Hollstein’s original bridging series between 350 and 400 CE while the mean series for Broichweiden had to be corrected from end date 365 to 503 CE. Furthermore, this new bridging chronology could be validated by comparing it to an independent chronology from southern Germany. This study thus proves that the integrity of Hollstein’s Central European Oak Chronology is not compromised by a flawed Late Antiquity bridging and that therefore dating based on the Roman part of this chronology can still be considered as absolute.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Artificial graying of wood can be solution for contemporary trends of using uncoated wood for the arrangement of external architecture. The presented work was aimed at investigation of colour changes ...of European oak (Quercus sp.) wood surface treated with iron (II) sulphate. Three different procedures differing in time (2 h and 24 h) and temperature (20 °C and 70 °C) were used, as well as three different concentrations of aqueous iron (II) sulphate solutions (10 %, 20 %, 30 %). Beside the colour itself, it was evaluated the stained oak wood discolouration due to natural weathering. Thanks to iron (II) sulphate, wood colour changed to dark grey. In general, the colour changes on tangential section of wood were higher than those on radial section what was result of wood structure, in particular parenchyma cells arrangement in wooden rays. Contrary to expectations, the concentration of the iron (II) sulphate solution was not of significant importance for wood staining. Usage of concentrations higher than 10 % for the modification of the colour of wood gives the same effects. However, with increasing solution used to wood staining, the colour stability of the wood decreases during external exposure. The parameters of the procedure were not significantly affected. This allows the application of the simplest and least time-consuming modification method to be considered.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The objects of the study are the old oak stands in Polissya and Forest Steppe, growing in conditions of fresh sugrud and fresh grud. The aim of the study is to identify climatic factors affecting the ...oak (Quercus robur L.) radial growth in Polissya and the Forest-Steppe and to compare its response to climate change in both natural areas. Standard dendrochronological methods were used to generate the Quercus Robur L. tree‐ring chronologies and to evaluate the relationship of the chronology with the meteorological records. In comparison, the influence of climate on the European oak radial growth in 1960 - 1988 and 1989 - 2013 for both natural areas there was in temperature increase in the second period compared with the first by 17-19%. In the second period in comparison with the first period temperatures increased most rapidly in Winter (by 34-41%) and early spring almost by four times in Polissya iand Forest Steppe. Precipitation trends are similar for both natural zones - there was an increase in the annual amount of precipitation, but during the growing season they fell less in April-June of the Polissya zone - by 11%, and for the forest-steppe zone - during July-August and the winter period - by 10% less. The reference years of maximum (1891, 1902, 1924, 1931, 1957, 1971, 1987) and minimum (1895, 1906, 1918, 1922, 1929, 1936, 1950, 1976, 1992, 2000, 2005) radial growth of European oak for Polissya were revealed as well as positive signature years for and Forest-Steppe (1971, 1978, 1987) and negative reference years (1918, 1922, 1929, 1936, 1950, 1976, 1992, 2000, 2005). Negative reference years are characterized by a deficit of precipitation, droughts of the growing season, cold or too warm winter and early spring periods, and positive - favorable for tree growth ratio of temperature and moisture. For the first period (1960-1988) the positive influence of winter and early spring temperatures on the radial growth of oak in Polissya and in the Forest-Steppe was revealed. In the second period (1989 - 2013) the opposite scenario took place - a significant increase in winter and early spring temperatures growth. In the second period, oak stands in Polissya suffered more from warm winters than plantations in the Forest-Steppe. The negative impact of vegetation droughts on growth increased in the second period for both plantations. During the second period, precipitation significantly lost its positive effect on plantations growth both in the Polissya and Forest-Steppe. The hypothesis of increasing the sensitivity of the European oak radial growth response on climate change in Polissya and Forest-Steppe has been confirmed.
The wood of five European species: black poplar (Populus nigra L.), European beech (Fagus sylvatica L.), European ash (Fraxinus excelsior L.), European oak (Quercus robur L.), and Scots pine (Pinus ...sylvestris L.) was subjected to thermal modification in nitrogen atmosphere at 190 °C during 6 h. Native and modified wood was varnished and oiled in industrial conditions. Thermally modified (TM) wood was characterized by a greater absorption of varnish and oil when applying the first layer to the surface, which finally resulted in higher application values compared to native wood. In particular, after varnishing, there was a significant increase in gloss and radical change of colour. Regardless of the wood species, finishing process (varnishing, oiling), the ΔE values were close to or higher than 6, which proves high colour changes. Modified poplar, ash, and oak after varnishing had a different colour (ΔE higher than 12). The surface colour changes as a result of UV photoaging was individual, depending on the wood species and the method of finishing. In the case of the thickness of varnish coatings, the wood structure was important, i.e., on ring-porous hardwood and softwood they were thicker. In the case of wood species with a lower density, i.e., black poplar and pine, the thermal modification in nitrogen atmosphere process did not reduce the resistance of the varnish coat, and in the case of species with a higher density (oak, ash, beech) it decreased by one level. Thermal modification reduced the Brinell hardness of wood with wide rays (oak and beech) by 11%. The applied process of surface finishing by double varnishing or oiling did not significantly change the hardness of tested wood.
Oak (Quercus robur L.), iroko (Milicia excelsa (Welw.) C.C. Berg), and tauari (Couratari spp.) wood were subjected to cyclic thermo-mechanical treatment (CTMT). The densification temperature amounted ...to 100 °C or 150 °C. The greatest changes in the modulus of rupture (MOR) value of the iroko wood, depending on the number of thermo-mechanical modification cycles, were noted. The MOR of the iroko wood, densified at 100 °C or 150 °C, after second thermo-mechanical modification cycle was twice as high as before the modification. No significant differences were observed between the modulus of elasticity (MOE) of oak wood before and after one modification cycle. Similar dependencies were noted in iroko wood. The thermo-mechanical modification performed over two cycles led to the highest increase, by about 56%, in MOE in oak wood densified at 150 °C. It was demonstrated that modification at 150 °C had a negative impact on iroko wood, which was manifested in the lower compression ratio of iroko at 150 °C than at 100 °C.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Although Slovakia is largely forested and rich in historical buildings, it is one of the few European countries without a millennium-long tree-ring chronology. In this study, we gather all available ...oak ring width data from Slovakia, establish a new composite chronology and assess its climate sensitivity. The nation-wide oak network includes 276 samples from historical buildings and 1028 modern series from material that was randomly collected at sawmills and wood submission sites across Slovakia. The final composite oak record covers the period from CE 967–2013, reflects a distinct hydroclimatic signal from late spring to early summer, and is highly correlated with other oak chronologies from surrounding countries. Although this study reveals a high degree of growth coherency and climate sensitivity inherent to the new Slovakian oak ring width chronology, changes in sample size at the transition from modern to relict material and further back in time limit any applicability to palaeoclimatic analysis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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