A microtome designed for the surface preparation of entire increment cores allows cutting plane surfaces on cores up to a length of 40
cm. Compared to the common sanding procedure, the wood cells of ...the annual rings remain open, not filled with swarf, and the cell walls are smooth and hence clearly visible. This article aims at describing the functionality of the microtome and the procedures needed for an accurate surface preparation to achieve a good contrast for subsequent image analysis. Possible applications for a more detailed analysis of variations in the tracheid structure of conifers and vessel sizes of oak are presented, which can be included in time series analyses.
Annually resolved summer temperatures for the European Alps are described. The reconstruction covers the A.D. 755–2004 period and is based on 180 recent and historic larch Larix deciduaMill. density ...series. The regional curve standardization method was applied to preserve interannual to multicentennial variations in this high-elevation proxy dataset. Instrumental measurements from high- (low-) elevation grid boxes back to 1818 (1760) reveal strongest growth response to current-year June–September mean temperatures. The reconstruction correlates at 0.7 with high-elevation temperatures back to 1818, with a greater signal in the higher-frequency domain (r= 0.8). Low-elevation instrumental data back to 1760 agree with the reconstruction’s interannual variation, although a decoupling between (warmer) instrumental and (cooler) proxy data before ~1840 is noted. This offset is larger than during any period of overlap with more recent high-elevation instrumental data, even though the proxy time series always contains some unexplained variance. The reconstruction indicates positive temperatures in the tenth and thirteenth century that resemble twentieth-century conditions, and are separated by a prolonged cooling from ~1350 to 1700. Six of the 10 warmest decades over the 755–2004 period are recorded in the twentieth century. Maximum temperature amplitude over the past 1250 yr is estimated to be 3.1°C between the warmest (1940s) and coldest (1810s) decades. This estimate is, however, affected by the calibration with instrumental temperature data. Warm summers seem to coincide with periods of high solar activity, and cold summers vice versa. The record captures the full range of past European temperature variability, that is, the extreme years 1816 and 2003, warmth during medieval and recent times, and cold in between. Comparison with regional- and large-scale reconstructions reveals similar decadal to longer-term variability.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The effects of climate change on Arctic ecosystems can range between various spatiotemporal scales and may include shifts in population distribution, community composition, plant phenology, primary ...productivity and species biodiversity. The growth rates and age structure of tundra vegetation as well as its response to temperature variation, however, remain poorly understood because high‐resolution data are limited in space and time. Anatomical and morphological stem characteristics were recorded to assess the growth behaviour and age structure of 871 dwarf shrubs from 10 species at 30 sites in coastal East Greenland at ˜70°N. Recruitment pulses were linked with changes in mean annual and summer temperature back to the 19th century, and a literature review was conducted to place our findings in a pan‐Arctic context. Low cambial activity translates into estimated average/maximum plant ages of 59/204 years, suggesting relatively small turnover rates and stable community composition. Decade‐long changes in the recruitment intensity were found to lag temperature variability by 2 and 6 years during warmer and colder periods, respectively (r = 0.85₁₉₆₁–₂₀₀₀ ₐₙd ₁₈₈₁–₁₉₂₀). Synthesis. Our results reveal a strong temperature dependency of Arctic dwarf shrub reproduction, a high vulnerability of circumpolar tundra ecosystems to climatic changes, and the ability of evaluating historical vegetation dynamics well beyond the northern treeline. The combined wood anatomical and plant ecological approach, considering insights from micro‐sections to community assemblages, indicates that model predictions of rapid tundra expansion (i.e. shrub growth) following intense warming might underestimate plant longevity and persistence but overestimate the sensitivity and reaction time of Arctic vegetation.
The Sun sporadically produces eruptive events leading to intense fluxes of solar energetic particles (SEPs) that dramatically disrupt the near-Earth radiation environment. Such events have been ...directly studied for the last decades but little is known about the occurrence and magnitude of rare, extreme SEP events. Presently, a few events that produced measurable signals in cosmogenic radionuclides such as
C,
Be and
Cl have been found. Analyzing annual
C concentrations in tree-rings from Switzerland, Germany, Ireland, Russia, and the USA we discovered two spikes in atmospheric
C occurring in 7176 and 5259 BCE. The ~2% increases of atmospheric
C recorded for both events exceed all previously known
C peaks but after correction for the geomagnetic field, they are comparable to the largest event of this type discovered so far at 775 CE. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records and provide critical information on the previous occurrence of extreme solar events which may threaten modern infrastructure.
1200 years of regular outbreaks in alpine insects Esper, Jan; Büntgen, Ulf; Frank, David C ...
Proceedings - Royal Society. Biological sciences/Proceedings - Royal Society. Biological Sciences,
03/2007, Letnik:
274, Številka:
1610
Journal Article
Recenzirano
Odprti dostop
The long-term history of Zeiraphera diniana Gn. (the larch budmoth, LBM) outbreaks was reconstructed from tree rings of host subalpine larch in the European Alps. This record was derived from 47 513 ...maximum latewood density measurements, and highlights the impact of contemporary climate change on ecological disturbance regimes. With over 1000 generations represented, this is the longest annually resolved record of herbivore population dynamics, and our analysis demonstrates that remarkably regular LBM fluctuations persisted over the past 1173 years with population peaks averaging every 9.3 years. These regular abundance oscillations recurred until 1981, with the absence of peak events during recent decades. Comparison with an annually resolved, millennium-long temperature reconstruction representative for the European Alps (r=0.72, correlation with instrumental data) demonstrates that regular insect population cycles continued despite major climatic changes related to warming during medieval times and cooling during the Little Ice Age. The late twentieth century absence of LBM outbreaks, however, corresponds to a period of regional warmth that is exceptional with respect to the last 1000+ years, suggesting vulnerability of an otherwise stable ecological system in a warming environment.
Advances in accelerator mass spectrometry have resulted in an unprecedented amount of new high-precision radiocarbon (14C) -dates, some of which will redefine the international 14C calibration curves ...(IntCal and SHCal). Often these datasets are unaccompanied by detailed quality insurances in place at the laboratory, questioning whether the 14C structure is real, a result of a laboratory variation or measurement-scatter. A handful of intercomparison studies attempt to elucidate laboratory offsets but may fail to identify measurement-scatter and are often financially constrained. Here we introduce a protocol, called Quality Dating, implemented at ETH-Zürich to ensure reproducible and accurate high-precision 14C-dates. The protocol highlights the importance of the continuous measurements and evaluation of blanks, standards, references and replicates. This protocol is tested on an absolutely dated German Late Glacial tree-ring chronology, part of which is intercompared with the Curt Engelhorn-Center for Archaeometry, Mannheim, Germany (CEZA). The combined dataset contains 170 highly resolved, highly precise 14C-dates that supplement three decadal dates spanning 280 cal. years in IntCal, and provides detailed 14C structure for this interval.
Ancient DNA from historical and subfossil wood has a great potential to provide new insights into the history of tree populations. However, its extraction and analysis have not become routine, mainly ...because contamination of the wood with modern plant material can complicate the verification of genetic information.
Here, we used sapwood tissue from 22 subfossil pines that were growing c. 13 000 yr BP in Zurich, Switzerland. We developed and evaluated protocols to eliminate surface contamination, and we tested ancient DNA authenticity based on plastid DNA metabarcoding and the assessment of post-mortem DNA damage.
A novel approach using laser irradiation coupled with bleaching and surface removal was most efficient in eliminating contaminating DNA. DNA metabarcoding confirmed which ancient DNA samples repeatedly amplified pine DNA and were free of exogenous plant taxa. Pine DNA sequences of these samples showed a high degree of cytosine to thymine mismatches, typical of post-mortem damage.
Stringent decontamination of wood surfaces combined with DNA metabarcoding and assessment of post-mortem DNA damage allowed us to authenticate ancient DNA retrieved from the oldest Late Glacial pine forest. These techniques can be applied to any subfossil wood and are likely to improve the accessibility of relict wood for genome-scale ancient DNA studies.
As the worldwide standard for radiocarbon (14C) dating over the past ca. 50,000 years, the International Calibration Curve (IntCal) is continuously improving towards higher resolution and ...replication. Tree-ring-based 14C measurements provide absolute dating throughout most of the Holocene, although high-precision data are limited for the Younger Dryas interval and farther back in time. Here, we describe the dendrochronological characteristics of 1448 new 14C dates, between ~11,950 and 13,160 cal BP, from 13 pines that were growing in Switzerland. Significantly enhancing the ongoing IntCal update (IntCal20), this Late Glacial (LG) compilation contains more annually precise 14C dates than any other contribution during any other period of time. Thus, our results now provide unique geochronological dating into the Younger Dryas, a pivotal period of climate and environmental change at the transition from LG into Early Holocene conditions.
Despite an increasing demand for Burgundy truffles (Tuber aestivum), gaps remain in our understanding of the fungus' overall lifecycle and ecology. Here, we compile evidence from three independent ...surveys in Hungary and Switzerland. First, we measured the weight and maturity of 2,656 T. aestivum fruit bodies from a three-day harvest in August 2014 in a highly productive orchard in Hungary. All specimens ranging between 2 and 755 g were almost evenly distributed through five maturation classes. Then, we measured the weight and maturity of another 4,795 T. aestivum fruit bodies harvested on four occasions between June and October 2015 in the same truffière. Again, different maturation stages occurred at varying fruit body size and during the entire fruiting season. Finally, the predominantly unrelated weight and maturity of 81 T. aestivum fruit bodies from four fruiting seasons between 2010 and 2013 in Switzerland confirmed the Hungarian results. The spatiotemporal coexistence of 7,532 small-ripe and large-unripe T. aestivum, which accumulate to ~182 kg, differs from species-specific associations between the size and ripeness that have been reported for other mushrooms. Although size-independent truffle maturation stages may possibly relate to the perpetual belowground environment, the role of mycelial connectivity, soil property, microclimatology, as well as other abiotic factors and a combination thereof, is still unclear. Despite its massive sample size and proof of concept, this study, together with existing literature, suggests consideration of a wider ecological and biogeographical range, as well as the complex symbiotic fungus-host interaction, to further illuminate the hidden development of belowground truffle fruit bodies.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Dendroecological research uses information stored in tree rings to understand how single trees and even entire forest ecosystems responded to environmental changes and to finally reconstruct such ...changes. This is done by analyzing growth variations back in time and correlating various plant-specific parameters to (for example) temperature records. Integrating wood anatomical parameters in these analyses would strengthen reconstructions, even down to intra-annual resolution. We therefore present a protocol on how to sample, prepare, and analyze wooden specimen for common macroscopic analyses, but also for subsequent microscopic analyses. Furthermore we introduce a potential solution for analyzing digital images generated from common small and large specimens to support time-series analyses. The protocol presents the basic steps as they currently can be used. Beyond this, there is an ongoing need for the improvement of existing techniques, and development of new techniques, to record and quantify past and ongoing environmental processes. Traditional wood anatomical research needs to be expanded to include ecological information to this field of research. This would support dendro-scientists who intend to analyze new parameters and develop new methodologies to understand the short and long term effects of specific environmental factors on the anatomy of woody plants.
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