•Survival of oaks depends on plant density, tending and Interspecific competition.•Admixed tree species have a positive effect on the oak quality parameters.•Interspecific competition can replace ...successfully intraspecific oak competition.•Reducing oak plant number at establishment without a loss of oak quality.
Due to a lack of oak seeds and planting material at the north-eastern limit of the distribution range of European oak forests (study area: Republic of Tatarstan, Russia), the high initial plant densities typical of oak stands established in central Europe for the production of valuable timber is not feasible in this region. In Russia, the low numbers of oak trees in planted stands (about 4500 oaks/ha) are complemented by abundant natural regeneration of admixed tree species. In this study, the chronosequence method was used to determine the probability of survival and the quality development of young oaks (10–27 years) in Tatarstan as a factor of initial plant numbers, interspecific competition (lime, maple, hazel), oak age and tending measures. The results provided by LMM and GLMM models revealed that the probability of oak survival rises with increasing initial oak plant density and tending, and declines with increasing competitive pressure of maple. While the competition exerted by all admixed tree species had a negative effect on oak growth parameters, it had a positive effect on important oak quality parameters (e.g., diameter and height of the thickest branches, branch-free bole length). However, a positive impact of high initial plant density on oak quality was reduced by strong interspecific competition. Age had a positive effect on oak quality development, and tending a negative effect.
The findings of this study demonstrate that the competitive pressure of admixed tree species can successfully compensate for the positive effects of oak intraspecific competition on oak quality, and may therefore be exploited by forest managers as a means to reduce the cost of oak establishment by using lower plant numbers without risking any loss of oak quality.
Complementary to measurements in Antarctic ice cores, stomatal frequency analysis of leaves of land plants preserved in peat and lake deposits can provide a proxy record of preindustrial atmospheric ...CO sub(2) concentration. CO sub(2) trends based on leaf remains of Quercus robur (English oak) from the Netherlands support the presence of significant CO sub(2) variability during the first half of the last millennium. The amplitude of the reconstructed multidecadal fluctuations, up to 34 parts per million by volume, considerably exceeds maximum shifts measured in Antarctic ice. Inferred changes in CO sub(2) radiative forcing are of a magnitude similar to variations ascribed to other mechanisms, particularly solar irradiance and volcanic activity, and may therefore call into question the concept of the Intergovernmental Panel on Climate Change, which assumes an insignificant role of CO sub(2) as a preindustrial climate-forcing factor. The stomata-based CO sub(2) trends correlate with coeval sea-surface temperature trends in the North Atlantic Ocean, suggesting the possibility of an oceanic source/sink mechanism for the recorded CO sub(2) changes.
Low-cost materials are promising aqueous pollutant adsorbents but when batch adsorption method is employed, separation of pollutant-loaded-adsorbents from water is a major challenge especially when ...dealing with a large volume of wastewater. Thus, biomass and biochar from Quercus robur fruits were valorized via magnetization (for easy post-adsorption separation) to prepare optimized biomass-magnetic hybrid (BMM 0.5:1) and biochar-magnetic hybrid (BCM 1:1). The BMM 0.5:1 and BCM 1:1 were employed for Pb(II) and Cd(II) removal from simulated contaminated water. The hybrids exhibited higher values of cation exchange capacity (CEC), BET surface area and pore sizes, as well as better thermal stability and the presence of pure spinal structures of Fe3O4, along with the characteristic functional groups of biomaterials (such as the hydroxyls, amides and carboxyls). The adsorption equilibria for both cations were attained within 180 min. Adsorption mechanism involved electrostatic interactions on both external and pore surfaces, with Pb(II) data fitting the Langmuir adsorption isotherm model while Cd(II) data fitted the Freundlich. The adsorption process was spontaneous and exothermic as solution temperature was increased from 292 to 310 and 328 K. The adsorption of Cd(II) initially increased with temperature but decreased on further temperature rise by similar percentages for both adsorbents. In contrast, adsorption of Pb(II) decreased continuously but the decrease was higher for BMM 0.5:1 than BCM 1:1 implying BCM is a more promising adsorbent. Adsorption capacities for BMM 0.5:1 are 63.6 and 21.0 mg/g, while BCM 1:1 has 58.2 mg/g and 21.3 mg/g for Pb(II) and Cd(II), respectively. These adsorption capacities were better than many low-cost adsorbents in literature. Thus magnetic valorization, apart from easing separation, enhances the adsorption capacity of low-cost adsorbents.
•Acorn–Quercus robur biosorbents are difficult to remove from water post-adsorption.•The biomasses were magnetically valorized to enhance separation/water treatment.•The preparation methods were facile, benign and achieved in a one-pot process.•The valorized adsorbents were effective for the removal of aqueous toxic metals.•Separation from water post-adsorption was under the influence of magnetic field.
Introduced pathogen microorganisms are important drivers of ecosystem change. This paper highlights the impact of the non-native pathogen mildew multi-species complex on the natural regeneration ...dynamics of pedunculate oak (Quercus robur). Pedunculate oak is a European keystone tree species, hosting a great amount of biodiversity, but its future role in (near-)natural forests is uncertain due to the lack of natural regeneration. We reviewed historical and recent ecological, pathological and forestry literature on topics related to the impact of mildew on the success of advanced natural regeneration of pedunculate oak in (near-)natural forests. We propose a novel hypothesis, the ‘pathogen mildew hypothesis’, to explain the failure of natural regeneration of pedunculate oak. Mildew reduces shade tolerance and vertical growth in seedlings and saplings, so sapling vitality and competitiveness have diminished considerably since it was unintentionally introduced to Europe in the early 20th century. Due to mildew infection, pedunculate oak in many cases no longer regenerates well naturally under its own canopy. We found that forest ecologists and conservationists often overlook the impacts of this ‘recent’ driver, while the ‘closed-forest’ and ‘wood-pasture’ hypotheses do not adequately help the management of pedunculate oak regeneration. Nature conservation and forest management plans should thus also consider the impact of mildew in order to improve natural regeneration, promote close-to-nature management of pedunculate oak forests, and support associated diversity. More generally, nature conservation, forest ecology and close-to-nature forestry should pay greater attention to the impact of introduced non-native microorganisms on the dynamics of natural ecosystems.
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•Ecologists and conservationists often overlook the impacts of alien microorganisms.•An alien microfungus impedes natural regeneration dynamics of a keystone species•Oak powdery mildew reduces shade tolerance and growth in seedlings and saplings.•Proposed hypothesis explains the failure of natural regeneration of pedunculate oak.•The alien microfungus threatens the rich biodiversity associated with oaks in Europe.
The Sentinel-2 program provides the opportunity to monitor terrestrial ecosystems with a high temporal and spectral resolution. In this study, a multi-temporal Sentinel-2 data set was used to ...classify common tree species over a mature forest in central Sweden. The tree species to be classified were Norway spruce (Picea abies), Scots pine (Pinus silvestris), Hybrid larch (Larix × marschlinsii), Birch (Betula sp.) and Pedunculate oak (Quercus robur). Four Sentinel-2 images from spring (7 April and 27 May), summer (9 July) and fall (19 October) of 2017 were used along with the Random Forest (RF) classifier. A variable selection approach was implemented to find fewer and uncorrelated bands resulting in the best model for tree species identification. The final model resulting in the highest overall accuracy (88.2%) came from using all bands from the four image dates. The single image that gave the most accurate classification result (80.5%) was the late spring image (27 May); the 27 May image was always included in subsequent image combinations that gave the highest overall accuracy. The five tree species were classified with a user’s accuracy ranging from 70.9% to 95.6%. Thirteen of the 40 bands were selected in a variable selection procedure and resulted in a model with only slightly lower accuracy (86.3%) than that using all bands. Among the highest ranked bands were the red edge bands 2 and 3 as well as the narrow NIR (near-infrared) band 8a, all from the 27 May image, and SWIR (short-wave infrared) bands from all four image dates. This study shows that the red-edge bands and SWIR bands from Sentinel-2 are of importance, and confirms that spring and/or fall images capturing phenological differences between the species are most useful to tree species classification.
•We carried out vegetation studies in the currently largest CWS project in Germany.•We analysed coppicing induced changes in vascular plant species richness.•CWS restoration led to an increase in ...species richness, particularly tree regeneration.•“Nitrogen time bomb” scenario after canopy opening did not happen in our study area.•True forest species are not negatively affected by coppicing.
Coppice-with-standards (CWS) management was one of the most important disturbances in Central European forests in the past. As our knowledge about the effects of coppicing on species richness and composition needs to be enhanced, we carried out vegetation studies in the currently largest CWS project in Germany. In this article we focus on two issues: 1. Coppicing induced changes and trends in species richness and composition from year to year and 2. Development of species richness and composition in 19 years of CWS restoration.
Salzgitter Höhenzug mountains between Liebenburg and Goslar, Lower Saxony, Germany. Climate: subatlantic to subcontinental; soil: Limestone rendzina with low water storage capacity.
In 2013 we resurveyed the plant species composition of 12 permanent plots analysed every year from 1994 till 2002. The dates of coppicing were recorded for all of these plots, which enabled us to analyse the dynamics of species richness and composition after coppicing on a year to year basis. Differences in species richness and composition were analysed using ANOVA, H-test, DCA and GLMM.
In 19 years of CWS restoration mean plot species richness increased significantly, mainly attributed to the increase in woody species, such as Quercus robur and Sorbus torminalis. The Ellenberg indicator value for nutrients decreased significantly, whereas the indicator value for light increased significantly. The typical dynamic after coppicing consists of a continuous increase in shrub layer coverage and an increase in herb layer coverage with a maximum in years 3 and 4 after coppicing. Total species richness as well as richness of open habitat and forest species and true forest species also showed an increase with its maximum in years 3 and 4 after coppicing.
Our results showed that the alternation of light and shaded phases had a positive impact on species richness, particularly on tree regeneration. Considering the trend of decreasing species richness level in Central European forests, CWS forests play a major role in the conservation of vascular plant species diversity. In contrast to other studies, the increase in species richness after coppicing did not result from an increase in weedy, nitrogen-demanding species. The so called “nitrogen time bomb” scenario (which other authors assumed to be happening after opening the canopy) did not occur in the studied area. The low water storage capacity of the limestone rendzina soil may be one reason, as there was not sufficient water and nitrogen for the more demanding species.
Dendroprovenancing provides critical information regarding the origin of wood, allowing further insights into economic exploitation strategies and source regions of timber products. Traditionally, ...dendroprovenancing relies on pattern-matching of tree rings, but its spatial resolution is limited by the geographical coverage of species-specific chronologies available for crossdating and, in the case of short-distance trades, by scarce environmental variability. Here, we present an approach to provenance timber with high spatial resolution from forested areas that have been exploited intensively throughout history, with the aim to understand the sustainability of the various woodland management practices used to supply timber products. To this end, we combined tree-ring width (TRW), wood anatomical and geochemical analyses in addition to multivariate statistical validation procedures to trace the origin of living oak trees (Quercus robur) sampled in four stands located within a 30-km radius around the city of Limoges (Haute-Vienne, France). We demonstrate that TRW and wood anatomical variables (and in particular cell density) robustly discriminate the eastern from the western site, while failing to trace the origin of trees from the northern and southern sites. Here, strontium isotopic ratios (87Sr/86Sr) and Ca concentrations identify clusters of trees which could not be identified with TRW or wood anatomy. Ultimately, our study demonstrates that the coupling of wood anatomy with geochemical signatures allows to correctly pinpoint the origin of trees. Given the small geographic scale of our study and the limited differences in elevation and climate between study sites, our results are particularly promising for future dendroprovenancing studies. We thus conclude that the combination of multiple approaches will not only increase the accuracy of dendroprovenancing studies at local scales, but could also be implemented at much larger scales to identify trends in historic timber supply throughout Europe.
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•Locating the origin of wood traditionally consists in matching tree-ring patterns.•The traditional method fails when differences in elevation and climate are scarce.•We combined tree-ring width data, wood anatomical measurements and 87Sr/86Sr ratios.•The combination of multiple proxies increased the accuracy of dendroprovenancing.
Beneficial effects of silicon (Si) on plants have primarily been studied in crop species under single stress. Moreover, nutrient acquisition-based responses to combination of biotic and abiotic ...stresses (a common situation in natural habitats) have rarely been reported, in particular in conjunction with soil amendments with Si. Pedunculate oak (
Quercus robur
L.), one of the ecologically and economically most important tree species in Europe, is facing a severe decline due to combined stresses, but also problems in assisted regeneration in nurseries. Here, we studied the effect of Si supply on the leaf nutriome, root traits and overall growth of 12-weeks-old oak seedlings exposed to abiotic stress low phosphorus (P) supply, biotic stress (
Phytophthora plurivora
root infection), and their combination. The application of Si had the strongest ameliorative effect on growth, root health and root phenome under the most severe stress conditions (i.e., combination of P deficiency and
P. plurivora
root infection), where it differentially affected the uptake and leaf accumulation in 11 out of 13 analysed nutrients. Silicon supply tended to reverse the pattern of change of some, but not all, leaf nutrients affected by stresses: P, boron (B) and magnesium (Mg) under P deficiency, and P, B and sulphur (S) under pathogen attack, but also nickel (Ni) and molybdenum (Mo) under all three stresses. Surprisingly, Si affected some nutrients that were not changed by a particular stress itself and decreased leaf Mg levels under all the stresses. On the other hand, pathogen attack increased leaf accumulation of Si. This exploratory work presents the complexity of nutrient crosstalk under three stresses, and opens more questions about genetic networks that control plant physiological responses. Practically, we show a potential of Si application to improve P status and root health in oak seedlings, particularly in nurseries.
•O. brumata and A. leucophaearia are the most abundant geometrids in oak stands.•Both phenological groups of geometrids can cause severe oak defoliation.•Oak defoliation depends on the density of ...geometrid females captured in collar traps.•New thresholds of female density are proposed for predicting the threat to oak stands.•Sample size (the number of traps/stand) was determined using Taylor’s Power Law.
Oak forests are of great ecological and socioeconomic values but are declining in many regions due to abiotic and biotic factors, including crown damage by defoliating insects. In Europe, several geometrid species reach outbreak densities and are then able to cause severe oak defoliation. Prior to control measures, the threat posed by defoliators must be reliably assessed to limit the treated area and consequently to minimize the negative environmental impacts and the costs of the insecticide application. Few methods have been developed so far to assess the threat to oak forests from geometrids, most of which have proven to be unreliable and/or labour-consuming. In this paper, we present a new method for predicting crown damage from geometrid defoliators based on the density of their flightless females assessed with the use of collar traps installed on tree trunks. The studies were conducted in 2014–2020 in 68 oak stands in Poland. Using beta regression, we estimated the relationship between the density of geometrid females (from genera: Operophtera, Erannis, Agriopis, Alsophila and Apocheima) in collar traps and subsequent defoliation caused by their progeny (i.e. larvae). We then proposed threshold numbers of female density to predict different levels of defoliation and calculated the numbers of collar traps that would be required to detect the threshold density of geometrid females indicating expected defoliation >30%. The new method allows forest managers to monitor populations of different species and phenological groups of geometrids and predict the threat (expected defoliation) to oak forests from these insects.
A long‐standing paradigm in ecology holds that herbivore pressure and thus plant defences increase towards lower latitudes. However, recent work has challenged this prediction where studies have ...found no relationship or opposite trends where herbivory or plant defences increase at higher latitudes. Here we tested for latitudinal variation in herbivory, chemical defences (phenolic compounds), and nutritional traits (phosphorus and nitrogen) in leaves of a long‐lived tree species, the English oak Quercus robur. We further investigated the underlying climatic and soil factors associated with such variation. Across 38 populations of Q. robur distributed along an 18° latitudinal gradient, covering almost the entire latitudinal and climatic range of this species, we observed strong but divergent latitudinal gradients in leaf herbivory and leaf chemical defences and nutrients. As expected, there was a negative relationship between latitude and leaf herbivory where oak populations from lower latitudes exhibited higher levels of leaf herbivory. However, counter to predictions there was a positive relationship between leaf chemical defences and latitude where populations at higher latitudes were better defended. Similarly, leaf phosphorus and nitrogen increased with latitude. Path analysis indicated a significant (negative) effect of plant chemical defences (condensed tannins) on leaf herbivory, suggesting that the latitudinal gradient in leaf herbivory was driven by an inverse gradient in defensive investment. Leaf nutrients had no independent influence on herbivory. Further, we found significant indirect effects of precipitation and soil porosity on leaf herbivory, which were mediated by plant chemical defences. These findings suggest that abiotic factors shape latitudinal variation in plant defences and that these defences in turn underlie latitudinal variation in leaf herbivory. Overall, this study contributes to a better understanding of latitudinal variation in plant–herbivore interactions by determining the identity and modus operandi of abiotic factors concurrently shaping plant defences and herbivory.
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