Electrochemical impedance spectroscopy, photoelectron spectroscopy, and Kelvin probe measurements on various TiO2 single-crystal surfaces show that the position of the Fermi level and the conduction ...band minimum depend significantly on the sample environment (vacuum, air, water vapor, and aqueous or aprotic electrolyte solutions). In most cases, the conduction-band minimum increases in the series: anatase < rutile < brookite. The offset between anatase and rutile indicates a type II staggered alignment if the environment is vacuum, air, water vapor, or aprotic electrolyte solution, but a type IV aligned configuration is found in an aqueous electrolyte solution. The photoelectron spectra in water vapor reveal a strong upshift of the conduction band, which is nearly reversible in the early stages of water/titania interactions. Our results rationalize various earlier contradictions and highlight the need for proper analytical techniques and experimental conditions for investigation of the band energetics, which is relevant to practical applications of titania materials.
Determining the drivers of shifting forest disturbance rates remains a pressing global change issue. Large‐scale forest dynamics are commonly assumed to be climate driven, but appropriately scaled ...disturbance histories are rarely available to assess how disturbance legacies alter subsequent disturbance rates and the climate sensitivity of disturbance. We compiled multiple tree ring‐based disturbance histories from primary Picea abies forest fragments distributed throughout five European landscapes spanning the Bohemian Forest and the Carpathian Mountains. The regional chronology includes 11,595 tree cores, with ring dates spanning the years 1750–2000, collected from 560 inventory plots in 37 stands distributed across a 1,000 km geographic gradient, amounting to the largest disturbance chronology yet constructed in Europe. Decadal disturbance rates varied significantly through time and declined after 1920, resulting in widespread increases in canopy tree age. Approximately 75% of current canopy area recruited prior to 1900. Long‐term disturbance patterns were compared to an historical drought reconstruction, and further linked to spatial variation in stand structure and contemporary disturbance patterns derived from LANDSAT imagery. Historically, decadal Palmer drought severity index minima corresponded to higher rates of canopy removal. The severity of contemporary disturbances increased with each stand's estimated time since last major disturbance, increased with mean diameter, and declined with increasing within‐stand structural variability. Reconstructed spatial patterns suggest that high small‐scale structural variability has historically acted to reduce large‐scale susceptibility and climate sensitivity of disturbance. Reduced disturbance rates since 1920, a potential legacy of high 19th century disturbance rates, have contributed to a recent region‐wide increase in disturbance susceptibility. Increasingly common high‐severity disturbances throughout primary Picea forests of Central Europe should be reinterpreted in light of both legacy effects (resulting in increased susceptibility) and climate change (resulting in increased exposure to extreme events).
Climate change has been linked to increasing forest disturbance rates and large‐scale disturbance histories are needed to assess how disturbance legacies modulate climate–disturbance dynamics. Historical disturbance rates (c. 1750–2000), reconstructed with tree cores collected from primary Picea abies forests throughout Central‐Eastern Europe, have exhibited moderate sensitivity to drought extremes; developmental feedbacks are important determinants of a forest's responsiveness to climate‐induced events. Widespread increases in forest age have occurred throughout the 20th century and these developmental patterns, in addition to climate change, are responsible for the severity of recent disturbances.
The growth of past, present, and future forests was, is and will be affected by climate variability. This multifaceted relationship has been assessed in several regional studies, but spatially ...resolved, large-scale analyses are largely missing so far. Here we estimate recent changes in growth of 5800 beech trees (Fagus sylvatica L.) from 324 sites, representing the full geographic and climatic range of species. Future growth trends were predicted considering state-of-the-art climate scenarios. The validated models indicate growth declines across large region of the distribution in recent decades, and project severe future growth declines ranging from -20% to more than -50% by 2090, depending on the region and climate change scenario (i.e. CMIP6 SSP1-2.6 and SSP5-8.5). Forecasted forest productivity losses are most striking towards the southern distribution limit of Fagus sylvatica, in regions where persisting atmospheric high-pressure systems are expected to increase drought severity. The projected 21
century growth changes across Europe indicate serious ecological and economic consequences that require immediate forest adaptation.
The expected future intensification of forest disturbance as a consequence of ongoing anthropogenic climate change highlights the urgent need to more robustly quantify associated biotic responses. ...Saproxylic beetles are a diverse group of forest invertebrates representing a major component of biodiversity that is associated with the decomposition and cycling of wood nutrients and carbon in forest ecosystems. Disturbance-induced declines or shifts in their diversity indicate the loss of key ecological and/or morphological species traits that could change ecosystem functioning. Functional and phylogenetic diversity of biological communities is commonly used to link species communities to ecosystem functions. However, our knowledge on how disturbance intensity alters functional and phylogenetic diversity of saproxylic beetles is incomplete. Here, we analyzed the main drivers of saproxylic beetle abundance and diversity using a comprehensive dataset from montane primary forests in Europe. We investigated cascading relationships between 250 years of historical disturbance mechanisms, forest structural attributes and the taxonomic, phylogenetic and functional diversity of present-day beetle communities. Our analyses revealed that historical disturbances have significant effects on current beetle communities. Contrary to our expectations, different aspects of beetle communities, that is, abundance, taxonomic, phylogenetic and functional diversity, responded to different disturbance regime components. Past disturbance frequency was the most important component influencing saproxylic beetle communities and habitat via multiple temporal and spatial pathways. The quantity of deadwood and its diameter positively influenced saproxylic beetle abundance and functional diversity, whereas phylogenetic diversity was positively influenced by canopy openness. Analyzing historical disturbances, we observed that current beetle diversity is far from static, such that the importance of various drivers might change during further successional development. Only forest landscapes that are large enough to allow for the full range of temporal and spatial patterns of disturbances and post-disturbance development will enable long-term species coexistence and their associated ecosystem functions.
Questions: What historical natural disturbances have shaped the structure and development of an old-growth, sub-alpine Picea abies forest? Are large-scale, high-severity disturbances (similar to the ...recent windthrow and bark beetle outbreaks in the region) within the historical range of variability for this forest ecosystem? Can past disturbances explain the previously described gradient in stand structure that had been attributed to an elevation gradient? Location: Šumava National Park (the Bohemian Forest) of the southwest Czech Republic. Methods: We reconstructed the site's disturbance history using dendroecological methods in a 20-ha study plot, established to span an elevation gradient. Growth patterns of 400 increment cores were screened for: (1 ) abrupt increases in radial growth indicating mortality of a former canopy tree and (2) rapid early growth rates indicating establishment in a former canopy gap. Results: Spatial and temporal patterns of canopy accession varied markedly over the 20-ha study area, resulting in disturbance pulses that corresponded to an elevation gradient. On the lower slope of the plot, the majority of the trees reached the canopy during two pulses (1770-1800 and 1820-1840), while most trees on the upper slope accessed the canopy in one pulse (1840-1860). Historically documented windstorms roughly coincide with peaks in our disturbance reconstruction. Conclusions: Our study provides strong evidence that these forests were historically shaped by infrequent, moderate- to high-severity natural disturbances. Our methods, however, could not definitively identify the agent(s) of these disturbances. Nevertheless, the recent mid-1990s windstorm and the ensuing spruce bark beetle outbreak may provide an analogue for past disturbance, as the duration and severity of these events could easily explain past patterns of growth response and recruitment in our results. Thus, it seems reasonable to assume the interaction of windstorms and bark beetles seen in the contemporary landscape has occurred historically. Finally, our results suggest that the previously documented elevation gradient in forest structure may not be related to elevation per se (lower temperatures and shorter growing season) but rather to changes in disturbance severity mediated by elevation.
► We studied the effect of logs features on Norway spruce seedling density. ► Log diameter and white-rot fungi were positively related to spruce density. ► Density was negatively related to ...brown-rot-causing
Fomitopsis pinicola. ► Large logs originating from wind uprooting are most appropriate for regeneration.
Decaying logs form the major seedbed for trees in European subalpine
Picea abies forests. However, many aspects related to seedling colonization pattern on logs remain unclear. The aim of this study was to analyze the relationships of
P. abies (Norway spruce) seedling (height <15
cm) and sapling (height ⩾15
cm) densities on decaying logs in relation to stage of wood decay, log diameter, ground contact of decaying log, assumed cause of tree death, presence of species of wood-decaying fungi and coverage by surrounding plants in the subalpine old-growth forests of the Bohemian Forest and Ash Mountains, in the Czech Republic. We have focused on how logs with different origin differ in their properties and how these properties influence seedling abundance. Seedling densities peaked on the medium-decayed logs and decreased thereafter. Sapling densities continually increased as the decay progressed. Seedling and sapling densities followed negative binomial distributions, with many logs of all decay stages having low regeneration densities. The degree of ground contact, white-rot-causing
Armillaria spp. presence, white-rot-causing
Phellinus nigrolimitatus presence and log diameter were positively related to both seedling and sapling density. Also tree death as a result of wind uprooting was positively related to sapling density. Conversely, the presence of brown-rot-causing
Fomitopsis pinicola and tree death as a result of bark beetle attack were negatively related to regeneration densities. The low cover of vegetation from sides positively affected seedling density; however, heavily covered logs were less occupied by seedlings. Our study provides evidence that large logs originating from wind uprooting or butt rot infection are most appropriate for retention to promote natural spruce regeneration in managed subalpine spruce forests.
Levinstein recently presented a challenge to accuracy-first epistemology. He claims that there is no strictly proper, truth-directed, additive, and differentiable scoring rule that recognises the ...contingency of varying importance, i.e., the fact that an agent might value the inaccuracy of her credences differently at different possible worlds. In my response, I will argue that accuracy-first epistemology can capture the contingency of varying importance while maintaining its commitment to additivity, propriety, truth-directedness, and differentiability. I will construct a scoring rule — a weighted scoring rule — and a global inaccuracy measure that has all four required properties and recognises the contingency of varying importance. I will show that Levinstein’s and my results coexist without contradicting each other
•B-doped diamond is nanostructured by corrosion-driven modifications occurring at carbonaceous impurity sites (sp2-carbons).•The electrochemical oxidation partly transforms a hydrogen-terminated ...diamond surface to O-terminated one, but the electrocatalytic activity of plasmatically O-terminated diamond is not achieved.•In contrast to all usual sp2 carbons, the Raman spectra of B-doped diamond electrodes do not change upon electrochemical charging/discharging.
Comparative studies of boron-doped diamonds electrodes (polycrystalline, single-crystalline, H-/O-terminated, and with different sp3/sp2 ratios) indicate morphological modifications of diamond which are initiated by corrosion at nanoscale. In-situ electrochemical AFM imaging evidences that the textural changes start at non-diamond carbonaceous impurity sites treated at high positive potentials (>2.2V vs. Ag/AgCl). The primary perturbations subsequently develop into sub-micron-sized craters. Raman spectroscopy shows that the primary erosion site is graphite-like (sp2-carbon), which is preferentially removed by anodic oxidation. Other non-diamond impurity, viz. tetrahedral amorphous carbon (t-aC), is less sensitive to oxidative decomposition. The diamond-related Raman features, including the B-doping-assigned modes, are intact during reversible electrochemical charging/discharging, which is a salient difference from all usual sp2-carbons. The electrochemical oxidation partly transforms a hydrogen-terminated diamond surface to O-terminated one, but the electrocatalytic activity of plasmatically O-terminated diamond is not achieved for a model redox couple, Fe3+/2+. Electrochemical impedance spectra were fitted to six different equivalent circuits. The determination of acceptor concentrations is feasible even for highly-doped diamond electrodes.
Accurately capturing medium- to low-frequency trends in tree-ring data is vital to assessing climatic response and developing robust reconstructions of past climate. Non-climatic disturbance can ...affect growth trends in tree-ring-width (RW) series and bias climate information obtained from such records. It is important to develop suitable strategies to ensure the development of chronologies that minimize these medium- to low-frequency biases. By performing high density sampling (760 trees) over a ~40-ha natural high-elevation Norway spruce (Picea abies) stand in the Romanian Carpathians, this study assessed the suitability of several sampling strategies for developing chronologies with an optimal climate signal for dendroclimatic purposes. There was a roughly equal probability for chronologies (40 samples each) to express a reasonable (r = 0.3–0.5) to non-existent climate signal. While showing a strong high-frequency response, older/larger trees expressed the weakest overall temperature signal. Although random sampling yielded the most consistent climate signal in all sub-chronologies, the outcome was still sub-optimal. Alternative strategies to optimize the climate signal, including very high replication and principal components analysis, were also unable to minimize this disturbance bias and produce chronologies adequately representing climatic trends, indicating that larger scale disturbances can produce synchronous pervasive disturbance trends that affect a large part of a sampled population. The Curve Intervention Detection (CID) method, used to identify and reduce the influence of disturbance trends in the RW chronologies, considerably improved climate signal representation (from r = 0.28 before correction to r = 0.41 after correction for the full 760 sample chronology over 1909–2009) and represents a potentially important new approach for assessing disturbance impacts on RW chronologies. Blue intensity (BI) also shows promise as a climatically more sensitive variable which, unlike RW, does not appear significantly affected by disturbance. We recommend that studies utilizing RW chronologies to investigate medium- to long-term climatic trends also assess disturbance impact on those series.
The mechanistic pathways connecting ocean-atmosphere variability and terrestrial productivity are well-established theoretically, but remain challenging to quantify empirically. Such quantification ...will greatly improve the assessment and prediction of changes in terrestrial carbon sequestration in response to dynamically induced climatic extremes. The jet stream latitude (JSL) over the North Atlantic-European domain provides a synthetic and robust physical framework that integrates climate variability not accounted for by atmospheric circulation patterns alone. Surface climate impacts of north-south summer JSL displacements are not uniform across Europe, but rather create a northwestern-southeastern dipole in forest productivity and radial-growth anomalies. Summer JSL variability over the eastern North Atlantic-European domain (5-40E) exerts the strongest impact on European beech, inducing anomalies of up to 30% in modelled gross primary productivity and 50% in radial tree growth. The net effects of JSL movements on terrestrial carbon fluxes depend on forest density, carbon stocks, and productivity imbalances across biogeographic regions.
PDF
